NAVLE (North American Veterinary Licensing Exam) — Questions and Answers

Question 1: On abdominal radiographs, which finding is MOST consistent with a congenital portosystemic shunt in a young dog?

Normal liver size with splenic mineralization
Microhepatica (small liver) with renomegaly (Correct answer)
Splenomegaly with portal vein dilation
Hepatomegaly with ascites

Correct answer: Microhepatica (small liver) with renomegaly

Congenital portosystemic shunts divert hepatotrophic factors away from the liver, causing microhepatica; compensatory renal hypertrophy often produces concurrent renomegaly.

Question 2: You are managing a cat that ingested topical permethrin flea spray (concentrated dog formulation) 90 minutes ago. The cat is tremoring severely. After decontamination with dish soap, which treatment combination is MOST appropriate for controlling permethrin-induced tremors in this cat?

Lipid emulsion therapy (ILE) as sole treatment, given permethrin's high lipophilicity
Cyproheptadine PO or per rectum combined with methocarbamol IV
Methocarbamol IV combined with diazepam; avoid pyrethroid-specific antidotes (Correct answer)
Atropine IV to block muscarinic hyperstimulation, followed by pralidoxime

Correct answer: Methocarbamol IV combined with diazepam; avoid pyrethroid-specific antidotes

Permethrin toxicosis in cats causes sodium channel dysfunction leading to repetitive neuronal firing, manifesting as tremors and seizures. The treatment of choice for tremor control is methocarbamol (a muscle relaxant; 44–220 mg/kg IV slowly to effect) combined with diazepam or other benzodiazepines for CNS sedation and seizure control. There is no specific antidote. Atropine + pralidoxime is the antidote regimen for organophosphate/carbamate toxicity (which acts via AChE inhibition), not pyrethroids. Cyproheptadine (a serotonin antagonist) is used for serotonin syndrome, not permethrin toxicosis. IVLipid emulsion can be a useful adjunct in severe refractory cases but is not the primary or sole treatment.

Question 3: A 3-year-old Quarter Horse gelding presents for acute onset of right forelimb lameness (grade 4/5) after a barrel racing event. Hoof testers elicit a strong positive reaction over the lateral heel. Perineural anesthesia of the lateral palmar digital nerve abolishes the lameness. Radiographs reveal a thin, radiolucent line through the lateral palmar process of the distal phalanx (P3). Which pathophysiologic mechanism best explains why this specific fracture configuration carries a guarded prognosis for return to competition?

Avascular necrosis of the distal phalanx due to disruption of the terminal arch
Chronic repetitive tension from the deep digital flexor tendon preventing fracture healing
Involvement of the distal interphalangeal joint articular surface increasing the risk of degenerative joint disease (Correct answer)
High risk of septic osteitis due to proximity to the white line

Correct answer: Involvement of the distal interphalangeal joint articular surface increasing the risk of degenerative joint disease

Palmar process (wing) fractures of P3 are classified by Sanders & Stashak. Non-articular fractures carry a good prognosis, but when the fracture line extends into the distal interphalangeal (coffin) joint, articular surface damage predisposes to post-traumatic osteoarthritis, significantly worsening the prognosis for return to high-performance competition. Avascular necrosis is not a primary mechanism in wing fractures. Septic osteitis is a complication of solar penetration wounds, not this fracture type specifically. DDFT tension is more relevant to the middle third fractures.

Question 4: A cat tests positive on FIV ELISA. The cat is 8 weeks old and was born to a seropositive queen. How should this result be interpreted?

False positive; FIV cannot infect kittens
Confirmed FIV infection requiring immediate antiviral therapy
Likely maternal antibody transfer; retest after 6 months of age (Correct answer)
Inconclusive; euthanasia is recommended

Correct answer: Likely maternal antibody transfer; retest after 6 months of age

FIV ELISA detects antibodies, and kittens can carry maternally derived antibodies until 6 months of age, yielding false-positive results.

Question 5: On CT myelography of a dog, an 'intramedullary' lesion is characterized by:

Widening of the subarachnoid space without cord deformation
Complete block of contrast flow with a concave meniscus
Fusiform swelling of the spinal cord with thinning of the contrast column on all sides (Correct answer)
Extradural deviation of the contrast column to one side only

Correct answer: Fusiform swelling of the spinal cord with thinning of the contrast column on all sides

Intramedullary lesions expand the cord itself, producing symmetric fusiform cord enlargement that thins the contrast column circumferentially.

Question 6: A cat presents with acute onset of severe muscle tremors, hyperthermia, and mydriasis after the owner applied a canine-specific flea and tick spot-on product. Which of the following toxicities is most likely, and what is the primary therapeutic agent used to control the tremors?

Permethrin toxicity; Methocarbamol (Correct answer)
Ethylene glycol toxicity; Fomepizole
Ivermectin toxicity; Intralipid emulsion
Organophosphate toxicity; Atropine

Correct answer: Permethrin toxicity; Methocarbamol

The clinical signs described are classic for permethrin toxicity, which occurs when concentrated canine flea products containing this pyrethroid are applied to cats. Cats are deficient in the enzymes needed to metabolize permethrin effectively. The primary treatment for the resulting muscle tremors and fasciculations is the centrally-acting muscle relaxant, methocarbamol. Atropine is for organophosphate toxicity, fomepizole for ethylene glycol, and intralipid emulsion is an adjunctive therapy for lipid-soluble toxins like ivermectin.

Question 7: Which local anesthetic has the highest risk of causing methemoglobinemia in cats?

Lidocaine
Bupivacaine
Ropivacaine
Benzocaine (Correct answer)

Correct answer: Benzocaine

Benzocaine, found in some topical sprays, rapidly induces methemoglobinemia in cats due to their limited ability to metabolize certain oxidizing agents.

Question 8: A 4-year-old male Dalmatian has recurrent stranguria. Survey abdominal radiographs are unremarkable. Given this breed's predisposition to radiolucent uroliths, which contrast study is most appropriate to definitively identify their presence within the bladder?

Double contrast cystogram (Correct answer)
Positive contrast cystogram
Negative contrast cystogram
Excretory urogram

Correct answer: Double contrast cystogram

Dalmatians are prone to forming urate uroliths, which are often radiolucent and not visible on survey radiographs. A double contrast cystogram is the ideal study in this case. This technique uses a small amount of positive contrast medium to coat the bladder wall and any uroliths, followed by distention with negative contrast (gas). The radiolucent uroliths are then outlined by the positive contrast, making them visible against the dark, gas-filled lumen. A positive contrast study alone could obscure the stones.

Question 9: A cat rescue organization routinely tests all cats for FeLV and FIV using a point-of-care ELISA combo test. A 2-year-old cat tests FIV antibody-positive. The organization plans to euthanize the cat per their protocol. The attending veterinarian recommends Western blot confirmatory testing. Which scenario would produce the MOST clinically significant false-positive FIV ELISA result and thus most strongly justify confirmatory testing?

The cat received a blood transfusion from an FIV-positive donor 2 weeks ago
The cat is a kitten under 6 months with maternally derived antibodies from an FIV-positive queen
The cat received an FIV vaccination (Fel-O-Vax FIV) within the past 4 years (Correct answer)
The cat has concurrent FeLV viremia causing cross-reactive antibody production

Correct answer: The cat received an FIV vaccination (Fel-O-Vax FIV) within the past 4 years

Vaccination with the killed whole-virus FIV vaccine (Fel-O-Vax FIV, no longer commercially available but cats vaccinated years ago may still be seropositive) induces antibodies that are indistinguishable from natural infection antibodies on standard ELISA and IFA tests — this is the most clinically important cause of false-positive FIV serology in adult cats. Western blot can help differentiate in some cases, but even WB may be positive post-vaccination. PCR is the most reliable confirmatory test in vaccinated cats. FeLV does not cause cross-reactive FIV antibodies. Blood transfusion-transferred antibodies would wane by 2 weeks and are not a major confounder. Maternal antibody interference is significant in kittens under 6 months but the question asks for the most significant false-positive in the described adult context.

Question 10: A veterinary technician performing a loco-regional block for feline dental extractions inadvertently injects bupivacaine 0.5% at a total dose of 4 mg/kg. Within 10 minutes the cat develops ventricular tachycardia refractory to lidocaine administration. Which treatment is MOST likely to restore sinus rhythm?

IV bretylium tosylate 5 mg/kg as an alternative antiarrhythmic
IV lipid emulsion (20%) 1.5 mL/kg bolus followed by a CRI (Correct answer)
Immediate cardioversion with 2 J/kg biphasic defibrillation
IV sodium bicarbonate 1 mEq/kg to alkalinize plasma and displace bupivacaine from sodium channels

Correct answer: IV lipid emulsion (20%) 1.5 mL/kg bolus followed by a CRI

Bupivacaine systemic toxicity produces cardiotoxicity that is notoriously refractory to standard antiarrhythmics and resuscitation because the drug avidly binds cardiac sodium channels. Intravenous lipid emulsion (ILE) therapy ('lipid rescue') works by creating a lipid sink that sequesters the highly lipophilic bupivacaine away from cardiac tissue, rapidly reducing free plasma concentrations. The protocol is 1.5 mL/kg of 20% lipid emulsion IV bolus, followed by a CRI of 0.25 mL/kg/min for 10–60 minutes. Sodium bicarbonate helps with lidocaine toxicity and can transiently help sodium-channel blockade but is not the primary rescue therapy for bupivacaine cardiac arrest. Bretylium is no longer commercially available in North America. Electrical cardioversion does not address the pharmacologic cause and is unlikely to maintain sinus rhythm while bupivacaine is still bound to channels.

Question 11: A dairy herd has a high prevalence of digital dermatitis (Mortellaro's disease). Which treatment is most effective for active, painful lesions?

Surgical debridement under general anesthesia
Topical oxytetracycline applied to the lesion and wrapped with a bandage (Correct answer)
Hoof trimming and copper sulfate footbath only
Systemic oxytetracycline injection

Correct answer: Topical oxytetracycline applied to the lesion and wrapped with a bandage

Topical oxytetracycline or lincomycin applied directly to digital dermatitis lesions after cleaning and drying, covered with a bandage, achieves the highest cure rates for active M2 lesions.

Question 12: Which drug is used to reverse the sedative and analgesic effects of medetomidine in dogs and cats?

Yohimbine
Atipamezole (Correct answer)
Naloxone
Flumazenil

Correct answer: Atipamezole

Atipamezole is a specific alpha-2 adrenergic antagonist used to reverse medetomidine and dexmedetomidine sedation in dogs and cats.

Question 13: A 6-year-old DSH cat with hyperthyroidism is started on methimazole. Two weeks later, the owner reports the cat is scratching its face intensely and has developed facial excoriations. Which statement BEST explains the pathophysiology and recommended management?

Methimazole-induced hypothyroidism has unmasked latent feline hyperesthesia syndrome; adjust thyroid hormone levels with levothyroxine supplementation
Facial pruritus is a known idiosyncratic drug reaction in cats, likely immune-mediated; discontinue methimazole and consider carbimazole or alternative definitive therapy (Correct answer)
This represents a Type II hypersensitivity reaction to methimazole; switch to radioactive iodine (I-131) therapy
Methimazole causes dose-dependent peripheral neuropathy; reduce the dose by 50% and monitor for resolution

Correct answer: Facial pruritus is a known idiosyncratic drug reaction in cats, likely immune-mediated; discontinue methimazole and consider carbimazole or alternative definitive therapy

Facial pruritus and self-excoriation is a well-documented idiosyncratic adverse effect of methimazole in cats, occurring in approximately 2–3% of treated cats, typically within the first 1–3 months of therapy. The mechanism is thought to be immune-mediated. This reaction is an indication to discontinue methimazole immediately, as continued use can lead to more severe reactions including hepatotoxicity, thrombocytopenia, or agranulocytosis. Carbimazole (a prodrug of methimazole) should theoretically cross-react, so definitive therapy with I-131, surgical thyroidectomy, or a prescription iodine-restricted diet (Hill's y/d) is preferred. This is not a dose-dependent effect and dose reduction is inadequate management.

Question 14: Which reproductive technology is used to synchronize estrus in beef heifers and cows to facilitate fixed-time artificial insemination (FTAI) without heat detection?

Gonadotropin-releasing hormone (GnRH) injection alone
Ovsynch or Select Synch protocols combining GnRH, progesterone (CIDR), and prostaglandin F2α (Correct answer)
Melengestrol acetate (MGA) in feed for 14 days without any hormonal synchronization
Human chorionic gonadotropin (hCG) injection alone

Correct answer: Ovsynch or Select Synch protocols combining GnRH, progesterone (CIDR), and prostaglandin F2α

The 7-day CO-Synch+CIDR or Ovsynch protocols combining GnRH, a CIDR insert, and prostaglandin F2α synchronize follicular wave and luteal regression to enable fixed-time AI without heat detection.

Question 15: A 4-year-old female spayed Standard Poodle presents with a 2-day history of lethargy, vomiting, and weakness. Physical exam reveals pale mucous membranes and tachycardia. A CBC shows a hematocrit of 15% with marked spherocytosis and autoagglutination. What is the MOST critical initial component of immunosuppressive therapy for this dog's condition?

Azathioprine
Cyclosporine
Mycophenolate mofetil
Glucocorticoids (Correct answer)

Correct answer: Glucocorticoids

The clinical signs and laboratory findings are highly suggestive of Immune-Mediated Hemolytic Anemia (IMHA). The cornerstone and first-line treatment for IMHA is aggressive immunosuppression, which is most rapidly and effectively achieved with glucocorticoids (e.g., prednisone or dexamethasone). While other immunosuppressive drugs like azathioprine, cyclosporine, and mycophenolate are often used as adjuncts, they are not the primary, initial therapy.

Question 16: On ultrasound of the urinary bladder, a dependent hyperechoic layer with acoustic shadowing that moves when the patient is repositioned most likely represents:

Uroliths (bladder stones) (Correct answer)
Transitional cell carcinoma
Bladder wall thickening
Blood clots

Correct answer: Uroliths (bladder stones)

Uroliths are hyperechoic foci with acoustic shadowing that are gravity-dependent and shift position when the patient moves, distinguishing them from wall masses.

Question 17: A 5-year-old Labrador Retriever is presented with acute collapse and hematemesis. On exam, the dog is tachycardic (HR 160 bpm), pale, and has a fluid wave on abdominal ballottement. PCV is 18%, total protein is 3.2 g/dL, and abdominal ultrasound reveals a large splenic mass with free abdominal fluid. After stabilization, a splenectomy is performed. Histopathology confirms splenic hemangiosarcoma. Which combination of prognostic factors is associated with the LONGEST median survival time post-splenectomy?

Stage III disease with adjuvant metronomic cyclophosphamide
Stage I disease with adjuvant doxorubicin chemotherapy (Correct answer)
Stage I disease with no adjuvant therapy
Stage II disease with adjuvant vincristine, doxorubicin, and cyclophosphamide (VAC)

Correct answer: Stage I disease with adjuvant doxorubicin chemotherapy

Splenic hemangiosarcoma staged as Stage I (tumor confined to spleen, no rupture, no metastasis) combined with adjuvant doxorubicin-based chemotherapy is associated with the longest median survival — approximately 4–6 months compared to 1–2 months with surgery alone. Stage II (ruptured or with regional spread) and Stage III (distant metastasis) carry significantly worse prognoses regardless of protocol. VAC has not consistently outperformed single-agent doxorubicin in canine HSA.

Question 18: A 4-year-old Boxer presents with episodic syncope. ECG reveals a wide, bizarre QRS complex occurring at a rate of 180 bpm with no preceding P waves. What is the most likely diagnosis?

Second-degree AV block
Ventricular tachycardia (Correct answer)
Supraventricular tachycardia with aberrant conduction
Atrial fibrillation

Correct answer: Ventricular tachycardia

Wide bizarre QRS complexes with no preceding P waves at a rapid rate are characteristic of ventricular tachycardia, common in Boxers with ARVC.

Question 19: Which of the following causes of exophthalmos in cattle occurs most frequently?

Extracranial meningioma
Sinusitis
Orbital arteriovenous fistula
Retrobulbar lymphosarcoma (Correct answer)

Correct answer: Retrobulbar lymphosarcoma

Retrobulbar lymphosarcoma is the most common cause of exophthalmos in cattle, especially in adult animals affected by Bovine Leukosis Virus (BLV). This neoplastic infiltration behind the globe creates a space-occupying lesion, pushing the eyeball forward. While other conditions can cause exophthalmos, lymphosarcoma is statistically the most frequent etiology in cattle.

Question 20: A dog presents with a rapidly growing subcutaneous mass on the trunk. Fine needle aspirate shows granules that stain metachromatically with toluidine blue. What is the diagnosis and recommended initial treatment?

Histiocytoma; conservative management as spontaneous regression occurs
Sebaceous adenoma; CO2 laser ablation
Mast cell tumor; wide surgical excision with 2-3 cm margins (Correct answer)
Lipoma; surgical excision with narrow margins

Correct answer: Mast cell tumor; wide surgical excision with 2-3 cm margins

Mast cell tumors contain metachromatic granules and require wide surgical margins of 2-3 cm laterally and one fascial plane deep to reduce local recurrence.

Question 21: A dog presents with acute epistaxis, petechiae on the gums, and prolonged bleeding after venipuncture. CBC reveals a platelet count of 8,000/μL. Coagulation times (PT and aPTT) are normal. What is the most likely diagnosis?

Rodenticide toxicosis
Immune-mediated thrombocytopenia (IMT) (Correct answer)
Disseminated intravascular coagulation
Von Willebrand disease

Correct answer: Immune-mediated thrombocytopenia (IMT)

IMT presents with severely low platelets causing mucosal bleeding and petechiae while PT and aPTT remain normal because coagulation factor function is intact.

Question 22: A green iguana is presented with metabolic bone disease. Which nutritional deficiency is most commonly responsible?

Calcium deficiency and/or inadequate UV-B exposure (Correct answer)
Vitamin E deficiency
Vitamin A deficiency
Phosphorus deficiency

Correct answer: Calcium deficiency and/or inadequate UV-B exposure

Metabolic bone disease in iguanas is primarily caused by calcium deficiency, improper Ca:P ratio, and lack of UV-B light needed for vitamin D3 synthesis.

Question 23: On a ventrodorsal thoracic radiograph of a 6-year-old DSH cat with acute respiratory distress, you observe symmetric bilateral perihilar interstitial-to-alveolar infiltrates that become more alveolar at the lung periphery, with air bronchograms visible in the caudal lung lobes. The cardiac silhouette is within normal limits (VHS 7.2). Pleural effusion is absent. Which diagnosis best explains this radiographic pattern, and what is the most critical next diagnostic step?

Pulmonary lymphoma; thoracic CT with contrast for mediastinal lymph node assessment
Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size (Correct answer)
Non-cardiogenic pulmonary edema (e.g., neurogenic or post-obstructive); measure systolic blood pressure and assess for underlying cause
Feline bronchopneumonia (bacterial); transtracheal wash for cytology and culture

Correct answer: Cardiogenic pulmonary edema; echocardiography to detect occult hypertrophic cardiomyopathy with normal cardiac size

This is a high-level discriminator: cats with hypertrophic cardiomyopathy (HCM) frequently develop cardiogenic pulmonary edema WITHOUT radiographic cardiomegaly, because the hypertrophied ventricle maintains near-normal external dimensions while left atrial pressure rises acutely. A VHS of 7.2 is within the feline reference range (≤8.0), but HCM can still produce fulminant pulmonary edema before the cardiac silhouette enlarges. The perihilar-to-peripheral alveolar pattern with air bronchograms in cats classically represents cardiogenic edema, which in cats distributes differently than in dogs (less perihilar-predominant). Echocardiography is the critical next step to detect left atrial enlargement, diastolic dysfunction, or outflow obstruction. Non-cardiogenic edema is possible but less common with this symmetric perihilar distribution. Lymphoma typically produces a patchy or nodular interstitial pattern with mediastinal involvement.

Question 24: A 6-year-old Labrador is undergoing a splenectomy under isoflurane anesthesia. The end-tidal CO2 rises to 65 mmHg. What is the most appropriate initial intervention?

Increase fresh gas flow rate
Administer sodium bicarbonate IV
Switch to sevoflurane
Increase respiratory rate on the ventilator (Correct answer)

Correct answer: Increase respiratory rate on the ventilator

Increasing the ventilator rate will increase minute ventilation and eliminate the excess CO2, correcting the hypercapnia.

Question 25: A 7-year-old male neutered Labrador Retriever presents with a 3-week history of progressive tetraparesis. MRI of the cervical spine reveals a T2-hyperintense, T1-isointense intramedullary lesion at C4-C5 that does not enhance with gadolinium contrast. The lesion has a 'flame-shaped' appearance on sagittal sequences. Which diagnosis is MOST consistent with these imaging findings?

Intramedullary meningioma
Intramedullary astrocytoma
Spinal cord infarction (fibrocartilaginous embolism) (Correct answer)
Syringomyelia

Correct answer: Spinal cord infarction (fibrocartilaginous embolism)

Spinal cord infarction (fibrocartilaginous embolism, FCE) classically appears as a T2-hyperintense, T1-isointense intramedullary lesion with a characteristic 'flame-shaped' or wedge-shaped appearance on sagittal MRI sequences. Crucially, FCE lesions do NOT enhance with gadolinium because there is no disruption of the blood-brain barrier by a mass—this distinguishes them from most intramedullary tumors. Syringomyelia appears as a fluid-filled cavity (CSF-isointense on all sequences). Astrocytomas and meningiomas typically show some degree of contrast enhancement.

Question 26: Cats develop more severe Heinz body hemolytic anemia from propylene glycol exposure than dogs given equivalent doses. Which mechanistic explanation best accounts for this species difference?

Feline hemoglobin contains approximately 8 reactive sulfhydryl groups per molecule — roughly twice as many as canine hemoglobin — making it disproportionately susceptible to oxidative denaturation (Correct answer)
Cats lack hepatic glucuronyl transferase activity, causing propylene glycol to accumulate in erythrocytes and directly oxidize membrane phospholipids
Propylene glycol is converted to hydrogen peroxide by feline erythrocyte catalase at a rate 4-fold higher than in canine red cells
Cats metabolize propylene glycol via alcohol dehydrogenase to methylglyoxal, which preferentially binds feline hemoglobin at the Bohr effect site

Correct answer: Feline hemoglobin contains approximately 8 reactive sulfhydryl groups per molecule — roughly twice as many as canine hemoglobin — making it disproportionately susceptible to oxidative denaturation

Feline hemoglobin is uniquely vulnerable to oxidative injury due to the greater number of reactive sulfhydryl (–SH) groups on its globin chains (~8 per molecule vs. ~4 in dogs). These free cysteine-associated sulfhydryl groups are readily oxidized, causing hemoglobin denaturation and Heinz body formation. This explains why cats are exquisitely sensitive to oxidant compounds — including propylene glycol, acetaminophen, benzocaine, onions, and methylene blue — that are tolerated at much higher doses in dogs. Propylene glycol was removed from cat foods specifically because of this risk.

Question 27: In avian medicine, which drug is contraindicated in pigeons and doves due to severe toxicity?

Metronidazole
Fenbendazole at high doses (Correct answer)
Enrofloxacin
Doxycycline

Correct answer: Fenbendazole at high doses

Fenbendazole at high doses or prolonged use causes fatal bone marrow suppression in pigeons and doves; caution with dosing is essential.

Question 28: In equine radiography, 'rotation' of the distal phalanx relative to the hoof wall is measured by which imaging technique?

Nuclear scintigraphy of the foot
Lateral radiograph with a reference marker on the dorsal hoof wall (Correct answer)
Ultrasound of the deep digital flexor tendon
Dorsopalmar radiograph of the foot

Correct answer: Lateral radiograph with a reference marker on the dorsal hoof wall

Lateral radiographs with a radio-opaque marker placed on the dorsal hoof wall allow measurement of the palmar angle and rotation of P3 in laminitic horses.

Question 29: Which of the following best describes the concept of 'One Health' in veterinary public health?

A single federal agency overseeing all animal and human health programs
An integrated approach recognizing the interconnection of human, animal, and environmental health (Correct answer)
A standardized vaccination protocol applied to all domestic species
A global treaty requiring nations to report animal disease outbreaks within 24 hours

Correct answer: An integrated approach recognizing the interconnection of human, animal, and environmental health

One Health is a collaborative, multisectoral approach recognizing that human, animal, and environmental health are interdependent.

Question 30: A 6-year-old male intact Beagle presents with a 4-month history of recurrent urinary tract infections and intermittent hematuria. Ultrasound reveals a 2.8 cm hyperechoic mass in the prostatic urethra. Biopsy confirms transitional cell carcinoma (TCC). Thoracic radiographs are clear. Which statement regarding treatment and prognosis is MOST accurate?

Surgical resection via total prostatectomy is curative in >50% of cases if margins are clean
COX-2 inhibitor therapy is indicated regardless of other treatment modality due to documented partial response rates (Correct answer)
Piroxicam alone provides equivalent survival to piroxicam plus mitoxantrone combination therapy
Urethral stenting is contraindicated because it promotes tumor seeding along the stent tract

Correct answer: COX-2 inhibitor therapy is indicated regardless of other treatment modality due to documented partial response rates

Canine TCC (now termed urothelial carcinoma) overexpresses COX-2, and piroxicam (a non-selective COX inhibitor) has documented partial response rates (~17%) and stable disease rates (~57%), making it a cornerstone of TCC management regardless of whether chemotherapy is added. Piroxicam plus mitoxantrone has shown improved response rates over piroxicam alone in studies (not equivalent). Surgical resection is rarely curative due to urethral/trigone involvement and high local recurrence. Urethral stenting is actually used palliatively for urethral obstruction in TCC dogs, with tumor seeding along stent tracts not a documented clinical contraindication.

Question 31: A 4-year-old blue-fronted Amazon parrot presents with progressive feather destructive behavior, intermittent regurgitation, and a 3-week history of weight loss. Endoscopy reveals thickened proventricular mucosa with dilated ventricular outflow. PCR of a crop biopsy returns positive for Avian Bornavirus (ABV). Which pathological mechanism best explains the neurological component of this disease?

Direct cytopathic destruction of enteric neurons in the myenteric and submucosal plexuses
ABV-encoded protease directly cleaving neurofilament proteins in vagal efferent fibers
Vascular occlusion of the celiac artery causing ischemic neuropathy of the proventriculus
Immune-mediated destruction of enteric neurons via CD8+ T-cell infiltration of ganglia (Correct answer)

Correct answer: Immune-mediated destruction of enteric neurons via CD8+ T-cell infiltration of ganglia

Proventricular Dilatation Disease (PDD) caused by Avian Bornavirus is characterized by a T-cell-mediated (predominantly CD8+) lymphoplasmacytic infiltration of enteric ganglia. The virus itself is relatively non-cytopathic; the immune response against infected neurons destroys the myenteric and submucosal plexuses, leading to dysmotility, dilatation, and malabsorption. This immune-mediated mechanism is why immunosuppressive therapy (e.g., meloxicam/COX-2 inhibition, corticosteroids in some protocols) can improve clinical signs without eliminating the virus.

Question 32: Which surveillance system in the US monitors antimicrobial resistance in zoonotic enteric pathogens from humans, animals, and retail meat?

NARMS (Correct answer)
APHIS VS
NAHMS
FSIS HACCP

Correct answer: NARMS

The National Antimicrobial Resistance Monitoring System (NARMS) tracks resistance trends across the human-animal-food interface.

Question 33: A 7-year-old intact male Golden Retriever presents with progressive exercise intolerance, muffled heart sounds, and jugular venous distension. Echocardiography reveals a large pericardial effusion. Cytology of the pericardial fluid shows hemorrhagic fluid with no neoplastic cells identified. Which of the following is the MOST likely underlying etiology?

Idiopathic pericardial effusion
Chemodectoma of the heart base
Hemangiosarcoma of the right atrium (Correct answer)
Mesothelioma

Correct answer: Hemangiosarcoma of the right atrium

In large-breed dogs, particularly Golden Retrievers and German Shepherds, hemorrhagic pericardial effusion is most commonly caused by hemangiosarcoma of the right atrium/auricle. Despite the hemorrhagic nature, cytology is frequently non-diagnostic because neoplastic cells exfoliate poorly into effusions and are difficult to distinguish from reactive mesothelial cells. Idiopathic pericarditis is the second most common cause but is a diagnosis of exclusion. Mesothelioma and chemodectoma occur but are less frequent than hemangiosarcoma in this breed and presentation.

Question 34: A cat from a shelter presents with vesicular oral lesions and limping. Which pathogen is most likely responsible?

Bordetella bronchiseptica
Feline leukemia virus
Feline herpesvirus-1
Feline calicivirus (Correct answer)

Correct answer: Feline calicivirus

Feline calicivirus causes oral ulcerations and acute lameness syndrome (virulent systemic FCV strains), distinguishing it from FHV-1 which rarely causes limb disease.

Question 35: A 2-year-old Thoroughbred colt has bilateral forelimb angular limb deformity (valgus) at the carpus identified at 4 months of age. Radiographs show the deformity originates at the distal radial physis. The foal is now presenting at 6 months without improvement. What surgical option should be considered?

Medial condylar resection of the distal radius
Arthrodesis of the radiocarpal joint
Transphyseal bridging (screw and wire or staple) on the convex side (Correct answer)
Periosteal stripping on the concave side of the deformity

Correct answer: Transphyseal bridging (screw and wire or staple) on the convex side

Transphyseal bridging on the convex (lateral) side of a carpal valgus deformity slows growth on that side, allowing the concave side to 'catch up' and correct the angular deformity.

Question 36: Which of the following imaging modalities is considered the gold standard for achieving a definitive diagnosis of a deep digital flexor tendon lesion within the equine hoof capsule?

Magnetic Resonance Imaging (MRI) (Correct answer)
Radiography
Nuclear Scintigraphy
Diagnostic Ultrasonography

Correct answer: Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is the gold standard for imaging soft tissues within the hoof capsule because it provides superior detail and is not impeded by the hoof wall. Radiography is best for bone, diagnostic ultrasound cannot effectively penetrate the hoof capsule to visualize all relevant structures, and nuclear scintigraphy identifies areas of increased bone metabolism ('hot spots') but lacks specific soft tissue detail.

Question 37: Which drug is used to treat urinary incontinence in spayed female dogs by increasing urethral sphincter tone?

Propranolol
Prazosin
Bethanechol
Phenylpropanolamine (PPA) (Correct answer)

Correct answer: Phenylpropanolamine (PPA)

Phenylpropanolamine is an alpha-adrenergic agonist that increases urethral sphincter muscle tone and is the drug of choice for hormone-responsive incontinence in spayed dogs.

Question 38: A 14-year-old cat presents with progressive muscle wasting, pot-bellied appearance, fragile skin that tears with routine handling, bilaterally symmetric alopecia, and a non-suppressed low-dose dexamethasone suppression test (LDDST). Endogenous ACTH is undetectable. Which diagnosis and most appropriate next step are correct?

Pituitary-dependent hyperadrenocorticism (PDH); proceed to high-dose dexamethasone suppression test to confirm
Iatrogenic hyperadrenocorticism; detailed medication history and cessation of exogenous glucocorticoids
Ectopic ACTH syndrome from a thoracic mass; perform thoracic CT to identify the source
Adrenal-dependent hyperadrenocorticism (ADH) due to adrenocortical tumor; perform abdominal imaging to characterize the adrenal glands (Correct answer)

Correct answer: Adrenal-dependent hyperadrenocorticism (ADH) due to adrenocortical tumor; perform abdominal imaging to characterize the adrenal glands

Undetectable endogenous ACTH in a cat with confirmed hyperadrenocorticism (non-suppression on LDDST) indicates an ACTH-independent source of cortisol excess — pointing to a functional adrenocortical tumor (adrenal-dependent HAC). In pituitary-dependent disease, ACTH would be elevated or high-normal. In iatrogenic HAC, ACTH is also suppressed, but this is distinguished by history of exogenous steroid administration (not mentioned here). The next step is abdominal imaging (ultrasound or CT) to evaluate the adrenal glands for asymmetric enlargement, mass, or mineralization. Feline skin fragility syndrome (fragile skin) is a hallmark of feline HAC.

Question 39: Calf scours causing the highest mortality in calves under 5 days of age on a US beef operation is most commonly caused by which pathogen?

Salmonella typhimurium
Rotavirus
Cryptosporidium parvum
Escherichia coli (enterotoxigenic) (Correct answer)

Correct answer: Escherichia coli (enterotoxigenic)

Enterotoxigenic E. coli (K99 fimbriae, F5 antigen) causes profuse watery diarrhea and rapid death in calves under 4 days old due to severe dehydration.

Question 40: A 10-year-old intact female dog presents with vaginal discharge, PU/PD, and leukocytosis with a left shift. Radiographs show a fluid-filled uterus. Which finding would support a closed-cervix pyometra over an open-cervix pyometra?

More severe azotemia and toxemia (Correct answer)
Presence of vaginal discharge
Lower white blood cell count
Lower serum progesterone

Correct answer: More severe azotemia and toxemia

Closed-cervix pyometra prevents drainage, leading to greater systemic toxemia, azotemia, and more severe clinical signs compared to open-cervix cases.

Question 41: A 6-year-old bearded dragon (Pogona vitticeps) presents with anorexia, lethargy, and swollen limbs. Radiographs show lytic bone lesions and periosteal proliferation. Bloodwork reveals marked heterophilia and a PCV of 18%. Cytology of a fine-needle aspirate from a swollen limb reveals large, round organisms with a clear halo and a basophilic nucleus consistent with yeast. Which diagnosis and treatment is most appropriate?

Disseminated Ophidiomyces ophiodiicola — voriconazole monotherapy
Disseminated Devriesea agamarum infection — enrofloxacin and supportive care
Chrysosporium anamorph of Nannizziopsis vriesii (CANV) infection — itraconazole and surgical debridement (Correct answer)
Basidiobolus ranarum infection — amphotericin B and potassium iodide

Correct answer: Chrysosporium anamorph of Nannizziopsis vriesii (CANV) infection — itraconazole and surgical debridement

CANV (Chrysosporium anamorph of Nannizziopsis vriesii) is a primary fungal pathogen of agamid lizards, including bearded dragons, causing deep mycosis with lytic bone lesions, skin ulceration, and systemic dissemination. The large round yeast with a clear halo on cytology is characteristic. Treatment requires long-term itraconazole combined with aggressive surgical debridement of affected tissue. Devriesea agamarum is a bacterial pathogen. Ophidiomyces is a snake fungal disease. Basidiobolus causes GI infections in reptiles but has a different clinical presentation.

Question 42: Which statement about the use of doxycycline in cats is most accurate?

Cats require twice the canine mg/kg dose due to faster hepatic clearance
Liquid or food must accompany doxycycline administration to prevent esophageal stricture (Correct answer)
Subcutaneous injection of doxycycline is preferred over oral administration
Doxycycline is contraindicated in cats under 6 months due to bone growth plate damage

Correct answer: Liquid or food must accompany doxycycline administration to prevent esophageal stricture

Doxycycline pills lodged in the feline esophagus cause chemical strictures; always follow tablets with food or water, or use liquid formulations.

Question 43: NSAIDs reduce pain and inflammation primarily by inhibiting which enzyme, thereby reducing prostaglandin synthesis?

Cyclooxygenase (COX) (Correct answer)
Lipoxygenase (LOX)
Phospholipase A2
Histidine decarboxylase

Correct answer: Cyclooxygenase (COX)

NSAIDs inhibit cyclooxygenase enzymes (COX-1 and/or COX-2), which are required to convert arachidonic acid into prostaglandins and thromboxanes, thereby reducing pain, inflammation, and fever.

Question 44: Grass tetany (hypomagnesemic tetany) in beef cattle grazing lush spring pastures is best prevented by supplementing which mineral?

Magnesium oxide in mineral mix (Correct answer)
Calcium carbonate in water
Zinc sulfate boluses
Sodium bicarbonate free-choice

Correct answer: Magnesium oxide in mineral mix

Grass tetany results from hypomagnesemia; magnesium oxide in a palatable mineral mix is the standard prevention because magnesium has no adequate body reserve.

Question 45: Which drug is the first-line treatment for feline arterial thromboembolism (ATE) prevention?

Aspirin
Clopidogrel (Correct answer)
Warfarin
Heparin

Correct answer: Clopidogrel

Clopidogrel (Plavix) is superior to aspirin for secondary prevention of ATE in cats with cardiomyopathy, as demonstrated in the FAT CAT study.

Question 46: In cats, which opioid analgesic and route of administration is generally PREFERRED for outpatient pain management due to high oral transmucosal bioavailability and safety?

Meperidine administered intramuscularly
Hydromorphone administered intravenously
Buprenorphine administered oral transmucosally (OTM) (Correct answer)
Morphine administered intramuscularly

Correct answer: Buprenorphine administered oral transmucosally (OTM)

Buprenorphine administered as an oral transmucosal (OTM) solution has approximately 100% bioavailability in cats due to their alkaline oral pH, providing effective analgesia without injections and making it practical for home use.

Question 47: A 9-year-old dog with a meningioma is receiving mannitol (0.5 g/kg IV) preoperatively to reduce intracranial pressure (ICP). Which of the following anesthetic agents would be the MOST appropriate choice for induction to avoid exacerbating elevated ICP?

Ketamine (5 mg/kg IV)
Propofol (4 mg/kg IV, titrated slowly) (Correct answer)
Tiletamine-zolazepam (2 mg/kg IV)
Alfaxalone (3 mg/kg IV bolus)

Correct answer: Propofol (4 mg/kg IV, titrated slowly)

Propofol reduces cerebral metabolic rate of oxygen consumption (CMRO2), cerebral blood flow, and ICP, making it the preferred induction agent in patients with elevated ICP. It should be titrated slowly to avoid hypotension, which would reduce cerebral perfusion pressure. Ketamine and tiletamine-zolazepam are contraindicated in patients with elevated ICP because they increase cerebral blood flow and ICP. Alfaxalone at a large bolus dose can cause cardiovascular depression and, unlike propofol, does not have the same well-established cerebroprotective profile in this context.

Question 48: A draft horse presents with chronic bilateral hindlimb swelling below the hock and painful, progressive lameness. The skin over the palmar pastern region is thickened with exudative crusts. What condition is most likely responsible for the lameness in addition to skin disease?

Thrombophlebitis of the digital veins
Lymphangitis secondary to Corynebacterium pseudotuberculosis
Pemphigus foliaceus
Pastern dermatitis (scratches) with secondary pastern cellulitis and possible pastern joint involvement (Correct answer)

Correct answer: Pastern dermatitis (scratches) with secondary pastern cellulitis and possible pastern joint involvement

Chronic pastern dermatitis (scratches/mud fever) in draft horses can progress to cellulitis and occasionally involve the pastern joint or digital flexor tendon sheath, causing significant lameness.

Question 49: A horse is prescribed rifampin as part of a combination regimen for Rhodococcus equi pneumonia. The foal is also receiving erythromycin. Three weeks into therapy, serum erythromycin levels are subtherapeutic despite appropriate dosing. What is the most likely mechanism?

Rifampin chelates erythromycin in the GI tract, reducing oral bioavailability
Erythromycin undergoes accelerated renal clearance due to rifampin-induced alkalinization of urine
Erythromycin inhibits its own absorption through downregulation of OATP transporters
Rifampin induces hepatic CYP3A4 and P-glycoprotein, markedly increasing erythromycin metabolism and efflux (Correct answer)

Correct answer: Rifampin induces hepatic CYP3A4 and P-glycoprotein, markedly increasing erythromycin metabolism and efflux

Rifampin is a potent inducer of cytochrome P450 enzymes (particularly CYP3A4) and P-glycoprotein. Erythromycin is a CYP3A4 substrate and P-glycoprotein substrate. Rifampin induction increases both first-pass hepatic metabolism and intestinal P-gp-mediated efflux of erythromycin, dramatically reducing its systemic bioavailability and plasma concentrations. This interaction is clinically significant in R. equi treatment and may compromise efficacy; azithromycin is often preferred as an alternative macrolide in this context.

Question 50: A beef cow herd experiences an outbreak of abortion storms affecting 30% of pregnant cows. PCR testing confirms Neospora caninum. What is the primary route of transmission in cattle?

Ingestion of oocysts from dog feces (horizontal)
Venereal transmission from infected bulls
Tick vector transmission
Transplacental (vertical) transmission from dam to fetus (Correct answer)

Correct answer: Transplacental (vertical) transmission from dam to fetus

Neospora caninum is perpetuated in beef herds primarily by transplacental transmission; congenitally infected calves become the next generation of chronically infected dams.

Question 51: A 6-year-old Standardbred pacer develops progressive bilateral hindlimb ataxia and weakness that worsens going downhill. Cervical radiographs show vertebral canal stenosis at C4-C5. What is the most likely diagnosis?

Stringhalt
Equine herpesvirus myeloencephalopathy
Cervical vertebral stenotic myelopathy (Wobbler syndrome) (Correct answer)
Equine protozoal myeloencephalitis (EPM)

Correct answer: Cervical vertebral stenotic myelopathy (Wobbler syndrome)

Cervical vertebral stenotic myelopathy (Wobbler syndrome) presents with progressive spinal cord compression causing symmetric ataxia and weakness, confirmed by vertebral canal stenosis on radiographs.

Question 52: On abdominal ultrasound of a cat with stranguria, a hyperechoic structure is identified in the center of the urinary bladder. The structure produces a clean, dark vertical band beneath it that obscures deeper tissues. Which of the following best describes this artifact and the most likely identity of the structure?

Side lobe artifact from a polyp
Reverberation artifact from a gas bubble
Acoustic shadowing from a urolith (Correct answer)
Acoustic enhancement from a cyst

Correct answer: Acoustic shadowing from a urolith

A urolith (bladder stone) is a mineralized, dense structure that is hyperechoic (bright) on ultrasound. It strongly reflects or attenuates the ultrasound beam, preventing it from passing through to the tissues below. This creates a signal void, or 'acoustic shadow,' which appears as a dark band deep to the stone. A gas bubble would also shadow but typically creates a 'dirty' shadow with reverberation. A blood clot is typically hyperechoic but not dense enough to cause shadowing. A polyp is a soft tissue structure and would not cause shadowing.

Question 53: A 10-year-old Quarter Horse mare has medial meniscal damage confirmed on MRI. What is the most accurate statement regarding equine stifle meniscal injuries?

Medial meniscal tears heal reliably with intra-articular steroids alone
Meniscal injuries rarely cause stifle effusion
Arthroscopic debridement is the preferred surgical treatment for partial tears (Correct answer)
Lateral meniscal tears are more common than medial tears in horses

Correct answer: Arthroscopic debridement is the preferred surgical treatment for partial tears

Arthroscopic debridement of damaged meniscal tissue is the preferred surgical approach for partial meniscal tears in horses, providing access to the caudal pouch of the femorotibial joint.

Question 54: In a One Health investigation of a novel influenza A virus detected in a Great Lakes commercial mink farm, whole-genome sequencing reveals a reassortant virus with PB2 from a North American H5N1 clade 2.3.4.4b wild bird isolate, PA and PB1 from a human seasonal H3N2 virus, and HA/NA from swine IAV-S. Which of the following statements BEST characterizes the public health threat assessment for farm workers?

The primary concern is avian influenza spread back to wild bird populations via mink feces, not direct human infection, because influenza A viruses require receptor binding site mutations in HA to infect humans regardless of internal gene composition
The swine-origin HA/NA is the primary risk factor because swine influenza has established pandemic potential through direct zoonotic transmission, and avian and human gene segments in internal proteins are epidemiologically irrelevant
The virus poses minimal risk because mink-to-human transmission has never been documented in peer-reviewed literature, and reassortant viruses are inherently less fit than parental strains
The PB2 gene segment origin from a highly pathogenic avian influenza (HPAI) strain warrants heightened concern because avian-origin PB2 (particularly the E627K or D701N mutation) is a key mammalian adaptation marker, and the presence of human seasonal gene segments suggests prior human-to-animal transmission that could facilitate further human adaptation (Correct answer)

Correct answer: The PB2 gene segment origin from a highly pathogenic avian influenza (HPAI) strain warrants heightened concern because avian-origin PB2 (particularly the E627K or D701N mutation) is a key mammalian adaptation marker, and the presence of human seasonal gene segments suggests prior human-to-animal transmission that could facilitate further human adaptation

The PB2 gene segment is critical in influenza A host adaptation. Avian-origin PB2 with mutations at position 627 (E627K) or 701 (D701N) dramatically increases replication efficiency at mammalian lower respiratory tract temperatures (33°C vs. 41°C in birds). Detection of human seasonal H3N2 internal gene segments in a mink-farm virus indicates prior reverse zoonosis (human→mink), meaning the virus has already had exposure to a mammalian host capable of selecting for human-adaptive mutations. Mink are also relevant historically — a 2021 Danish mink SARS-CoV-2 cluster demonstrated efficient mink-human transmission. Reassortant viruses are not inherently less fit; pandemic influenza strains (2009 H1N1) were reassortants. The HA receptor binding site is important, but internal gene constellations profoundly affect mammalian pathogenicity independent of HA binding.

Question 55: A rabbit presents with acute respiratory distress, cyanosis, and sudden death of several cage-mates over 24 hours. Necropsy reveals multifocal hepatic necrosis and pulmonary hemorrhage. The most likely etiologic agent is:

Encephalitozoon cuniculi
Pasteurella multocida
Rabbit hemorrhagic disease virus (RHDV) (Correct answer)
Myxoma virus

Correct answer: Rabbit hemorrhagic disease virus (RHDV)

Rabbit hemorrhagic disease virus causes peracute mortality with hepatic necrosis, disseminated intravascular coagulation, and pulmonary hemorrhage, often affecting multiple animals rapidly.

Question 56: A USDA veterinarian performing post-mortem inspection on a steer carcass finds multiple, well-demarcated, caseous abscesses in the lungs and associated mediastinal lymph nodes. What is the correct disposition for this carcass?

Pass for cooking only.
Condemn the entire carcass. (Correct answer)
Condemn the thoracic organs and pass the rest of the carcass.
Pass for human consumption after trimming affected parts.

Correct answer: Condemn the entire carcass.

The lesions described (caseous necrosis/granulomas in lungs and associated lymph nodes) are classic for bovine tuberculosis (*Mycobacterium bovis*). According to USDA regulations, evidence of generalized tuberculosis, which includes extensive lesions in the thoracic cavity, requires condemnation of the entire carcass due to its significant zoonotic potential and systemic nature.

Question 57: A dog presents with polydipsia, polyuria, and a urine specific gravity of 1.006. A water deprivation test is performed; after 8 hours the USG remains 1.007. Following ADH administration, USG rises to 1.022. What is the diagnosis?

Nephrogenic diabetes insipidus
Primary (psychogenic) polydipsia
Central diabetes insipidus (Correct answer)
Renal medullary washout

Correct answer: Central diabetes insipidus

Response to exogenous ADH (desmopressin) with concentration of urine confirms the kidneys can respond, indicating deficient ADH production from the pituitary — central diabetes insipidus.

Question 58: On a lateral thoracic radiograph of a dog, which structure should be used to assess left atrial enlargement?

Widening of the right cardiac border
Increased sternal contact of the cardiac silhouette
Dorsal elevation of the left mainstem bronchus (Correct answer)
Displacement of the trachea ventrally at the carina

Correct answer: Dorsal elevation of the left mainstem bronchus

Left atrial enlargement causes dorsal elevation and splaying of the left mainstem bronchus (carina angle >60°) on lateral radiographs.

Question 59: A 7-year-old Labrador Retriever presents with polyuria, polydipsia, and bilateral cataracts. Fasting blood glucose is 420 mg/dL. Which insulin type is most commonly used for initial management of canine diabetes mellitus?

Detemir (Levemir)
Regular insulin
NPH insulin (Correct answer)
Glargine (Lantus)

Correct answer: NPH insulin

NPH insulin is the first-line choice for canine diabetes mellitus due to its intermediate duration matching the dog's twice-daily feeding schedule.

Question 60: Polioencephalomalacia in adult cattle most commonly results from which underlying cause, distinct from the thiamine deficiency seen in sheep and young ruminants?

High dietary sulfur intake causing hydrogen sulfide (H2S) neurotoxicity (Correct answer)
Vitamin A deficiency causing increased CSF pressure
Sodium ion toxicosis (salt poisoning) following water deprivation
Molybdenum toxicity causing copper depletion

Correct answer: High dietary sulfur intake causing hydrogen sulfide (H2S) neurotoxicity

In adult cattle, PEM is increasingly associated with high dietary sulfur (from distillers grains, gypsum water, or sulfur supplements), which promotes rumen production of hydrogen sulfide — a neurotoxin that causes cortical necrosis. While thiamine deficiency also occurs in cattle, high-sulfur PEM is the emerging predominant cause and is sulfur-diet-associated rather than thiaminase-related. Sodium toxicosis causes cerebral edema/herniation rather than laminar cortical necrosis.

Question 61: A veterinarian is conducting a pre-breeding soundness exam (BSE) on a herd bull. According to the Society for Theriogenology minimum standards, what minimum total motility percentage is required for a 'satisfactory' classification?

50% total motility
25% progressive motility with normal morphology >70%
60% morphologically normal sperm
30% progressively motile sperm (Correct answer)

Correct answer: 30% progressively motile sperm

The SFT BSE minimum requires ≥30% progressively motile sperm and ≥70% morphologically normal sperm for a satisfactory potential breeder classification.

Question 62: A dog is receiving a fentanyl CRI at 5 mcg/kg/hr during a thoracotomy. The anesthesiologist wishes to transition to a multimodal protocol using an NMDA antagonist CRI to reduce opioid requirements and prevent central sensitization. Ketamine is chosen. Which statement about ketamine's analgesic mechanism at subanesthetic doses is MOST accurate?

Ketamine blocks voltage-gated sodium channels in dorsal horn neurons, reducing ascending pain transmission
Ketamine blocks open NMDA receptor-channels in a use-dependent manner, preventing wind-up and central sensitization (Correct answer)
Ketamine inhibits cyclooxygenase-2 in glial cells, reducing prostaglandin-mediated spinal sensitization
Ketamine provides analgesia primarily through κ-opioid receptor agonism in the periaqueductal gray

Correct answer: Ketamine blocks open NMDA receptor-channels in a use-dependent manner, preventing wind-up and central sensitization

At subanesthetic doses (CRI: 0.1–0.5 mg/kg/hr post-loading), ketamine's analgesic mechanism is primarily use-dependent (open-channel) blockade of NMDA receptors, specifically plugging the Mg²⁺ site within the ion channel when it is open (activated by glutamate). This prevents the temporal summation of C-fiber input that leads to 'wind-up' and central sensitization in dorsal horn neurons—a critical mechanism in preventing chronic post-surgical pain. It does have minor sodium channel effects (option A), but this is not its primary analgesic mechanism. Ketamine has very weak opioid receptor activity that is not clinically significant for analgesia. It has no clinically relevant COX-2 inhibition.

Question 63: Which vaccination protocol is most appropriate for preventing clostridial diseases (blackleg, malignant edema) in beef calves?

Two doses 3-4 weeks apart starting at 2-3 months of age with annual boosters (Correct answer)
Single dose at weaning only
Monthly intranasal vaccine starting at birth
Passive transfer via colostrum is sufficient without active vaccination

Correct answer: Two doses 3-4 weeks apart starting at 2-3 months of age with annual boosters

Clostridial vaccines require a primary series of two doses 3-4 weeks apart to achieve protective immunity, with annual boosters to maintain protection.

Question 64: Pinkeye (Infectious Bovine Keratoconjunctivitis) in a cow herd is most commonly caused by which organism?

Moraxella bovis (Correct answer)
Mycoplasma bovis
Pasteurella multocida
Listeria monocytogenes

Correct answer: Moraxella bovis

Moraxella bovis is the primary causative agent of IBK, producing a pilus that allows corneal attachment and a hemolysin that damages corneal epithelium.

Question 65: A 12-year-old cat with known hyperthyroidism controlled on methimazole develops acute azotemia (creatinine 3.8 mg/dL, BUN 58 mg/dL) after 3 weeks of therapy. Pre-treatment creatinine was 1.1 mg/dL. Which pathophysiologic explanation is most accurate?

Hypertensive nephrosclerosis worsening as cardiac output drops with treatment
Methimazole-induced immune-mediated glomerulonephritis
Unmasking of pre-existing chronic kidney disease as GFR normalizes with euthyroid state (Correct answer)
Direct tubular toxicity from methimazole metabolites accumulating in renal cortex

Correct answer: Unmasking of pre-existing chronic kidney disease as GFR normalizes with euthyroid state

Hyperthyroidism increases cardiac output and causes hyperfiltration, artificially elevating GFR and suppressing serum creatinine. When hyperthyroidism is treated and GFR normalizes, underlying CKD that was masked by the hyperfiltration state becomes apparent. This 'unmasking' phenomenon is well-documented in feline medicine and is why pre-treatment renal biomarkers can be misleadingly normal. The pre-treatment creatinine of 1.1 mg/dL was falsely low due to increased GFR, not because the kidneys were truly healthy.

Question 66: A 5-year-old male neutered Dachshund presents with acute onset severe abdominal pain, hematemesis, and collapse. PCV is 16% with adequate total protein (6.2 g/dL). Abdominal radiographs show a mild loss of serosal detail. Coagulation panel reveals: PT 28 sec (ref 7–12), PTT 98 sec (ref 60–90), fibrinogen 80 mg/dL (ref 150–400), d-dimers markedly elevated. Platelet count is 40,000/µL. Which of the following best explains this coagulopathy pattern?

Disseminated intravascular coagulation (DIC) secondary to a systemic disease process (Correct answer)
Inherited factor VIII deficiency (Hemophilia A) with concurrent thrombocytopenia
Vitamin K antagonist rodenticide toxicity causing factor II, VII, IX, X deficiency
Platelet dysfunction from aspirin ingestion with secondary hypofibrinogenemia

Correct answer: Disseminated intravascular coagulation (DIC) secondary to a systemic disease process

The combination of prolonged PT and PTT, thrombocytopenia, markedly elevated d-dimers, and critically low fibrinogen defines DIC (both the procoagulant and fibrinolytic phases). The consumption of clotting factors AND platelets combined with d-dimer elevation (cross-linked fibrin degradation products) is the hallmark. Rodenticide toxicity causes prolonged PT (extrinsic pathway factor VII is shortest half-life) but does NOT cause thrombocytopenia or elevated d-dimers or hypofibrinogenemia. Hemophilia A causes isolated PTT prolongation. Aspirin causes platelet dysfunction (prolonged closure time/buccal mucosal bleeding time) but not this global consumptive coagulopathy. The acute abdomen with hematemesis suggests an underlying trigger (splenic mass rupture, sepsis, or neoplasia) driving the DIC.

Question 67: Feline lower urinary tract disease (FLUTD) in a young male cat is most commonly attributable to which condition?

Idiopathic feline interstitial cystitis (FIC) (Correct answer)
Urolithiasis (struvite or oxalate)
Urethral neoplasia
Bacterial urinary tract infection

Correct answer: Idiopathic feline interstitial cystitis (FIC)

Idiopathic feline interstitial cystitis (FIC) accounts for approximately 55–65% of FLUTD cases in young cats, and bacterial UTI is rare in cats under 10 years.

Question 68: A state veterinarian receives a report of a cluster of human cases of hemolytic uremic syndrome (HUS) in a rural county. Epidemiological investigation links the cases to a small farm that sells raw milk and allows petting zoo visits. Which of the following zoonotic transmission pathways is MOST likely responsible, and what is the primary regulatory authority responsible for interstate commerce of the implicated product?

Direct contact transmission of Salmonella Typhimurium; CDC under the Public Health Service Act
Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO) (Correct answer)
Vector-borne transmission of Cryptosporidium parvum; EPA under the Safe Drinking Water Act
Aerosol transmission of Campylobacter jejuni; USDA-FSIS under the Federal Meat Inspection Act

Correct answer: Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO)

E. coli O157:H7 is the classic cause of HUS, particularly in children, and raw milk is a well-documented vehicle. The FDA regulates interstate raw milk commerce under the PMO (21 CFR Part 1240.61 prohibits interstate sale of raw milk for direct human consumption). The fecal-oral route from cattle reservoirs through unpasteurized milk is the primary pathway in this scenario. Campylobacter causes gastroenteritis but rarely HUS. Cryptosporidium is waterborne and causes diarrhea, not typically HUS. USDA-FSIS covers meat/poultry, not dairy.

Question 69: An 8-year-old Cocker Spaniel presents with a chronic cough, exercise intolerance, and a loud left apical systolic murmur (grade V/VI). Thoracic radiographs show pulmonary venous congestion. Which drug is indicated to reduce preload in this patient?

Atenolol
Furosemide (Correct answer)
Digoxin
Amlodipine

Correct answer: Furosemide

Furosemide, a loop diuretic, reduces preload by promoting sodium and water excretion, relieving pulmonary venous congestion in congestive heart failure.

Question 70: Which biosecurity measure is most effective at preventing introduction of Johne's disease (paratuberculosis) into a closed beef herd?

Purchasing animals from Johne's-tested herds and testing all additions (Correct answer)
Vaccinating all incoming animals with killed M. paratuberculosis vaccine
Quarantining new arrivals for 14 days in a separate pen
Testing fecal samples from all animals annually with PCR

Correct answer: Purchasing animals from Johne's-tested herds and testing all additions

Because no test has 100% sensitivity for Johne's disease, purchasing from certified low-prevalence herds combined with pre-purchase testing provides the best risk reduction.

Question 71: A 10-day-old foal presents with hypopyon, corneal vascularization, and joint effusion in the right tarsus. The most likely underlying cause is:

Herpesvirus-1 ocular infection
Rhodococcus equi pneumonia
Neonatal isoerythrolysis
Failure of passive transfer leading to septicemia (Correct answer)

Correct answer: Failure of passive transfer leading to septicemia

Septicemia secondary to failure of passive transfer is the leading cause of uveitis and septic arthritis in neonatal foals, as bacteria seed synovial and ocular tissues hematogenously.

Question 72: A 5-year-old intact female Boxer presents for abdominal radiographs due to acute vomiting. Radiographs reveal a markedly distended, gas-filled stomach with a soft tissue band ('shelf sign') in the mid-gastric region and the pylorus positioned to the left of midline on the VD projection. A small amount of free peritoneal gas is also noted. Which combination of conditions does this radiographic constellation represent?

Simple gastric dilatation with concurrent pneumoperitoneum from recent abdominocentesis
Gastric dilatation-volvulus (GDV) with gastric perforation (Correct answer)
Hiatal hernia with secondary pneumoperitoneum
Gastric foreign body with pyloric obstruction and diaphragmatic hernia

Correct answer: Gastric dilatation-volvulus (GDV) with gastric perforation

The combination of marked gastric gas distension, a 'shelf sign' (also called the 'double bubble' or compartmentalization created by torsion of the gastric wall), and pyloric displacement to the LEFT of midline on the VD view is pathognomonic for GDV. In GDV, the pylorus rotates clockwise (viewed from the patient's caudal aspect) to end up cranial and to the left. The presence of free peritoneal gas (pneumoperitoneum) indicates gastric rupture/perforation, which is a grave complication confirming the need for immediate surgical intervention. This constellation—GDV + perforation—carries the worst prognosis.

Question 73: A rabbit (Oryctolagus cuniculus) is presented for acute anorexia and abdominal distension. On physical exam, there is tympany in the cecal region, hypothermia (98.4°F), and the cecum is palpably enlarged and doughy. Radiographs confirm massive cecal dilation with a gas cap. The rabbit has been on a high-pellet, low-hay diet. Which statement MOST accurately describes the pathophysiology of cecal dysbiosis in this patient?

High-protein diet increases cecal ammonia concentrations, causing direct mucosal necrosis and secondary Escherichia coli bacteremia
Low-fiber diet reduces cecotroph production, leading to B-vitamin deficiency and secondary immunosuppression
Excess simple carbohydrates shift cecal pH toward alkaline conditions, favoring Clostridium spiroforme overgrowth and iota-toxin production (Correct answer)
Dietary carbohydrate overload reduces cecal volatile fatty acid production, causing mucosal barrier failure and systemic endotoxemia

Correct answer: Excess simple carbohydrates shift cecal pH toward alkaline conditions, favoring Clostridium spiroforme overgrowth and iota-toxin production

In rabbits, cecal dysbiosis (often called rabbit enterotoxemia or mucoid enteropathy complex) is precipitated by excess fermentable carbohydrates reaching the cecum. This substrate shift favors proliferation of Clostridium spiroforme, which produces iota-toxin (a binary toxin similar to Clostridium perfringens iota-toxin). The normal cecal pH is mildly acidic (5.9–6.8); carbohydrate overload and disrupted VFA production raise the pH, creating an environment favorable for clostridial overgrowth. Iota-toxin disrupts actin cytoskeleton of enterocytes, causing fluid secretion, mucosal damage, and the classic cecal dilation and tympany seen here. The condition carries a guarded to poor prognosis.

Question 74: A 3-year-old Thoroughbred presents with acute-onset severe lameness. Radiographs of the fetlock region are initially unremarkable. Nuclear scintigraphy (bone phase) shows a focal, intensely increased radiopharmaceutical uptake (IRU) at the palmar/plantar aspect of the proximal sesamoid bones. MRI performed 48 hours later shows a T2-hypointense linear signal defect traversing the body of the medial proximal sesamoid bone. What is the MOST likely diagnosis and its implication?

Abaxial fracture of the proximal sesamoid — surgical arthroscopy is curative
Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown (Correct answer)
Basilar fracture of the proximal sesamoid — low catastrophic failure risk if managed conservatively
Sesamoiditis (chronic degenerative change) — requires 4-6 weeks of stall rest

Correct answer: Body fracture of the proximal sesamoid — high risk for catastrophic failure and suspensory apparatus breakdown

A T2-hypointense linear defect traversing the body of the proximal sesamoid bone represents a body fracture — the most serious type of sesamoid fracture in racehorses. Unlike apical (tip) or abaxial (side) fractures, body fractures involve the entire cross-section of the bone and risk complete disruption of the suspensory apparatus, which can cause catastrophic breakdown. The scintigraphic hot spot on the palmar/plantar aspect with subsequent MRI correlation is the advanced imaging sequence used when plain radiographs are unremarkable early in the injury. Sesamoiditis causes diffuse rather than focal linear T2 hypointensity. Basilar fractures involve the base and have a better prognosis than body fractures.

Question 75: A gilt in a farrow-to-finish operation develops diamond-shaped, raised, red skin lesions over the trunk 2 days after moving to the breeding barn. The most appropriate treatment is:

Florfenicol IM and supportive care
Ivermectin SC and topical antifungal
Enrofloxacin IM and corticosteroids
Penicillin G IM, NSAIDs, and isolation (Correct answer)

Correct answer: Penicillin G IM, NSAIDs, and isolation

Diamond-shaped urticarial skin lesions (diamond skin disease) are classic for Erysipelothrix rhusiopathiae infection in pigs. Erysipelas responds well to penicillin G; NSAIDs reduce fever and inflammation. Corticosteroids are contraindicated in bacteremic animals; enrofloxacin has poor activity against Erysipelothrix.

Question 76: A 7-year-old spayed female cat is diagnosed with intermediate-grade small cell lymphoma of the GI tract confirmed via full-thickness biopsy showing transmural infiltration with loss of normal architecture. Which chemotherapy protocol is MOST appropriate compared to the standard low-grade (small cell) lymphoma protocol?

Toceranib phosphate targeting c-Kit mutation
CHOP-based protocol (cyclophosphamide, doxorubicin, vincristine, prednisolone) (Correct answer)
Single-agent lomustine (CCNU)
Chlorambucil and prednisolone (COP equivalent)

Correct answer: CHOP-based protocol (cyclophosphamide, doxorubicin, vincristine, prednisolone)

Intermediate- to high-grade feline GI lymphoma (large cell lymphoma) carries a significantly worse prognosis than the indolent small cell (low-grade) form and requires a more aggressive CHOP-based multi-agent protocol. The chlorambucil/prednisolone protocol used for small cell lymphoma is insufficient for large or intermediate cell disease. Single-agent lomustine has activity in some lymphomas but is not the standard of care here. Toceranib targets receptor tyrosine kinases and is not the treatment of choice for GI lymphoma.

Question 77: What is the recommended minimum colostrum quality (Brix refractometer reading) indicating adequate IgG concentration for feeding to neonatal calves?

≥10% Brix
≥30% Brix
≥22% Brix (Correct answer)
≥15% Brix

Correct answer: ≥22% Brix

A Brix refractometer reading of ≥22% correlates with IgG concentrations ≥50 g/L, which is the threshold for high-quality colostrum suitable for feeding neonatal calves.

Question 78: Following a bilateral thyroidectomy, a 11-year-old female domestic shorthair cat is released from the hospital. The patient is reevaluated two days later due to panting, agitation, and a recent seizure. Which postoperative complication is most likely to account for these clinical symptoms?

Horner's syndrome
Hypoparathyroidism (Correct answer)
Hypocalcemia
Renal disease

Correct answer: Hypoparathyroidism

Bilateral thyroidectomy in cats often involves inadvertent removal or damage to the parathyroid glands, which are closely associated with the thyroid. The parathyroid glands regulate calcium levels via PTH. Postoperative hypoparathyroidism leads to hypocalcemia, causing increased neuromuscular excitability that manifests as panting, agitation, and seizures, making it the most likely complication.

Question 79: A veterinarian treats a group of feeder calves for bovine respiratory disease (BRD) with enrofloxacin. What is the primary reason for the strict prohibition of extra-label use of this drug in food-producing animals?

It causes severe and irreversible nephrotoxicity in cattle.
There is a high risk of fatal anaphylactic reactions in human consumers.
It causes permanent discoloration of meat products.
It promotes the development of antimicrobial resistance in human pathogens. (Correct answer)

Correct answer: It promotes the development of antimicrobial resistance in human pathogens.

The FDA prohibits the extra-label use of fluoroquinolones like enrofloxacin in food animals primarily to mitigate the risk of promoting antimicrobial resistance. Bacteria such as Salmonella and Campylobacter can develop resistance, which may then be transferred to human populations through the food chain, compromising the efficacy of this critically important class of antibiotics in human medicine.

Question 80: A 6-year-old neutered male mixed-breed dog is presented for polydipsia, polyuria, and muscle weakness. Serum chemistry reveals sodium 158 mEq/L, potassium 2.8 mEq/L, and bicarbonate 30 mEq/L. Blood pressure is 178/110 mmHg. Urine aldosterone-to-creatinine ratio is markedly elevated. An adrenal mass (2.1 cm) is identified on ultrasound. Cortisol concentrations pre- and post-ACTH stimulation are within normal limits. What is the most appropriate next diagnostic step?

Urine culture and sensitivity to rule out secondary pyelonephritis
CT scan of the abdomen to evaluate for vascular invasion and characterize the mass (Correct answer)
Plasma renin activity measurement to confirm primary vs. secondary hyperaldosteronism
Low-dose dexamethasone suppression test to rule out concurrent hyperadrenocorticism

Correct answer: CT scan of the abdomen to evaluate for vascular invasion and characterize the mass

This presentation is classic for primary hyperaldosteronism (Conn's syndrome) in a dog — hypertension, hypokalemia, hypernatremia, metabolic alkalosis, and an adrenal mass with normal cortisol dynamics. Once primary hyperaldosteronism is biochemically confirmed (elevated aldosterone:creatinine), the critical next step before surgical adrenalectomy is CT imaging to assess mass characteristics, identify vascular invasion, detect contralateral adrenal involvement, and rule out metastatic disease — all of which dictate surgical candidacy and prognosis. Plasma renin activity is useful but not the most actionable immediate next step given that surgical planning takes priority.

Question 81: On thoracic radiographs of a 9-year-old DSH cat, you identify a soft tissue opacity in the cranial mediastinum that causes tracheal elevation and rightward deviation. Echocardiography confirms the heart is normal. The mass does not move independently from the cardiac silhouette on fluoroscopy. Which of the following is the LEAST likely differential diagnosis?

Thymoma
Cranial mediastinal cyst (branchial or thymic)
Aortic body chemodectoma (Correct answer)
Mediastinal lymphoma

Correct answer: Aortic body chemodectoma

Aortic body chemodectomas (heart base tumors) are rare in cats and arise at the heart base, not the cranial mediastinum; they typically cause a mass effect at the level of the great vessels rather than causing cranial mediastinal widening with tracheal elevation. Thymoma and mediastinal lymphoma are the two most common cranial mediastinal masses in cats, and cranial mediastinal cysts are an uncommon but recognized entity. The lack of independent cardiac movement on fluoroscopy helps exclude a cardiac origin but does not distinguish between the other differentials.

Question 82: Which dietary modification is considered most critical in slowing the progression of chronic kidney disease (CKD) in cats?

Restricted phosphorus (Correct answer)
Grain-free formulation
Increased high-quality protein
Increased sodium to encourage drinking

Correct answer: Restricted phosphorus

Restricting dietary phosphorus is a cornerstone of managing feline CKD and has been shown to slow the progression of the disease. While moderate protein restriction is also part of therapeutic renal diets, phosphorus restriction is considered more critical for slowing progression. Excessive sodium restriction is not recommended, and increasing protein is contraindicated in later stages. Grain-free formulations have no proven benefit for CKD.

Question 83: A veterinarian observes a horse trotting on a hard, flat surface and notes a consistent head nod. The lameness is not apparent at a walk but is easily seen at the trot. According to the American Association of Equine Practitioners (AAEP) Lameness Scale, what is the most appropriate grade?

Grade 3 (Correct answer)
Grade 2
Grade 4
Grade 1

Correct answer: Grade 3

The AAEP Lameness Scale defines a Grade 3 lameness as one that is consistently observable at a trot under all circumstances. Grade 2 lameness is difficult to observe at a trot in a straight line but is consistent under specific circumstances (e.g., circling). Grade 1 is difficult to observe, and Grade 4 is obvious at a walk. The description of a lameness not seen at a walk but consistently visible with a head nod at a trot fits Grade 3.

Question 84: A cat presents with acute onset of hindlimb paralysis, cold limbs, and absent femoral pulses. What is the most likely diagnosis?

Intervertebral disc disease
Fibrocartilaginous embolism
Aortic thromboembolism (Correct answer)
Traumatic spinal cord injury

Correct answer: Aortic thromboembolism

Aortic thromboembolism (saddle thrombus) classically presents in cats with acute hindlimb paresis/paralysis, cold extremities, and absent femoral pulses, often secondary to cardiomyopathy.

Question 85: During a PRRS (Porcine Reproductive and Respiratory Syndrome) outbreak investigation, a veterinary epidemiologist calculates a basic reproduction number (R₀) of 3.8 for the index swine production system. The system achieves 70% sow vaccination coverage with a vaccine that has 60% efficacy against transmission. What is the approximate effective reproduction number (Rₑ) after vaccination, and does it cross the epidemic threshold?

Rₑ ≈ 1.1; above threshold — epidemic continues
Rₑ ≈ 2.2; above threshold — epidemic continues (Correct answer)
Rₑ ≈ 0.9; below threshold — epidemic controlled
Rₑ ≈ 1.5; above threshold — epidemic continues

Correct answer: Rₑ ≈ 2.2; above threshold — epidemic continues

The effective reproduction number after vaccination is calculated as Rₑ = R₀ × (1 − vaccine efficacy × coverage) = 3.8 × (1 − 0.60 × 0.70) = 3.8 × (1 − 0.42) = 3.8 × 0.58 ≈ 2.2. Since Rₑ > 1, the epidemic threshold has not been crossed and transmission will continue, though at a reduced rate. To achieve herd immunity (Rₑ < 1), the product of efficacy × coverage would need to exceed 1 − 1/R₀ = 1 − 1/3.8 ≈ 0.74 (74%), meaning either higher coverage or a more efficacious vaccine is required.

Question 86: A 6-year-old Arabian endurance horse presents with acute right forelimb lameness of 4 days' duration following a 100-mile ride. The horse is grade 4/5 lame, resents flexion of the fetlock, and has a marked digital pulse. Radiographs are unremarkable. MRI reveals a complete palmar annular ligament desmitis with concurrent proximal digital annular ligament thickening and significant fluid accumulation within the digital flexor tendon sheath (DFTS). After conservative management fails at 6 weeks, you plan a surgical intervention. Which procedure is MOST appropriate to address the primary compressive pathology?

Neurectomy of the palmar digital nerves combined with palmar annular ligament desmotomy
Deep digital flexor tendon splitting via the palmar approach to decompress intrathecal pressure
Open desmotomy of the proximal digital annular ligament via a palmar midline approach
Tenoscopic release of the palmar annular ligament (PAL) with concurrent digital flexor tendon sheath lavage (Correct answer)

Correct answer: Tenoscopic release of the palmar annular ligament (PAL) with concurrent digital flexor tendon sheath lavage

Tenoscopic (endoscopic within the tendon sheath) release of the palmar annular ligament is the gold-standard surgical procedure for constricting palmar annular ligament syndrome confirmed on MRI, especially when accompanied by concurrent DFTS effusion. Tenoscopy allows direct visualization of the DFTS contents, assessment of the flexor tendon surfaces, concurrent debridement of damaged tissue, complete sheath lavage, and PAL transection under direct visualization with superior cosmesis and lower complication rates than open approaches. Open PAL desmotomy is an acceptable alternative but carries higher wound complication risk. Proximal digital annular ligament desmotomy addresses a different structure. Neurectomy is not appropriate as a primary treatment and carries welfare and regulatory concerns in competition horses. DDFT splitting is reserved for core DDFT lesions, not annular ligament compression.

Question 87: A 4-year-old spayed DSH with phenobarbital-refractory epilepsy is started on potassium bromide (KBr) as add-on therapy. Eight weeks later she presents with progressive coughing, expiratory dyspnea, and eosinophilia (1,800 cells/µL). Thoracic radiographs reveal a diffuse bronchial-interstitial pattern. The most likely diagnosis is:

Secondary bacterial pneumonia from phenobarbital-induced immunosuppression
Potassium bromide–induced eosinophilic bronchopneumopathy (Correct answer)
Feline idiopathic asthma triggered by bromide-induced mast cell degranulation
Aspiration pneumonia secondary to postictal laryngeal dysfunction

Correct answer: Potassium bromide–induced eosinophilic bronchopneumopathy

Potassium bromide causes eosinophilic bronchopneumopathy (EBP) in cats — a serious, species-specific adverse effect not observed in dogs. Clinical signs include coughing, dyspnea, and radiographic interstitial infiltrates with peripheral eosinophilia, typically developing weeks to months after initiation. This is distinct from feline asthma and resolves with KBr discontinuation. Because of this risk, KBr is generally avoided in cats; phenobarbital, levetiracetam, or zonisamide are preferred antiepileptic agents in this species.

Question 88: Which zoonotic pathogen is primarily transmitted to humans through contact with infected animal urine, particularly in flooded environments?

Francisella tularensis
Coxiella burnetii
Leptospira interrogans (Correct answer)
Brucella abortus

Correct answer: Leptospira interrogans

Leptospira interrogans is shed in animal urine and transmitted via water or soil contact, with flooding increasing exposure risk.

Question 89: What is the most typical cause of dystocia and egg binding in caged birds?

Oviduct damage
Genetic predisposition
Hypocalcemia (Correct answer)
Obesity

Correct answer: Hypocalcemia

Hypocalcemia is the most common cause of dystocia and egg binding in caged birds, particularly in reproductively active hens. Calcium is crucial for proper uterine muscle contractions during egg laying and for eggshell formation. A deficiency can lead to weak contractions, resulting in the egg becoming stuck in the oviduct (egg binding) and subsequent dystocia.

Question 90: Which feline coronavirus (FCoV) mutation is classically associated with the transition from enteric infection to feline infectious peritonitis (FIP)?

7b gene duplication
Nucleocapsid gene frameshift
3c gene loss-of-function mutation (Correct answer)
Spike protein S1 domain deletion

Correct answer: 3c gene loss-of-function mutation

Loss-of-function mutations in the 3c gene of feline enteric coronavirus are associated with the shift to macrophage tropism and development of FIP.

Question 91: A cow at 60 days postpartum has been anestrus. Body condition score is 2/5. Progesterone profiles confirm ovarian inactivity. The primary cause is most likely:

Ovarian cyst formation
Subclinical mastitis causing hormonal disruption
Persistent corpus luteum
Negative energy balance suppressing the hypothalamic-pituitary axis (Correct answer)

Correct answer: Negative energy balance suppressing the hypothalamic-pituitary axis

Postpartum anestrus in cattle is most commonly caused by negative energy balance, which suppresses GnRH pulsatility and LH release, preventing follicular maturation and ovulation.

Question 92: Which fluoroquinolone antibiotic is most associated with acute retinal degeneration and blindness in cats when used at high doses?

Orbifloxacin
Pradofloxacin
Marbofloxacin
Enrofloxacin (Correct answer)

Correct answer: Enrofloxacin

Enrofloxacin at doses above 5 mg/kg/day causes retinal degeneration in cats due to accumulation in the retinal pigment epithelium.

Question 93: A 3-year-old dairy goat presents with progressive weight loss, decreased milk production, and bilateral carpal swelling. Lung auscultation reveals diffuse crackles. Cerebrospinal fluid analysis shows mononuclear pleocytosis. The most likely diagnosis is:

Mycoplasma mycoides subsp. capri polyarthritis
Maedi-Visna virus infection
Caprine Arthritis Encephalitis (CAE) virus infection (Correct answer)
Caseous lymphadenitis (Corynebacterium pseudotuberculosis)

Correct answer: Caprine Arthritis Encephalitis (CAE) virus infection

CAE virus (a lentivirus) in adult goats classically presents as chronic progressive polyarthritis (especially carpal joints) combined with interstitial pneumonia and occasional leukoencephalomyelitis. Maedi-Visna is the sheep equivalent but does not cause arthritis as prominently. Caseous lymphadenitis causes abscessation, not arthritis + pneumonia. Mycoplasma causes acute febrile arthritis.

Question 94: A Quarter Horse presents with acute, severe forelimb lameness and a draining tract near the coronary band. Radiographs show gas lucency within the third phalanx. What condition do these findings most strongly suggest?

Sequestrum formation of the proximal phalanx
Navicular bone fracture
Coffin joint septic arthritis
Subsolar abscess with secondary osteomyelitis of the distal phalanx (Correct answer)

Correct answer: Subsolar abscess with secondary osteomyelitis of the distal phalanx

A draining tract at the coronary band combined with gas and lytic changes in the third phalanx are classic findings of a chronic subsolar abscess that has ascended and caused osteomyelitis of the distal phalanx.

Question 95: Which MRI finding is characteristic of syringomyelia (syrinx) in a Cavalier King Charles Spaniel with Chiari-like malformation?

T2 hypointense lesion in the dorsal columns
T1 hyperintense intramedullary lesion
T2 hyperintense fluid-filled cavity within the spinal cord (Correct answer)
Contrast-enhancing ring lesion within the cord

Correct answer: T2 hyperintense fluid-filled cavity within the spinal cord

A syrinx appears as a T2 hyperintense (fluid signal) cavity within the spinal cord parenchyma on MRI, reflecting the accumulation of CSF-like fluid.

Question 96: A nursery pig presents with acute onset of polyarthritis, meningitis, and sudden death. Gram-positive cocci in pairs and short chains are isolated from CSF. What is the most likely causative organism?

Erysipelothrix rhusiopathiae
Mycoplasma hyorhinis
Haemophilus parasuis
Streptococcus suis serotype 2 (Correct answer)

Correct answer: Streptococcus suis serotype 2

Streptococcus suis serotype 2 is a leading cause of meningitis, polyarthritis, and septicemia in nursery and weanling pigs. It is a Gram-positive coccus in pairs/short chains. Erysipelothrix is Gram-positive but rod-shaped; Haemophilus parasuis (Glässer's disease) is Gram-negative; Mycoplasma lacks a cell wall.

Question 97: A beef producer asks about strategies to reduce the use of medically important antimicrobials in the feedlot. Which intervention is the best alternative for reducing bovine respiratory disease (BRD) morbidity?

Implementing metaphylaxis only for high-risk cattle combined with optimization of vaccination protocols (Correct answer)
Switching from injectable to in-feed antibiotics exclusively
Eliminating all antibiotic use and relying on supportive care only
Increasing the dose of antibiotics to prevent resistance

Correct answer: Implementing metaphylaxis only for high-risk cattle combined with optimization of vaccination protocols

Targeted metaphylaxis in high-risk cattle combined with robust vaccination programs reduces BRD morbidity while minimizing overall antibiotic use, consistent with antimicrobial stewardship principles.

Question 98: Toxoplasma gondii infection in pregnant women is most commonly acquired in the US through:

Direct contact with infected cats
Consumption of undercooked meat containing tissue cysts (Correct answer)
Contaminated drinking water
Inhalation of aerosolized oocysts

Correct answer: Consumption of undercooked meat containing tissue cysts

In the US, most human T. gondii infections result from consuming undercooked meat containing bradyzoite tissue cysts.

Question 99: A green iguana is presented for severe metabolic bone disease refractory to standard calcium and UVB supplementation. Bloodwork shows hypocalcemia, hyperphosphatemia, and markedly elevated PTH. Renal function tests reveal azotemia. Which pathophysiologic mechanism BEST explains this presentation?

Primary hypoparathyroidism with compensatory skeletal calcium mobilization
Nutritional secondary hyperparathyroidism due to dietary calcium-to-phosphorus imbalance below 1:1
Vitamin D3 toxicosis causing soft-tissue mineralization and paradoxical hypocalcemia
Renal secondary hyperparathyroidism caused by impaired 1-alpha-hydroxylation of 25-hydroxyvitamin D3 and phosphate retention (Correct answer)

Correct answer: Renal secondary hyperparathyroidism caused by impaired 1-alpha-hydroxylation of 25-hydroxyvitamin D3 and phosphate retention

This iguana has renal secondary hyperparathyroidism. Azotemia indicates renal disease, which impairs 1-alpha-hydroxylation of 25-hydroxyvitamin D3 in the kidneys, reducing calcitriol production. Reduced calcitriol impairs intestinal calcium absorption, and phosphate retention by the failing kidneys further drives hypocalcemia. The resulting PTH elevation mobilizes bone, leading to metabolic bone disease. This is distinct from nutritional secondary hyperparathyroidism, which occurs without azotemia.

Question 100: A cat presents with open-mouth breathing, muffled heart sounds, and dull ventral lung sounds. Thoracocentesis yields chylous fluid. The most common underlying cause in cats is:

Mediastinal lymphoma
Cardiac disease (cardiomyopathy)
Idiopathic chylothorax (Correct answer)
Thoracic duct trauma

Correct answer: Idiopathic chylothorax

Idiopathic chylothorax is the most common cause in cats, though cardiac disease and neoplasia must be ruled out; true idiopathic cases have no identifiable underlying disorder.

Question 101: Which Salmonella serotype is most commonly associated with poultry products and represents the leading cause of salmonellosis in the US?

Salmonella Typhi
Salmonella Enteritidis (Correct answer)
Salmonella Dublin
Salmonella Choleraesuis

Correct answer: Salmonella Enteritidis

Salmonella Enteritidis is the most common serotype linked to poultry and eggs and is a major cause of human foodborne illness in the US.

Question 102: A 500-cow Holstein dairy has a bulk tank somatic cell count (BTSCC) averaging 380,000 cells/mL over 6 months. Individual cow linear scores show 22% of cows with linear score ≥5 (SCC ≥200,000). New infection rate (NIR) during lactation is 8%/month; cure rate (CR) during dry-off is 55%. The herd veterinarian wants to reduce BTSCC to <200,000 within 12 months. Which intervention is predicted to have the GREATEST single impact on achieving this goal, based on the epidemiologic data provided?

Add post-milking teat dipping with an iodine-based barrier dip to reduce the 8%/month new infection rate
Cull all cows with linear score ≥5 at current lactation stage to rapidly reduce the high-SCC reservoir
Improve dry cow therapy outcomes by switching to an internal teat sealant plus antibiotic DCT protocol for all eligible cows, targeting the 55% dry-period cure rate (Correct answer)
Implement a selective dry cow therapy program to reduce antibiotic use and focus resources on culture-positive quarters

Correct answer: Improve dry cow therapy outcomes by switching to an internal teat sealant plus antibiotic DCT protocol for all eligible cows, targeting the 55% dry-period cure rate

The epidemiologic data identifies two leverage points: an 8%/month NIR (high, normal is <2%) and a 55% dry-period cure rate (low, target is >75%). The BTSCC is driven by the large chronic reservoir (22% of cows with LS≥5). Improving dry-period cures from 55% to >75% by ensuring all eligible cows receive a combination of antibiotic DCT plus an internal teat sealant (which creates a physical barrier reducing new IMI during the dry period as well) would both eliminate existing chronic infections and prevent new ones during the critical dry period — the period of highest cure probability. This single intervention addresses chronic prevalence (the numerator of BTSCC) most powerfully. Culling all LS≥5 cows would reduce the reservoir acutely but would remove ~110 cows (economically catastrophic) and not address incoming infections. Improving post-dipping would reduce NIR, but at 8%/month the effect on the established chronic reservoir would take 12+ months to manifest meaningfully. Selective DCT, while appropriate for antibiotic stewardship, would likely lower cure rates further in this herd.

Question 103: A 4-year-old Labrador Retriever undergoes a routine CBC and is found to have a hematocrit of 20%, reticulocytosis, and spherocytes on blood smear. The Coombs test is positive. What is the most appropriate initial treatment?

Immunosuppressive doses of prednisone (Correct answer)
Intravenous iron supplementation
Blood transfusion only
Splenectomy

Correct answer: Immunosuppressive doses of prednisone

Immune-mediated hemolytic anemia is treated primarily with immunosuppressive corticosteroids such as prednisone to halt antibody-mediated red cell destruction.

Question 104: Which of the following findings on an ACTH stimulation test is most consistent with a diagnosis of typical hypoadrenocorticism (Addison's disease) in a dog?

Low baseline cortisol with an exaggerated response post-ACTH
Low baseline cortisol with a minimal to no response post-ACTH (Correct answer)
Normal baseline cortisol with an exaggerated response post-ACTH
High baseline cortisol with a minimal response post-ACTH

Correct answer: Low baseline cortisol with a minimal to no response post-ACTH

The definitive diagnosis of hypoadrenocorticism is made with an ACTH stimulation test. Dogs with Addison's disease have adrenal glands that cannot produce cortisol, so both the baseline (pre-ACTH) cortisol level and the post-ACTH cortisol level will be low, showing a minimal or flat-line response to stimulation.

Question 105: A 7-year-old Doberman Pinscher presents with exercise intolerance, ascites, and a gallop rhythm. Echocardiography shows a dilated left ventricle with reduced fractional shortening of 12%. What is the most likely diagnosis?

Pericardial effusion
Dilated cardiomyopathy (Correct answer)
Hypertrophic cardiomyopathy
Mitral valve endocardiosis

Correct answer: Dilated cardiomyopathy

Dilated cardiomyopathy with reduced fractional shortening and a dilated left ventricle is the classic presentation in Dobermans.

Question 106: A beef herd in the southeastern US has calves born with contracted tendons, cleft palate, and arthrogryposis. The dam grazed lupine between days 40–70 of gestation. Which teratogen is responsible?

Swainsonine (locoweed)
Nitrates from sudan grass
Anagyrine (quinolizidine alkaloid in lupine) (Correct answer)
Veratrum californicum alkaloids

Correct answer: Anagyrine (quinolizidine alkaloid in lupine)

Anagyrine in lupine species causes crooked calf disease (arthrogryposis and cleft palate) when dams graze lupine between days 40 and 70 of gestation.

Question 107: Histologic examination of a canine skin biopsy shows epidermal hyperplasia, parakeratosis, Munro microabscesses (neutrophil collections in the stratum corneum), and perivascular lymphocytic infiltrate in the superficial dermis. This pattern is most consistent with:

Psoriasiform-lichenoid dermatitis (Correct answer)
Pemphigus foliaceus
Mast cell tumor with epidermal reaction
Superficial bacterial pyoderma

Correct answer: Psoriasiform-lichenoid dermatitis

Psoriasiform-lichenoid dermatitis in dogs is characterized histologically by epidermal hyperplasia (psoriasiform), parakeratosis, intracorneal neutrophil accumulations (Munro microabscesses), and a lichenoid (interface) or superficial perivascular infiltrate. Pemphigus foliaceus shows acantholytic cells and subcorneal pustules; pyoderma shows suppurative folliculitis.

Question 108: A 9-year-old Miniature Schnauzer presents with vomiting, cranial abdominal pain, and a 'praying' posture. Abdominal radiographs are taken to rule out other causes. Which of the following radiographic signs would be most consistent with acute pancreatitis?

Generalized loss of serosal detail throughout the entire abdomen.
Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen. (Correct answer)
Mineralization within the soft tissue opacity of the liver.
A gas-filled and distended gallbladder (emphysematous cholecystitis).

Correct answer: Focal loss of serosal detail and increased soft tissue opacity in the right cranial abdomen.

The radiographic signs of pancreatitis are often subtle and non-specific, but they reflect the focal inflammation and peritonitis in the area of the pancreas. The most common findings are a focal loss of serosal detail (a 'ground glass' appearance) and a soft tissue mass effect in the right cranial abdomen, which may cause widening of the pyloro-duodenal angle.

Question 109: A cat is presented with a nasal mass and skin nodules; cytology reveals large encapsulated yeast with narrow-based budding. What is the most likely diagnosis?

Histoplasmosis
Cryptococcosis (Correct answer)
Blastomycosis
Sporotrichosis

Correct answer: Cryptococcosis

Cryptococcus neoformans/gattii appears as large encapsulated yeasts with narrow-based budding on cytology and commonly causes nasal and skin lesions in cats.

Question 110: A group of yearling beef cattle on pasture for the first time during late summer exhibit profuse watery diarrhea, poor growth, and submandibular edema ('bottle jaw'). Which of the following is the most likely diagnosis?

Bovine Viral Diarrhea Virus (BVDV)
Coccidiosis
Johne's Disease
Type I Ostertagiasis (Correct answer)

Correct answer: Type I Ostertagiasis

This clinical presentation is classic for Type I Ostertagiasis, caused by a heavy burden of the brown stomach worm, Ostertagia ostertagi. The parasites cause a protein-losing enteropathy, leading to hypoalbuminemia, which results in submandibular edema ('bottle jaw') and diarrhea. This typically affects young cattle in their first grazing season. Johne's disease typically affects older cattle, and while coccidiosis causes diarrhea, severe bottle jaw is less common.

Question 111: Which diagnostic test is most appropriate for confirming active Toxoplasma gondii infection (versus past exposure) in a cat with suspected toxoplasmosis?

Single high IgG titer
Skin test for delayed hypersensitivity
Fecal flotation for oocysts alone
Rising IgM titer or a fourfold rise in IgG titer on paired samples (Correct answer)

Correct answer: Rising IgM titer or a fourfold rise in IgG titer on paired samples

Rising IgM titers or a fourfold increase in IgG on paired samples 2-4 weeks apart indicate active or recent Toxoplasma infection rather than past exposure.

Question 112: Insulinoma in ferrets is a tumor of which cell type, and what is its primary clinical consequence?

Pancreatic alpha cells, causing hyperglycemia
Hepatic cells, causing hyperbilirubinemia
Adrenal cortex cells, causing hyperadrenocorticism
Pancreatic beta cells, causing hypoglycemia (Correct answer)

Correct answer: Pancreatic beta cells, causing hypoglycemia

Insulinoma is a pancreatic beta cell tumor that secretes excess insulin, causing episodic hypoglycemia, weakness, and seizures in ferrets.

Question 113: A 5-year-old Thoroughbred racehorse undergoes nuclear scintigraphy for investigation of right forelimb lameness that has not localized with nerve blocks. The bone scan shows markedly increased radiopharmaceutical uptake (IRU) in the mid-diaphysis of the right third metacarpal bone on the lateral cortex. What is the most appropriate next diagnostic step to characterize this lesion before formulating a treatment plan?

Repeat nuclear scintigraphy in 4 weeks to assess progression of uptake
CT of the right forelimb to characterize cortical integrity and quantify stress fracture propagation (Correct answer)
MRI of the distal forelimb in the standing horse to rule out concurrent navicular disease
Ultrasonography of the lateral aspect of the cannon bone to evaluate the periosteum

Correct answer: CT of the right forelimb to characterize cortical integrity and quantify stress fracture propagation

Focal high IRU in the diaphyseal cortex of the third metacarpus in a racehorse is highly suspicious for a stress fracture, which carries risk of complete catastrophic fracture if the horse is exercised. CT provides detailed cross-sectional characterization of cortical integrity, fracture line orientation, and propagation depth — information critical to differentiating a stable incomplete cortical stress fracture from one approaching propagation, which directly determines surgical vs. conservative management. Repeat scintigraphy delays diagnosis without adding anatomical detail. Ultrasonography evaluates periosteal soft tissue but cannot adequately assess cortical fracture geometry. Standing MRI of the distal limb does not image the mid-diaphysis.

Question 114: A dog is presented with acute onset of severe muscle tremors, hypersalivation, and miosis after potential exposure to a pesticide. Organophosphate toxicity is suspected. Which combination of drugs is the most appropriate treatment to counteract both the muscarinic and nicotinic effects?

Atropine and Pralidoxime (2-PAM) (Correct answer)
Diazepam and Fomepizole
Naloxone and Epinephrine
Vitamin K1 and Methocarbamol

Correct answer: Atropine and Pralidoxime (2-PAM)

The standard treatment for organophosphate toxicity involves a combination of Atropine and Pralidoxime (2-PAM). Atropine is a muscarinic antagonist that controls signs like salivation, urination, and bronchoconstriction. Pralidoxime is a cholinesterase reactivator that works to reverse the nicotinic effects, such as muscle tremors and paralysis, by breaking the bond between the organophosphate and the acetylcholinesterase enzyme.

Question 115: A 12-year-old Quarter Horse cutting horse presents with chronic bilateral hindlimb stiffness and a 'rope-walking' gait. On rectal palpation, crepitus is noted over the lumbosacral region. Standing radiographs are non-diagnostic. Scintigraphy reveals focal increased radiopharmaceutical uptake at L5-S1. Nuclear scintigraphy-guided infiltration of the lumbosacral space with corticosteroid provides marked temporary improvement. What is the most appropriate long-term management strategy if conservative therapy fails after two injection cycles?

Sacroiliac joint arthrodesis via percutaneous implant placement
Extracorporeal shock wave therapy (ESWT) targeted to the lumbosacral facet joints under ultrasound guidance (Correct answer)
Retirement from cutting, with consideration of mesotherapy along the thoracolumbar epaxial musculature
Computed tomography-guided chemical neurolysis of the dorsal sacral nerve roots

Correct answer: Extracorporeal shock wave therapy (ESWT) targeted to the lumbosacral facet joints under ultrasound guidance

For horses with confirmed lumbosacral pathology refractory to intra-articular corticosteroid, extracorporeal shock wave therapy (ESWT) targeted under ultrasound guidance to the lumbosacral facet articulations is a validated next-line intervention. ESWT delivers acoustic energy that modulates pain via nerve fiber hyperpolarization and stimulates local tissue remodeling. It is minimally invasive, can be repeated, and has demonstrated efficacy in peer-reviewed studies for horses with thoracolumbar and lumbosacral pain. Sacroiliac arthrodesis addresses the SI joint but not lumbosacral facets, and chemical neurolysis is not an accepted equine technique for this indication.

Question 116: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?

Dexmedetomidine
Acepromazine (Correct answer)
Butorphanol
Midazolam

Correct answer: Acepromazine

Acepromazine (a phenothiazine) causes splenic engorgement by relaxing the splenic capsule, which can significantly enlarge an existing splenic mass and complicate diagnosis or surgery.

Question 117: Rabbits are obligate nasal breathers. Which anatomical feature is responsible for this characteristic?

The epiglottis is permanently engaged with the soft palate (Correct answer)
The tongue occludes the pharynx at rest
The hard palate physically blocks the oral airway
The glottis remains closed during oral breathing

Correct answer: The epiglottis is permanently engaged with the soft palate

In rabbits, the epiglottis is anatomically locked against the soft palate, preventing oral breathing under normal circumstances.

Question 118: A dog that has been struck by a car typically has non-weight-bearing foreleg lameness. Physical examination reveals no fractures that can be felt. Without any movement or pain, the limb simply hangs there. It is also discovered that the dog has Horner's syndrome. What medical condition is most likely to account for these exam results?

Brachial plexus avulsion (Correct answer)
Radial nerve paralysis
Cervical disc disease
Arterial thromboembolism

Correct answer: Brachial plexus avulsion

The combination of non-weight-bearing foreleg lameness, a flaccid limb that 'just hangs there,' and the presence of Horner's syndrome is highly indicative of a brachial plexus avulsion. Horner's syndrome (miosis, ptosis, enophthalmos) occurs due to damage to sympathetic nerve fibers within the brachial plexus. The flaccid paralysis results from severe nerve root damage, typically from a traumatic pull on the limb.

Question 119: The 3-day history of moderate to severe episodes of left-sided epistaxis in a male fjord pony, 19, is evaluated. The pony is quiet, attentive, and receptive when presented. The rectal temperature was 101 degrees Fahrenheit, the heart rate is 60, and the respiration rate is 40. The total protein level is 6.5 g/dL, and the hematocrit is 31%. Airflow through each nostril is not especially restricted, and there is no sign of damage or swelling over the head's sinus area. Which of the following diagnostic procedures will give the most accurate results to support an assumed diagnosis?

Head/Thorax radiography
Transtracheal aspiration
Endoscopic examination (Correct answer)
Thoracic ultrasonography

Correct answer: Endoscopic examination

The pony's history of recurrent, unilateral epistaxis without obvious external trauma or swelling suggests a lesion within the nasal passages, paranasal sinuses, or guttural pouches. Endoscopic examination (rhinoscopy and guttural pouch endoscopy) is the most accurate diagnostic procedure to directly visualize these structures, identify the source of bleeding (e.g., fungal plaques, ethmoid hematoma, tumor), and guide further treatment.

Question 120: A dairy herd manager asks about dry cow therapy. Which approach describes selective dry cow therapy (SDCT)?

Withholding all treatment during the dry period
Treating only cows with elevated SCC or positive culture at dry-off (Correct answer)
Treating all cows with intramammary antibiotics at dry-off
Treating only fresh cows showing clinical mastitis

Correct answer: Treating only cows with elevated SCC or positive culture at dry-off

Selective dry cow therapy targets only cows with evidence of intramammary infection, reducing antibiotic use compared to blanket dry cow therapy.

Question 121: During a herd health visit to a 600-head beef cow-calf operation, you identify an outbreak of respiratory disease in calves 3–8 weeks of age. Morbidity is 28% and case-fatality rate is 9%. Nasal swabs from 6 acutely affected calves yield Mannheimia haemolytica in 4 and Histophilus somni in 2. Colostrum management records are excellent. Which pathogen-level finding MOST strongly suggests a vaccine-preventable gap in this herd's prevention program?

Mannheimia haemolytica isolation in calves under 3 weeks of age
Pasteurella multocida type A isolated from a calf that died despite florfenicol treatment
Bovine respiratory syncytial virus (BRSV) antigen detected on immunofluorescence of nasal swabs (Correct answer)
Histophilus somni isolation in calves 3–8 weeks of age with neurological signs

Correct answer: Bovine respiratory syncytial virus (BRSV) antigen detected on immunofluorescence of nasal swabs

BRSV is a primary viral pathogen in young calves that acts as a 'door-opener' for secondary bacterial pneumonia by disrupting mucociliary clearance and innate immunity. Its presence in calves this age with high morbidity despite good colostrum transfer points directly to a gap in dam vaccination (modified-live BRSV given pre-calving provides colostral antibody protection) or to inadequate calf vaccination timing. Mannheimia and Histophilus are secondary bacterial opportunists commonly cultured from BRD cases regardless of vaccination status. Pasteurella multocida type A treatment failure most suggests antimicrobial resistance or inadequate drug selection, not a specific vaccine gap.

Question 122: A cat's thoracic CT shows a pulmonary mass with a 'halo sign' (ground-glass opacity surrounding a solid nodule). This finding in cats is most associated with:

Pulmonary lymphoma
Fungal pneumonia (cryptococcosis) (Correct answer)
Primary lung adenocarcinoma
Feline asthma

Correct answer: Fungal pneumonia (cryptococcosis)

The CT halo sign represents hemorrhage or inflammatory infiltrate surrounding a fungal nodule and is classically associated with angioinvasive fungal infections including Cryptococcus in cats.

Question 123: During a pre-purchase examination, a 7-year-old Quarter Horse reining prospect shows a consistent 2/5 left hindlimb lameness. Perineural anesthesia of the high plantar nerve (abaxial sesamoid level) abolishes the lameness completely. However, intra-articular anesthesia of the tarsocrural, proximal intertarsal, distal intertarsal, and tarsometatarsal joints — performed sequentially over two days — fails to improve the lameness. What is the MOST likely primary diagnosis?

Cunean tendon bursitis
Proximal suspensory desmitis of the left hindlimb (Correct answer)
Fracture of the central tarsal bone
Osteochondrosis dissecans of the tarsocrural joint

Correct answer: Proximal suspensory desmitis of the left hindlimb

Proximal suspensory desmitis (PSD) of the hindlimb is notoriously blocked by high plantar anesthesia, which desensitizes the lateral plantar nerve branch supplying the proximal suspensory apparatus. Because PSD is a soft tissue structure — not a joint — all four tarsus joint blocks remain negative despite the lameness being in that region. This pattern (high plantar positive, all tarsus joints negative) is the classic diagnostic footprint of hindlimb PSD. Cunean tendon bursitis and central tarsal bone fracture would likely respond to tarsometatarsal or intertarsal blocks; OCD of the tarsocrural joint would be blocked by the tarsocrural anesthesia.

Question 124: Which program is used in the US to eradicate bovine tuberculosis caused by Mycobacterium bovis, and what is the testing method of choice for herd surveillance?

USDA Brucellosis Eradication Program using ELISA
Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT) (Correct answer)
National Animal Health Monitoring System using PCR of nasal swabs
APHIS-VS program using whole blood interferon-gamma assay only

Correct answer: Federal-State TB Eradication Program using the caudal fold tuberculin test (CFT)

The US Federal-State TB Eradication Program uses the caudal fold test (CFT) for initial herd testing, with positive reactors confirmed by the comparative cervical tuberculin (CCT) test.

Question 125: Under the 21 CFR Part 117 Preventive Controls rule, which of the following is classified as a 'process control'?

Supplier verification for incoming ingredients
Cooking step that kills pathogens to a safe level (Correct answer)
Employee hygiene training records
Environmental monitoring for Listeria

Correct answer: Cooking step that kills pathogens to a safe level

A process control is a procedure such as cooking that applies a lethal treatment to eliminate or reduce a biological hazard to an acceptable level.

Question 126: A veterinarian administers detomidine to a horse for standing sedation. This drug produces reliable sedation, muscle relaxation, and analgesia by acting as a potent agonist at which of the following receptors?

Mu-opioid receptor
NMDA receptor
GABA receptor
Alpha-2 adrenergic receptor (Correct answer)

Correct answer: Alpha-2 adrenergic receptor

Detomidine is a potent alpha-2 adrenergic agonist. Stimulation of these receptors in the central and peripheral nervous system inhibits the release of norepinephrine, which results in sedation, analgesia, and muscle relaxation. This class of drugs is commonly used for sedation in large animals.

Question 127: A 12-year-old Warmblood dressage horse presents with a 6-month history of progressive hindlimb ataxia and symmetric weakness. Cervical radiographs show dynamic stenosis at C3-C4. Myelography confirms spinal cord compression only during neck flexion. The owners request surgical intervention. Which procedure is most appropriate?

Foraminotomy to decompress nerve roots bilaterally
Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion) (Correct answer)
Subtotal corpectomy with polymethylmethacrylate stabilization
Dorsal laminectomy at C3-C4

Correct answer: Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion)

Cervical vertebral interbody fusion using a Bagby basket (or modified basket/screw technique) is the surgical standard for dynamic cervical stenosis (Wobbler syndrome) in horses. It eliminates instability-driven compression by fusing the affected motion segment. Dorsal laminectomy is unsuitable because the compression in dynamic cases is typically ventral/lateral, and the equine cervical anatomy makes dorsal approach impractical for decompression.

Question 128: A 7-year-old Quarter Horse cutting horse has a 2/5 right hindlimb lameness. Intra-articular analgesia of the tarsometatarsal and distal intertarsal joints produces 50% improvement. A subsequent high plantar nerve block produces complete resolution. MRI is unavailable. Which additional diagnostic step is MOST likely to differentiate proximal suspensory desmitis from a cunean tendon lesion as the remaining pain source?

Radiographic oblique views of the hock at 45° and 60°
Ultrasound of the proximal third metatarsal region in both transverse and sagittal planes (Correct answer)
Computed tomography of the distal tarsus under general anesthesia
Nuclear scintigraphy with focal uptake mapping of the mid-cannon bone

Correct answer: Ultrasound of the proximal third metatarsal region in both transverse and sagittal planes

After confirming the pain source is proximal to the plantar nerve block level (consistent with the high plantar block resolving lameness) and ruling out a tarsal joint contribution, ultrasound of the proximal suspensory ligament (PSL) in both transverse and sagittal planes is the most practical next step. PSL desmitis in hindlimbs frequently occurs without obvious fiber disruption and requires systematic probe placement on the palmaroproximal metatarsus. The cunean tendon runs superficially and can be distinguished from the PSL by its more medial course and distinct echogenic envelope. CT and scintigraphy provide complementary data but are less accessible and not the first-line differentiation tool.

Question 129: A 5-year-old Holstein cow has not shown estrus 60 days postpartum. Rectal palpation reveals a corpus luteum (CL) on one ovary with no other abnormalities. Which treatment protocol is most appropriate to initiate cyclicity?

Begin a progesterone-releasing intravaginal device (PRID) for 14 days
Administer GnRH to stimulate follicle-stimulating hormone release
Administer estradiol cypionate to induce a standing heat
Administer prostaglandin F2α (PGF2α) to lyse the CL and allow return to estrus (Correct answer)

Correct answer: Administer prostaglandin F2α (PGF2α) to lyse the CL and allow return to estrus

A persistent CL causing anestrus is treated with prostaglandin F2α (dinoprost or cloprostenol), which causes luteolysis — regression of the CL, progesterone levels drop, and the cow returns to estrus within 2–5 days. GnRH induces ovulation of the dominant follicle but does not address a persistent CL. PRIDs are used for synchronization, not CL regression.

Question 130: Which radiographic view is MOST useful for evaluating the flexor cortex of the navicular bone for lollipop lesions in a horse?

Dorsopalmar view
Flexor tangential (skyline) view (Correct answer)
Lateromedial view
Oblique view

Correct answer: Flexor tangential (skyline) view

The flexor tangential (skyline) view projects the flexor cortex of the navicular bone en face, allowing visualization of corticomedullary defects and lollipop lesions.

Question 131: Acoustic shadowing on ultrasound is caused by:

Amplification of returning echoes beyond the gain setting
Refraction of sound through soft tissue-fluid interfaces
Bending of the ultrasound beam at curved interfaces
Complete absorption or reflection of the sound beam by a highly attenuating structure (Correct answer)

Correct answer: Complete absorption or reflection of the sound beam by a highly attenuating structure

Dense structures such as calculi or bone absorb or reflect nearly all the ultrasound energy, preventing transmission and creating a shadow distal to the structure.

Question 132: A 10-year-old Quarter Horse with chronic, bilateral forelimb lameness undergoes a radiographic examination of the feet. Which of the following radiographic findings is most indicative of navicular disease (podotrochleosis)?

Narrowing of the distal interphalangeal joint space with extensive periarticular osteophytes.
Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone. (Correct answer)
Smooth, well-defined new bone formation on the extensor process of the distal phalanx.
Rotation and sinking of the distal phalanx (P3) within the hoof capsule.

Correct answer: Enlarged, flask-shaped synovial invaginations ('lollipops') on the distal border of the navicular bone.

While many radiographic changes can be seen with navicular disease, the presence of more than 6-7 enlarged, flask-shaped or branching synovial invaginations (vascular channels) on the distal border is a classic and significant finding. Other key signs include flexor cortex erosions and medullary sclerosis.

Question 133: A 350-cow dairy in the upper Midwest has a bulk tank somatic cell count (BTSCC) persistently between 320,000–380,000 cells/mL over the past 6 months. Milk culture of individual quarter samples from 40 randomly selected cows identifies: Staphylococcus aureus (6 cows), Streptococcus agalactiae (12 cows), coagulase-negative staphylococci (CNS) (8 cows), and no growth (14 cows). Which statement BEST describes the appropriate herd-level eradication target for this situation?

CNS should be targeted first with intramammary therapy because they represent the largest numerical contributor to the elevated BTSCC
Staphylococcus aureus should be the primary eradication target because it has higher within-herd transmission potential than Streptococcus agalactiae
Streptococcus agalactiae should be targeted for herd eradication because it is an obligate intramammary pathogen that can be eliminated with a blitz dry-cow therapy program (Correct answer)
All culture-positive cows should receive immediate intramammary therapy with pirlimycin to resolve infection before dry-off

Correct answer: Streptococcus agalactiae should be targeted for herd eradication because it is an obligate intramammary pathogen that can be eliminated with a blitz dry-cow therapy program

Streptococcus agalactiae is an obligate pathogen of the bovine mammary gland — it does not survive long in the environment — making it the only major mastitis pathogen amenable to true herd eradication. A 'blitz' program (treating all infected cows simultaneously with intramammary penicillin + stringent milking hygiene + test and cull if refractory) can eliminate S. agalactiae from a herd within weeks. With 12/40 cows infected (30%), this organism is almost certainly the dominant driver of the elevated BTSCC. S. aureus has very poor cure rates with lactating cow therapy (<25%) and is not eradicable herd-wide. CNS generally cause mild, self-limiting IMI and rarely require active treatment. Blanket intramammary pirlimycin for all positive cows is not evidence-based and raises antimicrobial stewardship concerns.

Question 134: A 3-year-old Quarter Horse presents with right forelimb lameness localized to the foot by perineural anesthesia. MRI (low-field standing unit) shows a hyperintense T2 signal lesion within the lateral lobe of the deep digital flexor tendon (DDFT) at the level of the navicular bone, with a corresponding hypointense T1 signal. The navicular bone shows focal subchondral signal loss on T1 at the flexor cortex. Which combination of lesions is present?

DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion (Correct answer)
DDFT insertional desmopathy with collateral sesamoidean ligament enthesopathy
Impar ligament desmitis with reactive navicular bone marrow edema
Navicular bursitis with secondary DDFT surface fibrillation (no intrinsic tendon lesion)

Correct answer: DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion

Hyperintense T2 / hypointense T1 signal within the DDFT substance indicates a fluid-filled cleft consistent with a longitudinal split tear (core lesion). This is distinct from surface fibrillation, which would show signal change only at the tendon margin without intrinsic disruption. The focal subchondral T1 hypointensity at the navicular flexor cortex indicates bone erosion or fibrocartilage loss — a recognized sequela of chronic DDFT pathology compressing the navicular bone. Navicular bursitis alone would show bursal distension with signal change in the bursal recess, not intrinsic tendon signal. Impar ligament desmitis produces signal change at the palmar distal navicular-P3 interface.

Question 135: An alpaca presents with progressive weight loss, bottle jaw, and anemia. Fecal flotation reveals strongyle-type eggs. Which anthelmintic class is most commonly used as first-line therapy in camelids with suspected Haemonchus?

Salicylanilides (e.g., closantel)
Imidazothiazoles (e.g., levamisole)
Benzimidazoles (e.g., fenbendazole)
Macrocyclic lactones (e.g., ivermectin) (Correct answer)

Correct answer: Macrocyclic lactones (e.g., ivermectin)

Macrocyclic lactones such as ivermectin are commonly used first-line in camelids for Haemonchus contortus, though resistance monitoring via fecal egg count reduction tests is recommended.

Question 136: You perform a palmar digital nerve block (PDN block) in a horse with a 3/5 lameness. Lameness improves by only 30%. You then perform an abaxial sesamoid nerve block, and lameness improves by 70% from the original score. What is the most accurate interpretation of these sequential block results?

Pain is localized to the palmar pastern and digital flexor tendon sheath below the fetlock
There is a pain source in the heel/caudal foot region AND a second source more proximal in the pastern or fetlock region (Correct answer)
The PDN block failed due to poor technique; the abaxial block localized pain to the hoof capsule
The pain source lies entirely within the pastern region innervated by the abaxial block but not the PDN

Correct answer: There is a pain source in the heel/caudal foot region AND a second source more proximal in the pastern or fetlock region

Sequential distal-to-proximal nerve blocks are additive. A 30% improvement with PDN (desensitizes caudal foot/heel) plus an additional 40% improvement with abaxial sesamoid block (adds the pastern/fetlock region) indicates two pain contributors: one in the heel/caudal foot and a second source in the region additionally desensitized by the abaxial block (pastern, proximal interphalangeal joint, palmar fetlock). Neither block alone accounted for the full lameness.

Question 137: A public health veterinarian is reviewing a food establishment's HACCP plan for a ready-to-eat deli meat facility. The plan identifies internal temperature of 160°F (71.1°C) as a Critical Control Point (CCP) for lethality. An inspector finds that logs show 12 consecutive batches reached only 158°F (70°C). Under HACCP principles, which action is MOST appropriate?

Issue a warning but allow product to proceed since 158°F is close to the CCP limit
Adjust the CCP limit downward to 158°F to reflect actual operational capacity
Require immediate corrective action documentation, reassess the disposition of all 12 affected batches, and evaluate root cause (Correct answer)
Suspend the HACCP plan and revert to traditional inspection methods pending retesting

Correct answer: Require immediate corrective action documentation, reassess the disposition of all 12 affected batches, and evaluate root cause

Under HACCP Principle 5, when a critical limit is not met, a pre-established corrective action must be implemented immediately. This includes: (1) correcting the process deviation, (2) determining the disposition of affected product (hold, test, or destroy), and (3) documenting the corrective action. All 12 batches where the CCP was not met require individual disposition decisions — they cannot proceed without evaluation. Adjusting CCP limits to match operational failure would compromise food safety integrity and violates HACCP validation requirements.

Question 138: A dog is receiving a fentanyl CRI at 5 mcg/kg/hr intraoperatively. Signs of opioid-induced bradycardia appear. Which drug reverses fentanyl's cardiovascular effects with the least effect on analgesia?

Flumazenil IV
Atipamezole IV
Glycopyrrolate IV to treat bradycardia without reversing opioid (Correct answer)
Naloxone full dose IV

Correct answer: Glycopyrrolate IV to treat bradycardia without reversing opioid

Glycopyrrolate treats opioid-induced bradycardia by blocking vagal tone without reversing analgesia, unlike naloxone which would eliminate pain control.

Question 139: A 2-year-old sheep presents with acute blindness, head pressing, and opisthotonus. The animal has been on a high-grain diet with limited forage. Blood thiamine levels are low. Which treatment should be administered immediately?

Magnesium sulfate IV to treat suspected hypomagnesemia
Dexamethasone 0.1 mg/kg IV to reduce cerebral edema
Intravenous dextrose 50% at 0.5 mL/kg
Thiamine (vitamin B1) 10–20 mg/kg IV or IM (Correct answer)

Correct answer: Thiamine (vitamin B1) 10–20 mg/kg IV or IM

Polioencephalomalacia (PEM) in sheep is caused by thiamine deficiency, often triggered by high-grain diets that favor thiaminase-producing rumen bacteria. Clinical signs include blindness, cortical signs, and opisthotonus. Immediate high-dose thiamine (B1) administration is the treatment of choice. Dextrose worsens thiamine deficiency; dexamethasone is adjunctive at best.

Question 140: A veterinarian is performing a herd-level investigation on a purebred beef operation with a history of recurrent Theileria orientalis (Ikeda genotype) outbreaks following tick exposure. Several cows in late gestation are showing pallor, jaundice, and decreased milk production. Which hematological finding would BEST differentiate Theileria orientalis hemolytic anemia from iron-deficiency anemia in these animals?

Presence of piroplasms within erythrocytes on Giemsa-stained thin blood smear, along with hemolytic indices (Correct answer)
Marked regenerative response with polychromasia, anisocytosis, and Howell-Jolly bodies on blood smear
Thrombocytopenia with a platelet count below 50,000/μL as the primary differentiating finding
Mean corpuscular volume (MCV) below 52 fL with microcytic, hypochromic erythrocytes

Correct answer: Presence of piroplasms within erythrocytes on Giemsa-stained thin blood smear, along with hemolytic indices

The definitive differentiating finding for Theileria orientalis hemolysis is the identification of intraerythrocytic piroplasms (characteristically appearing as 'signet ring,' 'rod,' or 'maltese cross' forms) on a Giemsa- or Wright-stained thin blood smear, combined with hemolytic indices (hyperbilirubinemia, hemoglobinuria, elevated indirect bilirubin). Iron-deficiency anemia presents as microcytic hypochromic anemia (A) — the opposite pattern to the normocytic or macrocytic regenerative anemia of hemolysis. Both conditions may show regenerative responses (B), making this non-differentiating. Thrombocytopenia (D) may occur in Theileria but is not the primary differentiating criterion — visualization of the parasite is definitive.

Question 141: A cat is found to have hypokalemia (K+ 2.8 mEq/L) and symmetric cervical ventroflexion. Which underlying disease is most commonly associated with this presentation in cats?

Hypothyroidism
Hyperaldosteronism (Conn's syndrome) (Correct answer)
Pheochromocytoma
Addison's disease

Correct answer: Hyperaldosteronism (Conn's syndrome)

Primary hyperaldosteronism (Conn's syndrome) causes chronic hypokalemia in cats, leading to hypokalemic polymyopathy characterized by ventroflexion of the neck.

Question 142: A 9-year-old Quarter Horse cutting horse presents with a 4-month history of bilateral hindlimb stiffness that is worse in the morning and improves with exercise. The horse shows a characteristic 'goose-stepping' gait. Intra-articular anesthesia of the distal intertarsal and tarsometatarsal joints produces marked improvement. Medical management has failed over 6 months. Chemical arthrodesis with sodium monoiodoacetate (MIA) is elected. Which of the following correctly describes the mechanism of action of sodium monoiodoacetate in inducing arthrodesis?

It chelates calcium ions within the synovial fluid, precipitating calcium monoiodoacetate crystals that mechanically abrade cartilage
It activates the complement cascade within the joint, inducing a sterile neutrophilic arthritis that ablates the synovial membrane
It directly stimulates osteoblastic activity at subchondral bone, promoting bridging osteophyte formation across the joint space
It inhibits glycolysis in chondrocytes by alkylating sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenase, causing chondrocyte death and cartilage destruction (Correct answer)

Correct answer: It inhibits glycolysis in chondrocytes by alkylating sulfhydryl groups of glyceraldehyde-3-phosphate dehydrogenase, causing chondrocyte death and cartilage destruction

Sodium monoiodoacetate (MIA) is a chondrotoxic agent that alkylates (irreversibly inhibits) the sulfhydryl group of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis. Since articular cartilage relies almost entirely on anaerobic glycolysis for energy, this inhibition causes rapid chondrocyte death, cartilage matrix degradation, and subsequent subchondral bone-to-bone apposition — eventually leading to bony fusion. MIA does not primarily stimulate osteoblasts directly, does not chelate calcium, and does not work via complement activation.

Question 143: A 4-year-old Greyhound is prescribed phenobarbital for epilepsy. Compared to a Labrador Retriever of the same weight, which pharmacokinetic difference most significantly affects dosing in Greyhounds?

Greyhounds have accelerated renal tubular secretion of phenobarbital, requiring higher doses to maintain therapeutic levels
Greyhounds have reduced hepatic CYP450 enzyme activity, leading to slower phenobarbital clearance
Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations (Correct answer)
Greyhounds exhibit increased P-glycoprotein expression at the blood-brain barrier, reducing CNS penetration

Correct answer: Greyhounds have a lower volume of distribution for lipophilic drugs due to minimal body fat, resulting in higher plasma concentrations

Greyhounds have exceptionally low body fat (1–3% vs. 15–25% in mixed breeds). Phenobarbital is a lipophilic drug that distributes into adipose tissue. With minimal fat stores, the volume of distribution is reduced, leading to higher peak plasma concentrations at standard mg/kg doses. This means Greyhounds are at greater risk for toxicity and often require lower initial doses. Hepatic clearance differences exist for some drugs (e.g., propofol, thiopental) but are not the primary concern with phenobarbital dosing.

Question 144: What is the primary mechanism by which ivermectin kills parasites?

Blocks tubulin polymerization
Disrupts parasite cell membrane integrity
Inhibits acetylcholinesterase
Potentiates glutamate-gated chloride channels causing paralysis (Correct answer)

Correct answer: Potentiates glutamate-gated chloride channels causing paralysis

Ivermectin potentiates glutamate-gated chloride channels in invertebrate nerve and muscle cells, causing hyperpolarization, paralysis, and death of the parasite.

Question 145: Which critical temperature range is considered the 'danger zone' for bacterial growth in potentially hazardous foods?

40°F to 140°F (4°C to 60°C) (Correct answer)
60°F to 180°F (16°C to 82°C)
50°F to 165°F (10°C to 74°C)
32°F to 40°F (0°C to 4°C)

Correct answer: 40°F to 140°F (4°C to 60°C)

The USDA defines the temperature danger zone as 40°F to 140°F (4°C to 60°C), where most foodborne pathogens multiply rapidly.

Question 146: A pregnant veterinary technician is assisting with a feline dystocia. The queen, a former stray, expels a large amount of brownish placental fluid. The supervising veterinarian should advise the technician that she is at an increased risk of exposure to which zoonotic agent via aerosolization of these birth fluids?

Coxiella burnetii (Correct answer)
Microsporum canis
Toxoplasma gondii
Bartonella henselae

Correct answer: Coxiella burnetii

*Coxiella burnetii*, the causative agent of Q fever, is shed in extremely high concentrations in the birth products (placenta, amniotic fluid) of infected animals, including cats. Transmission to humans often occurs through the inhalation of infectious aerosols, posing a significant risk to individuals assisting with parturition, especially pregnant women.

Question 147: Which opioid analgesic is commonly used in cats but must be used cautiously due to their limited glucuronidation capacity?

Fentanyl
Buprenorphine (Correct answer)
Hydromorphone
Morphine

Correct answer: Buprenorphine

Buprenorphine is preferred in cats because its partial agonist activity and high mu-receptor affinity make it effective at lower doses, reducing the risk of adverse effects from impaired glucuronidation.

Question 148: Which of the following is the recommended nutritional strategy to prevent osteochondrosis dissecans (OCD) in fast-growing market pigs?

Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate (Correct answer)
Supplementing vitamin E and selenium to prevent oxidative cartilage damage
High-calcium, low-phosphorus diet to maximize bone density
Restricting dietary lysine to slow growth rate

Correct answer: Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate

OCD in pigs is a developmental orthopedic disease linked to rapid growth, genetic selection for leanness, and mineral imbalances. A Ca:P ratio near 1.2:1 with adequate vitamin D3 and avoiding excess growth rate are the primary preventive strategies. Extreme calcium restriction or excess both impair endochondral ossification.

Question 149: A 4-year-old male German shepherd is examined because of recent development of severe weight loss, listlessness, and frequent, large feces. The patient is reportedly consuming more than usual, including his own feces, according to the owner. The body condition score after a physical assessment is 2/5. bad hair, slow thinking, and a general lack of thrift. When the patient urinates on the ground, it is a sign of steatorrhea. Which of the subsequent tests is best suited to support the prevailing diagnosis?

Intestinal biopsy
Trypsin-like immunoreactivity (Correct answer)
Ultrasonography
Fecal flotation

Correct answer: Trypsin-like immunoreactivity

The patient's symptoms, including severe weight loss, polyphagia, coprophagia, steatorrhea, and poor body condition, are classic signs of Exocrine Pancreatic Insufficiency (EPI). EPI is characterized by the pancreas's inability to produce sufficient digestive enzymes. The canine trypsin-like immunoreactivity (cTLI) test is the gold standard for diagnosing EPI, as it directly measures pancreatic enzyme levels in the bloodstream.

Question 150: A 6-week-old kitten from an unvaccinated litter presents in lateral recumbency with intention tremors, broad-based ataxic gait, and dysmetria. The dam had an unknown vaccine history. The kitten otherwise appears normally developed and alert. Which of the following MOST accurately explains the timing of viral injury required to produce this neurological syndrome?

Feline calicivirus caused neonatal cerebellar hypoplasia by infecting ependymal cells of the fourth ventricle, leading to obstructive hydrocephalus and secondary cerebellar compression.
FPV infection occurred after 4 weeks of age when the blood-brain barrier becomes more permeable, allowing viral access to mature cerebellar Purkinje cells.
Feline herpesvirus-1 caused meningoencephalitis in the neonatal period, selectively destroying Purkinje cells of the cerebellum and sparing cortical neurons.
Feline panleukopenia virus (FPV) infected the kitten in utero or within the first two weeks of postnatal life, targeting rapidly dividing granule cell precursors in the external germinal layer of the cerebellum. (Correct answer)

Correct answer: Feline panleukopenia virus (FPV) infected the kitten in utero or within the first two weeks of postnatal life, targeting rapidly dividing granule cell precursors in the external germinal layer of the cerebellum.

Feline panleukopenia virus is highly mitotropic and requires actively dividing cells. Cerebellar hypoplasia results from FPV infection during late gestation or within the first 1–2 weeks of life when the external germinal layer (EGL) of the cerebellum—a transient population of proliferating granule cell precursors—is present. Viral destruction of these precursors results in a hypoplastic cerebellum with characteristic non-progressive ataxia and tremors. After EGL involution (~2–3 weeks postnatal), FPV no longer produces cerebellar hypoplasia. FHV-1 and FCV are not causative agents of this syndrome.

Question 151: During a routine physical exam, a 4-month-old Bulldog puppy is noted to have a heart murmur. Echocardiography reveals obstruction of the right ventricular outflow tract and right ventricular hypertrophy. What is the definitive therapy?

Pacemaker implantation
Open-heart surgical valvotomy
Beta-blocker therapy alone
Balloon valvuloplasty via cardiac catheterization (Correct answer)

Correct answer: Balloon valvuloplasty via cardiac catheterization

Balloon valvuloplasty is the treatment of choice for pulmonic stenosis in dogs, providing effective relief of the outflow obstruction with low morbidity.

Question 152: Which MRI sequence best demonstrates hemorrhage of varying ages due to its sensitivity to paramagnetic effects of blood breakdown products?

T2-weighted FLAIR
Diffusion-weighted imaging (DWI)
Gradient echo (GRE/T2*) (Correct answer)
T1-weighted with contrast

Correct answer: Gradient echo (GRE/T2*)

Gradient echo sequences are highly sensitive to susceptibility effects caused by hemosiderin and deoxyhemoglobin, making them ideal for detecting hemorrhage.

Question 153: A herd of stocker cattle develops red-water disease (bacillary hemoglobinuria). Which organism and predisposing factor is responsible?

Clostridium perfringens type C, high-grain diet
Clostridium septicum, skin wounds in wet conditions
Clostridium novyi type A, wound contamination
Clostridium haemolyticum, liver fluke migration (Correct answer)

Correct answer: Clostridium haemolyticum, liver fluke migration

Bacillary hemoglobinuria is caused by C. haemolyticum (C. novyi type D), which proliferates in anaerobic zones created by migrating Fasciola hepatica liver flukes.

Question 154: A 10-year-old dog is diagnosed with stage 3 chronic kidney disease (IRIS). Which dietary modification is most appropriate?

Increased calcium supplementation
Phosphorus restriction with moderate protein reduction (Correct answer)
Sodium restriction only
High protein diet to offset catabolism

Correct answer: Phosphorus restriction with moderate protein reduction

Phosphorus restriction slows CKD progression by reducing renal secondary hyperparathyroidism, and moderate protein reduction decreases uremic toxin accumulation without worsening malnutrition.

Question 155: A 5-year-old dog presents with peracute collapse, pale mucous membranes, and abdominal distension. FAST ultrasound reveals free abdominal fluid and a splenic mass. PCV is 18%. Which statement is most accurate regarding the splenic mass?

Approximately 50% of splenic masses in dogs are malignant (hemangiosarcoma) (Correct answer)
Splenectomy is contraindicated until coagulopathy is corrected
Fine needle aspirate is diagnostic in the majority of splenic masses
Most splenic masses in dogs are benign hematomas

Correct answer: Approximately 50% of splenic masses in dogs are malignant (hemangiosarcoma)

In dogs with splenic masses and hemoabdomen, approximately 50% are hemangiosarcoma (malignant), 25% are other malignancies, and only 25% are benign nodular hyperplasia or hematoma.

Question 156: Scrapie is a prion disease of sheep. Which characteristic most accurately describes the diagnostic approach in suspect live animals?

Serum ELISA for PrPSc antibodies
Immunohistochemistry of lymphoid tissue (rectal biopsy or third eyelid) for PrPSc accumulation (Correct answer)
Cerebrospinal fluid analysis showing 14-3-3 protein elevation
PCR of blood for scrapie prion RNA

Correct answer: Immunohistochemistry of lymphoid tissue (rectal biopsy or third eyelid) for PrPSc accumulation

PrPSc (misfolded prion protein) accumulates in lymphoid tissues before neurologic signs appear. Immunohistochemistry (IHC) of rectal mucosa lymphoid tissue or the third eyelid can detect PrPSc antemortem in live sheep. There are no antibodies to prions (immune tolerance), and prions have no nucleic acid, making serology and PCR impossible.

Question 157: A 10-year-old Quarter Horse presents with recurrent episodes of forelimb lameness that worsen after exercise. Radiographs of the navicular region reveal radiolucent 'lollipop' lesions (synovial invaginations) in the distal border of the navicular bone with concurrent cortical thinning of the flexor cortex. Nuclear scintigraphy shows markedly increased radiopharmaceutical uptake in the palmar aspect of the foot. Which finding on MRI would MOST specifically confirm active navicular disease (podotracheritis) versus normal aging change?

Thickening of the deep digital flexor tendon insertion
Fluid signal within the navicular bursa on T2-weighted sequences
T2 hyperintensity within the navicular bone marrow
Ill-defined T1 hypointensity in the navicular bone correlating with the scintigraphic hot spot (Correct answer)

Correct answer: Ill-defined T1 hypointensity in the navicular bone correlating with the scintigraphic hot spot

Ill-defined T1 hypointensity (bone marrow edema pattern) within the navicular bone that correlates spatially with the scintigraphic hot spot is the MRI finding most specifically linked to active pathology (edema, vascular compromise, remodeling) rather than incidental aging change. T2 hyperintensity alone can represent fluid or edema but is less specific. Navicular bursal fluid (T2 fluid signal) can be physiologic. DDFT thickening is a complication but not specific for active navicular bone disease itself. The T1 hypointensity + scintigraphy correlation confirms the lesion is metabolically active.

Question 158: Intra-articular injection of which substance is used as a visco-supplementation therapy to improve synovial fluid quality in horses with joint disease?

Hyaluronic acid (sodium hyaluronate) (Correct answer)
Polysulfated glycosaminoglycan (Adequan)
Platelet-rich plasma (PRP)
Methylprednisolone acetate

Correct answer: Hyaluronic acid (sodium hyaluronate)

Sodium hyaluronate (hyaluronic acid) is injected intra-articularly to restore viscosity and lubrication of synovial fluid, acting as visco-supplementation in arthritic joints.

Question 159: A dairy herd is diagnosed with Brucella abortus. Which federal program mandates testing and slaughter of reactor animals in the US?

Voluntary Johne's Disease Herd Status Program
Brucellosis Eradication Program (Correct answer)
National Animal Health Monitoring System
National Poultry Improvement Plan

Correct answer: Brucellosis Eradication Program

The USDA Brucellosis Eradication Program requires identification, testing, and depopulation of Brucella-positive herds.

Question 160: On ultrasound of the urinary bladder, a non-shadowing, gravity-dependent echogenic material that shifts with patient repositioning is MOST consistent with:

Blood clot
Cystic calculi too small to shadow (sludge/crystalluria) (Correct answer)
Transitional cell carcinoma
Polypoid cystitis

Correct answer: Cystic calculi too small to shadow (sludge/crystalluria)

Fine echogenic material that is gravity-dependent and moves freely with repositioning but does not shadow is consistent with fine crystalluria or bladder sludge.

Question 161: A 7-year-old cat with hyperthyroidism is well-controlled on methimazole. The owner reports the cat has developed facial pruritus, excoriations, and a mild leukopenia on recent CBC. What is the MOST appropriate next step?

Switch to carbimazole, as it has a completely different adverse effect profile than methimazole
Discontinue methimazole immediately and transition to radioactive iodine (I-131) or surgical thyroidectomy after stabilization (Correct answer)
Reduce the methimazole dose by 50% and add prednisolone to manage the immune-mediated reaction
Continue methimazole and treat the pruritus symptomatically; leukopenia is expected and not clinically significant

Correct answer: Discontinue methimazole immediately and transition to radioactive iodine (I-131) or surgical thyroidectomy after stabilization

Facial pruritus/excoriations and hematologic abnormalities (leukopenia, thrombocytopenia, agranulocytosis) are recognized adverse effects of methimazole in cats, occurring in approximately 15–20% of treated cats. Agranulocytosis is the most life-threatening hematologic complication. When these reactions occur, methimazole must be discontinued — not dose-reduced — because rechallenge carries high risk of recurrence. Carbimazole is a prodrug that is converted to methimazole in vivo, so it carries the same adverse effect risk and is NOT a safe alternative. After methimazole withdrawal and patient stabilization, definitive therapy (radioactive iodine or surgical thyroidectomy) is the recommended path forward.

Question 162: During a pre-purchase examination, a 5-year-old Dutch Warmblood mare shows a 2/5 lameness on the lunge that is eliminated by an abaxial sesamoid nerve block but NOT by a palmar digital nerve block. High-field MRI of the pastern and foot is normal. Which structure, when anesthetized by the abaxial block but not the palmar digital block, MOST likely harbors the pathology?

The deep digital flexor tendon at the level of the navicular bursa
The impar ligament of the distal sesamoid bone
The digital annular ligaments of the fetlock
The collateral ligaments of the proximal interphalangeal (PIP) joint (Correct answer)

Correct answer: The collateral ligaments of the proximal interphalangeal (PIP) joint

The palmar digital nerve block desensitizes the caudal third of the foot including the navicular region, the DIP joint, and solar corium. The abaxial sesamoid block additionally desensitizes the PIP joint, fetlock, and proximal pastern structures. When the abaxial block is positive but the palmar digital block is negative, the pathology must lie in the region uniquely anesthetized by the more proximal block — most commonly the collateral ligaments or the PIP joint itself. MRI being normal of the distal foot further narrows the source to the pastern/PIP region.

Question 163: A cat with chronic vomiting undergoes endoscopic biopsy showing diffuse infiltration of small lymphocytes in the lamina propria. PARR testing confirms clonality. Which diagnosis is confirmed?

Mast cell tumor
Large cell lymphoma
Inflammatory bowel disease
Small cell lymphoma (Correct answer)

Correct answer: Small cell lymphoma

Clonal small lymphocyte infiltration confirmed by PCR for antigen receptor rearrangement (PARR) distinguishes small cell lymphoma from IBD, which is polyclonal.

Question 164: Osteochondrosis dissecans (OCD) in horses most commonly affects which joint when presenting as tarsal lameness in young Thoroughbreds?

Tarsometatarsal joint
Distal intertarsal joint
Proximal interphalangeal (pastern) joint
Tarsocrural (tibiotarsal) joint (Correct answer)

Correct answer: Tarsocrural (tibiotarsal) joint

OCD most commonly affects the tarsocrural joint in horses, particularly the distal intermediate ridge of the tibia and the lateral trochlear ridge of the talus.

Question 165: Which class of drugs can cause crystalluria and urinary obstruction in dogs, particularly in acidic urine?

Sulfonamides (Correct answer)
Aminoglycosides
Tetracyclines
Fluoroquinolones

Correct answer: Sulfonamides

Sulfonamides can precipitate in acidic urine and form crystals, potentially causing crystalluria, hematuria, and renal tubular obstruction.

Question 166: A 7-year-old female spayed Standard Poodle presents with a history of waxing and waning lethargy, vomiting, and anorexia. On physical examination, she is quiet but responsive, with a heart rate of 60 bpm and weak femoral pulses. Bloodwork reveals hyponatremia, hyperkalemia, and azotemia. Which of the following is the most definitive diagnostic test for this dog's suspected condition?

Abdominal ultrasound
Endogenous ACTH concentration
ACTH stimulation test (Correct answer)
Low-dose dexamethasone suppression test

Correct answer: ACTH stimulation test

The clinical signs (lethargy, vomiting, anorexia), signalment (Standard Poodle), and classic electrolyte abnormalities (hyponatremia, hyperkalemia) are highly suggestive of hypoadrenocorticism (Addison's disease). The definitive diagnosis of hypoadrenocorticism is made by performing an ACTH stimulation test, which will show a low resting cortisol and a negligible response to ACTH administration.

Question 167: Which reproductive toxin produced by endophyte-infected tall fescue grass causes 'summer slump' and reduced pregnancy rates in beef cows?

Ergovaline (Correct answer)
Fumonisin B1
Deoxynivalenol
Zearalenone

Correct answer: Ergovaline

Ergovaline from the Neotyphodium coenophialum endophyte causes vasoconstriction, hyperthermia, and poor reproductive performance in cattle grazing infected fescue.

Question 168: During a routine health exam on a 3-year-old Burmese python, you palpate a mid-body mass. Ultrasound reveals a well-defined, echogenic structure with posterior acoustic shadowing adjacent to the left kidney. The snake has been fed a rodent diet exclusively and appears otherwise healthy. What is the most likely diagnosis and the most important next diagnostic step?

Renal calculus — measure uric acid and perform contrast radiography to assess urinary outflow (Correct answer)
Hepatic lipidosis — obtain a liver biopsy via endoscopy to confirm lipid vacuolation
Paramyxovirus-associated hepatocellular carcinoma — submit serology for Ferlavirus antibodies
Nutritional secondary hyperparathyroidism — measure ionized calcium and PTH levels

Correct answer: Renal calculus — measure uric acid and perform contrast radiography to assess urinary outflow

In snakes, a well-defined echogenic structure with posterior acoustic shadowing adjacent to the kidney is characteristic of a nephrolith (renal calculus). Snakes are uricotelic, and uric acid nephropathy with urolithiasis is the most common renal pathology in captive pythons, often secondary to dehydration, excess protein, or renal disease. The critical next step is measuring uric acid (hyperuricemia suggests active renal impairment) and using contrast radiography or CT to determine if urinary outflow is obstructed. Hepatic lipidosis and hepatocellular carcinoma are not consistent with acoustic shadowing adjacent to the kidney.

Question 169: Both FIP types are fatal and progressive.

False
True (Correct answer)

Correct answer: True

Both the 'wet' (effusive) and 'dry' (non-effusive) forms of Feline Infectious Peritonitis (FIP) are progressive and, if left untreated, are almost invariably fatal. The disease causes widespread inflammation and organ damage, leading to a rapid decline in health, making the statement true.

Question 170: A commercial sow farm reports a sudden increase in late-term abortions, stillbirths, and weak-born piglets across multiple farrowing rooms. Serology confirms Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). Which viral characteristic best explains the reproductive failure observed?

PRRSV preferentially infects uterine endometrial cells, causing direct placental necrosis
PRRSV crosses the placenta during early gestation and integrates into fetal DNA
PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester (Correct answer)
PRRSV causes reproductive failure exclusively through induction of hyperprogesteronemia

Correct answer: PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester

PRRSV targets porcine alveolar macrophages (PAMs) and monocyte-derived cells. During viremia — which is most consequential in the last trimester — virus crosses into the fetoplacental unit, causing fetal infection, death, and mummification. Early gestation infection rarely causes fetal loss; late gestation is the vulnerable window.

Question 171: Amlodipine is the first-line treatment for systemic hypertension in cats. What is its primary mechanism of action?

Beta-adrenergic receptor blockade
Calcium channel blockade (Correct answer)
Angiotensin-converting enzyme (ACE) inhibition
Alpha-adrenergic receptor antagonism

Correct answer: Calcium channel blockade

Amlodipine is a dihydropyridine calcium channel blocker. Its primary effect is to block the influx of calcium into vascular smooth muscle cells, which leads to peripheral vasodilation and a subsequent decrease in systemic blood pressure. ACE inhibitors (like benazepril), beta-blockers (like atenolol), and alpha-antagonists (like prazosin) are other classes of antihypertensive drugs with different mechanisms of action.

Question 172: After falling from a 25-foot cliff, a 6-year-old corgi develops opisthotonus, thoracic limb hyperextension, and rear limb paraplegia. Which of the following is the lesion's most likely location?

C1-C5
T3-L3 (Correct answer)
S1-S3
C6-T2

Correct answer: T3-L3

Opisthotonus, thoracic limb hyperextension (Schiff-Sherrington posture), and rear limb paraplegia are classic signs of a severe spinal cord lesion in the thoracolumbar region (T3-L3). The Schiff-Sherrington posture indicates a lesion between T3 and L3, which disinhibits the extensor muscles of the thoracic limbs, while the paraplegia points to the primary lesion affecting the spinal cord segments controlling the hind limbs.

Question 173: A positive response to a distal limb flexion test in a horse is most useful for localizing pain to which general anatomical area?

Carpus and proximal metacarpal region
Stifle and tarsus
Metacarpophalangeal joint and structures distal to it (Correct answer)
Elbow and shoulder

Correct answer: Metacarpophalangeal joint and structures distal to it

The distal limb flexion test specifically applies pressure to the joints and associated soft tissues of the fetlock, pastern, and coffin joint. A positive response (an increase in lameness after the hold) suggests a pain source within this region. While not perfectly specific, it effectively rules out primary pain from more proximal structures like the carpus, stifle, or shoulder, which are not significantly stressed by this particular test.

Question 174: Which federal regulation requires interstate shipment of livestock to be accompanied by a Certificate of Veterinary Inspection (CVI)?

Virus-Serum-Toxin Act
Federal Meat Inspection Act
Animal Health Protection Act (Correct answer)
Animal Welfare Act

Correct answer: Animal Health Protection Act

The Animal Health Protection Act authorizes USDA APHIS to regulate interstate movement of animals, requiring CVIs for most livestock shipments.

Question 175: A 3-year-old Thoroughbred filly sustained a non-displaced condylar fracture of the third metacarpus during a race. What is the recommended surgical treatment to allow return to racing?

Stall rest with a full limb cast for 12 weeks
Condylar resection
Robert Jones bandage and controlled exercise
Internal fixation with cortical lag screws placed perpendicular to the fracture line (Correct answer)

Correct answer: Internal fixation with cortical lag screws placed perpendicular to the fracture line

Non-displaced condylar fractures of the third metacarpus are best managed with internal fixation using cortical lag screws to provide interfragmentary compression and allow earlier return to training.

Question 176: A 9-year-old Miniature Schnauzer presents with acute pancreatitis confirmed on abdominal ultrasound and elevated spec cPL. Three days into hospitalization with IV fluids and analgesia, the dog develops icterus. Bilirubin is 8.2 mg/dL (predominantly direct). ALP is 1,200 U/L and GGT is 180 U/L. The dog remains anorexic. Abdominal ultrasound now shows a dilated common bile duct at 6 mm. What is the most likely underlying cause of the new icterus?

Hepatic lipidosis developing from prolonged anorexia
Drug-induced cholestasis from opioid administration
Extrahepatic biliary obstruction (EHBO) secondary to pancreatic inflammation (Correct answer)
Concurrent immune-mediated hemolytic anemia triggered by pancreatitis

Correct answer: Extrahepatic biliary obstruction (EHBO) secondary to pancreatic inflammation

The combination of acute pancreatitis, predominantly direct (conjugated) hyperbilirubinemia, markedly elevated ALP and GGT (cholestatic pattern), and a dilated common bile duct (>5 mm in dogs is abnormal) is classic for extrahepatic biliary obstruction (EHBO). Pancreatic inflammation causes edema and compression of the common bile duct as it traverses the mesoduodenum adjacent to the pancreas. IMHA would cause predominantly indirect (unconjugated) hyperbilirubinemia with spherocytes and a positive Coombs test. Hepatic lipidosis is more characteristic of cats. Opioid-induced sphincter of Oddi spasm can cause mild biliary dilation but typically does not cause this degree of bilirubinemia.

Question 177: A cat ingests mouse bait containing brodifacoum. How long after ingestion can clinical signs of coagulopathy be expected?

3–5 days (Correct answer)
7–10 days
12–24 hours
Within 2 hours

Correct answer: 3–5 days

Brodifacoum depletes vitamin K-dependent clotting factors; signs appear after existing factors are consumed, typically 3–5 days post-ingestion.

Question 178: A 3-year-old Thoroughbred filly in training develops acute hindlimb lameness after a workout. A 'popping' sound was heard at the moment of injury, and there is marked stifle effusion. The MOST likely diagnosis is:

Upward fixation of the patella
Hip luxation
Femoral nerve paralysis
Patellar fracture or cranial cruciate ligament injury (Correct answer)

Correct answer: Patellar fracture or cranial cruciate ligament injury

Acute onset of severe stifle lameness with an audible pop and joint effusion in a performance horse is most consistent with patellar fracture or stifle ligament injury.

Question 179: A veterinarian discovers a dog imported from a rabies-endemic country without documentation of vaccination. The appropriate immediate action under US regulations is:

Quarantine the dog for up to 6 months (Correct answer)
File a report with the CDC within 72 hours
Vaccinate and release within 24 hours
Euthanize the dog immediately

Correct answer: Quarantine the dog for up to 6 months

CDC regulations require dogs imported from high-risk countries without valid rabies vaccination to be quarantined for up to 6 months.

Question 180: A 7-year-old Labrador Retriever presents with progressive hindlimb paresis. MRI of the thoracolumbar spine reveals a T2-hyperintense, T1-isointense intradural-extramedullary mass at T10-T11 that shows homogeneous contrast enhancement. The most likely diagnosis is:

Intramedullary astrocytoma
Meningioma (Correct answer)
Nerve sheath tumor
Nephroblastoma

Correct answer: Meningioma

Meningiomas are the most common intradural-extramedullary spinal tumors in dogs. Their MRI characteristics include T2 hyperintensity, T1 isointensity relative to spinal cord, homogeneous contrast enhancement, and a 'dural tail' sign. They are extramedullary (outside the cord but inside the dura), distinguishing them from intramedullary tumors like astrocytomas. Nerve sheath tumors are also intradural-extramedullary but more commonly affect nerve roots and show heterogeneous enhancement. Nephroblastoma occurs in the spinal cord of young dogs but is intramedullary.

Question 181: Which test best differentiates a vaccinated cat from a truly FeLV-infected cat when using a standard ELISA?

Virus isolation in culture
The ELISA detects p27 antigen which vaccines do not induce (Correct answer)
Western blot for gp70 antigen
PCR for proviral DNA

Correct answer: The ELISA detects p27 antigen which vaccines do not induce

FeLV ELISA tests detect the p27 core antigen released by replicating virus, not antibody, so vaccination does not produce a positive result.

Question 182: A 2-year-old Border Collie presents with episodic muscle tremors and facial rubbing after exercise. Ionized calcium is 0.78 mmol/L (normal 1.12–1.40). Which condition is the most common cause of hypocalcemia in young adult dogs?

Chronic renal failure
Primary hypoparathyroidism
Vitamin D deficiency
Eclampsia (puerperal tetany) (Correct answer)

Correct answer: Eclampsia (puerperal tetany)

Eclampsia due to calcium loss through milk production in periparturient females is the most common cause of acute hypocalcemia in young adult dogs.

Question 183: A cat on long-term phenobarbital for seizure control is started on chloramphenicol for a resistant infection. Two weeks later the owner reports markedly increased sedation and ataxia with no dose change of phenobarbital. What is the most likely pharmacokinetic explanation?

Chloramphenicol inhibits hepatic cytochrome P450 enzymes, reducing phenobarbital clearance and raising its serum concentration (Correct answer)
Chloramphenicol directly potentiates GABA-A receptor activity, synergizing with phenobarbital
Chloramphenicol competes with phenobarbital for plasma protein binding, increasing free phenobarbital fraction
Chloramphenicol induces P-glycoprotein, increasing CNS penetration of phenobarbital

Correct answer: Chloramphenicol inhibits hepatic cytochrome P450 enzymes, reducing phenobarbital clearance and raising its serum concentration

Chloramphenicol is a potent inhibitor of hepatic cytochrome P450 enzymes (particularly CYP2B and CYP3A isoforms) in cats. Phenobarbital is primarily metabolized by these hepatic CYP enzymes. When chloramphenicol inhibits phenobarbital's metabolism, clearance decreases and phenobarbital plasma concentrations rise significantly — often into toxic ranges — despite no change in dose. This is a clinically important drug interaction in feline practice. Phenobarbital monitoring (serum levels) is mandatory when adding chloramphenicol, and dose reduction is frequently required.

Question 184: A 7-year-old German Shepherd presents with progressive, non-painful pelvic limb ataxia and weakness over 12 months. The dog is ambulatory but shows proprioceptive deficits bilaterally. Spinal radiographs are normal. CSF is normal. Which diagnosis is most consistent with this presentation?

Degenerative myelopathy (DM) (Correct answer)
Fibrocartilaginous embolism (FCE)
Lumbosacral stenosis (cauda equina syndrome)
Meningomyelitis due to Neospora caninum

Correct answer: Degenerative myelopathy (DM)

Degenerative myelopathy (DM) in German Shepherds is a progressive, non-painful, symmetric upper motor neuron disease of late middle-age to older dogs, with normal imaging and CSF. It is associated with the SOD1 gene mutation. FCE is acute and often asymmetric. Lumbosacral stenosis causes pain and lower motor neuron signs. Neospora causes a painful, ascending LMN polyradiculoneuritis.

Question 185: A 7-year-old German Shepherd presents with progressive rear limb ataxia. Spinal MRI reveals a well-defined, intradural extramedullary lesion at T10-T11 that is isointense on T1, hyperintense on T2, and demonstrates marked homogeneous contrast enhancement. The adjacent cord shows a 'cap sign' (hemosiderin deposition). Which diagnosis is MOST consistent with these findings?

Peripheral nerve sheath tumor
Meningioma (Correct answer)
Nephroblastoma (spinal)
Arachnoid diverticulum

Correct answer: Meningioma

Meningiomas are the most common intradural extramedullary spinal tumors in dogs, typically appearing isointense on T1, hyperintense on T2, with intense homogeneous contrast enhancement. The 'cap sign'—hemosiderin staining at the poles of the mass—is a specific MRI feature strongly associated with spinal meningiomas due to chronic microhemorrhage. Nephroblastomas occur in young dogs and are typically intramedullary. Peripheral nerve sheath tumors tend to extend through neural foramina. Arachnoid diverticula do not enhance with contrast.

Question 186: An ultrasound of a 10-year-old cat's liver reveals a hyperechoic nodule with a distal 'ring-down' artifact. This artifact pattern is most consistent with which finding?

Biliary cystadenoma with gas-forming bacteria
A focal area of hepatic lipidosis causing acoustic enhancement
Hepatic mineralization or dystrophic calcification within the nodule (Correct answer)
A mast cell tumor metastasis producing intracellular histamine granules

Correct answer: Hepatic mineralization or dystrophic calcification within the nodule

Ring-down artifact (also called comet-tail artifact in certain contexts) appears as a series of reverberating echoes trailing deep to a reflective interface — classically associated with mineralization, metal, or gas. A hyperechoic hepatic nodule with this artifact is characteristic of dystrophic calcification or mineralized granuloma (e.g., old inflammatory lesion, fungal granuloma). Gas-containing lesions produce true ring-down/comet-tail artifacts but would be expected in a different clinical context. Lipidosis produces diffuse hyperechogenicity, not a discrete nodule with distal artifact.

Question 187: In a cow-calf operation managing johne's disease (paratuberculosis), a producer asks about the MAP (Mycobacterium avium subsp. paratuberculosis) fecal PCR sensitivity in different clinical stages of disease. You are designing a test-and-cull program and want to maximize detection of infectious animals before they show clinical signs. Which statement MOST accurately reflects the limitations of fecal PCR in this context?

A single negative fecal PCR in a seronegative animal rules out MAP infection with >98% specificity
Fecal PCR sensitivity is highest in late subclinical/early clinical animals but drops significantly in early subclinical animals due to intermittent low-level shedding (Correct answer)
Fecal PCR has >95% sensitivity in subclinical animals with low-level MAP shedding, making a single test sufficient for herd clearance
Fecal PCR is unreliable in cattle under 24 months because passive fecal shedding of ingested MAP confounds results

Correct answer: Fecal PCR sensitivity is highest in late subclinical/early clinical animals but drops significantly in early subclinical animals due to intermittent low-level shedding

MAP infection in cattle follows a long subclinical incubation (often 2–5 years) during which shedding is intermittent and at very low levels — below the detection threshold of fecal PCR. Sensitivity of a single fecal PCR in early subclinical animals is estimated at only 15–30%, rising to 50–70% in late subclinical/early clinical animals with heavier continuous shedding, and approaching 90%+ in clinically affected animals with protein-losing enteropathy. This is the critical limitation: test-and-cull programs based on a single fecal PCR will miss the majority of infected animals in the subclinical phase — exactly when you most want to detect them. Repeated annual testing over 3–5 years is required to achieve meaningful herd prevalence reduction. Passive shedding in young calves is a real concern for ELISA interpretation but less so for PCR at the clone level. Specificity of PCR is high (>99%) but sensitivity is the Achilles heel.

Question 188: During anesthesia of a ball python for surgical removal of a retained spectacle, the veterinarian notes apnea persisting more than 10 minutes after isoflurane is discontinued. Which of the following BEST explains why reptiles are particularly susceptible to prolonged post-anesthetic apnea compared to mammals?

Reptiles have a tripartite heart with significant right-to-left cardiac shunting that recirculates anesthetic vapor and delays washout
The reptilian lung has a more extensive blood-gas barrier that delays anesthetic elimination via pulmonary routes
Reptiles have a higher metabolic rate and consume anesthetic agents more rapidly, leading to prolonged tissue saturation
Reptiles rely primarily on peripheral chemoreceptors sensitive to PO2 rather than central CO2/pH-driven ventilatory drive, making hypercapnia a poor respiratory stimulus (Correct answer)

Correct answer: Reptiles rely primarily on peripheral chemoreceptors sensitive to PO2 rather than central CO2/pH-driven ventilatory drive, making hypercapnia a poor respiratory stimulus

Reptiles have a blunted central chemoreceptor response to hypercapnia compared to mammals. Their ventilatory drive depends more on peripheral oxygen sensing, and they tolerate wide swings in PCO2 with minimal respiratory response. This means rising CO2 after anesthesia does not reliably stimulate breathing, causing prolonged apnea. The cardiac shunt (option D) contributes to anesthetic uptake/elimination differences but is not the primary reason for post-anesthetic apnea.

Question 189: What is the significance of 'air bronchograms' on thoracic radiographs?

The bronchi contain fluid while the alveoli are normally aerated
Air-filled bronchi are visible because surrounding alveoli are fluid-filled, indicating alveolar disease (Correct answer)
Pleural air outlines the bronchi from the outside
Gas is present within the bronchial walls

Correct answer: Air-filled bronchi are visible because surrounding alveoli are fluid-filled, indicating alveolar disease

Air bronchograms occur when alveolar consolidation or fluid makes normally invisible air-filled bronchi visible by contrast.

Question 190: Which of the following best describes the pharmacokinetic term 'volume of distribution' (Vd)?

The rate at which a drug is eliminated from the body
The time for plasma drug concentration to decrease by 50%
A theoretical volume relating plasma drug concentration to total drug in the body (Correct answer)
The fraction of an oral dose reaching systemic circulation

Correct answer: A theoretical volume relating plasma drug concentration to total drug in the body

Volume of distribution is a theoretical volume that relates the total amount of drug in the body to the concentration measured in plasma.

Question 191: During evaluation of a 9-year-old Andalusian with chronic bilateral forelimb lameness, distal limb flexion tests are strongly positive. MRI of the foot reveals a core lesion of the deep digital flexor tendon (DDFT) within the navicular bursa. Intra-bursal analgesia eliminates 90% of lameness bilaterally. Conservative management has failed after 8 months. Which surgical option directly addresses the pathological tension on the DDFT core lesion while preserving limb function?

Inferior check ligament desmotomy (accessory ligament of the DDFT) (Correct answer)
Coffin joint arthrodesis
Navicular suspensory ligament desmotomy via a palmar approach
Palmar digital neurectomy at the level of the proximal sesamoid bones

Correct answer: Inferior check ligament desmotomy (accessory ligament of the DDFT)

Inferior check ligament (accessory ligament of the DDFT) desmotomy reduces tension on the DDFT by eliminating the static tethering effect of the accessory ligament, allowing the DDFT to bear reduced load and facilitating healing of the core lesion. It is the preferred surgical option when MRI confirms DDFT pathology within the navicular bursa. Palmar digital neurectomy provides analgesia but does not address the biomechanical cause and carries risks of catastrophic tendon rupture.

Question 192: An 8-year-old Cavalier King Charles Spaniel undergoes brain MRI for evaluation of vestibular signs and progressive cerebellar ataxia. Sagittal T2-weighted images reveal caudal displacement of the cerebellar vermis through the foramen magnum with effacement of the cisterna magna. There is no hydrocephalus. Additionally, a longitudinal fluid-filled cavity is identified within the cervical spinal cord parenchyma that is isointense to CSF on all sequences. Which TWO conditions are being described together?

Dandy-Walker malformation and hydromyelia
Caudal occipital malformation syndrome (COMS) and syringomyelia (Correct answer)
Cerebellar cortical abiotrophy and central canal dilation
Chiari-like malformation type II and diplomyelia

Correct answer: Caudal occipital malformation syndrome (COMS) and syringomyelia

Caudal occipital malformation syndrome (COMS), also called Chiari-like malformation, is extremely prevalent in the Cavalier King Charles Spaniel breed. It is characterized by caudal displacement of the cerebellum through the foramen magnum, effacement of the cisterna magna, and obstruction of CSF flow. This impaired CSF circulation leads to the formation of a syrinx (syringomyelia)—a CSF-filled cavity within the spinal cord parenchyma that is isointense to CSF on all MRI sequences. The combination of COMS + syringomyelia is a well-described clinicopathological entity in this breed. Dandy-Walker involves cerebellar hypoplasia with a cystic posterior fossa, not caudal herniation.

Question 193: A 7-year-old Thoroughbred mare undergoes emergency celiotomy for small colon impaction. The surgeon identifies a mesenteric rent through which small intestine has passed and become strangulated. After reducing the hernia and assessing the intestine, the surgeon should:

Perform a bypass anastomosis without closing the rent
Leave the mesenteric rent open to prevent recurrence
Close the mesenteric rent with simple interrupted sutures after intestinal assessment (Correct answer)
Pack the rent with omentum and close the abdomen

Correct answer: Close the mesenteric rent with simple interrupted sutures after intestinal assessment

Mesenteric rents must be closed after reducing the herniated intestine to prevent recurrence of internal herniation and strangulation.

Question 194: A 6-month-old calf dies acutely. Necropsy reveals a 'paint-brush' hemorrhage pattern on the epicardium, fibrinonecrotic plaques in the abomasum, and hemorrhagic lymph nodes. Which pathologic process most likely caused these lesions?

Johne's disease with chronic protein-losing enteropathy
Septicemia with gram-negative lipopolysaccharide-mediated disseminated intravascular coagulation (DIC) (Correct answer)
Vitamin E/selenium deficiency (white muscle disease)
Copper toxicity with intravascular hemolysis

Correct answer: Septicemia with gram-negative lipopolysaccharide-mediated disseminated intravascular coagulation (DIC)

Petechial/ecchymotic hemorrhages (paint-brush pattern) on serosal surfaces combined with hemorrhagic lymph nodes and mucosal necrosis are classic findings of endotoxemia-induced DIC in calves, most commonly from gram-negative septicemia (e.g., Salmonella, E. coli). LPS activates the coagulation cascade, consuming clotting factors and causing bleeding diathesis. White muscle disease shows pale streaking of skeletal/cardiac muscle.

Question 195: During lameness examination on the lunge, a horse with LEFT forelimb lameness will characteristically:

Show a hip hike when the left forelimb strikes
Nod the head DOWN when the right forelimb strikes
Lower the croup when lunging to the right
Nod the head UP when the left forelimb strikes (Correct answer)

Correct answer: Nod the head UP when the left forelimb strikes

With a painful forelimb, the horse lifts (nods up) the head when the painful limb contacts the ground to reduce load, and nods down on the sound limb.

Question 196: Which anatomical site is preferred for intramuscular injections in birds?

Wing web
Epaxial muscle
Quadriceps muscle
Pectoral muscle (Correct answer)

Correct answer: Pectoral muscle

The pectoral muscle is the preferred IM injection site in birds because of its large mass and easy accessibility.

Question 197: A 12-year-old Warmblood sport horse presents with insidious-onset bilateral forelimb lameness that is worse on hard surfaces and improves after 20 minutes of work. Flexion tests are mildly positive bilaterally. Nerve blocks are unremarkable through the pastern. Radiographs reveal bilateral palmar osteochondral fragments at the proximal interphalangeal joint. Which finding on MRI would most strongly implicate the distal interphalangeal joint collateral ligaments as the primary pain source in this presentation?

Diffuse synovial thickening of the distal interphalangeal joint with moderate joint effusion
Increased T1 signal in the navicular bone medullary cavity
Cartilage thinning on the lateral condyle of the middle phalanx
T2 hyperintensity within the collateral ligament substance with associated focal subchondral bone edema at the ligament enthesis (Correct answer)

Correct answer: T2 hyperintensity within the collateral ligament substance with associated focal subchondral bone edema at the ligament enthesis

T2 hyperintensity within the collateral ligament substance paired with focal subchondral bone edema at the enthesis indicates active ligamentous injury with an enthesopathy response — the hallmark MRI signature of collateral ligament desmitis at the DIP joint. Joint effusion and synovial thickening are nonspecific secondary findings, cartilage thinning points to osteoarthritis rather than ligamentous origin, and increased T1 navicular signal suggests fatty change or sclerosis, not collateral ligament pathology.

Question 198: A cow in early lactation is treated with systemic flunixin meglumine (2.2 mg/kg IV) for acute coliform mastitis. Which mechanism best explains why this NSAID may paradoxically worsen endotoxemia outcomes despite reducing fever?

Blockade of prostacyclin (PGI2) synthesis removes a protective vasodilatory signal in splanchnic vasculature, worsening gut ischemia (Correct answer)
Flunixin competitively inhibits TNF-α receptors, impairing the cytokine cascade needed for bacterial clearance
COX inhibition shifts arachidonic acid metabolism toward the 5-lipoxygenase pathway, increasing leukotriene-mediated vascular permeability
Flunixin upregulates thromboxane A2 production by sparing COX-2 activity in platelets, promoting microthrombi formation

Correct answer: Blockade of prostacyclin (PGI2) synthesis removes a protective vasodilatory signal in splanchnic vasculature, worsening gut ischemia

In endotoxemia, prostacyclin (PGI2) serves a protective role in maintaining splanchnic blood flow through vasodilation. Flunixin inhibits both COX-1 and COX-2, blocking PGI2 synthesis. Loss of this protective vasodilation in the gut vasculature worsens mucosal ischemia and intestinal barrier failure, potentially allowing greater endotoxin translocation. While fever reduction is clinically desirable, the trade-off in severe endotoxemia is impaired splanchnic perfusion. This explains why outcome data on NSAID use in severe bovine endotoxemia is mixed and dose timing matters.

Question 199: Tritrichomonas foetus causes large-bowel diarrhea in cats. Which drug is currently recommended for treatment despite limited efficacy data?

Metronidazole
Fenbendazole
Ronidazole (Correct answer)
Sulfadimethoxine

Correct answer: Ronidazole

Ronidazole is the only drug shown to eliminate Tritrichomonas foetus in cats, though resistance and neurotoxicity at high doses are concerns.

Question 200: A 5-year-old dog presents with acute vomiting and abdominal pain. Abdominal radiographs reveal a segment of small intestine that is severely dilated with gas, proximal to a segment of normal-caliber, empty-appearing small intestine. What is this radiographic finding, often referred to as 'two populations of bowel,' most indicative of?

Functional ileus
Pancreatitis
Mechanical obstruction (Correct answer)
Gastroenteritis

Correct answer: Mechanical obstruction

The presence of two distinct populations of bowel (one severely dilated and one normal or empty) is a classic radiographic sign of a complete or high-grade mechanical obstruction. The intestine proximal to the blockage becomes distended with gas and fluid, while the intestine distal to the obstruction remains empty. Functional ileus and gastroenteritis typically cause a more generalized, mild to moderate dilation of the intestines without a clear transition point.

Question 201: A 9-year-old dog with a 3-week history of polyuria/polydipsia has a urine specific gravity of 1.008, sodium of 158 mEq/L, and fails to concentrate urine after water deprivation but responds to exogenous ADH. The diagnosis is:

Central diabetes insipidus (Correct answer)
Hyperadrenocorticism
Psychogenic polydipsia
Nephrogenic diabetes insipidus

Correct answer: Central diabetes insipidus

Central diabetes insipidus is confirmed when the patient fails the water deprivation test but concentrates urine in response to exogenous ADH (desmopressin), indicating a lack of endogenous ADH production.

Question 202: A 9-year-old warmblood mare shows intermittent right forelimb lameness that is consistently worse the day after competition and improves with rest. On evaluation, the horse exhibits a prominent 'head nod' lameness of 3/5 at the trot on a hard surface that reduces to 1/5 on a soft surface. Palmar digital nerve blocks are negative. Low 4-point blocks are negative. An abaxial sesamoid nerve block on the right forelimb abolishes the lameness. However, intrasynovial anesthesia of the metacarpophalangeal joint, the navicular bursa, and the distal interphalangeal joint are all negative. What anatomical structure, frequently underdiagnosed, should be the primary focus of further diagnostic workup?

The digital flexor tendon sheath, with particular attention to the proximal digital annular ligament and manica flexoria (Correct answer)
The collateral ligaments of the proximal interphalangeal joint
The ergot and associated fibrocartilage of the palmar fetlock
The distal sesamoidean impar ligament

Correct answer: The digital flexor tendon sheath, with particular attention to the proximal digital annular ligament and manica flexoria

When an abaxial sesamoid block is positive but all three major intrasynovial blocks (MCP joint, navicular bursa, DIP joint) are negative, the pain source is within the digital flexor tendon sheath (DFTS) or its associated structures. The DFTS was not blocked in this sequence. Within the sheath, the manica flexoria (the sleeve of SDFT that partially encircles the DDFT) and the proximal digital annular ligament are frequently overlooked sources of pathology — particularly in sport horses with repetitive athletic loading. The next step is intrasynovial analgesia of the DFTS itself, followed by high-field MRI or tenoscopy if positive. The other listed structures would have been blocked or at least partially desensitized by the negative blocks already performed.

Question 203: In llamas, the most typical source of bony facial tumors is

Facial bone fracture
Osteomyelitis
Ossifying fibroma
Tooth root abscess (Correct answer)

Correct answer: Tooth root abscess

In llamas, tooth root abscesses are a very common cause of bony facial tumors or swellings. The infection and inflammation associated with an abscess can lead to significant osteomyelitis and reactive bone proliferation in the surrounding facial bones. This presents as a firm, bony mass, making tooth root abscesses the most frequent etiology for such lesions in this species.

Question 204: A horse undergoes exploratory laparotomy for small intestinal volvulus. After 3 hours of surgery, the horse develops tachycardia, hypotension, and pale mucous membranes. Lactate is 12 mmol/L. What does this lactate value primarily indicate?

Normal response to surgical stress
Excessive intraoperative fluids causing hemodilution
Severe tissue hypoperfusion and anaerobic metabolism (Correct answer)
Hepatic failure from anesthetic agents

Correct answer: Severe tissue hypoperfusion and anaerobic metabolism

A lactate of 12 mmol/L indicates severe systemic hypoperfusion with anaerobic metabolism, which is a poor prognostic indicator in equine colic surgery.

Question 205: A dog presents with a suspected diaphragmatic hernia. Which radiographic finding would MOST suggest a peritoneopericardial diaphragmatic hernia (PPDH) rather than a traumatic diaphragmatic hernia?

Acute onset following trauma
Enlarged globoid cardiac silhouette without pleural effusion (Correct answer)
Gas-filled bowel loops in the pleural space
Discontinuity of the diaphragmatic line

Correct answer: Enlarged globoid cardiac silhouette without pleural effusion

PPDH is a congenital defect where abdominal organs herniate into the pericardial sac, causing an enlarged cardiac silhouette, unlike traumatic hernias where organs enter the pleural space.

Question 206: A dairy herd has a transition cow period disorder rate of 25% for clinical ketosis. Which nutritional management strategy is most effective at reducing periparturient ketosis?

Feeding high-grain diet 6 weeks before calving
Implementing a negative DCAD (Dietary Cation-Anion Difference) diet prepartum
Increasing body condition score to 4.0 or higher at dry-off
Feeding propylene glycol as a preventive drench in the close-up dry period (Correct answer)

Correct answer: Feeding propylene glycol as a preventive drench in the close-up dry period

Propylene glycol is a glucogenic precursor that, when drenched preventively in the close-up period or early postpartum, reduces the incidence of clinical ketosis by supporting hepatic gluconeogenesis.

Question 207: Abdominal ultrasound in a 9-year-old spayed Labrador reveals a 3.2 cm splenic mass with a heterogeneous echotexture containing multiple anechoic cavities and a hyperechoic rim. Doppler interrogation shows no internal vascularity within the cavities. Fine-needle aspirate of the solid component yields blood only. Which imaging feature most strongly argues AGAINST a diagnosis of splenic hemangioma in favor of hemangiosarcoma?

Absence of internal Doppler signal within the cavities
Anechoic cavities within the mass representing blood-filled sinusoids
Hyperechoic peripheral rim representing compressed splenic parenchyma
Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture (Correct answer)

Correct answer: Simultaneous detection of a hypoechoic hepatic nodule with similar internal architecture

Splenic hemangioma and hemangiosarcoma can appear nearly identical on ultrasound — both produce heterogeneous masses with blood-filled cavities, and non-diagnostic FNA is common in both. The single most distinguishing imaging feature suggesting malignancy (hemangiosarcoma) is multifocal involvement: a synchronous hepatic lesion with the same architecture strongly implies metastatic hemangiosarcoma, as the liver is the most common metastatic site. Anechoic cavities and absent Doppler flow within cavities are seen in both benign and malignant vascular tumors. The hyperechoic rim is a nonspecific finding seen with any expansile splenic mass causing parenchymal compression.

Question 208: Which antifungal drug is currently the first-line treatment for aspergillosis in birds?

Amphotericin B
Griseofulvin
Ketoconazole
Voriconazole (Correct answer)

Correct answer: Voriconazole

Voriconazole is the preferred antifungal for avian aspergillosis due to its superior efficacy and safety compared to older azoles.

Question 209: On CT of the nasal cavity in a dog with nasal discharge, which finding most strongly suggests fungal rhinitis (Aspergillus) rather than nasal neoplasia?

Mass with smooth margins crossing the midline
Turbinate destruction with preserved nasal septum (Correct answer)
Fluid-filled nasal cavity with intact turbinates
Periosteal reaction along the frontal bones

Correct answer: Turbinate destruction with preserved nasal septum

Aspergillus rhinitis typically causes extensive turbinate lysis/destruction while often leaving the nasal septum relatively intact, unlike neoplasia which often crosses the midline.

Question 210: During dynamic evaluation of a horse on a lunge circle, the examiner notices that forelimb lameness is most pronounced on the OUTSIDE limb when tracking left on a firm surface, but this pattern reverses on soft footing. Which pathological process is most consistent with this footing-dependent reversal?

Proximal suspensory desmitis with axial fiber involvement
Solar bruising of the lateral heel
Distal sesamoidean impar ligament desmopathy
Medial collateral ligament desmitis of the coffin joint (Correct answer)

Correct answer: Medial collateral ligament desmitis of the coffin joint

Collateral ligament desmitis of the distal interphalangeal (coffin) joint produces mediolateral loading-dependent lameness. On firm footing, the inside limb bears greater concussive medial load, but on the outside limb the lateral collateral structure is loaded via centrifugal ground reaction force. Soft footing attenuates peak impact loading and shifts the dominant force vector, reversing which limb appears lame. MRI is the gold standard for confirming collateral ligament lesions that are often missed on radiographs.

Question 211: A cow-calf producer in a selenium-deficient region is using injectable sodium selenite (0.5 mg Se/lb BW) in neonatal calves to prevent white muscle disease. He now wants to supplement pregnant cows pre-calving to improve passive transfer of selenium via colostrum. He asks about adding selenium to the mineral mix at 120 ppm. Which response is most accurate?

This is inappropriate; selenium cannot be supplemented via mineral mixes in cattle and must only be given via injectable or slow-release bolus forms
This is appropriate if the mineral is fed free-choice, because cattle self-regulate selenium intake
This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis (Correct answer)
This is appropriate because dry matter intake of minerals is low enough that 120 ppm selenium is safe and will effectively raise colostral selenium

Correct answer: This is inappropriate; the legal maximum for selenium in cattle mineral supplements is 120 ppm, but actual intake must not exceed 3 mg Se/head/day, which requires calculating expected mineral consumption to avoid toxicosis

The FDA-mandated maximum for selenium in mineral supplements is 90 ppm in complete feeds and up to 700 ppm in salt-based mineral mixes (with a label restriction to 0.3 mg/kg of total diet DM), but the critical practical constraint is that total selenium intake must not exceed 3 mg/head/day to avoid selenium toxicosis. At 120 ppm Se in a mineral mix, if cows consume even 50 g of mineral/day they intake 6 mg Se — double the safe limit. Cattle do NOT self-regulate selenium intake (option C is false). Selenium CAN be supplemented via minerals (option D is false). The key is that the producer must calculate actual mineral consumption and adjust selenium concentration accordingly to stay ≤3 mg/head/day — the concentration alone does not guarantee safety.

Question 212: What is the PRIMARY purpose of measuring the palmar angle of the distal phalanx on a lateral radiograph in a horse with laminitis?

To assess the degree of rotation and aid in corrective shoeing (Correct answer)
To determine the degree of coffin joint arthritis
To evaluate navicular bone morphology
To measure third phalanx bone density

Correct answer: To assess the degree of rotation and aid in corrective shoeing

The palmar angle of P3 on a lateral radiograph quantifies the degree of coffin bone rotation relative to the hoof wall, guiding corrective trimming and shoeing to restore proper alignment.

Question 213: A veterinarian wants to use tramadol for postoperative analgesia in a cat. Which metabolic difference limits tramadol's efficacy in cats compared to humans?

Cats over-express mu-opioid receptors, making them hypersensitive to tramadol
Cats excrete tramadol unchanged in bile, reducing systemic exposure
Cats have reduced CYP2D6 activity and produce very little O-desmethyltramadol (M1), the active opioid metabolite (Correct answer)
Cats rapidly glucuronidate tramadol into an inactive metabolite

Correct answer: Cats have reduced CYP2D6 activity and produce very little O-desmethyltramadol (M1), the active opioid metabolite

Cats have low CYP2D6 activity and generate minimal M1 metabolite, so tramadol's analgesic effect via opioid receptors is substantially reduced.

Question 214: Feline leukemia virus (FeLV) is classified into subtypes based on host range. Which subtype is associated with the most rapid disease progression and immunosuppression?

FeLV-T (Correct answer)
FeLV-A
FeLV-B
FeLV-C

Correct answer: FeLV-T

FeLV-T is highly pathogenic, targets T lymphocytes directly causing profound lymphopenia and accelerated immunodeficiency.

Question 215: A 5-year-old event horse has hindlimb lameness localized to the sacroiliac region by positive pressure on the tuber sacrale and a positive response to gluteal muscle palpation. The BEST imaging modality for confirming sacroiliac pathology is:

Radiography of the pelvis
CT scan of the hindlimb
Radiography of the lumbar spine only
Nuclear scintigraphy or ultrasound of the sacroiliac joint (Correct answer)

Correct answer: Nuclear scintigraphy or ultrasound of the sacroiliac joint

The sacroiliac joint is difficult to image radiographically due to its deep location; nuclear scintigraphy and transrectal or transcutaneous ultrasound are the most effective modalities for evaluating this region.

Question 216: A 7-year-old Great Dane presents with acute, non-productive retching, hypersalivation, and a distended, tympanic abdomen. A right lateral abdominal radiograph is taken. Which radiographic finding is most pathognomonic for gastric dilatation-volvulus (GDV)?

A soft tissue opacity compartmentalizing the gas-filled stomach, creating a 'double bubble' appearance. (Correct answer)
Displacement of the small intestines to the right cranial abdomen.
The presence of gravel or foreign material within the gastric lumen.
Severe gaseous distention of the entire stomach with a normal pyloric position.

Correct answer: A soft tissue opacity compartmentalizing the gas-filled stomach, creating a 'double bubble' appearance.

The classic radiographic sign for GDV on a right lateral view is the compartmentalization of the stomach by a soft tissue band, which is the pylorus folding over the fundus. This creates what is often described as a 'double bubble', 'Smurf hat', or 'Popeye arm' appearance and is pathognomonic for the condition.

Question 217: A 4-year-old DSH cat is being treated for chronic pain with buprenorphine. The owner inadvertently administers a full tablet of acetaminophen (500 mg) intended for herself. Which mechanism is primarily responsible for acetaminophen toxicity in cats compared to dogs and humans?

Cats have enhanced CYP2E1 activity that produces excessive NAPQI from acetaminophen
Cats preferentially shunt acetaminophen through the sulfation pathway, producing toxic sulfate conjugates
Cats lack glutathione reductase, preventing regeneration of glutathione stores
Cats lack sufficient UDP-glucuronosyltransferase 1A6 (UGT1A6) activity to conjugate NAPQI, leading to accumulation (Correct answer)

Correct answer: Cats lack sufficient UDP-glucuronosyltransferase 1A6 (UGT1A6) activity to conjugate NAPQI, leading to accumulation

Cats are exceptionally susceptible to acetaminophen toxicity due to a genetic deficiency in UGT1A6 (and related isoforms), the glucuronidation enzyme responsible for conjugating NAPQI — the reactive intermediate produced by CYP450 metabolism of acetaminophen. Without adequate glucuronidation capacity, NAPQI accumulates, depletes glutathione, and binds covalently to hemoglobin (causing methemoglobinemia and Heinz body formation) and hepatocytes (causing hepatic necrosis). Dogs and humans can glucuronidate NAPQI efficiently; cats largely cannot. The sulfation pathway is also limited in cats and becomes quickly saturated.

Question 218: Methicillin-resistant Staphylococcus aureus (MRSA) has been identified as an occupational zoonosis. Which livestock species is most closely linked to the LA-MRSA (livestock-associated MRSA) ST398 strain?

Swine (Correct answer)
Small ruminants
Poultry
Dairy cattle

Correct answer: Swine

LA-MRSA ST398 is strongly associated with swine and pig farm workers, representing a major veterinary public health concern.

Question 219: Which parameter is most commonly monitored as a critical control point (CCP) during pasteurization of milk?

pH of the final product
Time and temperature of heat treatment (Correct answer)
Coliform count before processing
Fat content percentage

Correct answer: Time and temperature of heat treatment

Time and temperature are the critical control point parameters for pasteurization, as they determine whether pathogens are eliminated.

Question 220: Under the National Incident Management System (NIMS), which position within the Incident Command System (ICS) coordinates animal care activities during a disaster response?

Public Information Officer
Safety Officer
Animal/Technical Specialist or Veterinary Medical Officer (Correct answer)
Logistics Section Chief

Correct answer: Animal/Technical Specialist or Veterinary Medical Officer

Veterinary Medical Officers or Animal Technical Specialists serve within ICS to coordinate animal care, biosecurity, and zoonotic disease control during disasters.

Question 221: A 7-year-old intact male Golden Retriever presents with a 3-week history of progressive tetraparesis, bilateral pelvic limb weakness, and marked muscle wasting. MRI reveals an intradural-extramedullary mass at T3. CSF analysis shows albuminocytologic dissociation. Histopathology of the mass is most consistent with which diagnosis?

Spinal cord astrocytoma
Nephroblastoma
Meningioma
Peripheral nerve sheath tumor (Correct answer)

Correct answer: Peripheral nerve sheath tumor

Peripheral nerve sheath tumors (PNSTs) are the most common intradural-extramedullary spinal tumors in dogs, particularly large breeds. They arise from Schwann cells or perineural fibroblasts, and CSF frequently shows albuminocytologic dissociation (elevated protein without significant pleocytosis) due to blood-brain barrier disruption adjacent to the mass. Meningiomas are more common in the intracranial compartment in dogs. Nephroblastomas are typically intramedullary and occur in young dogs (usually <3 years) at T10–L2. Astrocytomas are intramedullary.

Question 222: A 7-year-old Poodle presents with a PCV of 18%, MCV of 110 fL (macrocytosis), and a low serum cobalamin (B12). What is the most likely cause?

Chronic disease anemia
Cobalamin deficiency causing megaloblastic anemia (Correct answer)
Iron deficiency anemia
Feline leukemia virus-like anemia

Correct answer: Cobalamin deficiency causing megaloblastic anemia

Cobalamin deficiency impairs DNA synthesis in RBC precursors, causing large, immature red cells (macrocytosis) and non-regenerative megaloblastic anemia.

Question 223: A cat presents with bilateral anterior uveitis. FIP testing is negative. Which other infectious agent should be high on the differential list?

Toxoplasma gondii (Correct answer)
Feline calicivirus
Feline panleukopenia virus
Feline parvovirus

Correct answer: Toxoplasma gondii

Toxoplasma gondii is a leading cause of feline uveitis and should be tested via serology when FIP is ruled out.

Question 224: On orthogonal radiographs of a long bone, periosteal new bone with a 'sunburst' pattern is MOST characteristic of:

Septic osteomyelitis
Primary bone tumor (osteosarcoma) (Correct answer)
Nutritional secondary hyperparathyroidism
Hypertrophic osteopathy

Correct answer: Primary bone tumor (osteosarcoma)

A sunburst or spiculated periosteal reaction radiating perpendicular to the cortex is a classic aggressive pattern associated with osteosarcoma.

Question 225: A 10-year-old castrated male mixed-breed dog presents for evaluation of a 3-month history of regurgitation, weight loss, and occasional aspiration pneumonia. Cervical radiographs and fluoroscopic swallowing study confirm cricopharyngeal achalasia-like dysphagia with normal esophageal motility. EMG of the cricopharyngeal muscle shows spontaneous fibrillation potentials and positive sharp waves. Serology for acetylcholine receptor antibodies is negative. Which diagnostic step is MOST likely to reveal a treatable underlying systemic cause for this dog's condition?

Thoracic CT for anterior mediastinal mass
Repetitive nerve stimulation study for a decremental response indicating myasthenia gravis
Muscle biopsy of the temporalis for inflammatory polymyositis (Correct answer)
Serum thyroxine (T4) and TSH measurement for hypothyroidism

Correct answer: Muscle biopsy of the temporalis for inflammatory polymyositis

Acquired cricopharyngeal dysfunction with EMG evidence of spontaneous activity (fibrillation potentials, positive sharp waves) indicates active muscle denervation or myopathy rather than a pure neuromuscular junction disorder. In an older dog with dysphagia and muscle EMG changes, inflammatory polymyositis — particularly masticatory muscle myositis (MMM) or a generalized immune-mediated myopathy — is a key treatable cause. Muscle biopsy (temporalis, masseter, or limb muscle) with type 2M fiber immunostaining can confirm MMM. Seronegative MG is possible but the normal esophageal motility and EMG fibrillations make a pure NMJ disorder less likely. Hypothyroidism rarely causes cricopharyngeal dysfunction as a primary presentation.

Question 226: Ketamine is commonly used as an induction agent, particularly in cats. What is its PRIMARY mechanism of anesthetic action?

NMDA receptor antagonism (Correct answer)
Alpha-2 adrenergic agonism
GABA-A receptor potentiation
Mu-opioid receptor agonism

Correct answer: NMDA receptor antagonism

Ketamine produces dissociative anesthesia primarily by non-competitive antagonism of NMDA (N-methyl-D-aspartate) glutamate receptors, which also contributes to its analgesic properties.

Question 227: Anaplasmosis in cattle is transmitted primarily by which vector in the US?

Dermacentor andersoni and Dermacentor variabilis ticks (Correct answer)
Haematobia irritans horn flies
Aedes aegypti mosquitoes
Stomoxys calcitrans stable flies

Correct answer: Dermacentor andersoni and Dermacentor variabilis ticks

Anaplasma marginale is transmitted by Dermacentor tick species in the US, though mechanical transmission by biting flies and blood-contaminated instruments also occurs.

Question 228: A 4-year-old African grey parrot presents with progressive ataxia, regurgitation, and a dilated proventriculus on radiograph. Crop biopsy reveals lymphoplasmacytic infiltration of the myenteric ganglia. Which of the following is the MOST accurate statement regarding the etiologic agent?

It is a double-stranded DNA virus in the family Herpesviridae that induces T-cell lymphoma in the myenteric plexus
It is a positive-sense, single-stranded RNA virus in the family Coronaviridae that primarily damages proventricular smooth muscle
It is a negative-sense, segmented RNA virus in the family Orthomyxoviridae that causes secondary demyelination of enteric nerves
It is a negative-sense, single-stranded RNA virus in the family Bornaviridae that targets glial cells and neurons of the enteric and central nervous systems (Correct answer)

Correct answer: It is a negative-sense, single-stranded RNA virus in the family Bornaviridae that targets glial cells and neurons of the enteric and central nervous systems

Proventricular Dilatation Disease (PDD) is caused by Avian Bornavirus (ABV), a non-segmented, negative-sense, single-stranded RNA virus in the family Bornaviridae. It targets neurons and glial cells of both the enteric (myenteric plexus) and central nervous systems, producing lymphoplasmacytic ganglioneuritis. The other options describe incorrect viral families or pathomechanisms.

Question 229: A 5-year-old FeLV-positive cat presents with a rapidly growing sublumbar mass. Fine-needle aspirate reveals a monomorphic population of large lymphocytes with prominent nucleoli and scant cytoplasm. Immunophenotyping shows CD3-negative, CD20-positive cells. Which statement about this neoplasm's relationship to FeLV is MOST accurate?

FeLV envelope glycoprotein gp70 directly transforms B-lymphocytes through binding to the thiamine transporter receptor
Reverse transcriptase error during FeLV replication generates B-cell-tropic recombinant proviruses in somatic tissue
FeLV proviral integration near c-myc via insertional mutagenesis is the primary oncogenic mechanism for this B-cell phenotype
This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype (Correct answer)

Correct answer: This B-cell lymphoma likely arose independently of FeLV; FeLV-associated lymphomas are almost exclusively T-cell in immunophenotype

FeLV-associated lymphomas are overwhelmingly T-cell in origin (>90%), typically thymic/mediastinal lymphoma in young cats. B-cell lymphomas, such as this sublumbar presentation, are generally NOT FeLV-associated and likely arose through FeLV-independent mechanisms (e.g., chronic antigenic stimulation, Helicobacter-associated alimentary lymphoma). The co-occurrence with FeLV positivity is incidental in this case. Understanding immunophenotype-retrovirus associations is critical for prognosis and etiology — FeLV-positive T-cell lymphomas carry a particularly poor prognosis. The FeLV receptor is the thiamine transporter (THTR1), but this does not directly transform B-cells.

Question 230: Which statement correctly describes the feline estrous cycle?

Queens are induced ovulators; without mating or coital stimulation, they undergo repeated estrous cycles during the breeding season (Correct answer)
Queens are spontaneous ovulators with a 21-day cycle similar to dogs
Queens ovulate spontaneously mid-estrus and develop a functional CL regardless of mating
Queens are seasonally polyestrous induced ovulators with luteal phase length of 2–3 weeks after infertile mating

Correct answer: Queens are induced ovulators; without mating or coital stimulation, they undergo repeated estrous cycles during the breeding season

Cats are seasonally polyestrous (long-day breeders) and induced ovulators — ovulation requires coital stimulation of the vagina/cervix causing a neuroendocrine GnRH surge. Without mating, queens cycle repeatedly through estrus (lasting 4–7 days) and interestrus periods throughout the breeding season without forming a CL. If mating occurs but does not result in pregnancy, a pseudopregnancy of ~35–40 days follows.

Question 231: A 9-year-old dog is presented for chronic, unilateral nasal discharge. To evaluate the extent of disease, including potential bone destruction of the nasal turbinates and integrity of the cribriform plate, which advanced imaging modality is superior?

Computed Tomography (CT) (Correct answer)
Rhinoscopy with biopsy
Dental radiography
Magnetic Resonance Imaging (MRI)

Correct answer: Computed Tomography (CT)

Computed Tomography (CT) is the imaging modality of choice for evaluating the nasal passages because of its excellent spatial resolution and superior ability to detail bone. It eliminates the superimposition of structures seen on radiographs and is better than MRI for assessing fine bony changes like turbinate destruction or lysis of the cribriform plate, which is critical for staging nasal tumors or fungal disease. While rhinoscopy is needed for biopsy, CT provides the best anatomical map for surgical or radiation planning.

Question 232: Which disinfection method is considered most effective for inactivating Cryptosporidium parvum oocysts in drinking water?

Ozonation at low concentrations
Chlorination at standard doses
Filtration alone without disinfection
UV irradiation (Correct answer)

Correct answer: UV irradiation

Cryptosporidium oocysts are highly resistant to chlorine; UV irradiation effectively inactivates them by damaging their DNA.

Question 233: A 7-year-old Thoroughbred racehorse undergoes nuclear scintigraphy after a 4-week history of right hindlimb lameness. The scan shows intense increased radiopharmaceutical uptake (IRU) at the right tuber sacrale. Standing rectal palpation reveals mild asymmetry. Radiographs are normal. Which diagnosis BEST explains these findings, and what is the primary mechanism of injury?

Stress fracture of the ilial wing from compressive axial loading
Septic sacroiliac arthritis from hematogenous seeding
Supraspinous ligament desmopathy causing referred pain to the pelvis
Sacroiliac joint desmopathy secondary to repetitive torsional loading during racing (Correct answer)

Correct answer: Sacroiliac joint desmopathy secondary to repetitive torsional loading during racing

Sacroiliac joint desmopathy is the most common cause of intense IRU at the tuber sacrale in racehorses with hindlimb lameness and pelvic asymmetry. The SI joint undergoes repetitive torsional and shear forces during gallop and tight turns, causing ligamentous strain and enthesopathy without early radiographic changes. Scintigraphy is the most sensitive early modality. Stress fractures of the ilial wing would show IRU at a different site, and septic arthritis would typically present with systemic signs.

Question 234: A cat presents with acute rodenticide toxicosis from ingestion of brodifacoum. Vitamin K1 therapy is initiated. Which statement best describes the pharmacodynamic basis for why high doses and prolonged treatment (3–6 weeks) are required compared to warfarin toxicosis?

Brodifacoum irreversibly alkylates the vitamin K epoxide reductase enzyme complex
Brodifacoum has a much shorter half-life than warfarin, requiring more frequent dosing
Brodifacoum depletes stores of vitamins K2 and K3, which cannot be replaced by K1 supplementation alone
Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion (Correct answer)

Correct answer: Brodifacoum undergoes extensive enterohepatic recirculation, maintaining toxic tissue concentrations long after ingestion

Brodifacoum is a long-acting anticoagulant rodenticide with extensive enterohepatic recirculation and high lipophilicity, resulting in a plasma half-life of weeks to months in companion animals. This prolonged tissue retention means that even after a single ingestion, the drug continues to inhibit vitamin K epoxide reductase for an extended period. Treatment with vitamin K1 must continue until all brodifacoum is eliminated, typically 3–6 weeks, verified by PT/aPTT testing 48–72 hours after cessation.

Question 235: A 6-year-old castrated male DSH is prescribed oral diazepam (1 mg PO BID) for urine marking behavior. On day 4, the owner reports acute lethargy, jaundice, and anorexia. ALT is 1,840 U/L and total bilirubin is 8.2 mg/dL. What is the most accurate characterization of this adverse reaction?

Predictable accumulation of diazepam's active metabolite desmethyldiazepam due to impaired feline glucuronidation
Cholestatic hepatopathy caused by benzodiazepine-induced bile duct compression in cats with subclinical biliary disease
Type B hypersensitivity reaction triggered by benzodiazepine ring oxidation products in genetically susceptible cats
Idiosyncratic acute hepatic necrosis unique to cats receiving oral benzodiazepines, unrelated to dose or duration (Correct answer)

Correct answer: Idiosyncratic acute hepatic necrosis unique to cats receiving oral benzodiazepines, unrelated to dose or duration

Oral diazepam causes idiosyncratic acute hepatic necrosis in cats — a reaction that is unpredictable, not dose-dependent, and appears to be specific to the oral route. Affected cats can deteriorate rapidly within 2–5 days of initiating therapy. The mechanism is not fully elucidated but is not simply pharmacokinetic accumulation. IV diazepam carries much lower risk. This is why oral diazepam is generally contraindicated in cats, with alternatives such as gabapentin or environmental modification preferred for behavioral indications.

Question 236: Which radiographic finding is MOST consistent with pyloric outflow obstruction in a dog?

Free peritoneal gas on the VD view
Dilated small intestinal loops > 3x rib width
Retroperitoneal effusion with loss of serosal detail
Markedly distended stomach with delayed gastric emptying (Correct answer)

Correct answer: Markedly distended stomach with delayed gastric emptying

Pyloric obstruction causes gastric outflow failure, producing marked gastric distension with delayed or absent contrast passage on fluoroscopy.

Question 237: Which electrolyte abnormality is most commonly associated with hypoadrenocorticism (Addison's disease) in dogs?

Hypernatremia and hypokalemia
Hypomagnesemia and hypochloremia
Hypercalcemia and hyperphosphatemia
Hyponatremia and hyperkalemia (Correct answer)

Correct answer: Hyponatremia and hyperkalemia

Lack of mineralocorticoids in Addison's disease leads to sodium wasting and potassium retention, producing hyponatremia and hyperkalemia with a Na:K ratio below 27.

Question 238: A cat is prescribed methimazole for hyperthyroidism. Which adverse effect is most commonly reported in the first 1–3 months of therapy?

Hepatotoxicity
Peripheral neuropathy
Facial pruritus and excoriation (Correct answer)
Bone marrow aplasia

Correct answer: Facial pruritus and excoriation

Facial pruritus, excoriation, and self-induced facial lesions are the most common early adverse effects of methimazole in cats.

Question 239: Ultrasonography of a 9-year-old Labrador Retriever with suspected splenic disease reveals a large, heterogeneous splenic mass with multiple hyperechoic foci casting acoustic shadows, admixed with anechoic cavitations. The most likely diagnosis is:

Splenic hemangiosarcoma
Splenic myelolipoma (Correct answer)
Nodular hyperplasia
Extramedullary hematopoiesis

Correct answer: Splenic myelolipoma

Splenic myelolipomas are rare benign tumors composed of mature adipose and hematopoietic tissue. On ultrasound, they appear as heterogeneous masses with hyperechoic foci (fat) causing acoustic shadowing and may contain cystic areas. This mixed echogenicity with shadowing foci is characteristic. Hemangiosarcoma is typically a large, heterogeneous cavitated mass but does not contain shadowing foci from calcification or fat. Nodular hyperplasia and extramedullary hematopoiesis are diffuse or multiple small nodular changes without the discrete mass architecture and shadowing foci described.

Question 240: A cow presents with acute right-sided abomasal displacement progressing to volvulus (RDA/RAV) in a freshly calved dairy cow. Which finding on physical exam is most consistent with this diagnosis?

Left-sided ping in the paralumbar fossa on simultaneous auscultation and percussion
Left-sided rumen atony with no ping detected
High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia (Correct answer)
Bilateral pings with fluid splashing sounds in the lower abdomen

Correct answer: High-pitched ping over a large area on the right side between ribs 9-12, with signs of toxemia and tachycardia

Right abomasal volvulus produces a large-area right-sided ping (ribs 9-12), signs of severe toxemia, tachycardia, and rapid cardiovascular deterioration due to venous outflow obstruction.

Question 241: A 9-year-old cat with a 2-month history of small-bowel diarrhea and weight loss undergoes intestinal biopsy. Histopathology reveals mucosal architectural distortion, villous blunting, and a mixed population of lymphocytes and plasma cells. Immunohistochemistry shows a CD3+/CD20− predominant infiltrate. What is the most appropriate next diagnostic step to distinguish small cell lymphoma from inflammatory bowel disease?

Repeat biopsy using endoscopic forceps to obtain deeper tissue samples
Trial therapy with prednisolone — clinical response definitively differentiates IBD from lymphoma
Serum cobalamin and folate measurement to confirm small intestinal involvement
PARR (PCR for antigen receptor rearrangement) to assess clonality of the lymphocyte population (Correct answer)

Correct answer: PARR (PCR for antigen receptor rearrangement) to assess clonality of the lymphocyte population

Distinguishing feline small cell (low-grade) lymphoma from lymphoplasmacytic IBD is one of the most challenging problems in feline gastroenterology, as both share similar histologic appearances and CD3+ T-cell infiltrates. PARR (PCR for antigen receptor rearrangement) assesses whether the lymphocyte population is clonal (lymphoma) or polyclonal (reactive/IBD) and is the gold-standard adjunct test when histology is equivocal. Response to steroids is not definitive because both IBD and small cell lymphoma can respond to chlorambucil/prednisolone. Cobalamin/folate confirms small intestinal involvement but does not differentiate the two diseases. Deeper biopsies improve histologic yield but do not resolve the clonality question.

Question 242: A 3-year-old Quarter Horse mare is presented with a history of recurrent episodes of mild colic, weight loss despite a good appetite, and loose feces. Fecal egg count is 0 EPG. Serum chemistry reveals hypoalbuminemia (2.1 g/dL) and elevated beta-globulins. Rectal palpation reveals thickened large colon walls. Which condition is highest on the differential list?

Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence (Correct answer)
Equine proliferative enteropathy due to Lawsonia intracellularis
Right dorsal colitis secondary to NSAID toxicity
Granulomatous enteritis (multisystemic eosinophilic epitheliotropic disease)

Correct answer: Cyathostominosis (larval cyathostomiasis) with mucosal larval emergence

Larval cyathostomiasis (Type II cyathostominosis) occurs when large numbers of encysted early third-stage (EL3) cyathostomin larvae simultaneously emerge from the intestinal mucosa, causing protein-losing enteropathy, diarrhea, weight loss, and colic. Critically, adult egg-shedding larvae are absent during this phase, so fecal egg counts are zero or very low — this is a key distinguishing feature. Hypoalbuminemia and elevated beta-globulins reflect the protein loss and acute-phase response. Thickened colon walls on rectal palpation support mucosal infiltration. Equine proliferative enteropathy (Lawsonia) is seen primarily in weanlings and yearlings. Right dorsal colitis would have a history of NSAID use. MEED is rare and typically involves multiple organ systems.

Question 243: A beef cow herd in the northern Great Plains experiences a cluster of late-term abortions in January. Fetuses are autolyzed, placentas are retained, and Brucella testing is negative. PCR on placental tissue detects Neospora caninum. Which epidemiological pattern would most strongly support vertical (transplacental) rather than horizontal (postnatal oral) transmission as the dominant route in this herd?

Outbreak resolution after removing dogs and coyotes from the property
Seroprevalence highest in heifers purchased from a single sale barn the prior autumn
Abortion rate significantly higher in daughters of seropositive dams compared to daughters of seronegative dams, regardless of exposure to definitive hosts (Correct answer)
Abortions occurring in cows of all parities clustered temporally around a single feed source change

Correct answer: Abortion rate significantly higher in daughters of seropositive dams compared to daughters of seronegative dams, regardless of exposure to definitive hosts

Neospora caninum is transmitted both vertically (cow to calf in utero) and horizontally (ingestion of oocysts shed by definitive hosts — canids). The hallmark of vertical transmission dominance is a familial clustering pattern: daughters of seropositive dams have dramatically higher seroprevalence and abortion risk independent of canid exposure. This dam-to-offspring clustering across generations is the epidemiological fingerprint of congenital transmission. Temporal clustering around a feed change or purchase event would suggest horizontal exposure, and removal of definitive hosts would reduce horizontal but not vertical risk.

Question 244: Which of the following best describes the primary mechanism by which non-steroidal anti-inflammatory drugs (NSAIDs) can induce acute kidney injury in a cat that is dehydrated or hypotensive?

Inhibition of prostaglandin-mediated renal vasodilation (Correct answer)
Immune-mediated glomerulonephritis
Direct nephron apoptosis via oxidative damage
Formation of obstructive crystals within the renal tubules

Correct answer: Inhibition of prostaglandin-mediated renal vasodilation

In states of decreased renal perfusion (like dehydration or hypotension), the kidneys rely on locally produced prostaglandins (PGE2 and PGI2) to cause afferent arteriole vasodilation, which maintains glomerular filtration rate (GFR). NSAIDs inhibit cyclooxygenase (COX) enzymes, thereby blocking prostaglandin synthesis. This inhibition prevents the compensatory vasodilation, leading to a profound reduction in renal blood flow, decreased GFR, and potential ischemic acute tubular necrosis.

Question 245: During fluoroscopic evaluation of a 9-month-old Labrador Retriever with regurgitation, barium swallow demonstrates a persistent filling defect in the dorsal esophagus at the level of the heart base that does not change shape with peristalsis. A 'reversed 3 sign' or 'E sign' is noted on the aortic knob region. What is the most likely diagnosis?

Esophageal foreign body at the thoracic inlet
Esophageal leiomyoma at the gastroesophageal junction
Aberrant left subclavian artery causing extrinsic esophageal compression
Persistent right aortic arch (PRAA) with secondary megaesophagus (Correct answer)

Correct answer: Persistent right aortic arch (PRAA) with secondary megaesophagus

The classic radiographic and fluoroscopic presentation of persistent right aortic arch (PRAA) in a young large-breed dog includes: cranial esophageal dilation (megaesophagus cranial to the heart base), a persistent filling defect at the level of the heart base that does not peristalse away, and — on plain radiographs or fluoroscopy — a 'reversed 3 sign' or 'E sign' on the left lateral view, reflecting the anomalous aortic arch indenting the esophagus. PRAA is the most common vascular ring anomaly in dogs. Aberrant left subclavian artery causes a more caudal/lateral compression and lacks the classic reversed-3 sign. The location (heart base, not thoracic inlet) excludes foreign body.

Question 246: A beef producer has a 3% calf crop loss from scours annually. To calculate the cost of a calf scours prevention program, which parameter is NOT included in the basic cost-benefit analysis?

Labor costs for treatment
Value of calves saved
Cost of the vaccine program
Breed of the dam (Correct answer)

Correct answer: Breed of the dam

Dam breed is not a direct economic variable in a cost-benefit analysis of a vaccination program; the relevant inputs are vaccine cost, calf value, morbidity/mortality rates, and treatment costs.

Question 247: A 6-year-old male Dachshund presents acutely with inability to walk in the hind limbs and deep pain perception is absent bilaterally. MRI confirms a thoracolumbar Hansen type I disc extrusion at T13-L1. What is the most critical prognostic indicator?

Body weight of the patient
Duration of clinical signs before surgery
Degree of spinal cord swelling on MRI
Presence or absence of deep pain perception (Correct answer)

Correct answer: Presence or absence of deep pain perception

Presence or absence of deep pain perception is the single most important prognostic factor; dogs with intact deep pain have >90% recovery rates while those without have significantly lower rates.

Question 248: Among the currently used inhalant anesthetics, which has the LOWEST blood:gas partition coefficient, resulting in the fastest induction and recovery?

Halothane
Desflurane (Correct answer)
Isoflurane
Sevoflurane

Correct answer: Desflurane

Desflurane has the lowest blood:gas partition coefficient (~0.42), meaning it equilibrates rapidly between blood and alveoli, producing the fastest induction and recovery of the available inhalants.

Question 249: A rabbit undergoing ovariohysterectomy shows bradycardia (HR 120 bpm) under isoflurane. What is the most likely cause and initial treatment?

Hyperkalemia — administer calcium gluconate
Vagal stimulation — administer atropine IV
Anesthetic overdose — reduce vaporizer setting (Correct answer)
Hyperthermia — apply cooling

Correct answer: Anesthetic overdose — reduce vaporizer setting

Reducing the isoflurane vaporizer setting addresses anesthetic-induced bradycardia by decreasing myocardial depression from excessive anesthetic depth.

Question 250: A bird (psittacine) presents with a bacterial infection. Which antibiotic class should be avoided due to risk of fatal dysbiosis?

Beta-lactams
Aminoglycosides
Fluoroquinolones
Lincosamides and macrolides at high doses (Correct answer)

Correct answer: Lincosamides and macrolides at high doses

Lincosamides (e.g., clindamycin) and certain macrolides can cause fatal disruption of the GI microbiome in birds, similar to the antibiotic-associated enterocolitis seen in other species.

Question 251: Which radiographic sign is MOST characteristic of a diaphragmatic hernia in a dog?

Increased sternal contact of the cardiac silhouette
Pleural fissure lines at the lung margins
Loss of diaphragmatic outline with abdominal organs in the thorax (Correct answer)
Air bronchograms within the pulmonary parenchyma

Correct answer: Loss of diaphragmatic outline with abdominal organs in the thorax

Loss of the normal diaphragmatic outline combined with abdominal viscera (e.g., intestinal loops, stomach) visible in the thoracic cavity is the hallmark of diaphragmatic hernia.

Question 252: A 4-year-old spayed female Doberman Pinscher is presented for a pre-breeding cardiac clearance (owner is unaware she is spayed). Auscultation reveals a soft, grade II/VI left apical systolic murmur. Echo shows mild left ventricular dilation with an ejection fraction of 48%. Which statement most accurately describes the appropriate management and genetic counseling?

Begin enalapril therapy; the murmur is most likely due to mitral valve degeneration at this age
No treatment indicated; repeat echo in 6 months, and inform the owner the dog is spayed before discussing breeding (Correct answer)
Begin pimobendan therapy immediately; the dog should not be bred regardless of spay status due to DLVM genetic risk
Recheck echocardiogram in 6 months; this likely represents physiologic athlete's heart in an active breed

Correct answer: No treatment indicated; repeat echo in 6 months, and inform the owner the dog is spayed before discussing breeding

The dog has pre-clinical dilated cardiomyopathy (DCM), which is common in Doberman Pinschers. Current evidence (PROTECT study) supports pimobendan initiation when occult DCM is confirmed by echo criteria (LVIDd >46mm or LVIDs >38mm in females, or EF <50%). However, the immediate priority in the clinical scenario is to address the factual error — the dog is spayed and cannot be bred. Pimobendan would be appropriate once DCM criteria are confirmed, but answering the counseling question requires first correcting the owner's misunderstanding. Enalapril alone is not first-line for pre-clinical DCM in Dobermans.

Question 253: A 5-year-old cat with severe Mycoplasma haemofelis infection requires aggressive antibiotic therapy. The attending clinician wants to use enrofloxacin. Which of the following statements most accurately describes the risk-benefit consideration for enrofloxacin in this patient?

Retinal toxicity risk is substantially increased at doses exceeding 5 mg/kg/day; lesions typically occur within days and are irreversible (Correct answer)
Enrofloxacin-induced retinopathy in cats is fully reversible if the drug is discontinued within 48 hours of the first visual deficit
Young cats under 1 year are uniquely susceptible due to incomplete retinal development, while adult cats tolerate standard doses safely
Enrofloxacin causes retinal degeneration in a dose-independent fashion; even a single dose at any concentration poses equal risk

Correct answer: Retinal toxicity risk is substantially increased at doses exceeding 5 mg/kg/day; lesions typically occur within days and are irreversible

Enrofloxacin causes acute retinal degeneration (cone-rod degeneration leading to blindness) in cats in a dose-dependent manner. The FDA label restricts enrofloxacin in cats to a maximum of 5 mg/kg/day for this reason. Toxicity can occur within days of high-dose use and the photoreceptor damage is generally irreversible — vision loss is permanent once significant retinal degeneration has occurred. Lower doses are associated with acceptable risk, making dose precision critical. Doxycycline is frequently preferred for Mycoplasma haemofelis to avoid this risk.

Question 254: A 6-year-old domestic shorthair cat with vocal discomfort is examined for acute bilateral hind limb paralysis. A grade 3/6 left-sided systolic murmur is audible during a physical examination. The patient's footpads are chilly and pallid, and there are no femoral pulses. Additionally, the gastrocnemius and quadriceps muscles have painful contracture. Which of the following ailments has the highest likelihood of being diagnosed?

Intervertebral dis disease
Spinal cord neoplasia
Arterial thromboembolism (Correct answer)
Fibrocartilaginous infarct

Correct answer: Arterial thromboembolism

Acute bilateral hind limb paralysis, vocal discomfort, cold and pale footpads, absence of femoral pulses, and painful contracture of hind limb muscles in a cat with a heart murmur are pathognomonic signs of an arterial thromboembolism (ATE), often referred to as 'saddle thrombus.' This condition typically results from a thrombus (blood clot) originating in the heart (often due to underlying heart disease like hypertrophic cardiomyopathy) that dislodges and lodges at the aortic trifurcation, blocking blood flow to the hind limbs.

Question 255: An 11-year-old Andalusian dressage horse presents with progressive bilateral forelimb 'pottery' gait, stumbling, and a short, stabbing stance phase. Nerve blocks are unhelpful. Radiographs show extensive remodeling and irregular sclerosis of both proximal sesamoid bones with fragmentation at the base. Which long-term structural consequence makes the prognosis for return to full work GUARDED to POOR?

Chronic deep digital flexor tendon core lesion from altered fetlock alignment
Secondary navicular bone remodeling from altered weight-bearing biomechanics
Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity (Correct answer)
Bilateral coffin joint synovitis from compensatory toe-first landing

Correct answer: Progressive failure of the suspensory apparatus with risk of catastrophic fetlock breakdown due to compromised sesamoid bone structural integrity

Chronic sesamoiditis with fragmentation and sclerosis represents advanced degenerative disease of the proximal sesamoid bones, which are critical structural components of the suspensory apparatus. The sesamoid bones serve as the fulcrum for the suspensory ligament and distal sesamoidean ligaments; structural failure predisposes to catastrophic breakdown — fetlock 'drop,' complete support limb failure, or fracture under athletic loading. This is distinct from navicular disease or DDFT pathology, which are secondary events. The bilateral involvement and advanced bony changes make return to high-level sport inadvisable.

Question 256: A 9-year-old male neutered Golden Retriever presents with progressive forelimb lameness. Radiographs of the shoulder reveal a 'moth-eaten' lytic lesion of the proximal humerus with periosteal reaction and cortical destruction. What is the most likely diagnosis and treatment?

Hypertrophic osteodystrophy; supportive care
Septic osteomyelitis; long-term antibiotics
Osteosarcoma; limb amputation with adjuvant carboplatin chemotherapy (Correct answer)
Osteochondrosis dissecans; arthroscopic debridement

Correct answer: Osteosarcoma; limb amputation with adjuvant carboplatin chemotherapy

Osteosarcoma most commonly affects the proximal humerus in large breeds; amputation combined with carboplatin or doxorubicin chemotherapy provides the best median survival.

Question 257: A dog is suspected to have toxicosis from xylitol ingestion 30 minutes ago. Which clinical signs would you expect first?

Acute renal failure and anuria
Hepatic necrosis and coagulopathy
Hypoglycemia and seizures (Correct answer)
Hemolytic anemia and methemoglobinemia

Correct answer: Hypoglycemia and seizures

Xylitol causes rapid insulin release in dogs leading to profound hypoglycemia within 30-60 minutes; hepatic necrosis can occur later with larger doses.

Question 258: A 7-year-old male castrated Persian cat presents with episodic vomiting, weight loss, and small-intestinal diarrhea. Jejunal biopsy reveals lymphocytic-plasmacytic infiltration with villous blunting. Serum folate is elevated and cobalamin is severely low. Which statement best explains the cobalamin deficiency in this patient?

Cobalamin malabsorption due to loss of ileal cubilin/amnionless receptors from mucosal disease (Correct answer)
Bacterial overgrowth consuming cobalamin before ileal absorption can occur
Exocrine pancreatic insufficiency causing absent intrinsic factor production
Hepatic failure impairing cobalamin storage and enterohepatic recirculation

Correct answer: Cobalamin malabsorption due to loss of ileal cubilin/amnionless receptors from mucosal disease

In cats, intrinsic factor is produced by the pancreas but cobalamin absorption occurs via cubilin/amnionless receptor complexes in the ileum. Diffuse small intestinal mucosal disease (as seen here with IBD/lymphoma) damages ileal absorptive receptors, causing cobalamin malabsorption despite normal pancreatic IF production. Elevated folate suggests proximal small intestinal bacterial overgrowth or intact proximal mucosa with bacteria producing folate. EPI would cause both low folate and low cobalamin. Severe ileal mucosal loss is the direct mechanism here.

Question 259: A FIV-positive cat living indoors is otherwise healthy. Which of the following management strategies is most appropriate?

Lifelong antiviral therapy starting immediately
Immediate corticosteroid therapy to prevent lymphoma
Euthanasia is recommended to prevent disease progression
Regular veterinary visits, indoor-only lifestyle, neutering, and monitoring for opportunistic infections (Correct answer)

Correct answer: Regular veterinary visits, indoor-only lifestyle, neutering, and monitoring for opportunistic infections

FIV-positive cats can live normal lifespans with appropriate management including indoor confinement, routine monitoring, and prompt treatment of secondary infections.

Question 260: A primiparous Labrador Retriever bitch delivered 6 puppies 18 hours ago. She is now febrile (40.5°C), depressed, and has a malodorous dark vaginal discharge. Abdominal palpation reveals uterine discomfort. The most likely diagnosis and first-line treatment are:

Mastitis — hot-pack mammary glands and oxytocin to promote drainage
Acute metritis — broad-spectrum antibiotics (amoxicillin-clavulanate), oxytocin, and supportive care (Correct answer)
Subinvolution of placental sites — supportive care and monitoring
Eclampsia — IV calcium gluconate 10% slowly to effect

Correct answer: Acute metritis — broad-spectrum antibiotics (amoxicillin-clavulanate), oxytocin, and supportive care

Acute postpartum metritis presents with fever, depression, malodorous uterine discharge, and uterine pain within the first week after delivery. Treatment includes broad-spectrum antibiotics (covering gram-negative organisms and anaerobes), oxytocin or PGF2α to promote uterine evacuation, and IV fluid support. Eclampsia presents with tetany/seizures, not discharge.

Question 261: A horse presents with chronic forelimb lameness localized to the coffin joint. Radiographs show marked osteolysis and periarticular new bone formation. Synoviocentesis yields thick, turbid fluid with 85,000 WBC/μL (>90% neutrophils) and a glucose concentration much lower than serum. What is the next most critical step?

Repeat radiographs in 2 weeks
Perform arthroscopic debridement under general anesthesia immediately without lavage
Perform through-and-through joint lavage and systemic antimicrobials (Correct answer)
Initiate systemic corticosteroids

Correct answer: Perform through-and-through joint lavage and systemic antimicrobials

Septic arthritis requires immediate joint lavage (through-and-through or arthroscopic) combined with systemic and intra-articular antimicrobials to remove bacteria and inflammatory mediators.

Question 262: A 3-year-old intact male cat tests FIV-positive. What is the most reliable route of transmission for this virus?

Shared food bowls
Fomite contact
Vertical transmission via placenta
Bite wounds (Correct answer)

Correct answer: Bite wounds

FIV is most efficiently transmitted through bite wounds because high viral loads are present in saliva.

Question 263: A dairy producer utilizes a timed artificial insemination (TAI) protocol that includes Ovsynch. Which hormone is administered to cause luteolysis, or regression of the corpus luteum, thereby allowing the cow to return to estrus?

Prostaglandin F2α (PGF2α) (Correct answer)
Progesterone
Gonadotropin-releasing hormone (GnRH)
Oxytocin

Correct answer: Prostaglandin F2α (PGF2α)

Prostaglandin F2α (PGF2α) is the hormone responsible for causing luteolysis, which is the breakdown of the corpus luteum (CL). In synchronization protocols like Ovsynch, PGF2α is given when a mature CL is expected to be present, causing a drop in progesterone and allowing a new follicular wave to progress towards ovulation. GnRH is used to cause ovulation or start a new follicular wave, while progesterone (e.g., in a CIDR) is used to prevent estrus.

Question 264: A 15-year-old Hanoverian dressage horse is evaluated for progressive bilateral hindlimb weakness and hindlimb lameness. The horse exhibits a characteristic 'goose-stepping' gait, excessive hip drop bilaterally, and difficulty backing. Intra-articular analgesia of the sacroiliac joints dramatically improves the lameness score from 3/5 to 1/5. Which diagnostic imaging modality is considered gold standard for confirming sacroiliac joint pathology in the horse, and what finding would confirm active joint disease?

Radiography demonstrating subchondral sclerosis and periarticular osteophyte formation
Nuclear scintigraphy showing bilaterally increased IRU at the sacroiliac joints; subchondral uptake pattern
Transrectal ultrasonography revealing hypoechoic joint margins and loss of normal joint contour (Correct answer)
CT myelography showing nerve root compression at the lumbosacral junction

Correct answer: Transrectal ultrasonography revealing hypoechoic joint margins and loss of normal joint contour

Transrectal ultrasonography (TRUS) is considered the gold standard for imaging the sacroiliac joint in horses because it allows direct visualization of the ventral joint margin, synovium, and surrounding structures with high resolution. Findings confirming active SI joint disease include hypoechoic (thickened/inflamed) joint capsule, loss of normal smooth joint contour, and irregularity of the subchondral surfaces. Nuclear scintigraphy is useful but less specific — it reflects bone remodeling activity, not active synovitis. Standard radiography cannot adequately image the SI joint due to overlying structures. CT myelography evaluates spinal cord compression, not SI joint pathology.

Question 265: A cat colony manager reports that 4 of 20 colony cats have died with signs of acute vomiting, hemorrhagic diarrhea, and profound leukopenia (WBC 400 cells/µL). The colony was vaccinated against feline panleukopenia virus (FPV) 3 years ago with an inactivated vaccine. Necropsy reveals villous blunting with crypt necrosis. Which scenario MOST plausibly explains vaccine failure in this outbreak?

Cold-chain failure during vaccine storage causing loss of adjuvant efficacy without affecting antigen content
Canine parvovirus type 2c (CPV-2c) infection, which is not cross-neutralized by antibodies induced by FPV inactivated vaccines
Antigenic drift in circulating FPV strains rendering the inactivated vaccine antigenically mismatched
Waning humoral immunity below protective thresholds after 3 years combined with a high environmental viral load (Correct answer)

Correct answer: Waning humoral immunity below protective thresholds after 3 years combined with a high environmental viral load

Inactivated FPV vaccines in cats provide shorter duration of immunity than modified live vaccines — protective titers may wane below threshold levels by 2–3 years in some individuals, particularly in colony settings where annual or triennial boosters may be inconsistent. FPV is environmentally hardy (survives years in fomites), so high environmental pressure combined with waned immunity is the most plausible explanation. CPV-2c does infect cats and causes panleukopenia-like disease, but antibodies from FPV vaccines DO cross-neutralize CPV-2 variants due to high antigenic homology (>98% capsid similarity). FPV shows no significant antigenic drift. Cold-chain failure would affect antigen integrity more than adjuvant.

Question 266: A 6-year-old bearded dragon (Pogona vitticeps) presents with bilateral periocular swelling, lethargy, and anorexia. Cytology of aspirated periocular material reveals caseous debris with heterophils. Culture yields Salmonella arizonae. Which of the following statements about treatment is MOST accurate?

Chloramphenicol is the first-line agent because fluoroquinolones fail to penetrate reptilian ocular tissue
Surgical debridement of caseous exudate combined with systemic antimicrobials is required, as reptilian heterophilic pus does not liquefy and will not resolve with antibiotics alone (Correct answer)
Enrofloxacin is contraindicated in bearded dragons because it causes irreversible cartilage damage at therapeutic doses
Systemic fluoroquinolone therapy alone is curative because Salmonella arizonae is invariably susceptible and the caseous material resolves with antimicrobials

Correct answer: Surgical debridement of caseous exudate combined with systemic antimicrobials is required, as reptilian heterophilic pus does not liquefy and will not resolve with antibiotics alone

Reptiles lack the enzymatic machinery to liquefy caseous (inspissated) pus as mammals do — their heterophils do not produce the proteases needed for liquefaction. Consequently, antibiotic therapy alone cannot eliminate the solid caseous mass; surgical debridement or curettage is mandatory to remove the inspissated material, followed by systemic antimicrobials based on culture and sensitivity. Enrofloxacin is routinely used in bearded dragons and is not contraindicated; cartilage concerns apply more to immature large-breed dogs.

Question 267: Postweaning multisystemic wasting syndrome (PMWS) associated with Porcine Circovirus type 2 (PCV2) is diagnosed in a 6-week-old pig. Which histologic lesion in lymph nodes is considered pathognomonic?

Granulomatous lymphadenitis with central caseation
Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies (Correct answer)
Lymphoid hyperplasia with germinal center formation
Lymphocytic vasculitis with fibrinoid necrosis

Correct answer: Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies

PCV2-associated PMWS characteristically produces lymphoid depletion with replacement by histiocytes/macrophages that contain intracytoplasmic basophilic inclusion bodies (viral antigen). This combination is considered pathognomonic. Lymphoid hyperplasia is the opposite of what occurs.

Question 268: A cat anesthetized with ketamine/diazepam develops prolonged apnea after induction. Which characteristic of ketamine best explains this risk?

Ketamine inhibits NMDA receptors in the brainstem
Ketamine causes dose-dependent respiratory depression at high doses (Correct answer)
Ketamine stimulates mu-opioid receptors
Ketamine increases upper airway secretions causing obstruction

Correct answer: Ketamine causes dose-dependent respiratory depression at high doses

While ketamine is generally considered a respiratory-sparing agent, high or rapidly administered doses can cause dose-dependent apnea in cats.

Question 269: When treating a reptile patient, why is it essential to maintain the animal within its preferred optimal temperature zone (POTZ)?

Temperature has no effect on antibiotic efficacy in reptiles
Reptiles are ectotherms, so immune function and drug metabolism depend on environmental temperature (Correct answer)
POTZ only affects reproductive behavior, not clinical outcomes
POTZ is important only for feeding, not medical treatment

Correct answer: Reptiles are ectotherms, so immune function and drug metabolism depend on environmental temperature

As ectotherms, reptiles rely on external heat sources for all metabolic processes including immune response and pharmacokinetics.

Question 270: During a reproductive program audit on a 550-cow dairy, you find that 22% of cows diagnosed pregnant at 30 days post-AI by transrectal ultrasonography are subsequently found non-pregnant at the 60-day confirmation exam. Progesterone supplementation (CIDR insert days 14–25 post-AI) was trialed with no improvement in pregnancy loss rate. Necropsy of three aborted fetuses at 45–55 days gestation reveals placentitis with intranuclear inclusion bodies on histopathology. Which pathogen is MOST consistent with this pattern of reproductive loss?

Bovine herpesvirus 4 (BoHV-4) causing placentitis in the second trimester (Correct answer)
Bovine viral diarrhea virus (BVDV) causing early embryonic death in PI-exposed heifers
Neospora caninum causing recurrent abortion clustering in multiparous cows
Leptospira borgpetersenii serovar Hardjo causing mid-gestation abortion storms

Correct answer: Bovine herpesvirus 4 (BoHV-4) causing placentitis in the second trimester

Bovine herpesvirus 4 (BoHV-4) causes sporadic to endemic placentitis in dairy cattle, typically presenting as pregnancy losses between 30 and 120 days of gestation. The hallmark histopathological finding is intranuclear inclusion bodies (Cowdry type A) in trophoblast and endometrial cells — a feature of herpesvirus replication. This distinguishes it from Neospora (which causes protozoal placentitis without inclusion bodies), Leptospira (which causes interstitial nephritis in the fetus and a characteristic 'abortion storm' pattern), and BVDV (which causes embryonic death before recognizable placentitis at 30+ days). The failure of progesterone supplementation rules out luteal insufficiency. BoHV-4 is underdiagnosed and often overlooked in differential lists for early-to-mid gestation loss with histologic lesions.

Question 271: A 9-year-old spayed female Bernese Mountain Dog is evaluated for a 6-month history of polyuria/polydipsia, weight loss, and a pendulous abdomen. Bloodwork shows a persistent lymphopenia (400 cells/μL), eosinopenia, elevated ALP (1,800 U/L), and mildly elevated ALT. Urine cortisol:creatinine ratio is elevated on two morning samples. A low-dose dexamethasone suppression test (LDDST) shows less than 50% suppression at 4 hours but greater than 50% suppression at 8 hours. What is the MOST appropriate next diagnostic step?

No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH) (Correct answer)
Adrenal ultrasonography to rule out adrenal-dependent hyperadrenocorticism
High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH
Endogenous ACTH concentration measurement

Correct answer: No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH)

In interpreting the LDDST, suppression of cortisol to <50% of baseline at the 4-hour or 8-hour time point is diagnostic for PDH (pituitary-dependent hyperadrenocorticism). When there is escape at 4 hours but suppression at 8 hours, this pattern (called 'delayed suppression') is considered diagnostic for PDH with approximately 98% specificity — meaning no further differentiation testing is required. The 8-hour suppression (>50% below baseline) essentially rules out an autonomously functioning adrenal tumor, which would not suppress at any time point. An HDDST would be redundant, and while ultrasound and endogenous ACTH are useful adjuncts, the 8-hour LDDST suppression pattern alone confirms PDH.

Question 272: An 8-year-old Arabian endurance horse undergoes elective arthroscopy of the left carpal joints. During closure, the surgeon notes excessive hemorrhage from the dorsal aspect of the antebrachiocarpal joint. Which vessel, if lacerated during carpal arthroscopy via the standard dorsolateral or dorsomedial portals, is the most common source of significant intraoperative hemorrhage and what is the recommended immediate management?

Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery (Correct answer)
Accessory cephalic vein; oversew the arthroscopic portal with a horizontal mattress suture
Cephalic vein; apply digital pressure followed by ligation if bleeding persists post-lavage
Medial palmar vein; tourniquet application proximal to the carpus

Correct answer: Dorsal carpal branch of the radial artery; controlled lavage with epinephrine-containing saline and direct cautery

The dorsal carpal branch of the radial artery crosses the dorsal aspect of the carpus and is at risk during portal placement or instrument manipulation in equine carpal arthroscopy. Significant hemorrhage from arterial origin can obscure visualization and complicate closure. Initial management includes copious joint lavage to clear the field, followed by direct electrocautery of the vessel if it can be visualized arthroscopically. Epinephrine in irrigation fluid is used as an adjunct to promote vasoconstriction. The cephalic and accessory cephalic veins are also at risk but produce lower-pressure venous bleeding more readily managed with pressure alone.

Question 273: A cat tests positive for FeLV by ELISA antigen test. Which follow-up test best determines if the cat is persistently viremic vs. regressor?

FeLV PCR on bone marrow
Repeat ELISA in 30 days
FeLV antibody titer
IFA (immunofluorescence assay) on blood smear (Correct answer)

Correct answer: IFA (immunofluorescence assay) on blood smear

IFA detects FeLV p27 antigen within neutrophils and platelets; a positive IFA confirms progressive (persistent) viremia, whereas a negative IFA after a positive ELISA suggests a regressor or discordant result.

Question 274: A poultry flock develops acute respiratory distress, cyanosis of the comb and wattles, and hemorrhagic tracheitis with 40% mortality over 5 days. Which disease is most consistent with these findings?

Infectious bronchitis
Newcastle disease (velogenic form)
Infectious laryngotracheitis (ILT) (Correct answer)
Avian influenza (HPAI)

Correct answer: Infectious laryngotracheitis (ILT)

Infectious laryngotracheitis, caused by Gallid alphaherpesvirus 1, presents with severe hemorrhagic tracheitis, bloody mucus, gasping, and high mortality in affected flocks.

Question 275: A 4-week-old foal presents with a carpal valgus deformity of the right forelimb. The deviation is moderate and has not improved with stall rest and corrective hoof trimming. What is the most appropriate next step in managing this case to achieve a successful outcome?

Recommend euthanasia due to a poor prognosis for athletic function.
Continue conservative management as the growth plates will close soon.
Perform periosteal stripping on the medial aspect of the distal radius. (Correct answer)
Perform transphyseal bridging on the medial aspect of the distal radius.

Correct answer: Perform periosteal stripping on the medial aspect of the distal radius.

For a moderate carpal valgus (knock-kneed) deformity in a 4- to 6-week-old foal that is not responding to conservative therapy, periosteal stripping (also called a hemicircumferential periosteal transection and elevation) on the concave side (medial aspect) of the limb is the appropriate surgical intervention. This procedure is thought to accelerate growth on the slower-growing side of the physis. Transphyseal bridging is used on the convex (lateral) side to slow growth and is typically reserved for more severe deformities or older foals. Continuing conservative management is inappropriate as the optimal window for surgical correction is during rapid growth.

Question 276: A dog is diagnosed with leptospirosis after exposure to wildlife. Which organ system is MOST commonly affected, leading to the clinical presentation seen in acute leptospirosis?

Central nervous system
Renal and hepatic systems (Correct answer)
Respiratory system primarily
Musculoskeletal system

Correct answer: Renal and hepatic systems

Leptospira organisms have a particular tropism for renal tubular epithelium and hepatocytes, leading to acute kidney injury and hepatopathy as the dominant clinical syndrome.

Question 277: During a routine splenectomy in a 6-year-old DSH cat for splenic mast cell tumor, the surgeon encounters unexpected difficulty controlling hemorrhage from the short gastric vessels. Intraoperatively, the cat develops a sudden drop in systolic BP to 55 mmHg, bradycardia (HR 48 bpm), and becomes unresponsive. Which drug combination is MOST appropriate as the FIRST intervention?

Vasopressin 0.4 units/kg IV + atropine 0.02 mg/kg IV
Dopamine CRI at 5 µg/kg/min
Epinephrine 0.01 mg/kg IV alone
Atropine 0.04 mg/kg IV + epinephrine 0.01 mg/kg IV (Correct answer)

Correct answer: Atropine 0.04 mg/kg IV + epinephrine 0.01 mg/kg IV

This presentation — profound hypotension + bradycardia + unresponsiveness during mast cell tumor manipulation — is consistent with a massive histamine/tryptase release event (anaphylaxis or mast cell degranulation crisis). The combination of hypotension AND bradycardia (rather than the reflex tachycardia of simple hemorrhage) with intraoperative mast cell tumor handling strongly implicates degranulation. Atropine addresses the vagotonic bradycardia, and epinephrine is the drug of choice for anaphylaxis — it reverses bronchospasm, causes vasoconstriction (α1), and positive chronotropy/inotropy (β1/β2). Vasopressin is a second-line vasopressor but does not address the bradycardia or anaphylactic mechanism. A dopamine CRI has too slow an onset in this acute crisis.

Question 278: A 4-year-old Thoroughbred racehorse presents with acute onset severe (grade 4/5) right forelimb lameness following a morning workout. Ultrasonography reveals a complete core lesion of the superficial digital flexor tendon (SDFT) at the mid-metacarpal level with a cross-sectional area 40% greater than the contralateral limb. The owner inquires about intralesional platelet-rich plasma (PRP) therapy. Which statement most accurately reflects current evidence-based understanding of PRP in equine SDFT repair?

PRP provides superior outcomes compared to adipose-derived stem cells for core lesions >30% cross-sectional area
PRP accelerates early fiber alignment and reduces re-injury rates in racehorses when injected within the first 30 days
PRP has not consistently demonstrated improved long-term outcomes over controlled exercise rehabilitation alone in controlled trials (Correct answer)
PRP increases the ratio of type I to type III collagen in healed tendon, improving biomechanical strength

Correct answer: PRP has not consistently demonstrated improved long-term outcomes over controlled exercise rehabilitation alone in controlled trials

Despite widespread clinical use, PRP has not consistently shown superior long-term outcomes compared to controlled exercise rehabilitation alone in rigorous controlled clinical trials for equine SDFT injuries. While PRP contains growth factors (TGF-β, PDGF, IGF-1) that theoretically promote tendon healing, prospective blinded studies in racehorses have failed to demonstrate significant differences in re-injury rates or return-to-sport timelines. The evidence base remains limited by small sample sizes and methodological heterogeneity, making controlled exercise rehabilitation the only consistently evidence-supported intervention.

Question 279: A 3-year-old Soft-Coated Wheaten Terrier presents with hypoalbuminemia (1.4 g/dL), ascites, and normal liver enzymes. Protein-losing enteropathy is suspected. Which finding on intestinal biopsy would be most consistent with lymphangiectasia?

Dilated lacteals and lipid-laden macrophages (Correct answer)
Eosinophilic infiltration of the mucosa
Crypt abscesses and villous blunting
Plasma cell and lymphocyte infiltration of the lamina propria

Correct answer: Dilated lacteals and lipid-laden macrophages

Dilated lacteals with lipid-laden macrophages (lipogranulomas) are the hallmark histopathologic findings of intestinal lymphangiectasia.

Question 280: During a herd health visit to a 600-cow feedlot, you identify a pen of 150 steers (day 14 on feed) with a 9% morbidity rate. Pulled animals show biphasic fever, nasal discharge, and decreased rumination. At necropsy of a non-responder, you find cranioventral pulmonary consolidation, fibrinous pleuritis, and isolation of Mannheimia haemolytica serotype 1. The owner's current protocol uses metaphylaxis with tulathromycin on arrival. Which finding is MOST consistent with a failure of metaphylactic protocol rather than a true treatment failure?

A 9% morbidity rate is within acceptable limits for a high-risk pen and does not indicate protocol failure
Fibrinous pleuritis indicates a chronic infection predating arrival that metaphylaxis cannot address
M. haemolytica serotype 1 is intrinsically resistant to tulathromycin, indicating a wrong drug selection
The majority of morbidity cases are occurring between days 10–21 post-arrival, suggesting the 96-hour effective plasma concentration window of tulathromycin was exceeded before challenge (Correct answer)

Correct answer: The majority of morbidity cases are occurring between days 10–21 post-arrival, suggesting the 96-hour effective plasma concentration window of tulathromycin was exceeded before challenge

Tulathromycin achieves concentrations above the MIC for M. haemolytica in lung tissue for approximately 96 hours (4 days) post-injection, though tissue concentrations remain elevated longer. However, protection against clinical BRD is generally considered most effective for the first 10–14 days post-treatment. Morbidity clustering at days 10–21 indicates the window of metaphylactic protection has passed before the peak of viral/bacterial challenge — a pharmacokinetic/epidemiological timing mismatch. M. haemolytica serotype 1 retains susceptibility to macrolides including tulathromycin in most North American feedlot populations. Fibrinous pleuritis in a necropsy animal likely reflects disease progression in that individual, not herd-wide chronicity. A 9% rate in a high-risk pen is above acceptable thresholds (typically <5–8% depending on risk classification).

Question 281: A llama is treated with flunixin meglumine IV at the bovine label dose for 5 consecutive days for GI pain. Which adverse effect is MOST likely due to the species-specific pharmacokinetic difference compared to cattle?

Nephrotoxicity worsened by the llama's slower drug elimination half-life (Correct answer)
Right dorsal colitis from prolonged COX-1 inhibition in the hindgut
Bone marrow suppression from camelid sensitivity to NSAIDs
Hepatotoxicity from cytochrome P450 accumulation

Correct answer: Nephrotoxicity worsened by the llama's slower drug elimination half-life

Camelids (llamas, alpacas) have a significantly longer elimination half-life for flunixin meglumine (~10-12 hours) compared to cattle (~3-4 hours). Using the bovine dose and frequency leads to drug accumulation in camelids, with renal papillary necrosis and nephrotoxicity being the primary concern due to sustained COX-1 inhibition reducing renal prostaglandin synthesis. Right dorsal colitis is classically associated with horses on prolonged NSAIDs, not camelids.

Question 282: Which ultrasonographic finding is MOST consistent with gastric dilatation-volvulus (GDV) versus simple dilatation in a dog?

Compartmentalization of the stomach into two gas-filled regions on the right lateral view (Correct answer)
Inability to obtain gastric images due to gas artifact
Uniform gastric distension with fluid content
Thickening of the gastric wall with loss of wall layering

Correct answer: Compartmentalization of the stomach into two gas-filled regions on the right lateral view

GDV causes the stomach to rotate, creating a compartmentalized 'double bubble' appearance, whereas simple dilatation shows uniform distension.

Question 283: A goat kid presents at 2 days of age with failure to nurse, profuse watery diarrhea, and rapid dehydration. Feces are negative for Cryptosporidium and E. coli. Rotavirus ELISA is positive. Treatment priorities include:

Anthelmintic deworming
Corticosteroids to reduce intestinal inflammation
Sulfonamide antibiotics and probiotics
Oral electrolyte fluid therapy and supportive care (Correct answer)

Correct answer: Oral electrolyte fluid therapy and supportive care

Rotavirus diarrhea in neonatal ruminants is managed supportively with oral electrolyte replacement because the disease is viral and antibiotics are ineffective; correction of dehydration is paramount.

Question 284: A 12-year-old female spayed Domestic Shorthair cat is presented with a 2-month history of progressive weight loss despite a ravenous appetite (polyphagia). The owner also reports occasional vomiting and restlessness. On physical examination, you note a heart rate of 230 bpm, a thin body condition, and an unkempt haircoat. Which of the following is the most likely diagnosis?

Diabetes mellitus
Hyperthyroidism (Correct answer)
Inflammatory bowel disease
Chronic kidney disease

Correct answer: Hyperthyroidism

The combination of weight loss with polyphagia, tachycardia, and hyperactivity in an older cat is classic for hyperthyroidism. Diabetes mellitus can cause weight loss and polyphagia but is not typically associated with tachycardia or hyperactivity. Chronic kidney disease usually presents with weight loss and polyuria/polydipsia, but often with a decreased appetite. Inflammatory bowel disease typically involves weight loss, vomiting, and/or diarrhea, but not the other clinical signs noted.

Question 285: On a lateral thoracic radiograph, 'sternal contact' of the heart is increased in which cardiac condition?

Pericardial effusion
Left atrial enlargement
Right ventricular enlargement (Correct answer)
Pulmonary hypertension

Correct answer: Right ventricular enlargement

Right ventricular enlargement causes the heart to shift cranioventrally, increasing its contact with the sternum on the lateral view.

Question 286: A chinchilla presents with drooling, difficulty eating, and sharp molar spurs on oral exam. This condition is best described as:

Cheek pouch impaction
Oral candidiasis
Stomatitis
Slobbers (dental malocclusion) (Correct answer)

Correct answer: Slobbers (dental malocclusion)

Dental malocclusion in chinchillas, commonly called 'slobbers,' results from molar spurs that lacerate the tongue and cause hypersalivation.

Question 287: Gabapentin is increasingly used in veterinary patients for chronic and neuropathic pain. What is its primary mechanism of action?

NMDA glutamate receptor blockade
Mu-opioid receptor agonism
Cyclooxygenase-2 inhibition
Voltage-gated calcium channel alpha-2-delta subunit inhibition (Correct answer)

Correct answer: Voltage-gated calcium channel alpha-2-delta subunit inhibition

Gabapentin binds to the alpha-2-delta subunit of voltage-gated calcium channels in the dorsal horn of the spinal cord, reducing excitatory neurotransmitter release and dampening central sensitization.

Question 288: Which antifungal is the treatment of choice for feline cryptococcosis affecting the CNS?

Terbinafine
Ketoconazole
Fluconazole (Correct answer)
Amphotericin B alone

Correct answer: Fluconazole

Fluconazole achieves excellent CNS penetration and is the preferred long-term treatment for feline cryptococcal meningoencephalitis.

Question 289: An 8-month-old kitten presents with intention tremors of the head, broad-based stance, hypermetria, and falling toward the right. The neurologic examination is otherwise normal with no weakness. Which region of the nervous system is affected?

Right C1-C5 spinal cord segment
Right vestibular apparatus (peripheral)
Right side of the cerebellum (Correct answer)
Right cerebral hemisphere (forebrain)

Correct answer: Right side of the cerebellum

Intention tremors, hypermetria, and broad-based stance without weakness are signs of cerebellar disease. Falling/rolling ipsilaterally (toward the lesion side) with a unilateral cerebellar lesion reflects ipsilateral cerebellar hemispheric dysfunction (cerebellum has ipsilateral control). Forebrain lesions cause contralateral deficits with normal gait quality. Peripheral vestibular disease causes head tilt and nystagmus without hypermetria or intention tremor.

Question 290: A 3-year-old male neutered domestic ferret presents with episodic weakness, muscle fasciculations, and apparent 'stargazing' that resolves after eating. Blood glucose at presentation is 42 mg/dL. After dextrose bolus, the ferret stabilizes. Abdominal ultrasound reveals a 0.8 cm hypoechoic nodule in the left pancreatic lobe. Which statement about medical management while awaiting surgery is MOST accurate?

Frequent high-protein, low-carbohydrate meals alone are sufficient medical management for insulinoma without pharmacologic intervention
Diazoxide at 5–30 mg/kg/day is preferred over prednisone as first-line because it avoids adrenal suppression in a species prone to hyperadrenocorticism (Correct answer)
Octreotide SC injections are the first-line treatment of choice due to superior efficacy over prednisone in ferrets
Prednisone at 0.5–1 mg/kg PO BID is the preferred first-line medical management for insulinoma in ferrets

Correct answer: Diazoxide at 5–30 mg/kg/day is preferred over prednisone as first-line because it avoids adrenal suppression in a species prone to hyperadrenocorticism

Diazoxide inhibits insulin secretion and is actually the preferred first-line pharmacologic agent in ferrets when medical management is needed, particularly because ferrets are extremely prone to adrenocortical disease (hyperadrenocorticism). Using prednisone long-term risks masking adrenal disease signs and contributes to iatrogenic immunosuppression and muscle wasting. Diazoxide at 5–30 mg/kg/day (divided BID) avoids these concerns. Dietary management alone is insufficient for documented insulinoma with severe hypoglycemia. Octreotide has variable efficacy in ferrets and is not first-line. Prednisone is used but carries significant species-specific drawbacks that make diazoxide preferable when available.

Question 291: A cat with pleural effusion undergoes thoracocentesis. Analysis reveals chylous effusion (triglycerides > serum). What is the most common underlying cause in cats?

Thoracic duct lymphoma
Diaphragmatic hernia
Idiopathic chylothorax (Correct answer)
Congestive heart failure

Correct answer: Idiopathic chylothorax

Idiopathic chylothorax is the most common cause in cats when lymphoma and cardiac disease have been excluded, though thoracic duct abnormalities are suspected.

Question 292: A 7-year-old intact male Golden Retriever presents with polyuria, polydipsia, and a pendulous abdomen. Bloodwork reveals mild hyperglycemia, elevated ALP, and hypokalemia. Urine cortisol:creatinine ratio is elevated. A low-dose dexamethasone suppression test fails to suppress cortisol at 8 hours. An ACTH stimulation test shows an exaggerated response. Abdominal ultrasound reveals bilateral adrenal enlargement. Which additional finding would most strongly suggest concurrent occult neoplasia rather than PDH alone?

Urinary tract infection with Escherichia coli
Neurological signs with a pituitary mass > 1 cm on MRI (Correct answer)
Serum alkaline phosphatase > 1000 U/L
Failure to suppress at the 4-hour low-dose dexamethasone time point

Correct answer: Neurological signs with a pituitary mass > 1 cm on MRI

A pituitary macroadenoma (> 1 cm) detected on MRI in a dog with PDH indicates a large pituitary tumor that carries a worse prognosis and may cause neurological signs (circling, behavior change, blindness). This is distinct from a microadenoma and strongly shifts management toward radiation therapy in addition to or instead of medical adrenal blockade. Elevated ALP, UTI, and failure to suppress at 4 hours are all common features of PDH itself and do not specifically indicate concurrent occult neoplasia.

Question 293: In a dog with suspected intervertebral disc disease, which myelographic finding confirms extradural compression?

Complete absence of contrast cranial to the lesion
Pooling of contrast material within the spinal cord
Widening of the subarachnoid space at the lesion site
Thinning or deviation of the contrast column on one or both sides (Correct answer)

Correct answer: Thinning or deviation of the contrast column on one or both sides

Extradural compression from a disc extrusion causes thinning or lateral deviation of the myelographic contrast column at the lesion level.

Question 294: A 6-year-old Miniature Poodle has chronic small bowel diarrhea. Serum TLI is 2.0 µg/L (normal >2.5 µg/L). What is the most likely diagnosis?

Intestinal lymphoma
Lymphangiectasia
Exocrine pancreatic insufficiency (Correct answer)
Inflammatory bowel disease

Correct answer: Exocrine pancreatic insufficiency

A serum TLI below 2.5 µg/L is diagnostic for exocrine pancreatic insufficiency, reflecting markedly reduced pancreatic enzyme secretion.

Question 295: Feline calicivirus virulent systemic strain (VS-FCV) outbreaks are characterized by which distinctive clinical sign NOT typical of classic FCV?

Conjunctivitis
Oral ulceration
Sneezing
Subcutaneous edema and facial swelling (Correct answer)

Correct answer: Subcutaneous edema and facial swelling

VS-FCV causes severe systemic disease including facial and limb edema, skin ulceration, and high mortality, distinguishing it from classical FCV.

Question 296: A cat presents with corneal sequestrum and chronic ocular discharge. Which herpesvirus is most commonly implicated in this condition?

Feline leukemia virus
Feline immunodeficiency virus
Feline herpesvirus-1 (Correct answer)
Feline calicivirus

Correct answer: Feline herpesvirus-1

Feline herpesvirus-1 (FHV-1) is strongly associated with corneal sequestrum formation due to chronic corneal inflammation and ulceration.

Question 297: Which internal parasite of cattle causes 'bottle jaw' (submandibular edema) due to hypoproteinemia?

Ostertagia ostertagi
Cooperia oncophora
Haemonchus placei (Correct answer)
Trichostrongylus axei

Correct answer: Haemonchus placei

Haemonchus placei is a blood-sucking abomasal parasite that causes significant protein loss, leading to hypoproteinemia and the classic sign of submandibular edema (bottle jaw).

Question 298: A 9-year-old spayed female Labrador Retriever presents with a 4-month history of progressive rear limb weakness. The owner reports the dog can walk but stumbles, especially on slippery floors, and has difficulty rising. On neurologic exam, you observe proprioceptive deficits in both pelvic limbs (worse on the right), preserved but slightly diminished patellar reflexes bilaterally, and normal perineal reflex and anal tone. MRI of the thoracolumbar spine is unremarkable. Which diagnosis best explains this constellation of findings?

Fibrocartilaginous embolism at T12-T13
Myasthenia gravis (focal form)
Degenerative myelopathy (Correct answer)
Lumbosacral stenosis (cauda equina syndrome)

Correct answer: Degenerative myelopathy

Degenerative myelopathy (DM) classically presents as a slowly progressive, non-painful upper motor neuron (UMN) spastic paraparesis in older large-breed dogs (especially Labradors, GSDs, and Boxers), with proprioceptive ataxia and no sensory deficits. A critical diagnostic clue is that MRI is normal early in the disease — DM is a clinical and genetic diagnosis (SOD1 mutation) confirmed histopathologically. FCE would present acutely, not over 4 months. Cauda equina syndrome causes hyporeflexia, tail and perineal deficits, and lumbosacral pain. Focal MG causes megaesophagus/regurgitation, not proprioceptive deficits.

Question 299: A cattery owner presents with a problem of recurrent feline calicivirus (FCV) outbreaks despite strict vaccination protocols using modified-live calicivirus vaccines. PCR confirms FCV in affected cats. Affected cats display high fever (>106°F), facial and limb edema, skin ulceration, and 40% case fatality rate — a pattern different from classic FCV upper respiratory disease. Which statement BEST characterizes the virological basis of this outbreak and the limitation of current vaccines?

Virulent systemic FCV (VS-FCV) strains have undergone antigenic drift sufficient to escape neutralizing antibodies induced by vaccine strains, as FCV has an ssRNA genome with high mutation rates (Correct answer)
VS-FCV outbreaks are caused by FCV recombination with feline coronavirus, creating a chimeric virus not covered by monovalent vaccines
VS-FCV is a prion-mediated conformational variant of classic FCV that is resistant to inactivation by standard disinfectants used in cattery settings
Current vaccines fail because VS-FCV exclusively targets macrophages via a different receptor (junctional adhesion molecule-1 rather than feline junctional adhesion molecule)

Correct answer: Virulent systemic FCV (VS-FCV) strains have undergone antigenic drift sufficient to escape neutralizing antibodies induced by vaccine strains, as FCV has an ssRNA genome with high mutation rates

Virulent systemic FCV (VS-FCV or hemorrhagic fever-like FCV) represents highly pathogenic FCV strains capable of causing systemic disease with high mortality. FCV is a positive-sense single-stranded RNA virus (Caliciviridae) with a high mutation rate, allowing continuous antigenic drift. Studies have demonstrated that VS-FCV strains show reduced cross-neutralization by antibodies raised against vaccine strains — a key reason why fully vaccinated cats in outbreaks can still become severely ill. FCV does not recombine with coronavirus. Feline junctional adhesion molecule (fJAM-A) is the receptor for both classic and VS-FCV strains. VS-FCV is not prion-mediated. FCV is susceptible to bleach (1:32 dilution) but survives many quaternary ammonium compounds.

Question 300: A dog with a confirmed MDR1 (ABCB1) mutation (homozygous mutant) requires antiparasitic treatment for generalized demodicosis. Which drug combination poses the GREATEST risk of neurotoxicity in this patient?

Ivermectin + ketoconazole (Correct answer)
Doramectin + doxycycline
Selamectin + lufenuron
Milbemycin oxime + spinosad (Trifexis)

Correct answer: Ivermectin + ketoconazole

Ivermectin is a P-glycoprotein (P-gp) substrate; in MDR1-mutant dogs, reduced P-gp function allows accumulation of ivermectin in the CNS. Ketoconazole is a potent CYP3A4 and P-glycoprotein inhibitor. Co-administration of ketoconazole with ivermectin in a P-gp-deficient dog compounds the risk dramatically: ivermectin is already not being effluxed from the CNS, and ketoconazole further inhibits any residual P-gp activity and slows ivermectin hepatic metabolism. This combination has caused fatal neurotoxicity. Milbemycin + spinosad is approved for use in MDR1-mutant dogs at label doses. Selamectin has a wide safety margin even in MDR1-mutant dogs. Doramectin carries risk in MDR1 dogs, but the combination with doxycycline does not add a pharmacokinetic interaction that amplifies CNS accumulation.

Question 301: A herd of 30 beef cow-calf pairs is experiencing an outbreak of bloody diarrhea in calves 5–21 days of age. Mortality has reached 30% despite oral electrolyte therapy. Post-mortem findings include hemorrhagic enteritis of the jejunum and ileum with villous necrosis and blunting. Gram-positive, spore-forming rods are visualized on intestinal smear. PCR of intestinal contents is positive for NetB toxin gene. Which pathogen and the toxin most responsible for villous destruction are correctly identified?

Clostridium perfringens Type A; alpha toxin
Clostridium perfringens Type D; epsilon toxin
Clostridium difficile; toxin B
Clostridium perfringens Type C; beta toxin (Correct answer)

Correct answer: Clostridium perfringens Type C; beta toxin

NetB toxin is produced by Clostridium perfringens Type C and is a pore-forming toxin. However, the primary virulence factor in Type C hemorrhagic enteritis of neonatal calves is beta toxin (cpb gene), which causes severe necrotizing enteritis by disrupting intestinal epithelium. Beta toxin is protease-sensitive, which is why it preferentially affects neonates lacking tryptic activity. Type A causes mild diarrhea via alpha toxin; Type D causes pulpy kidney/edema disease via epsilon toxin; C. difficile produces toxins A and B in a different syndrome. The NetB gene in the PCR confirms Type C.

Question 302: A 7-year-old intact male dog is being treated with ketoconazole for a systemic fungal infection. The owner also mentions the dog is on cyclosporine for immune-mediated thrombocytopenia. Which pharmacokinetic mechanism best explains the expected drug interaction between these two agents?

Ketoconazole displaces cyclosporine from plasma protein binding sites, increasing free drug
Cyclosporine competitively inhibits ketoconazole absorption at intestinal transporters
Ketoconazole induces P-glycoprotein, increasing cyclosporine efflux from enterocytes
Ketoconazole inhibits CYP3A4, reducing cyclosporine metabolism and increasing its plasma concentration (Correct answer)

Correct answer: Ketoconazole inhibits CYP3A4, reducing cyclosporine metabolism and increasing its plasma concentration

Ketoconazole is a potent inhibitor of cytochrome P450 3A4 (CYP3A4), the primary enzyme responsible for cyclosporine metabolism. Inhibition of this enzyme markedly reduces cyclosporine clearance, leading to elevated plasma concentrations and potential nephrotoxicity and neurotoxicity. Clinicians sometimes exploit this interaction intentionally to reduce cyclosporine dosing costs, but it requires careful monitoring.

Question 303: On thoracic radiographs, a cat with hypertrophic cardiomyopathy (HCM) most commonly shows which cardiac silhouette shape on the VD view?

Valentine heart shape (biatrial enlargement) (Correct answer)
Normal silhouette despite severe disease
Globoid (round) silhouette
Right-sided enlargement with D-shape

Correct answer: Valentine heart shape (biatrial enlargement)

HCM in cats classically produces a 'valentine heart' shape on VD radiographs due to bilateral atrial enlargement, though some cats have relatively normal-appearing hearts.

Question 304: A horse with forelimb lameness has a positive response to hoof testers over the medial heel region. After palmar digital nerve block the lameness is only partially improved. The MOST appropriate next step is:

Block the navicular bursa directly
Apply a bar shoe and reassess in 6 weeks
Repeat the palmar digital block with a higher volume
Perform an intra-articular coffin joint block (Correct answer)

Correct answer: Perform an intra-articular coffin joint block

When a palmar digital block provides only partial improvement, an intra-articular coffin joint block helps determine whether the DIP joint is contributing to the residual lameness.

Question 305: A dog receives an overdose of acepromazine. Which statement about acepromazine reversal is correct?

Reversal can be achieved with atipamezole
There is no specific reversal agent; treatment is supportive (Correct answer)
Naloxone effectively reverses acepromazine sedation
Flumazenil fully reverses phenothiazine effects

Correct answer: There is no specific reversal agent; treatment is supportive

Acepromazine, a phenothiazine tranquilizer, has no specific reversal agent; management consists of supportive care including IV fluids and vasopressors for hypotension.

Question 306: Which urine specific gravity value is most consistent with isosthenuria in a cat with suspected chronic kidney disease?

1.005
1.012 (Correct answer)
1.025
1.040

Correct answer: 1.012

Isosthenuria (USG 1.008–1.012) indicates the kidneys cannot concentrate or dilute urine beyond plasma osmolality, a hallmark of significant tubular dysfunction.

Question 307: A 4-year-old male Shar-Pei presents with recurrent fever episodes lasting 1–3 days, swollen hocks, and intermittent vomiting. Between episodes the dog appears normal. CBC and chemistry during a febrile episode show neutrophilia with a left shift and mildly elevated BUN. Urinalysis shows 3+ proteinuria. Which underlying pathophysiologic mechanism is most directly responsible for the proteinuria in this dog?

Immune-complex glomerulonephritis secondary to chronic interleukin-6 overproduction
Pyelonephritis from recurrent bacteremia during febrile crises
Tubular proteinuria from aminoglycoside nephrotoxicity used to treat febrile episodes
Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome (Correct answer)

Correct answer: Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome

Shar-Peis are predisposed to Shar-Pei Autoinflammatory Disease (SPAID), formerly called Familial Shar-Pei Fever, caused by dysregulation of the inflammasome with markedly elevated IL-6 and IL-18. Chronic inflammation drives sustained serum amyloid A (SAA) production. SAA fibrils deposit as reactive amyloid A (AA amyloidosis) preferentially in the renal medullary interstitium and glomeruli in Shar-Peis, causing progressive proteinuria and eventual renal failure — a pattern distinct from other breeds where hepatic deposition predominates. Immune-complex GN is a feature of some breeds but is not the primary mechanism in SPAID-associated renal disease.

Question 308: A 4-year-old ferret presents with muscle wasting, hindlimb weakness, and hypoglycemia (blood glucose 40 mg/dL) that resolves with dextrose. The most likely diagnosis is:

Aleutian disease
Insulinoma (Correct answer)
Adrenal gland disease
Lymphoma

Correct answer: Insulinoma

Insulinoma is the most common pancreatic tumor in ferrets over 3 years old and classically causes fasting hypoglycemia, weakness, and neurological signs relieved by glucose administration.

Question 309: Among commonly used local anesthetics in veterinary medicine, which agent provides the LONGEST duration of nerve block?

Lidocaine
Procaine
Bupivacaine (Correct answer)
Mepivacaine

Correct answer: Bupivacaine

Bupivacaine has the longest duration of action among common local anesthetics (4–8 hours for nerve blocks) due to its high protein binding and lipid solubility, making it ideal for postoperative pain management.

Question 310: A veterinarian administers a drug that causes dose-dependent sinus bradycardia in a horse. Atropine is given but produces no improvement. Which drug class most likely caused this atropine-resistant bradycardia?

Cardiac glycoside (e.g., digoxin)
Calcium channel blocker (e.g., diltiazem) (Correct answer)
Opioid agonist (e.g., butorphanol)
Alpha-2 adrenergic agonist (e.g., detomidine)

Correct answer: Calcium channel blocker (e.g., diltiazem)

Calcium channel blockers such as diltiazem decrease SA node automaticity and AV node conduction by blocking L-type calcium channels — a mechanism entirely independent of muscarinic receptors. Atropine works by blocking vagal (parasympathetic) tone via muscarinic receptor antagonism. Because diltiazem's bradycardic effect does not rely on acetylcholine-mediated vagal input, atropine cannot reverse it. Alpha-2 agonists (e.g., detomidine) cause bradycardia primarily through increased vagal tone and are at least partially responsive to atropine. Opioids cause mild bradycardia that is vagally mediated and atropine-responsive. Digoxin toxicity may respond partially to atropine for its vagomimetic effects.

Question 311: Metabolic bone disease (MBD) in captive reptiles is most commonly caused by which combination of factors?

Excess vitamin D3 supplementation
Hyperthyroidism
Calcium/phosphorus imbalance and UV-B light deficiency (Correct answer)
Bacterial osteomyelitis secondary to trauma

Correct answer: Calcium/phosphorus imbalance and UV-B light deficiency

MBD in reptiles results from inadequate dietary calcium, improper Ca:P ratios, and insufficient UV-B light for endogenous vitamin D3 synthesis.

Question 312: A county health department requests a veterinary public health consultation after identifying a Brucella melitensis cluster: 3 human cases linked to consumption of imported soft cheese from a country where small ruminant brucellosis is enzootic. The cheese was sold at a single specialty grocery. Under the FDA Food Safety Modernization Act (FSMA) and related frameworks, which of the following agency actions and legal authorities most accurately describes the coordinated federal response?

FDA issues a mandatory recall under FSMA Section 206 authority (Mandatory Recall) for the implicated cheese lot; CDC coordinates human case investigation under Epi-Aid protocol; USDA-APHIS is NOT involved because the cheese is an imported finished food product, not live animals or animal semen (Correct answer)
USDA-FSIS issues the mandatory recall because Brucella is a Class A bioterrorism agent and all biological threat responses fall under USDA jurisdiction; CDC conducts the outbreak investigation under the Emergency Operations Center framework
FDA and USDA-FSIS have co-equal recall authority for all imported foods; both agencies must jointly sign any mandatory recall order, creating a mandatory 72-hour interagency consultation period before any public notification
CDC has primary recall authority for foodborne illness outbreaks involving zoonotic pathogens because CDC is the lead agency for all zoonotic disease response under the Public Health Service Act Section 361

Correct answer: FDA issues a mandatory recall under FSMA Section 206 authority (Mandatory Recall) for the implicated cheese lot; CDC coordinates human case investigation under Epi-Aid protocol; USDA-APHIS is NOT involved because the cheese is an imported finished food product, not live animals or animal semen

Under FSMA (21 USC §350l), FDA has mandatory recall authority for food products — including imported cheese — when there is reasonable probability the food is adulterated or misbranded and will cause serious adverse health consequences. Before FSMA (2011), FDA only had voluntary recall authority. The CDC coordinates human epidemiological investigation (case finding, exposure interviews, Epi-Aid deployment) but does not have recall authority. USDA-FSIS regulates meat, poultry, and egg products — not dairy imported as finished food. USDA-APHIS is relevant for live animal imports and animal product imports that could introduce foreign animal disease, but imported pasteurized/semi-soft cheese falls under FDA. Brucella melitensis is indeed a Tier 1 select agent, but that designation triggers additional USDA/CDC select agent program notification, not a transfer of recall authority to USDA-FSIS.

Question 313: A radiograph of a cat's elbow shows periarticular soft tissue swelling and subchondral bone lysis without significant new bone production. This pattern is most consistent with:

Degenerative joint disease
Osteochondrosis dissecans
Septic arthritis (Correct answer)
Hypertrophic osteodystrophy

Correct answer: Septic arthritis

Septic arthritis characteristically causes joint space narrowing, subchondral bone lysis, and periarticular soft tissue swelling with minimal productive bone response.

Question 314: During an arthroscopic surgery of the equine tarsocrural joint, you inadvertently lacerate the medial branch of the deep peroneal nerve. Which immediate postoperative complication is most specifically associated with this iatrogenic injury in the horse?

Inability to extend the digit, resulting in knuckling at the fetlock
Persistent swelling of the dorsomedial tarsocrural joint pouch due to impaired lymphatic drainage
Loss of sensation over the dorsal metatarsus with no motor deficit (Correct answer)
Denervation atrophy of the extensor digitorum longus muscle

Correct answer: Loss of sensation over the dorsal metatarsus with no motor deficit

The medial branch of the deep peroneal (fibular) nerve in the horse is primarily sensory to the dorsal metatarsus and dorsal fetlock region. Damage to this branch produces analgesia/hypoalgesia of the dorsal metatarsus without meaningful motor loss, since the motor contributions to the digital extensors arise from the main trunk more proximally. Knuckling at the fetlock results from damage to the extensor branches of the peroneal nerve much more proximally, or from true extensor muscle denervation — not from the medial branch at the tarsocrural level. Lymphatic effects are not attributable to this nerve.

Question 315: A 5-year-old spayed female domestic shorthair cat presents with a 2-day history of open-mouth breathing and severe dyspnea. On auscultation, heart sounds are muffled ventrally and lung sounds are absent in the ventral thorax bilaterally. Thoracocentesis yields 180 mL of milky, white-opaque fluid from each hemithorax. Cytology shows small lymphocytes predominating with a triglyceride concentration greater than serum. What is the most likely underlying etiology in this cat?

Diaphragmatic hernia with hepatic incarceration
Cardiac lymphoma causing thoracic duct obstruction
Right-sided heart failure from hypertrophic cardiomyopathy
Idiopathic chylothorax (Correct answer)

Correct answer: Idiopathic chylothorax

Idiopathic chylothorax is the most common cause of chylothorax in cats (~50% of cases). While lymphoma and cardiac disease are differentials, lymphoma would typically show neoplastic lymphocytes on cytology, and HCM-associated chylothorax is relatively rare. The milky fluid with chylomicrons (triglycerides > serum triglycerides) and small lymphocyte predominance is classic chylothorax; without neoplastic cells and with a normal-appearing cardiac silhouette bilaterally, idiopathic etiology is most likely.

Question 316: A dairy herd has an elevated somatic cell count (SCC) averaging 450,000 cells/mL despite a rigorous post-dip protocol and dry cow therapy. Bulk tank cultures repeatedly grow Streptococcus agalactiae. Which intervention is MOST likely to eliminate this pathogen from the herd?

Implement selective dry cow therapy based on individual cow SCC thresholds above 200,000 cells/mL
Switch post-dip solution from iodine to chlorhexidine and increase milking frequency to three times daily
Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy (Correct answer)
Administer a Streptococcus agalactiae bacterin vaccine to all lactating cows to reduce new infection rate

Correct answer: Segregate and cull all chronically infected cows, treat all culture-positive cows with intramammary penicillin, and implement herd-level blanket dry cow therapy

Streptococcus agalactiae is a contagious mastitis pathogen that is obligately associated with the bovine mammary gland. It is exquisitely sensitive to penicillin and can be eradicated from a herd through a combination of treating all infected cows (culture-positive), applying blanket dry cow therapy, segregating or culling chronic cases, and strict milking hygiene. Switching teat dip chemistry (B) addresses teat-end exposure but does not treat existing infections. There is no licensed S. agalactiae bacterin shown to eliminate an active herd infection (C). Selective dry cow therapy (D) would leave infected cows untreated at dry-off, perpetuating the reservoir.

Question 317: Cunean bursitis in horses with bone spavin is associated with inflammation of which structure?

Bicipital bursa of the shoulder
Navicular bursa of the hind foot
Calcaneal bursa
Bursa beneath the cunean (medial) branch of the cranial tibial tendon (Correct answer)

Correct answer: Bursa beneath the cunean (medial) branch of the cranial tibial tendon

Cunean bursitis involves the bursa located beneath the cunean branch of the cranial tibial tendon as it crosses the medial aspect of the hock, often concurrent with bone spavin.

Question 318: A commercial feedlot is experiencing a higher-than-expected prevalence of respiratory disease in newly arrived cattle. Bovine Respiratory Disease Complex (BRDC) risk modeling suggests the cattle are high-risk. The veterinarian is evaluating metaphylaxis protocols. Which of the following statements BEST reflects evidence-based practice regarding metaphylactic antimicrobial selection?

The antimicrobial selected for metaphylaxis should be a different class from the anticipated treatment antimicrobial to preserve treatment options (Correct answer)
Florfenicol should be avoided in metaphylaxis because it selects for multi-drug resistant Mannheimia haemolytica
Tulathromycin is preferred because its 14-day tissue half-life provides sustained bacteriostatic activity, eliminating the need for re-treatment in most animals
Enrofloxacin is the most effective metaphylactic agent because fluoroquinolones are concentration-dependent and achieve high lung-to-plasma ratios

Correct answer: The antimicrobial selected for metaphylaxis should be a different class from the anticipated treatment antimicrobial to preserve treatment options

Evidence-based antimicrobial stewardship in feedlot medicine recommends that the drug class used for metaphylaxis (mass treatment at arrival) should differ from the class reserved for treatment of clinical cases. If the same class is used for both, animals that fail metaphylaxis and develop BRD are then treated with a related drug to which the pathogen may already have reduced susceptibility. Using a different class preserves efficacy at the treatment step. Option A overstates tulathromycin's efficacy — a significant proportion of animals still require re-treatment. Option B is not supported by evidence as a primary reason to avoid florfenicol. Option D is misleading: enrofloxacin (a fluoroquinolone) is a critically important antimicrobial class and its use in metaphylaxis is controversial from a stewardship standpoint, and it is not the most effective choice for this reason.

Question 319: A 9-year-old Golden Retriever is diagnosed with protein-losing nephropathy. UPC ratio is 4.8. Which antihypertensive class is considered first-line therapy to reduce proteinuria?

Beta-blockers
Calcium channel blockers
ACE inhibitors (Correct answer)
Loop diuretics

Correct answer: ACE inhibitors

ACE inhibitors (e.g., enalapril, benazepril) reduce glomerular capillary pressure and proteinuria and are first-line therapy for PLN.

Question 320: Which drug class is contraindicated in cats due to their deficiency in UDP-glucuronosyltransferase?

Aminoglycosides
Fluoroquinolones
Macrolide antibiotics
NSAIDs metabolized via glucuronidation (Correct answer)

Correct answer: NSAIDs metabolized via glucuronidation

Cats lack sufficient UDP-glucuronosyltransferase activity, making drugs like acetaminophen and certain NSAIDs dependent on glucuronidation highly toxic.

Question 321: A 6-year-old intact male English Bulldog is scheduled for soft palate resection. During inhalant anesthesia with isoflurane, the patient develops a ventricular bigeminy rhythm. Which of the following inhalant agents, if used instead, would have posed the GREATEST risk for sensitizing the myocardium to catecholamine-induced arrhythmias in this patient?

Desflurane
Sevoflurane
Halothane (Correct answer)
Isoflurane

Correct answer: Halothane

Halothane is well-documented to sensitize the myocardium to catecholamine-induced arrhythmias, a property far more pronounced than with modern agents like isoflurane, sevoflurane, or desflurane. This is particularly relevant in brachycephalic patients where hypoxia and hypercapnia can elevate endogenous catecholamines. Halothane's arrhythmogenic potential was a major reason it fell out of favor in veterinary and human anesthesia.

Question 322: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?

Mu-opioid receptor agonism
Alpha-2 adrenergic receptor agonism (Correct answer)
GABA-A receptor potentiation
NMDA receptor antagonism

Correct answer: Alpha-2 adrenergic receptor agonism

Alpha-2 adrenergic agonists such as xylazine and dexmedetomidine bind presynaptic and postsynaptic alpha-2 receptors in the CNS and periphery, producing dose-dependent sedation, muscle relaxation, and analgesia.

Question 323: A 3-year-old intact male ferret presents with insulinoma-related hypoglycemia. The clinician elects to use diazoxide as medical management. Which mechanism of action makes diazoxide appropriate for this condition?

It opens ATP-sensitive potassium channels in pancreatic beta cells, hyperpolarizing the membrane and inhibiting insulin release (Correct answer)
It blocks GLUT-2 transporters in beta cells, preventing glucose sensing and suppressing insulin secretion
It competitively inhibits glucokinase in beta cells, reducing glucose-stimulated insulin secretion
It stimulates hepatic glycogenolysis via glucagon receptor agonism, raising blood glucose independent of insulin

Correct answer: It opens ATP-sensitive potassium channels in pancreatic beta cells, hyperpolarizing the membrane and inhibiting insulin release

Diazoxide acts by opening ATP-sensitive potassium channels (K-ATP channels) in pancreatic beta cells. This hyperpolarizes the cell membrane, preventing calcium influx through voltage-gated calcium channels, and thereby inhibiting insulin exocytosis. This directly counteracts the excessive autonomous insulin secretion from insulinoma cells. In contrast, sulfonylureas (like glipizide) close these same K-ATP channels, stimulating insulin release — making them contraindicated in insulinoma. Glucokinase inhibition, GLUT-2 blockade, or glucagon receptor agonism are not diazoxide's mechanisms.

Question 324: A 3-year-old Labrador Retriever ingested approximately 6 mg/kg of acetaminophen 2 hours ago. It is asymptomatic. What is the most appropriate treatment?

Vitamin K1 administration
Induced emesis only
Activated charcoal alone
N-acetylcysteine and supportive care (Correct answer)

Correct answer: N-acetylcysteine and supportive care

N-acetylcysteine replenishes glutathione stores and is the antidote for acetaminophen toxicity; it should be combined with supportive care even in an asymptomatic patient presenting within 4 hours of ingestion.

Question 325: Which dietary management strategy implemented during the final 2-3 weeks of the dry period is most effective for preventing periparturient hypocalcemia (milk fever) in dairy cows?

Feeding a diet high in calcium to 'prime' the system.
Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD). (Correct answer)
Maximizing dietary potassium to improve rumen function.
Supplementing with high levels of intravenous calcium.

Correct answer: Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD).

Feeding a diet with a negative Dietary Cation-Anion Difference (DCAD), also known as an acidogenic diet, is the most effective nutritional strategy to prevent milk fever. This diet induces a mild metabolic acidosis, which improves the cow's ability to mobilize calcium from bone and absorb it from the gut in response to parathyroid hormone (PTH) when the massive demand for calcium begins at calving. Feeding high calcium pre-calving or high potassium actually increases the risk of milk fever. IV calcium is a treatment, not a preventative feeding strategy.

Question 326: Which serum biomarker is most specific for acute pancreatitis diagnosis in cats?

Serum amylase
Serum lipase
Feline pancreatic lipase immunoreactivity (fPLI/Spec fPL) (Correct answer)
Serum trypsin-like immunoreactivity (fTLI)

Correct answer: Feline pancreatic lipase immunoreactivity (fPLI/Spec fPL)

Feline pancreatic lipase immunoreactivity (Spec fPL) is the most sensitive and specific biomarker for pancreatitis diagnosis in cats, unlike amylase and lipase which lack specificity.

Question 327: A horse is found dead in the pasture after a period of colic. Necropsy reveals a segment of jejunum that is dark red-black, wet, and lacks motility when manipulated, with a well-demarcated transition from normal bowel. The mesenteric vessels to this segment contain thrombi. This pattern is most consistent with:

Strangulating obstruction with venous infarction from mesenteric thrombus (Correct answer)
Large colon displacement — non-strangulating obstruction
Strangulating lipoma causing small intestinal volvulus
Anterior enteritis (proximal duodenojejunitis)

Correct answer: Strangulating obstruction with venous infarction from mesenteric thrombus

Dark red-black discoloration ('red infarction') with a sharp demarcation line and mesenteric thrombosis indicates strangulating obstruction with venous occlusion leading to hemorrhagic infarction. The bowel is non-viable. Strangulating lipomas cause physical constriction but don't typically involve mesenteric thrombi as the primary lesion. Non-strangulating obstructions do not produce immediate full-thickness ischemic necrosis.

Question 328: A cat with feline asthma is presented in respiratory distress with expiratory wheezes. After initial stabilization with oxygen, which drug is preferred for acute bronchodilation?

Terbutaline (subcutaneous) (Correct answer)
Cyproheptadine (oral)
Prednisolone (oral)
Theophylline (oral)

Correct answer: Terbutaline (subcutaneous)

Terbutaline given subcutaneously or IM is the drug of choice for acute bronchospasm in cats because of its rapid onset as a beta-2 agonist.

Question 329: A new pen-side antigen test for Bovine Respiratory Syncytial Virus (BRSV) is evaluated in a group of 300 calves. The results are as follows: 85 calves that are truly positive for BRSV test positive. 190 calves that are truly negative for BRSV test negative. 15 truly positive calves test negative. 10 truly negative calves test positive. What is the specificity of this new test?

95.0% (Correct answer)
85.0%
91.7%
90.9%

Correct answer: 95.0%

Specificity measures a test's ability to correctly identify disease-free individuals. The formula is: Specificity = [True Negatives / (True Negatives + False Positives)] * 100. In this scenario, the True Negatives are 190 and the False Positives are 10. Therefore, Specificity = [190 / (190 + 10)] * 100 = [190 / 200] * 100 = 95.0%.

Question 330: A 450 kg dairy cow at 10 days postpartum develops acute septic metritis with a fetid red-brown uterine discharge, fever of 40.8°C, and milk drop. Culture yields a pure growth of Trueperella pyogenes. Her BCS at dry-off was 4.0/5.0, and she had a twins delivery. You elect to treat with intrauterine cephapirin. Which additional systemic treatment is MOST pharmacologically justified given the likely concurrent metabolic status of this cow?

Flunixin meglumine IV to reduce endotoxemia and support uterine motility
Dexamethasone IM to suppress the systemic inflammatory cascade
Oxytocin IM to enhance uterine involution and lochia drainage
Propylene glycol oral drench to address subclinical ketosis compounding immunosuppression (Correct answer)

Correct answer: Propylene glycol oral drench to address subclinical ketosis compounding immunosuppression

This cow is at high risk for subclinical or clinical ketosis: she was over-conditioned at dry-off (BCS 4.0/5.0) and carried twins, both major risk factors for negative energy balance postpartum. Ketosis causes significant immunosuppression — neutrophil function is directly impaired by elevated BHBA — which underlies her susceptibility to metritis. Propylene glycol drenching addresses this by serving as a gluconeogenic precursor to restore energy balance and normalize immune function. Flunixin is reasonable for pain and anti-endotoxin effects but does not address the root immunosuppression. Oxytocin has limited efficacy beyond 48 hours post-partum once receptors downregulate. Dexamethasone is contraindicated as it will further suppress immunity.

Question 331: A dog undergoes hindlimb amputation. Which regional anesthetic technique would provide the MOST comprehensive perioperative analgesia for this procedure?

Lumbosacral epidural with morphine and lidocaine (Correct answer)
Wound soaker catheter only
Intrapleural bupivacaine instillation
Brachial plexus block

Correct answer: Lumbosacral epidural with morphine and lidocaine

A lumbosacral epidural combining an opioid (morphine) for prolonged analgesia and a local anesthetic (lidocaine/bupivacaine) for sensory and motor blockade provides the most effective and comprehensive analgesia for hindlimb amputations.

Question 332: A veterinarian is assessing a feedlot for bovine respiratory disease (BRD). Which scoring system is most widely used to objectively evaluate respiratory signs in individual cattle at the pen level?

FAMACHA scoring system
California Mastitis Test (CMT) adaptation for BRD
Bovine Respiratory Disease Scoring System (BRDS) by McGuirk (Correct answer)
Body condition scoring (BCS)

Correct answer: Bovine Respiratory Disease Scoring System (BRDS) by McGuirk

The McGuirk Bovine Respiratory Disease Scoring System evaluates rectal temperature, nasal discharge, eye discharge, ear position, and head carriage to provide an objective BRD score for pull decisions.

Question 333: Which radiographic view is most useful for evaluating the dens (odontoid process) of the axis (C2) in a dog for atlantoaxial instability?

Lateral cervical with extension
Lateral cervical with flexion
Oblique cervical
Open-mouth ventrodorsal (Correct answer)

Correct answer: Open-mouth ventrodorsal

The open-mouth ventrodorsal view projects the dens through the mouth and allows direct visualization of the atlantoaxial articulation and dens morphology.

Question 334: A veterinarian performs an abdominal ultrasound on a dog with acute vomiting and anorexia. Which finding is most specific for a mechanical small intestinal obstruction?

Peristaltic waves are increased to 6-7 contractions per minute throughout the small intestine.
Hyperechoic mesenteric fat is noted surrounding the entire small bowel.
A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point. (Correct answer)
The intestinal wall is diffusely thickened with preserved layering.

Correct answer: A segment of intestine is severely dilated with fluid (>1.6 times the diameter of the aorta) proximal to a distinct transition point.

The most reliable ultrasonographic sign of a mechanical small intestinal obstruction is segmental dilation of the intestine proximal to the obstruction. A commonly used objective criterion is a small intestinal diameter greater than 1.6 times the diameter of the aorta. Other signs include a visible foreign body, plication, or intussusception.

Question 335: Cryptosporidium serpentis infection in ball pythons most characteristically affects which organ, producing a pathognomonic clinical sign?

Kidneys, causing gout
Liver, causing icterus
Stomach, causing mid-body swelling and regurgitation (Correct answer)
Small intestine, causing chronic diarrhea

Correct answer: Stomach, causing mid-body swelling and regurgitation

Cryptosporidium serpentis causes gastric hypertrophy in snakes, manifesting as a classic mid-body bulge and chronic regurgitation.

Question 336: During a TPLO in a dog, the surgeon requests addition of an NSAID for multimodal analgesia. The dog has received acepromazine and morphine as premedication. Which consideration is most important before administering carprofen?

Carprofen is contraindicated with morphine due to serotonin syndrome risk
Carprofen must be given at least 2 hours before morphine to avoid drug interaction
NSAIDs are contraindicated with acepromazine due to additive CNS depression
Confirm the dog has normal renal perfusion before NSAID administration (Correct answer)

Correct answer: Confirm the dog has normal renal perfusion before NSAID administration

NSAIDs inhibit prostaglandin-mediated afferent arteriolar dilation in the kidney; adequate renal perfusion must be confirmed before perioperative NSAID use to prevent acute kidney injury.

Question 337: A 9-year-old Labrador Retriever is diagnosed with stage 3 chronic kidney disease (IRIS). Serum phosphorus is 6.8 mg/dL. Which intervention is most important to slow CKD progression?

Phosphate restriction and phosphate binders (Correct answer)
IV fluid diuresis three times weekly
Increased protein supplementation
Sodium restriction alone

Correct answer: Phosphate restriction and phosphate binders

Phosphate restriction through diet and phosphate binders reduces renal mineralization and is one of the most evidence-based strategies to slow CKD progression.

Question 338: Which of the following medications is a potent, broad-spectrum antiemetic that functions by antagonizing neurokinin-1 (NK-1) receptors in the central vomiting center?

Ondansetron
Maropitant (Correct answer)
Famotidine
Metoclopramide

Correct answer: Maropitant

Maropitant is a neurokinin-1 (NK-1) receptor antagonist. It works by blocking the binding of Substance P, a key neurotransmitter in the emetic pathway, at NK-1 receptors located in the vomiting center and the chemoreceptor trigger zone. This mechanism makes it highly effective against vomiting from both central and peripheral stimuli. Ondansetron is a serotonin (5-HT3) antagonist, metoclopramide is primarily a dopamine (D2) antagonist, and famotidine is an H2-receptor antagonist used to reduce stomach acid.

Question 339: During a pre-purchase exam of a 5-year-old Quarter Horse, grade 3/5 left forelimb lameness is localized to the foot with a palmar digital nerve block. Radiographs reveal navicular bone erosions and synovial invaginations. The diagnosis is:

Laminitis with rotation
Pedal osteitis
Distal phalanx fracture
Navicular syndrome (palmar foot pain) (Correct answer)

Correct answer: Navicular syndrome (palmar foot pain)

Navicular syndrome is characterized by palmar foot pain, positive response to palmar digital nerve block, and radiographic changes including synovial fossae and flexor cortex erosions of the navicular bone.

Question 340: A dog has a myelogram that shows a contrast column that is deviated to one side and compressed at a single level but does not completely stop. This pattern is most consistent with:

Intradural-extramedullary mass
Normal variant
Extradural compression (disc herniation) (Correct answer)
Intramedullary lesion (tumor/edema)

Correct answer: Extradural compression (disc herniation)

Extradural lesions (such as disc material or vertebral bone) deviate and compress the contrast column from the outside without interrupting the intrathecal flow completely.

Question 341: On a ventrodorsal thoracic radiograph, the cardiac silhouette of a healthy dog should not exceed what percentage of the thoracic width at the level of the 8th rib?

75%
70%
50%
60% (Correct answer)

Correct answer: 60%

The cardiac silhouette on a VD projection normally occupies no more than 60% of the thoracic width at the level of the 8th intercostal space.

Question 342: A 2-year-old indoor cat is presented to the emergency clinic with acute onset of vomiting, lethargy, and anorexia. The owner recently received a floral arrangement containing lilies. On physical examination, the cat is dehydrated and has painful kidneys on palpation. Bloodwork reveals severe azotemia. Which of the following is the most critical initial treatment for this suspected toxicity?

N-acetylcysteine administration
Intravenous fluid diuresis (Correct answer)
Peritoneal dialysis
Administration of activated charcoal and a cathartic

Correct answer: Intravenous fluid diuresis

Ingestion of any part of a lily plant (Lilium or Hemerocallis species) can cause severe, acute renal failure in cats. The primary mechanism is acute tubular necrosis. The cornerstone of treatment is aggressive intravenous fluid therapy to support renal perfusion, promote diuresis, and flush out the unknown nephrotoxin. While decontamination with activated charcoal is useful if ingestion was very recent, fluid therapy is the most critical life-saving intervention once clinical signs have developed. N-acetylcysteine is the antidote for acetaminophen toxicity, and peritoneal dialysis is reserved for anuric patients unresponsive to fluid therapy.

Question 343: A 900-cow Holstein dairy herd participates in a reproductive program using GnRH-based synchronization (Ovsynch). Despite high estrus synchronization compliance, 21-day pregnancy rates have plateaued at 18%. Detailed records show: AI submission rate 92%, conception rate (CR) 21%, pregnancy loss 12% (day 28–56). The reproductive specialist suspects subclinical endometritis. Which diagnostic criterion BEST defines subclinical endometritis in lactating dairy cows, and what is the recommended threshold for treatment intervention in this herd?

Uterine cytology showing ≥8% PMNs (≥35–47 days postpartum) or ≥18% PMNs (≥20–33 days postpartum); treat cows above threshold with intrauterine cefapirin (Correct answer)
Vaginoscopy revealing mucopurulent discharge (Metricheck score ≥2) at any point in the first 60 days in milk; treat with systemic ceftiofur at 35 DIM
Rectal palpation detecting a uterus >10 cm diameter at 28 days postpartum; treat with PGF2α to induce luteolysis
Uterine cytology showing ≥5% polymorphonuclear neutrophils (PMNs) at 21–33 days postpartum; treat all cows exceeding this threshold with intrauterine cefapirin

Correct answer: Uterine cytology showing ≥8% PMNs (≥35–47 days postpartum) or ≥18% PMNs (≥20–33 days postpartum); treat cows above threshold with intrauterine cefapirin

Subclinical endometritis (SCE) is definitively diagnosed by uterine cytology (cytobrush or lavage) rather than visual discharge scoring. The validated thresholds differ by postpartum timing: ≥18% PMNs at 20–33 DIM and ≥8% PMNs at 34–47 DIM, reflecting the physiological decline in uterine PMNs as the postpartum period progresses. Intrauterine cefapirin (a first-generation cephalosporin with broad uterine penetration and no systemic withdrawal concerns) is the most evidence-supported treatment for SCE. Vaginoscopy and Metricheck detect clinical endometritis/metritis but miss subclinical disease by definition. Systemic ceftiofur is used for acute puerperal metritis, not SCE. Uterine diameter by palpation does not reliably diagnose SCE.

Question 344: The following types of inflammation are typically linked to FIP:

Pyogranulonatous (Correct answer)
Serous
No inflammation associated
Purulent

Correct answer: Pyogranulonatous

Feline Infectious Peritonitis (FIP) is characterized by a distinctive inflammatory response known as pyogranulomatous inflammation. This type of inflammation involves a mixture of neutrophils and macrophages, leading to the formation of characteristic lesions in various organs, especially in the 'wet' form with effusions and in the 'dry' form with granulomas.

Question 345: During a contrast-enhanced CT of the abdomen in a 9-year-old Golden Retriever, a hepatic lesion shows marked arterial phase enhancement followed by rapid 'washout' (hypoattenuation relative to liver parenchyma in the portal venous phase). What is the MOST likely diagnosis?

Biliary cystadenoma
Hepatocellular carcinoma (HCC) (Correct answer)
Hepatic cavernous hemangioma
Nodular hyperplasia

Correct answer: Hepatocellular carcinoma (HCC)

The 'arterial enhancement followed by portal venous phase washout' pattern is the hallmark of hepatocellular carcinoma on contrast CT, reflecting the lesion's dependence on arterial blood supply and rapid contrast clearance. Hemangiomas classically show peripheral nodular enhancement that fills in centripetally (similar to human hemangiomas). Nodular hyperplasia typically appears iso- or hypoattenuating without dramatic washout. Biliary cystadenomas are cystic or multilocular and do not enhance in this arterial-dominant pattern. This washout sign carries high specificity for HCC in dogs.

Question 346: On thoracic radiographs of a dog, you notice the cardiac silhouette occupies more than 75% of the thoracic width on the VD view. What does this most likely indicate?

Pulmonary consolidation
Pneumothorax
Cardiomegaly (Correct answer)
Pleural effusion

Correct answer: Cardiomegaly

A cardiac silhouette exceeding 75% of thoracic width on the VD view is consistent with cardiomegaly.

Question 347: A 5-year-old Golden Retriever is presented for acute-onset cervical pain and tetraparesis. MRI reveals a T2-hyperintense, well-defined intramedullary lesion at C5-C6 with a characteristic 'golf ball on a tee' appearance. CSF analysis shows xanthochromia with elevated protein and no pleocytosis. Which condition BEST explains these findings?

Acute non-compressive nucleus pulposus extrusion (ANNPE) (Correct answer)
Neospora caninum myelitis with focal granuloma formation
Fibrocartilaginous embolism (FCE) affecting the cervical spinal cord
Spinal cord astrocytoma with intratumoral hemorrhage

Correct answer: Acute non-compressive nucleus pulposus extrusion (ANNPE)

Acute non-compressive nucleus pulposus extrusion (ANNPE) presents with peracute onset of pain and neurological deficits, often following exercise. MRI shows an intramedullary T2-hyperintense lesion that can have a 'golf ball on a tee' or 'smoke signal' appearance due to the nucleus pulposus material extruded directly into the cord parenchyma. CSF xanthochromia with elevated protein and no pleocytosis is consistent with parenchymal injury without inflammation. FCE also presents acutely and is non-painful after the initial event, but the MRI appearance and CSF xanthochromia better fit ANNPE. Neospora would show pleocytosis, and astrocytoma would be a more gradual progression.

Question 348: A 5-year-old, male neutered Doberman Pinscher presents for evaluation. Echocardiography reveals a dilated left ventricle with decreased fractional shortening. The owner reports episodes of coughing and exercise intolerance. Which of the following long-term oral medications has been shown to delay the onset of clinical signs and extend the life of Dobermans in the occult stage of this disease?

Enalapril
Pimobendan (Correct answer)
Spironolactone
Furosemide

Correct answer: Pimobendan

Pimobendan, an inodilator, has been proven to delay the onset of congestive heart failure and prolong survival in Doberman Pinschers with preclinical (occult) dilated cardiomyopathy (DCM). While furosemide, enalapril, and spironolactone are used to manage congestive heart failure once it develops, pimobendan is the key therapy for the occult stage.

Question 349: Which drug is the specific reversal agent for alpha-2 adrenergic agonist sedation (e.g., medetomidine, dexmedetomidine) in veterinary patients?

Atipamezole (Correct answer)
Naloxone
Flumazenil
Neostigmine

Correct answer: Atipamezole

Atipamezole is a selective alpha-2 adrenergic antagonist that rapidly reverses the sedation, analgesia, and cardiovascular effects of alpha-2 agonists such as medetomidine and dexmedetomidine.

Question 350: A beef cattle producer wishes to use a medicated feed containing chlortetracycline to control an active anaplasmosis infection. What must a veterinarian provide to legally authorize the producer to obtain and use this feed?

A valid Veterinary Feed Directive (VFD) order. (Correct answer)
A standard prescription on a state-approved script pad.
Verbal authorization communicated directly to the feed mill.
A signed letter on clinic letterhead describing the intended use.

Correct answer: A valid Veterinary Feed Directive (VFD) order.

The FDA classifies chlortetracycline as a medically important antimicrobial. Its use in or on animal feed is regulated under the Veterinary Feed Directive (VFD) final rule. To legally purchase and administer this medicated feed, the producer must have a valid VFD order issued by a licensed veterinarian with whom they have an established veterinarian-client-patient relationship (VCPR).

Question 351: When using buprenorphine in cats, which route of administration achieves good bioavailability due to the cat's naturally alkaline oral pH?

Intravenous
Intramuscular
Transmucosal (sublingual/buccal) (Correct answer)
Subcutaneous

Correct answer: Transmucosal (sublingual/buccal)

The alkaline oral pH of cats promotes ionization of buprenorphine at mucosal surfaces, giving transmucosal administration ~100% bioavailability.

Question 352: Which of the following is the most critical control point for eliminating Bovine Viral Diarrhea Virus (BVDV) from a beef cow-calf herd?

Identifying and removing persistently infected (PI) animals. (Correct answer)
Implementing a comprehensive fly and vector control program.
Treating all clinically ill animals with supportive care and antibiotics.
Vaccinating all adult animals annually with a modified-live virus (MLV) vaccine.

Correct answer: Identifying and removing persistently infected (PI) animals.

Persistently infected (PI) animals are the primary reservoir and source of BVDV shedding within a herd. They become infected in utero and shed the virus throughout their lives. While vaccination is a key part of prevention, it may not be fully effective in the face of the massive viral load shed by a PI animal. Therefore, the most critical step for eradication is to test for, identify, and remove these PI animals from the population.

Question 353: Which inhalant anesthetic is associated with the GREATEST cardiovascular depression and sensitization of the myocardium to catecholamine-induced arrhythmias?

Isoflurane
Halothane (Correct answer)
Desflurane
Sevoflurane

Correct answer: Halothane

Halothane causes significant myocardial depression, decreased cardiac output, and sensitizes the heart to catecholamine-induced arrhythmias, making it the most cardiotoxic of the inhalants; it is rarely used in modern veterinary practice for this reason.

Question 354: The Hazard Analysis Critical Control Point (HACCP) system was originally developed to ensure food safety for which population?

Hospitalized immunocompromised patients
Military personnel in field operations
NASA astronauts (Correct answer)
Commercial airline passengers

Correct answer: NASA astronauts

HACCP was originally developed by NASA and Pillsbury in the 1960s to ensure food safety for astronauts in space missions.

Question 355: A goat herd experiences multiple does with profuse watery diarrhea, weight loss, and bottle jaw (submandibular edema) over several months. Fecal egg counts reveal heavy Haemonchus contortus burdens. Which anthelmintic resistance testing method is most appropriate to guide drug selection?

Baermann technique to detect larvae in feces
McMaster flotation to identify the species causing disease
Larval development assay using pooled fecal cultures
Fecal Egg Count Reduction Test (FECRT) comparing pre- and post-treatment counts (Correct answer)

Correct answer: Fecal Egg Count Reduction Test (FECRT) comparing pre- and post-treatment counts

The Fecal Egg Count Reduction Test (FECRT) is the gold-standard field test for anthelmintic resistance. Fecal egg counts are performed before and 14 days after treatment; <95% reduction indicates resistance. The Baermann technique detects lungworm larvae, not strongyles. McMaster identifies eggs but not resistance status.

Question 356: A 5-year-old Dachshund presents with sudden-onset paraplegia, absent deep pain perception in both pelvic limbs, and urinary retention. The lesion localizes to T3-L3 myelopathy. MRI confirms an acute Hansen Type I disc extrusion at T12-T13. The most important prognostic indicator for functional recovery is:

Presence or absence of deep pain perception in the pelvic limbs (Correct answer)
Age of the patient at time of surgery
Severity of disc extrusion on MRI (Grasso scale grade)
Duration of clinical signs before surgery

Correct answer: Presence or absence of deep pain perception in the pelvic limbs

Presence of deep pain perception (DPP) is the single most important prognostic factor in spinal cord injury from IVDD. Dogs that retain DPP have >90% chance of functional recovery with decompressive surgery. Dogs that have lost DPP have approximately 50–60% recovery rates, and those with absent DPP for >48 hours have a significantly poorer prognosis. Duration matters but DPP status is the most critical indicator.

Question 357: Necropsy of an 8-year-old dog reveals a 4 cm hepatic mass with a tan cut surface, no central necrosis, and a pushing border compressing but not invading adjacent parenchyma. Histology shows well-differentiated hepatocytes in a solid pattern. The most appropriate classification is:

Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative (Correct answer)
Nodular hyperplasia — no treatment required
Metastatic carcinoma — full staging required
Hepatocellular carcinoma — aggressive treatment warranted

Correct answer: Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative

Hepatocellular adenomas (hepatomas) are well-encapsulated, well-differentiated benign tumors in dogs with a pushing border and no invasion. Hepatocellular carcinoma shows vascular invasion, necrosis, and nuclear pleomorphism. Nodular hyperplasia is typically multifocal and small (≤1 cm). Metastatic carcinoma would show an infiltrative pattern and non-hepatocyte histology.

Question 358: Which drug class is contraindicated in cats with urethral obstruction due to risk of worsening urethral tone?

Alpha-1 adrenergic antagonists
Non-depolarizing neuromuscular blockers
Opioid agonists (Correct answer)
Benzodiazepines

Correct answer: Opioid agonists

Pure opioid agonists (e.g., morphine) increase urethral sphincter tone in cats and can worsen urinary obstruction.

Question 359: A 4-year-old indoor cat develops acute epistaxis and retinal hemorrhages. Blood pressure is 225/160 mmHg. Which primary disease is most commonly responsible for severe hypertension in cats under 7 years of age?

Pheochromocytoma
Chronic kidney disease
Hyperthyroidism
Primary hyperaldosteronism (Correct answer)

Correct answer: Primary hyperaldosteronism

Primary hyperaldosteronism is an important cause of severe hypertension in younger cats and should be investigated when CKD and hyperthyroidism are absent.

Question 360: Which form of feline upper respiratory infection is most likely to cause chronic rhinosinusitis as a sequela following acute infection?

Bordetella bronchiseptica infection
Feline calicivirus infection
Chlamydia felis infection
Feline herpesvirus-1 infection (Correct answer)

Correct answer: Feline herpesvirus-1 infection

FHV-1 establishes latency in the trigeminal ganglion and can cause turbinate destruction leading to chronic rhinosinusitis after reactivation episodes.

NAVLE (North American Veterinary Licensing Exam)

The NAVLE (North American Veterinary Licensing Exam) exam validates essential knowledge and skills required for certification or licensure in this field.

360

Questions

420 min

Time Limit

65%

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