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

Question 1: A dog with dilated cardiomyopathy is started on digoxin. Which electrolyte abnormality increases the risk of digoxin toxicity?

Hypernatremia
Hypercalcemia
Hypokalemia (Correct answer)
Hyperkalemia

Correct answer: Hypokalemia

Hypokalemia potentiates digoxin toxicity because potassium and digoxin compete for the same binding site on Na+/K+-ATPase; low potassium increases digoxin binding and effect.

Question 2: 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)
Gonadotropin-releasing hormone (GnRH)
Oxytocin
Progesterone

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 3: A veterinarian conducting a pre-export health certificate inspection for cattle destined to a country in the EU discovers one animal with an ear-tag discrepancy — the tag number does not match the USDA premises registration record but the animal otherwise appears healthy. Under the USDA-APHIS Export Verification Program and EU import requirements, what is the MOST appropriate immediate action?

Replace the ear tag with a new USDA official tag, update the premises record, and proceed with certification after confirming no other discrepancies
Accept the animal and annotate the health certificate with a notation that the tag was visually verified but registry entry is pending correction
Reject the animal from the export lot, document the discrepancy on Form VS 17-140, and notify the APHIS District Office — the animal cannot be certified without verified identity (Correct answer)
Retest the animal for all required export diseases and issue a conditional certificate pending APHIS review within 30 days

Correct answer: Reject the animal from the export lot, document the discrepancy on Form VS 17-140, and notify the APHIS District Office — the animal cannot be certified without verified identity

Under USDA-APHIS Export Verification (EV) programs and EU Regulation (EU) 2016/429 requirements, traceability — including verified official identification linked to premises of origin — is a non-negotiable prerequisite for export certification. An animal whose tag cannot be matched to a USDA premises record has an unverifiable identity chain; certifying it would constitute a false official statement on a federal document (VS 17-140), which carries both regulatory and criminal liability. The correct action is to reject the animal from the consignment, document the discrepancy, and notify the APHIS District Veterinarian. Re-tagging and retroactively updating records at the time of certification is not permissible under federal traceability rules — the identity must have been established prior to certification, not created to enable it.

Question 4: A 9-year-old cat presents with hypercalcemia (total Ca 14.2 mg/dL), weight loss, and peripheral lymphadenopathy. Which condition is most likely?

Hypervitaminosis D
Lymphoma (Correct answer)
Primary hyperparathyroidism
Idiopathic hypercalcemia

Correct answer: Lymphoma

Lymphoma is the most common cause of hypercalcemia of malignancy in cats, mediated by PTHrP secretion.

Question 5: 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 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
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

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 6: A cat with hepatic lipidosis secondary to anorexia requires nutritional support. What is the preferred route of alimentation?

Total parenteral nutrition via jugular catheter
Esophagostomy tube feeding (Correct answer)
Voluntary oral high-protein diet
Nasogastric tube feeding

Correct answer: Esophagostomy tube feeding

Esophagostomy tube placement is the preferred long-term enteral feeding route for hepatic lipidosis as it allows owner-administered home feeding, is well tolerated, and provides adequate caloric delivery.

Question 7: A cat ingests mouse bait containing brodifacoum. How long after ingestion can clinical signs of coagulopathy be expected?

7–10 days
Within 2 hours
3–5 days (Correct answer)
12–24 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 8: A 3-year-old Quarter Horse mare is given detomidine (20 µg/kg IV) and butorphanol (0.02 mg/kg IV) for standing sedation during a laceration repair. Thirty minutes later the mare becomes ataxic and recumbent. The veterinarian decides to partially reverse the sedation. Which reversal strategy is MOST pharmacologically precise?

Administer naloxone IV only, as opioid reversal will restore enough arousal without alpha-2 reversal
Administer yohimbine IV to fully reverse both detomidine and butorphanol
Administer atipamezole IV to selectively reverse detomidine, accepting residual opioid sedation (Correct answer)
Administer atipamezole IV to reverse detomidine, and naloxone IV to reverse butorphanol

Correct answer: Administer atipamezole IV to selectively reverse detomidine, accepting residual opioid sedation

Atipamezole is a highly selective alpha-2 adrenergic antagonist with high affinity for alpha-2 receptors, making it the most appropriate reversal agent for detomidine. Administering atipamezole alone allows partial reversal — removing the more profound alpha-2 component (responsible for most of the sedation and ataxia in horses) while leaving mild butorphanol analgesia intact, which is beneficial for a painful laceration repair. Full reversal with naloxone would eliminate analgesia. Yohimbine is a less selective alpha-2 antagonist (it also blocks alpha-1 receptors) with a lower therapeutic index in horses and is not the preferred reversal agent. Atipamezole is licensed for small animals but used off-label in horses; medetomidine and atipamezole are better-matched pairs, though atipamezole still reverses detomidine effectively.

Question 9: In llamas, the most typical source of bony facial tumors is

Osteomyelitis
Ossifying fibroma
Facial bone fracture
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 10: 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?

Inflammatory bowel disease
Exocrine pancreatic insufficiency (Correct answer)
Lymphangiectasia
Intestinal lymphoma

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 11: 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:

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
Perform a bypass anastomosis without closing the rent

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 12: 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?

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

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 13: Which fluoroquinolone is known to cause retinal degeneration in cats, particularly at high doses?

Enrofloxacin (Correct answer)
Ciprofloxacin
Marbofloxacin
Pradofloxacin

Correct answer: Enrofloxacin

Enrofloxacin at high doses has been associated with acute retinal degeneration and blindness in cats, and dosing must be carefully limited in this species.

Question 14: 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?

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

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 15: A 4-year-old DSH cat is being treated for hyperthyroidism with methimazole. Three weeks into therapy, the owner notices the cat is scratching its face intensely and has developed periocular excoriations. CBC reveals eosinophilia. Which of the following is the most appropriate next step?

Reduce methimazole dose by 50% and recheck CBC in 2 weeks
Discontinue methimazole, initiate radioactive iodine therapy or surgical thyroidectomy as definitive treatment (Correct answer)
Add prednisolone to suppress the immune-mediated reaction and continue methimazole
Switch to carbimazole and monitor for cross-reactivity

Correct answer: Discontinue methimazole, initiate radioactive iodine therapy or surgical thyroidectomy as definitive treatment

Facial pruritus and excoriations are a classic idiosyncratic adverse reaction to methimazole in cats, occurring in up to 20% of patients. Because carbimazole is converted to methimazole in vivo, cross-reactivity is nearly guaranteed, making it a poor alternative. Simply reducing the dose does not eliminate the antigen driving the reaction, and steroids would suppress but not resolve the underlying cause while allowing hyperthyroidism to continue. The correct approach is to discontinue methimazole entirely and pursue a definitive treatment — radioactive iodine (I-131) or surgical thyroidectomy — which resolves both the drug reaction and the underlying disease.

Question 16: Which drug is the specific reversal agent for alpha-2 adrenergic agonist sedation (e.g., medetomidine, dexmedetomidine) in veterinary patients?

Neostigmine
Flumazenil
Atipamezole (Correct answer)
Naloxone

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

Nutritional secondary hyperparathyroidism
Primary bone tumor (osteosarcoma) (Correct answer)
Septic osteomyelitis
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 18: 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?

NSAIDs are contraindicated with acepromazine due to additive CNS depression
Carprofen must be given at least 2 hours before morphine to avoid drug interaction
Carprofen is contraindicated with morphine due to serotonin syndrome risk
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 19: On abdominal ultrasound, an anechoic structure with distal acoustic enhancement in the kidney is MOST consistent with:

Renal abscess
Nephrolithiasis
Simple renal cyst (Correct answer)
Transitional cell carcinoma

Correct answer: Simple renal cyst

Simple cysts are anechoic with a thin wall and show distal acoustic enhancement due to the lack of sound attenuation by fluid.

Question 20: A 9-year-old spayed female Boxer is presented with episodic weakness, syncope, and a heart rate of 40 bpm. ECG reveals a P wave with no associated QRS complex occurring at irregular intervals. What is the diagnosis?

Third-degree (complete) AV block (Correct answer)
Atrial fibrillation
Sick sinus syndrome
Ventricular tachycardia

Correct answer: Third-degree (complete) AV block

Third-degree AV block is characterized by complete dissociation of P waves and QRS complexes with a slow escape rhythm, causing bradycardia and syncope.

Question 21: Gabapentin is increasingly used in veterinary patients for chronic and neuropathic pain. What is its primary mechanism of action?

Voltage-gated calcium channel alpha-2-delta subunit inhibition (Correct answer)
Mu-opioid receptor agonism
Cyclooxygenase-2 inhibition
NMDA glutamate receptor blockade

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 22: 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:

Distal phalanx fracture
Laminitis with rotation
Pedal osteitis
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 23: A 9-year-old Cairn Terrier has chronic hepatitis with copper accumulation on liver biopsy (>2000 µg/g dry weight). Which chelation agent is most commonly used in dogs to reduce hepatic copper?

EDTA
Deferoxamine
D-penicillamine (Correct answer)
Deferasirox

Correct answer: D-penicillamine

D-penicillamine is the most widely used copper chelator in dogs with copper-associated hepatopathy, mobilizing hepatic copper for urinary excretion.

Question 24: A 5-year-old Thoroughbred racehorse has a complete transverse fracture of the proximal sesamoid bone following a race. Which statement best describes the prognosis for return to racing?

Prognosis depends solely on which sesamoid (medial vs. lateral) is fractured
Good prognosis with 6 weeks of stall rest alone
Guarded to poor prognosis; most horses are retired from racing after this injury (Correct answer)
Excellent prognosis with internal fixation using lag screws

Correct answer: Guarded to poor prognosis; most horses are retired from racing after this injury

Complete transverse fractures of the proximal sesamoid bone carry a guarded to poor prognosis for return to racing due to disruption of the suspensory apparatus and risk of fetlock hyperextension.

Question 25: A 6-month-old Labrador Retriever puppy presents for evaluation of exercise intolerance and a loud continuous 'machinery' murmur heard best at the left heart base. What is the most likely congenital defect?

Ventricular septal defect
Aortic stenosis
Pulmonic stenosis
Patent ductus arteriosus (Correct answer)

Correct answer: Patent ductus arteriosus

Patent ductus arteriosus produces the classic continuous 'machinery' murmur due to left-to-right shunting throughout the cardiac cycle via the unclosed ductus.

Question 26: A backyard chicken flock presents with sudden death, cyanosis of the comb and wattles, and neurological signs. Which disease should be the primary differential?

Newcastle disease (velogenic strain) (Correct answer)
Fowl pox
Infectious bronchitis
Marek's disease

Correct answer: Newcastle disease (velogenic strain)

Velogenic Newcastle disease causes acute high mortality with concurrent respiratory, nervous, and circulatory signs including cyanosis.

Question 27: Which toxin from Rhododendron spp. causes salivation, vomiting, bradycardia, and hypotension in cats by activating sodium channels?

Andromedotoxin
Andromedotoxin and grayanotoxin are the same compound (Correct answer)
Taxine
Grayanotoxin

Correct answer: Andromedotoxin and grayanotoxin are the same compound

Grayanotoxin and andromedotoxin are synonymous names for the same sodium channel-activating diterpene in Rhododendron/Azalea plants.

Question 28: A 9-year-old Paint Horse gelding presents with a 3-month history of weight loss, fever of unknown origin, and a firm, non-painful enlargement in the inguinal region. Aspiration reveals thick, greenish pus. What is the most likely diagnosis?

Squamous cell carcinoma of the inguinal lymph node
Strangles (Streptococcus equi subsp. equi) abscessation
Ulcerative lymphangitis (Corynebacterium pseudotuberculosis abscess) (Correct answer)
Inguinal hernia strangulation

Correct answer: Ulcerative lymphangitis (Corynebacterium pseudotuberculosis abscess)

Corynebacterium pseudotuberculosis causes caseous lymphadenitis (pigeon fever) with characteristic thick, greenish pus in firm subcutaneous or inguinal abscesses, often with systemic signs.

Question 29: Which opioid analgesic is classified as a partial mu-opioid receptor agonist and exhibits a ceiling effect for analgesia at higher doses?

Hydromorphone
Fentanyl
Buprenorphine (Correct answer)
Morphine

Correct answer: Buprenorphine

Buprenorphine is a partial mu-opioid agonist with very high receptor affinity; because it is a partial agonist, increasing the dose beyond a threshold does not produce proportionally greater analgesia, resulting in a ceiling effect.

Question 30: A cat presents with sedation, hypersalivation, and ataxia after grooming itself following topical permethrin application intended for dogs. What is the most appropriate treatment?

Bathe with mild dish soap and provide supportive care including muscle relaxants (Correct answer)
Administer activated charcoal via nasogastric tube
Give vitamin K1 orally
Administer atropine IV

Correct answer: Bathe with mild dish soap and provide supportive care including muscle relaxants

Permethrin toxicity in cats causes neurological signs; bathing removes the toxin and methocarbamol or diazepam controls tremors.

Question 31: Osteochondrosis dissecans (OCD) in horses most commonly affects which joint when presenting as tarsal lameness in young Thoroughbreds?

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

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 32: To perform a complete low four-point nerve block on a forelimb, a veterinarian must anesthetize the medial and lateral palmar nerves as well as which other two nerves?

Axillary and musculocutaneous nerves
Deep and superficial branches of the radial nerve
Medial and lateral cutaneous antebrachial nerves
Medial and lateral palmar metacarpal nerves (Correct answer)

Correct answer: Medial and lateral palmar metacarpal nerves

The low four-point block is designed to desensitize the entire fetlock and structures distal to it. This requires blocking the medial and lateral palmar nerves (which run down the back of the leg) and the medial and lateral palmar metacarpal nerves (which run alongside the splint bones and provide deep/dorsal sensation to the fetlock). The other nerve pairs listed are located much more proximally in the equine forelimb.

Question 33: A 6-year-old Maine Coon cat presents in acute respiratory distress. Physical exam reveals a heart murmur, gallop rhythm, and crackles on lung auscultation. A thoracic radiograph shows cardiomegaly and pulmonary edema. Echocardiography confirms hypertrophic cardiomyopathy (HCM). In addition to oxygen therapy, which medication is most critical for initial stabilization of this cat's congestive heart failure?

Clopidogrel
Atenolol
Benazepril
Furosemide (Correct answer)

Correct answer: Furosemide

Furosemide, a potent loop diuretic, is the most critical initial medication for a cat in congestive heart failure (CHF) secondary to HCM. Its primary function is to reduce fluid volume by promoting urination, which alleviates pulmonary edema and relieves respiratory distress. Clopidogrel is an anti-platelet drug used to prevent aortic thromboembolism but does not treat CHF. Atenolol (a beta-blocker) and benazepril (an ACE inhibitor) may be used for long-term management but are not the first-line emergency drugs for reducing pulmonary edema.

Question 34: 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
Eclampsia (puerperal tetany) (Correct answer)
Vitamin D deficiency
Primary hypoparathyroidism

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 35: Coxiella burnetii (Q fever agent) is classified as a Category B bioterrorism agent. Which animal reservoir is the primary source of human infection?

Domestic ruminants (cattle, sheep, goats) (Correct answer)
Wild birds
Dogs and cats
Wild rodents

Correct answer: Domestic ruminants (cattle, sheep, goats)

Cattle, sheep, and goats are the primary reservoirs; parturient materials (placenta, birth fluids) contain extremely high concentrations of C. burnetii.

Question 36: You are consulting on a biosecurity plan for a seedstock beef operation importing 15 breeding bulls from three different sources. Johne's disease (paratuberculosis) is a primary concern. Which combination of testing and quarantine procedures reflects current AAVLD/USAHA Voluntary Johne's Disease Herd Status Program (VJDHSP) Tier 3 recommendations for incoming animals?

One negative serum ELISA on arrival plus one negative fecal culture at 30 days during quarantine
Two negative fecal PCR tests 30 days apart during a 60-day quarantine before introduction (Correct answer)
Negative fecal culture on a single pooled sample from all 15 bulls after a 30-day quarantine
Two consecutive negative fecal PCR tests at entry and exit of a 14-day quarantine period

Correct answer: Two negative fecal PCR tests 30 days apart during a 60-day quarantine before introduction

Under the VJDHSP framework, bulls entering a Tier 3 or higher herd should ideally have two negative high-sensitivity fecal tests (PCR or culture) performed at least 30 days apart during a quarantine period of at least 60 days. Fecal PCR has largely supplanted fecal culture as the preferred diagnostic due to faster turnaround and comparable sensitivity in intermittent shedders. A single serum ELISA has poor sensitivity in subclinical animals (50–60%) and is insufficient alone. Pooled samples reduce sensitivity further and are inappropriate for individual animal clearance. A 14-day quarantine is insufficient to detect intermittent shedders and does not meet Tier 3 biosecurity standards.

Question 37: A slaughter plant veterinarian observes a pig with depression, erythematous skin lesions, and sudden death in the pen. The most important zoonotic differential diagnosis to consider is:

Classical swine fever
Erysipelothrix rhusiopathiae infection (Correct answer)
Porcine circovirus disease
Porcine reproductive and respiratory syndrome

Correct answer: Erysipelothrix rhusiopathiae infection

Erysipelothrix rhusiopathiae causes erysipelas in swine and can cause erysipeloid in humans who handle infected carcasses.

Question 38: A dog is suspected to have toxicosis from xylitol ingestion 30 minutes ago. Which clinical signs would you expect first?

Hypoglycemia and seizures (Correct answer)
Hepatic necrosis and coagulopathy
Hemolytic anemia and methemoglobinemia
Acute renal failure and anuria

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 39: 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?

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

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 40: Which grading scale is the standard used in the United States to assess equine lameness severity?

AAEP lameness scale 0-5 (Correct answer)
Obel grading system
British Equine Veterinary Association (BEVA) 1-10 scale
FEI grading 0-4

Correct answer: AAEP lameness scale 0-5

The American Association of Equine Practitioners (AAEP) 0-5 lameness scale is the standard used in the US, with 0 being sound and 5 being non-weight-bearing.

Question 41: A pig farm reports sudden death in 3-week-old piglets with gross necropsy findings of fibrinous polyserositis, arthritis, and meningitis. The most likely causative agent is:

Mycoplasma hyorhinis
Streptococcus suis type 2
Actinobacillus pleuropneumoniae
Haemophilus parasuis (Glässer's disease) (Correct answer)

Correct answer: Haemophilus parasuis (Glässer's disease)

Haemophilus parasuis causes Glässer's disease in young pigs, characterized by fibrinous polyserositis (peritonitis, pleuritis, pericarditis), arthritis, and meningitis at 3–8 weeks of age.

Question 42: Which internal parasite of cattle causes 'bottle jaw' (submandibular edema) due to hypoproteinemia?

Haemonchus placei (Correct answer)
Ostertagia ostertagi
Trichostrongylus axei
Cooperia oncophora

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 43: A cat presents comatose after ingesting ethylene glycol. Which diagnostic finding would confirm ethylene glycol toxicity?

Calcium oxalate monohydrate crystalluria (Correct answer)
Elevated blood ammonia with hepatic encephalopathy
Hypocalcemia with prolonged QT interval on ECG
Presence of uric acid crystals in urine sediment

Correct answer: Calcium oxalate monohydrate crystalluria

Ethylene glycol is metabolized to oxalic acid, which combines with calcium to form calcium oxalate monohydrate crystals visible in urine sediment.

Question 44: Under the Food Safety Modernization Act (FSMA), which rule specifically addresses hazard analysis and preventive controls for human food facilities?

Preventive Controls for Human Food Rule (Correct answer)
Foreign Supplier Verification Rule
Produce Safety Rule
Sanitary Transportation Rule

Correct answer: Preventive Controls for Human Food Rule

The Preventive Controls for Human Food Rule requires food facilities to implement hazard analysis and risk-based preventive controls.

Question 45: 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?

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)
Implement selective dry cow therapy based on individual cow SCC thresholds above 200,000 cells/mL
Administer a Streptococcus agalactiae bacterin vaccine to all lactating cows to reduce new infection rate
Switch post-dip solution from iodine to chlorhexidine and increase milking frequency to three times daily

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 46: A 6-year-old Dachshund presents with acute onset of non-ambulatory paraparesis and spinal hyperesthesia localized to the T3-L3 region. Which imaging modality is considered the gold standard for definitively diagnosing intervertebral disc extrusion and assessing the degree of spinal cord compression?

Myelography
Survey spinal radiography
Magnetic Resonance Imaging (MRI) (Correct answer)
Computed Tomography (CT)

Correct answer: Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is the gold standard for imaging the spinal cord and associated soft tissues. It provides excellent detail of the disc material, spinal cord parenchyma, and nerve roots, allowing for precise localization of the extruded disc and evaluation of secondary cord changes like edema or hemorrhage. While CT and myelography can identify cord compression, MRI offers superior soft tissue contrast without the need for intrathecal contrast injection.

Question 47: A cat presents with acute onset of hindlimb paralysis, cold limbs, and absent femoral pulses. What is the most likely diagnosis?

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

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 48: Which of the following reproductive strategies describes the boa constrictor?

Parthenogenetic — reproduces without fertilization
Ovoviviparous — retains eggs internally and gives birth to live young (Correct answer)
Oviparous — lays eggs that develop externally
Viviparous — has a true placenta like mammals

Correct answer: Ovoviviparous — retains eggs internally and gives birth to live young

Boa constrictors are ovoviviparous; eggs are retained and develop internally with the female giving birth to live young without a true placenta.

Question 49: A 6-year-old warmblood gelding has MRI findings consistent with a deep digital flexor tendon (DDFT) lesion within the hoof capsule. Which treatment has shown the most promise for core lesions of the DDFT in the foot?

Palmar digital neurectomy alone
Deep digital flexor tenotomy
Intralesional injection of platelet-rich plasma (PRP) combined with corrective shoeing (Correct answer)
Full-limb casting for 6 months

Correct answer: Intralesional injection of platelet-rich plasma (PRP) combined with corrective shoeing

Intralesional PRP combined with corrective shoeing (heel elevation and/or egg bar shoe) is the current evidence-based approach for DDFT core lesions within the foot.

Question 50: A bird (psittacine) presents with a bacterial infection. Which antibiotic class should be avoided due to risk of fatal dysbiosis?

Beta-lactams
Fluoroquinolones
Lincosamides and macrolides at high doses (Correct answer)
Aminoglycosides

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 51: A sugar glider presents with self-mutilation of the scrotum and hindquarters. The most common underlying cause is:

Stress and/or inappropriate husbandry (Correct answer)
Fungal dermatitis
Nutritional secondary hyperparathyroidism
Ectoparasite infestation

Correct answer: Stress and/or inappropriate husbandry

Self-mutilation in sugar gliders is most commonly associated with stress, social isolation, or inappropriate diet and environmental conditions.

Question 52: Which test is used to diagnose pregnancy toxemia (ketosis) in beef cows and can be performed on-farm using a handheld meter?

Serum total protein
Packed cell volume (PCV)
Blood beta-hydroxybutyrate (BHB) measurement (Correct answer)
Serum calcium measurement

Correct answer: Blood beta-hydroxybutyrate (BHB) measurement

Handheld ketone meters measuring blood beta-hydroxybutyrate (BHB) provide rapid on-farm diagnosis of subclinical and clinical ketosis, with subclinical ketosis defined as BHB ≥1.2 mmol/L.

Question 53: During recovery from general anesthesia following orthopedic surgery, a horse makes multiple violent attempts to stand and sustains a fracture of the contralateral limb. This type of complication is best prevented by which approach?

Prolonging anesthesia until the horse is fully awake
Administering acepromazine immediately post-surgery
Using an assisted recovery system (head/tail ropes) with quiet, padded recovery stall (Correct answer)
Placing the horse in dorsal recumbency during recovery

Correct answer: Using an assisted recovery system (head/tail ropes) with quiet, padded recovery stall

Assisted recovery using head and tail ropes in a well-padded, quiet stall helps guide the horse to a controlled, coordinated standing position, minimizing the risk of fractures and post-anesthetic myopathy.

Question 54: A 4-year-old Siberian Husky presents with PU/PD. Water deprivation test shows urine osmolality of 180 mOsm/kg after 12 hours. After desmopressin administration, urine osmolality rises to 650 mOsm/kg. What is the diagnosis?

Central diabetes insipidus (Correct answer)
Nephrogenic diabetes insipidus
Primary (psychogenic) polydipsia
Chronic renal failure

Correct answer: Central diabetes insipidus

A robust response to exogenous ADH (desmopressin) indicates intact renal tubular response, confirming central (hypothalamic/pituitary) diabetes insipidus.

Question 55: A cat diagnosed with nasal lymphoma has disease confined to the nasal cavity. Which treatment modality offers the best local control and median survival?

Systemic chemotherapy alone
Intranasal corticosteroids
Rhinotomy and debulking
Radiation therapy alone (Correct answer)

Correct answer: Radiation therapy alone

Radiation therapy is the treatment of choice for nasal lymphoma in cats, providing excellent local control with median survival times of 18–24 months.

Question 56: Which statement about the use of doxycycline in cats is most accurate?

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

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 57: 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)
Sporotrichosis
Blastomycosis

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 58: A veterinarian suspects a case of highly pathogenic avian influenza (HPAI) in a commercial flock. The first regulatory notification must be made to:

State veterinarian or USDA APHIS (Correct answer)
FDA Center for Veterinary Medicine
Local law enforcement
CDC influenza division

Correct answer: State veterinarian or USDA APHIS

HPAI is a federally reportable disease; the state veterinarian and USDA APHIS must be notified immediately upon suspicion.

Question 59: Which drug is used to reverse the sedative and analgesic effects of medetomidine in dogs and cats?

Yohimbine
Naloxone
Atipamezole (Correct answer)
Flumazenil

Correct answer: Atipamezole

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

Question 60: 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?

Propylene glycol oral drench to address subclinical ketosis compounding immunosuppression (Correct answer)
Oxytocin IM to enhance uterine involution and lochia drainage
Flunixin meglumine IV to reduce endotoxemia and support uterine motility
Dexamethasone IM to suppress the systemic inflammatory cascade

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 61: 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?

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

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 62: A cat with chronic kidney disease (CKD) stage 3 is found to have a blood pressure of 195/130 mmHg. Which antihypertensive is considered first-line therapy in cats?

Hydralazine
Atenolol
Enalapril
Amlodipine (Correct answer)

Correct answer: Amlodipine

Amlodipine, a calcium channel blocker, is the first-line antihypertensive in cats due to its efficacy and tolerability.

Question 63: 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?

Prednisolone (oral)
Cyproheptadine (oral)
Theophylline (oral)
Terbutaline (subcutaneous) (Correct answer)

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 64: A 10-year-old Miniature Schnauzer with a history of hyperlipidemia presents with acute onset of vomiting, anorexia, and cranial abdominal pain. Physical examination reveals a 'praying posture.' Laboratory findings include neutrophilia, elevated amylase, and markedly elevated lipase. Which of the following is the most appropriate initial treatment?

Immediate exploratory laparotomy
High-fat, high-protein diet to stimulate appetite
Broad-spectrum antibiotics and oral corticosteroids
Aggressive intravenous fluid therapy, analgesia, and antiemetics (Correct answer)

Correct answer: Aggressive intravenous fluid therapy, analgesia, and antiemetics

The signalment, history, and clinical signs are classic for acute pancreatitis. The cornerstone of treatment is supportive care, which includes aggressive intravenous fluid therapy to correct dehydration and maintain pancreatic perfusion, potent analgesia to manage pain, and antiemetics to control vomiting. A low-fat diet is indicated once the patient can tolerate oral intake, and surgery is not typically the first-line treatment unless complications like an abscess or obstruction are present.

Question 65: A dog under isoflurane anesthesia has an end-tidal CO2 (ETCO2) reading of 62 mmHg. What does this finding indicate?

Adequate ventilation
Hyperventilation with CO2 washout
Hypoventilation with CO2 retention (Correct answer)
Adequate tissue oxygenation

Correct answer: Hypoventilation with CO2 retention

Normal ETCO2 in anesthetized patients is 35–45 mmHg; a value of 62 mmHg indicates hypoventilation, meaning the patient is not eliminating CO2 adequately and intervention (e.g., manual or mechanical ventilation) is needed.

Question 66: 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?

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

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 67: Which opioid is most appropriate for epidural administration in dogs to provide extended postoperative analgesia with minimal motor blockade?

Fentanyl
Butorphanol
Meperidine
Morphine (Correct answer)

Correct answer: Morphine

Preservative-free morphine administered epidurally provides long-duration analgesia (12–24 hours) with minimal motor effects due to its hydrophilicity.

Question 68: A cat is diagnosed with diabetes mellitus. Which insulin type is currently recommended as first-line therapy in cats?

Regular insulin (short-acting)
NPH insulin
Glargine insulin (long-acting) (Correct answer)
Detemir insulin

Correct answer: Glargine insulin (long-acting)

Glargine (insulin glargine) is preferred in cats because its long, peakless action matches the feline glucose profile and facilitates diabetic remission.

Question 69: 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 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)
Brodifacoum irreversibly alkylates the vitamin K epoxide reductase enzyme complex

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 70: A cat presents with pleural effusion. On thoracic radiographs, which finding best differentiates pleural effusion from pulmonary consolidation?

Loss of cardiac silhouette border
Air bronchograms within the opacity
Increased opacity in the perihilar region
Retraction of lung lobes from the thoracic wall (Correct answer)

Correct answer: Retraction of lung lobes from the thoracic wall

Pleural effusion causes lung lobes to retract away from the thoracic wall, whereas consolidated lung lobes remain in contact with the chest wall.

Question 71: On thoracic auscultation of an 8-year-old Cavalier King Charles Spaniel, you hear a grade IV/VI left apical systolic heart murmur. Echocardiography shows myxomatous mitral valve disease with moderate left atrial enlargement (LA:Ao ratio 1.7). Which ACVIM staging is most appropriate?

Stage B2 (Correct answer)
Stage C
Stage B1
Stage A

Correct answer: Stage B2

Stage B2 MMVD is defined by cardiac remodeling (LA:Ao ≥1.6 or normalized left ventricular internal diameter in diastole >1.7) without clinical signs of heart failure.

Question 72: A closed beef herd of 300 Angus cows has had three consecutive years of late-gestation abortions (>7 months), averaging 4.5% abortion rate. Aborted fetuses show autolysis. Paired serology on 15 aborting cows shows no significant titer rise to IBR, BVD, leptospirosis (5-serovar panel), or Neospora caninum. Fetal abomasal content culture is negative. The pastures border a large white-tailed deer population. Which diagnostic step has the HIGHEST probability of identifying the etiology?

Submit soil and water samples from border pastures for Nitrate/nitrite quantification and mycotoxin panel
Test the herd for bovine viral diarrhea virus (BVDV) persistent infection by antigen ELISA ear notch on all animals
Submit fresh and formalin-fixed fetal tissues for PCR and histopathology targeting Epizootic Hemorrhagic Disease virus (EHD) and Bluetongue virus (Correct answer)
Perform Brucella abortus serology on all cows using card test and ELISA, with culture of placenta on Farrell's medium

Correct answer: Submit fresh and formalin-fixed fetal tissues for PCR and histopathology targeting Epizootic Hemorrhagic Disease virus (EHD) and Bluetongue virus

The epidemiologic profile — late-gestation abortions, proximity to white-tailed deer (the primary amplifying host), and negative results for common abortifacients — strongly implicates an Orbivirus. EHD virus (serotypes 1, 2, 6, 7) and Bluetongue virus are transmitted by Culicoides midges, are amplified in deer populations, and can cause late-term abortion, fetal edema, and hemorrhage in cattle — often with autolytic fetuses making serology the only ante-mortem option in the dam. Importantly, EHD is frequently under-diagnosed because standard bovine abortion panels do not routinely include it. PCR on fresh fetal spleen, lung, and brain, combined with histopathology showing fetal vasculitis, would be confirmatory. Brucellosis is a legitimate consideration but would be unusual in a closed, vaccinated herd with no travel history and is mandatorily reportable, making it higher-profile. BVDV-PI cattle cause early losses, not clustering in late gestation.

Question 73: 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?

Perform through-and-through joint lavage and systemic antimicrobials (Correct answer)
Perform arthroscopic debridement under general anesthesia immediately without lavage
Repeat radiographs in 2 weeks
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 74: Grass tetany (hypomagnesemic tetany) in beef cattle grazing lush spring pastures is best prevented by supplementing which mineral?

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

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 75: A 6-year-old Standardbred pacer presents with an acute onset Grade 4/5 right forelimb lameness after a race. On examination there is moderate fetlock effusion, periarticular swelling, and pain on deep palpation of the lateral proximal sesamoid bone. Radiographs reveal a mid-body, sagittal fracture of the lateral proximal sesamoid bone without articular involvement. The horse is otherwise systemically healthy. Which treatment offers the BEST prognosis for return to racing performance in this specific fracture configuration?

Conservative management with box rest, support bandaging, and NSAIDs for 6–12 months
Neurectomy of the palmar digital nerve to provide long-term pain control and allow return to work
Sesamoidectomy of the lateral proximal sesamoid bone to prevent non-union
Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia (Correct answer)

Correct answer: Lag screw fixation with a 4.5 mm cortical screw placed perpendicular to the fracture plane under general anesthesia

Mid-body sagittal fractures of the proximal sesamoid bone that do not involve the articular surface and are not comminuted carry the best prognosis when treated with lag screw fixation. The lag screw creates interfragmentary compression that promotes primary bone healing and restores the structural integrity of the sesamoid bone, which is essential for resuming the biomechanical demands of racing. Conservative management alone has poor outcomes for racing soundness. Sesamoidectomy is reserved for apical or basal fractures. Neurectomy treats pain but does not address the structural problem and carries welfare concerns for performance horses.

Question 76: 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?

Idiopathic chylothorax (Correct answer)
Cardiac lymphoma causing thoracic duct obstruction
Diaphragmatic hernia with hepatic incarceration
Right-sided heart failure from hypertrophic cardiomyopathy

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 77: A cat presents with a 3-week history of weight loss, icterus, and anorexia. Abdominal ultrasound reveals a diffusely hyperechoic liver. Cytology of a fine-needle aspirate shows >50% of hepatocytes containing large cytoplasmic lipid vacuoles. Serum ALT is 3× ULN; ALP is only mildly elevated. Which statement about this condition is most accurate?

Aggressive nutritional support via feeding tube is a cornerstone of treatment, as anorexia perpetuates the condition (Correct answer)
This condition is primary and self-limiting; supportive care with fluid therapy alone is curative
ALP is markedly elevated in this condition because feline ALP has a short half-life, making marked elevation impossible
The mildly elevated ALP confirms biliary cirrhosis as the underlying cause rather than lipidosis

Correct answer: Aggressive nutritional support via feeding tube is a cornerstone of treatment, as anorexia perpetuates the condition

This is hepatic lipidosis (HL), the most common hepatopathy in cats. Unlike dogs, cats have low hepatic ALP activity and a short isoenzyme half-life, so ALP elevation is often mild even in severe HL — making option A partially true but not the most clinically useful statement. The critical management principle is that HL is driven by continued anorexia and negative energy balance; aggressive nutritional support (esophagostomy or gastrostomy tube) is essential to reverse hepatocyte lipid accumulation. HL is not self-limiting without intervention, and mild ALP does not distinguish HL from biliary disease by itself.

Question 78: A cat with cholangiohepatitis has a liver aspirate showing a neutrophilic infiltrate. Which organism should be cultured, and what is the most appropriate antibiotic class?

Toxoplasma gondii; clindamycin
Enteric bacteria (E. coli, Enterococcus); fluoroquinolone or amoxicillin-clavulanate (Correct answer)
Mycobacterium spp.; rifampicin
Cryptococcus neoformans; fluconazole

Correct answer: Enteric bacteria (E. coli, Enterococcus); fluoroquinolone or amoxicillin-clavulanate

Neutrophilic cholangitis is typically caused by ascending enteric bacteria; culture-guided treatment with fluoroquinolones or amoxicillin-clavulanate targets gram-negative and anaerobic organisms.

Question 79: 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 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)
DDFT core lesion (longitudinal split tear) with navicular bone flexor cortex erosion (Correct answer)

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 80: Feline calicivirus virulent systemic strain (VS-FCV) outbreaks are characterized by which distinctive clinical sign NOT typical of classic FCV?

Oral ulceration
Sneezing
Subcutaneous edema and facial swelling (Correct answer)
Conjunctivitis

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 81: Aminoglycoside antibiotics (e.g., gentamicin) should be used with extreme caution in patients with which condition?

Pulmonary disease
Renal insufficiency (Correct answer)
Cardiac arrhythmias
Hepatic disease

Correct answer: Renal insufficiency

Aminoglycosides are nephrotoxic and require renal elimination; pre-existing renal insufficiency greatly increases the risk of drug accumulation and toxicity.

Question 82: 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?

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

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 83: 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:

Septic arthritis (Correct answer)
Hypertrophic osteodystrophy
Degenerative joint disease
Osteochondrosis dissecans

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 84: Which of the following is a primary therapeutic goal in the management of a dog with chronic kidney disease (CKD) and proteinuria?

Increasing dietary protein to counteract losses
Controlling systemic hypertension and reducing phosphorus intake (Correct answer)
Supplementing with high doses of Vitamin D to manage secondary hyperparathyroidism
Administering loop diuretics to increase GFR

Correct answer: Controlling systemic hypertension and reducing phosphorus intake

Management of canine CKD focuses on slowing disease progression and improving quality of life. Key goals include controlling systemic hypertension, which can exacerbate kidney damage, and reducing dietary phosphorus intake to manage renal secondary hyperparathyroidism. Protein restriction (not increase) is often indicated, and while diuretics have a role in specific situations, they don't increase GFR. Vitamin D supplementation must be done cautiously to avoid hypercalcemia.

Question 85: 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 ergot and associated fibrocartilage of the palmar fetlock
The collateral ligaments of the proximal interphalangeal joint
The distal sesamoidean impar ligament
The digital flexor tendon sheath, with particular attention to the proximal digital annular ligament and manica flexoria (Correct answer)

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 86: You are evaluating thoracic radiographs of an older cat with a history of a previously removed mammary carcinoma. The lung fields show multiple, well-defined, variably sized nodules of soft tissue opacity. Which of the following is the most likely interpretation of this pulmonary pattern?

Cardiogenic pulmonary edema
Metastatic neoplasia (Correct answer)
Allergic bronchitis (asthma)
Fungal pneumonia

Correct answer: Metastatic neoplasia

The presence of multiple, well-defined, soft tissue nodules (often called a 'cannonball' pattern, though they can be small) throughout the lung fields is the classic radiographic appearance of hematogenous metastatic neoplasia. Fungal pneumonia can also be nodular but is often less defined. Feline asthma typically presents with a bronchial pattern ('donuts' and 'tram lines'). Cardiogenic edema usually appears as an unstructured interstitial to alveolar pattern, often with a patchy distribution.

Question 87: In a dog with suspected intervertebral disc disease, which myelographic finding confirms extradural compression?

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)
Complete absence of contrast cranial to the lesion

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 88: During a pre-purchase examination, you find a 4/5 grade on the AAEP lameness scale in the right forelimb. According to the AAEP scale, this means the horse:

Is lame only under certain circumstances (hard surface, circles)
Lame at the walk, occasionally non-weight-bearing (Correct answer)
Is non-weight-bearing at all times
Consistently lame but weight-bearing at the walk and trot

Correct answer: Lame at the walk, occasionally non-weight-bearing

AAEP grade 4/5 describes a horse that is lame at the walk and consistently lame at the trot, occasionally non-weight-bearing; grade 5 is non-weight-bearing at all times.

Question 89: A veterinarian working for a state health department is asked to evaluate a One Health surveillance system for Brucella melitensis in small ruminants. Which epidemiological measure best quantifies the probability that an animal testing positive by ELISA truly has brucellosis when the true prevalence in the population is 1%?

Negative predictive value
Sensitivity
Specificity
Positive predictive value (Correct answer)

Correct answer: Positive predictive value

Positive predictive value (PPV) is the probability that a test-positive animal is truly infected and is critically dependent on the prevalence of disease in the tested population. At low prevalence (1%), even a highly specific test will yield a low PPV, generating many false positives. Sensitivity measures the test's ability to correctly identify true positives; specificity measures correct identification of true negatives. Neither sensitivity nor specificity alone accounts for disease prevalence, making PPV the correct measure in this clinical and public health decision-making context.

Question 90: A 320-cow spring-calving beef herd experiences a 22% calf scours rate in calves aged 3–10 days, with 6 deaths. ELISA fecal antigen testing of 12 affected calves yields: Cryptosporidium parvum positive in 10/12, rotavirus positive in 5/12, and coronavirus positive in 2/12. Bulk colostrum Brix refractometer readings average 18%. Which management interpretation is MOST accurate?

The colostrum quality is inadequate; failure of passive transfer (FPT) is the primary predisposing cause, and the dominant pathogen profile reflects FPT-associated opportunistic infections
Rotavirus is the index pathogen because its prevalence exceeds coronavirus; vaccination targeting rotavirus alone would control this outbreak
Cryptosporidium parvum is a secondary opportunist; the 10/12 prevalence reflects co-infection only and does not warrant targeted anti-cryptosporidial treatment
Colostrum quality is acceptable; the outbreak is driven by environmental pathogen pressure from a calving area that has exceeded its safe carrying capacity (Correct answer)

Correct answer: Colostrum quality is acceptable; the outbreak is driven by environmental pathogen pressure from a calving area that has exceeded its safe carrying capacity

A Brix reading of ≥22% is the standard threshold for high-quality bovine colostrum (correlating with IgG ≥50 g/L). At 18% average Brix, colostrum quality is actually borderline-to-acceptable (most thresholds are ≥21–22% for 'excellent'), but notably the dominant pathogen is Cryptosporidium parvum—which is NOT prevented by colostrum-derived antibodies in any meaningful clinical sense because C. parvum pathogenesis occurs intraluminally and FPT does not specifically predispose to cryptosporidiosis. The 10/12 prevalence of C. parvum with calves 3–10 days old is the classic epidemiologic signature of environmental fecal-oral contamination pressure, typically amplified by overcrowding, reuse of calving areas, and accumulation of oocysts in the environment (the 'herd effect' or Ames Iowa model). The calving area has almost certainly exceeded its safe pathogen load. While colostrum quality should still be optimized, the outbreak driver here is environmental pressure, not FPT.

Question 91: A 5-year-old Thoroughbred racehorse undergoes emergency surgery for a complete lateral condylar fracture of the right third metacarpal bone sustained during a race. The fracture is repaired with lag screw fixation. Three weeks postoperatively, the horse develops acute non-weight-bearing lameness and radiographs show implant loosening with bone lysis around the screw tracks. Bacterial culture of joint fluid grows Staphylococcus aureus resistant to beta-lactam antibiotics. Which systemic antibiotic protocol is most appropriate while awaiting full susceptibility results?

Enrofloxacin 5 mg/kg IV once daily (Correct answer)
Chloramphenicol 50 mg/kg PO QID
Trimethoprim-sulfamethoxazole 30 mg/kg PO BID
Vancomycin 7.5 mg/kg IV TID with therapeutic drug monitoring

Correct answer: Enrofloxacin 5 mg/kg IV once daily

Enrofloxacin is the most practical systemic option for methicillin-resistant Staphylococcus aureus (MRSA) or beta-lactam-resistant staphylococcal infections in horses pending full susceptibility data. Fluoroquinolones achieve excellent bone and synovial fluid penetration and have demonstrated efficacy against many resistant staphylococci in equine clinical practice. Vancomycin is theoretically ideal for MRSA but is nephrotoxic in horses, poorly studied pharmacokinetically, and logistically challenging (TID IV). TMP-sulfa has variable efficacy against S. aureus and poor bone penetration. Chloramphenicol has public health implications (aplastic anemia risk in humans via residues) and is rarely used in performance horses.

Question 92: A ball python is presented for anorexia and regurgitation. Endoscopy reveals thickened gastric mucosa with abundant mucus. The most likely causative organism is:

Cryptosporidium serpentis (Correct answer)
Salmonella spp.
Ophidiomyces ophiodiicola
Nidovirus

Correct answer: Cryptosporidium serpentis

Cryptosporidium serpentis causes hypertrophic gastritis in snakes, presenting with chronic regurgitation and thickened gastric mucosa on endoscopy.

Question 93: Which surveillance system in the US monitors antimicrobial resistance in zoonotic enteric pathogens from humans, animals, and retail meat?

NARMS (Correct answer)
APHIS VS
FSIS HACCP
NAHMS

Correct answer: NARMS

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

Question 94: A 15-year-old Quarter Horse gelding has a chronic, non-healing wound over the lateral aspect of the pastern with a fistulous tract. Probing reveals contact with bone. Radiographs show cortical lysis of the lateral proximal phalanx. What is the definitive treatment?

Cast application for 8 weeks
Long-term systemic penicillin without debridement
Surgical debridement and sequestrum removal (Correct answer)
Intra-articular antibiotic perfusion only

Correct answer: Surgical debridement and sequestrum removal

Sequestrum formation requires surgical removal of the devitalized bone fragment combined with debridement of the surrounding infected tissue to allow healing.

Question 95: A cat presents with a 'ground-glass' opacity on thoracic radiographs. Which condition is MOST associated with this finding?

Pleural effusion
Rib fracture
Pulmonary edema (Correct answer)
Pneumothorax

Correct answer: Pulmonary edema

Ground-glass opacity reflects partial alveolar filling, most commonly seen with pulmonary edema in cats.

Question 96: 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
Medial palmar vein; tourniquet application proximal to the carpus
Cephalic vein; apply digital pressure followed by ligation if bleeding persists post-lavage

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 97: A 6-year-old German Shepherd has chronic small bowel diarrhea, weight loss, and hypocobalaminemia. Serum folate is elevated. What is the most likely diagnosis?

Exocrine pancreatic insufficiency
Inflammatory bowel disease
Lymphangiectasia
Small intestinal bacterial overgrowth (SIBO) / dysbiosis (Correct answer)

Correct answer: Small intestinal bacterial overgrowth (SIBO) / dysbiosis

Elevated folate (produced by bacteria) combined with low cobalamin (consumed by bacteria) is the classic pattern for small intestinal bacterial overgrowth/dysbiosis.

Question 98: A shelter veterinarian is investigating a cluster of cats with a highly virulent calicivirus (VS-FCV) outbreak. Affected cats exhibit facial and limb edema, ulceration of the nasal planum, pinnae necrosis, jaundice, and a mortality rate approaching 60%. Which of the following distinguishes VS-FCV from classical FCV strains and has the MOST direct implication for infection control?

VS-FCV is antigenically identical to classical FCV strains, so current vaccines provide complete cross-protective immunity and vaccination immediately halts outbreak spread.
VS-FCV only affects immunocompromised cats; fully vaccinated immunocompetent adults are not susceptible regardless of exposure dose.
VS-FCV is significantly more resistant to commonly used disinfectants, including quaternary ammonium compounds, and requires 1:32 dilution household bleach with extended contact time; it also causes high mortality in vaccinated adult cats. (Correct answer)
VS-FCV is exclusively transmitted via aerosolized droplets and does not persist on fomites, making hand hygiene the sole critical control measure.

Correct answer: VS-FCV is significantly more resistant to commonly used disinfectants, including quaternary ammonium compounds, and requires 1:32 dilution household bleach with extended contact time; it also causes high mortality in vaccinated adult cats.

VS-FCV (virulent systemic FCV) is notable for causing severe systemic disease and death even in vaccinated adult cats, highlighting the limitations of current vaccines against divergent strains. Like classical FCV, it is non-enveloped and highly environmentally stable, resistant to many disinfectants; dilute bleach (1:32) with adequate contact time remains effective. Fomite transmission is a critical route, making environmental decontamination and isolation essential. Vaccines do not provide sterilizing immunity against VS-FCV. Immunocompetent vaccinated adults can and do die.

Question 99: A 10-year-old Andalusian stallion used for breeding has a 6-month history of insidious right hindlimb lameness. Rectal palpation reveals firm enlargement of the right sacroiliac region. Intra-articular sacroiliac injection under ultrasound guidance produces 70% improvement. Bone scan shows focal increased radiopharmaceutical uptake at the right sacral wing. Which additional finding on standing MRI of the pelvis would MOST specifically confirm active sacroiliac joint disease versus sacral stress fracture as the primary lesion?

Asymmetric gluteal muscle atrophy visible on T2-weighted sequences
Cortical irregularity of the dorsal sacral foramina on T1 sequences
Disruption of the interosseous sacroiliac ligament with periarticular edema on T2-STIR (Correct answer)
T2-hyperintense signal within the sacral wing cancellous bone

Correct answer: Disruption of the interosseous sacroiliac ligament with periarticular edema on T2-STIR

Disruption or thickening of the interosseous sacroiliac ligament with periarticular soft tissue edema on T2-STIR sequences is specifically diagnostic of sacroiliac joint disease (sacroiliitis or desmopathy), distinguishing it from a primary sacral stress fracture. T2-hyperintense signal in cancellous bone is consistent with bone marrow edema from either a stress fracture or joint disease. Cortical irregularity of sacral foramina and gluteal atrophy are indirect, nonspecific findings. The interosseous ligament finding directly localizes pathology to the joint interface, correlating with the analgesia response and scintigraphic uptake pattern.

Question 100: You are investigating a cluster of sudden deaths in a cow-calf beef herd on lush spring pasture. Three 6-month-old calves died within 24 hours; post-mortem findings include bloat, hemorrhagic abomasitis, and a characteristic smell of recently mown grass from rumen contents. Clostridium septicum is isolated from the abomasal wall. What is the MOST likely predisposing factor that allowed this organism to become pathogenic?

Failure of passive transfer leading to hypogammaglobulinemia
Concurrent bovine viral diarrhea virus (BVDV) immunosuppression enabling clostridial overgrowth
Copper deficiency suppressing neutrophil function
Abomasal mucosal damage from rapid dietary change causing hemorrhagic abomasitis that created an anaerobic microenvironment (Correct answer)

Correct answer: Abomasal mucosal damage from rapid dietary change causing hemorrhagic abomasitis that created an anaerobic microenvironment

Braxy (caused by Clostridium septicum) classically occurs when sudden ingestion of large quantities of cold, lush, or frosted forage causes abomasal mucosal inflammation and focal necrosis. The resulting damaged, poorly perfused mucosa creates the anaerobic, protein-rich microenvironment that permits C. septicum spores (normally ingested without consequence) to germinate and proliferate. The toxins produced cause local and systemic disease. While copper deficiency (A) and BVDV (D) can cause immunosuppression, they are not the primary predisposing mechanism for braxy specifically. Failure of passive transfer (C) is relevant to neonatal septicemia, not braxy in 6-month-old calves.

Question 101: Which of the following causes of exophthalmos in cattle occurs most frequently?

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

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 102: 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?

Renal amyloid A deposition in glomeruli and medullary interstitium leading to nephrotic syndrome (Correct answer)
Tubular proteinuria from aminoglycoside nephrotoxicity used to treat febrile episodes
Immune-complex glomerulonephritis secondary to chronic interleukin-6 overproduction
Pyelonephritis from recurrent bacteremia during febrile crises

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 103: Bovine trichomoniasis (caused by Tritrichomonas foetus) is a venereal disease affecting beef cattle. Which control strategy is most effective in eliminating trichomoniasis from an infected beef herd?

Vaccination of all cows with the T. foetus vaccine to prevent abortion
Systemic metronidazole treatment of all infected bulls
Antibiotic treatment of all cattle and 30-day quarantine
Culling infected bulls and resting infected cows for 90+ days to allow self-clearance (Correct answer)

Correct answer: Culling infected bulls and resting infected cows for 90+ days to allow self-clearance

Bulls are permanent carriers and cannot be treated; culling PCR-positive bulls and resting exposed cows (which self-clear in approximately 90 days of sexual rest) is the standard eradication approach.

Question 104: 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 competes with phenobarbital for plasma protein binding, increasing free phenobarbital fraction
Chloramphenicol induces P-glycoprotein, increasing CNS penetration of phenobarbital
Chloramphenicol directly potentiates GABA-A receptor activity, synergizing with 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 105: 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?

Sodium restriction alone
IV fluid diuresis three times weekly
Increased protein supplementation
Phosphate restriction and phosphate binders (Correct answer)

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 106: 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?

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

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 107: 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:

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

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 108: A 9-year-old cat presents with pleural effusion. Thoracocentesis yields a fluid with total protein 5.2 g/dL, nucleated cell count 4,200 cells/µL (predominantly non-degenerate neutrophils and macrophages), and a cholesterol-to-triglyceride ratio less than 1. Fluid triglycerides are 320 mg/dL. What is the MOST likely diagnosis?

Cardiac-origin transudative pleural effusion
Chylothorax (Correct answer)
Pyothorax secondary to migrating foreign body
Feline infectious peritonitis (FIP) with pleural involvement

Correct answer: Chylothorax

Chylothorax is characterized by a milky, triglyceride-rich effusion. The hallmark diagnostic criteria include pleural fluid triglycerides exceeding serum triglycerides (and typically >100 mg/dL) and a cholesterol-to-triglyceride ratio less than 1. Cytology typically shows small lymphocytes and non-degenerate neutrophils/macrophages, consistent with this case. FIP effusions are typically high-protein exudates but with lower cell counts and a higher cholesterol:triglyceride ratio. Pyothorax produces a septic exudate with degenerate neutrophils and intracellular bacteria. A pure transudate would have low protein and low cellularity.

Question 109: A 12-year-old cat with well-regulated hyperthyroidism (post-radioiodine therapy, now euthyroid) develops azotemia (creatinine 3.1 mg/dL, BUN 58 mg/dL). Prior to treatment, renal parameters were within normal limits. What is the MOST likely explanation for this finding?

Radioiodine therapy caused direct nephrotoxicity to the renal tubules
Concurrent pyelonephritis developed secondary to immune suppression from the hyperthyroid state
Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it (Correct answer)
Post-treatment hypothyroidism caused renal vasoconstriction and acute ischemic injury

Correct answer: Hyperthyroidism increased GFR and masked pre-existing chronic kidney disease; euthyroidism unmasked it

Hyperthyroidism increases cardiac output and renal blood flow, artificially elevating GFR and masking underlying CKD by keeping creatinine and BUN within normal limits. Once hyperthyroidism is treated and the cat becomes euthyroid, GFR normalizes (or decreases), and pre-existing CKD is 'unmasked.' This is a well-recognized phenomenon in feline medicine and is why a post-treatment renal function decline does not necessarily indicate a treatment complication. Radioiodine is not directly nephrotoxic, and acute ischemic injury from mild post-treatment hypothyroidism is not a recognized complication.

Question 110: Which flea and tick preventive acts as a selective antagonist of insect GABA-gated chloride channels?

Spinosad
Imidacloprid
Fipronil (Correct answer)
Selamectin

Correct answer: Fipronil

Fipronil selectively blocks GABA-gated chloride channels in insects and arachnids, causing CNS hyperexcitability and death; it has low affinity for mammalian receptors.

Question 111: A horse presents with acute colic, nasogastric reflux >2 L, absent borborygmi on the right side, and tachycardia of 68 bpm. What is the most likely diagnosis?

Duodenitis-proximal jejunitis (Correct answer)
Cecal impaction
Simple large colon impaction
Large colon displacement to the right (right dorsal displacement)

Correct answer: Duodenitis-proximal jejunitis

Large volumes of nasogastric reflux (>2 L) combined with absent right-sided borborygmi, severe tachycardia, and acute pain are classic for duodenitis-proximal jejunitis (anterior enteritis).

Question 112: A 6-year-old indoor-outdoor cat presents with a 2 cm subcutaneous mass over the interscapular region that appeared 3 months after vaccination. Histopathology shows a high-grade spindle cell tumor with inflammation at the periphery. The diagnosis is:

Fibrosarcoma unrelated to injection
Feline injection-site sarcoma (FISS) (Correct answer)
Mast cell tumor
Lipoma with atypical features

Correct answer: Feline injection-site sarcoma (FISS)

Feline injection-site sarcoma is an aggressive high-grade spindle cell tumor arising at vaccination or injection sites, characterized by peripheral inflammation and a high recurrence rate after excision.

Question 113: A 5-year-old outdoor cat presents with a chronic non-healing ulcer on the nasal planum, conjunctivitis with corneal ulceration, and recurrent mucopurulent nasal discharge. Herpesvirus (FHV-1) is confirmed by PCR from conjunctival swab. The owner asks about long-term management. Which antiviral strategy has the STRONGEST evidence base for reducing FHV-1-associated ocular disease severity in cats, with the LEAST systemic toxicity concern?

Systemic acyclovir at 50 mg/kg PO q8h due to its established safety in cats
Topical 0.5% cidofovir ophthalmic solution applied twice daily to the affected eye(s) (Correct answer)
Oral famciclovir 90 mg/kg PO q8h as the first-line systemic antiviral
Topical 3% vidarabine ointment applied 5 times daily combined with oral lysine supplementation at 500 mg/day

Correct answer: Topical 0.5% cidofovir ophthalmic solution applied twice daily to the affected eye(s)

Topical 0.5% cidofovir (a nucleotide analog) applied twice daily has been shown in clinical studies to significantly reduce FHV-1 conjunctival disease severity and viral shedding with minimal systemic absorption and low local toxicity — making it superior in the topical antiviral category for feline herpesvirus ocular disease. Famciclovir is the preferred oral antiviral (prodrug converted to penciclovir in cats), but the dose is 90 mg/kg PO q12h (NOT q8h) and it is reserved for severe systemic disease. Acyclovir is CONTRAINDICATED in cats due to severe nephrotoxicity and bone marrow suppression. Lysine supplementation has been shown in multiple systematic reviews to have NO benefit for FHV-1 management and is no longer recommended by the American Association of Feline Practitioners (AAFP).

Question 114: A 10-year-old female Labrador Retriever presents with a history of panting, pot-bellied appearance, bilateral symmetrical alopecia, and PU/PD. Urine cortisol:creatinine ratio is elevated. Which test best differentiates pituitary-dependent from adrenal-dependent hyperadrenocorticism?

Low-dose dexamethasone suppression test (LDDST)
ACTH stimulation test
Urine cortisol:creatinine ratio
High-dose dexamethasone suppression test (HDDST) (Correct answer)

Correct answer: High-dose dexamethasone suppression test (HDDST)

The HDDST suppresses cortisol by >50% in most pituitary-dependent cases because the tumor retains some feedback sensitivity, while adrenal tumors do not suppress.

Question 115: 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 positive-sense, single-stranded RNA virus in the family Coronaviridae that primarily damages proventricular smooth muscle
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)
It is a double-stranded DNA virus in the family Herpesviridae that induces T-cell lymphoma in the myenteric plexus
It is a negative-sense, segmented RNA virus in the family Orthomyxoviridae that causes secondary demyelination of enteric nerves

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 116: A 7-year-old male intact Golden Retriever presents with a firm, painless swelling at the base of the tail. Cytology reveals sheets of round cells with prominent nucleoli and vacuolated cytoplasm. What is the most likely diagnosis?

Perianal adenocarcinoma
Anal sac adenocarcinoma (Correct answer)
Perianal adenoma
Mast cell tumor

Correct answer: Anal sac adenocarcinoma

Anal sac adenocarcinoma presents as a firm mass in the anal sac region and cytology shows epithelial cells with malignant features; it is not hormone-dependent unlike perianal adenomas.

Question 117: Which radiographic view is most useful for evaluating the dens (odontoid process) of the axis (C2) in a dog for atlantoaxial instability?

Open-mouth ventrodorsal (Correct answer)
Lateral cervical with extension
Oblique cervical
Lateral cervical with flexion

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 118: Which federal agency is responsible for the inspection of meat and poultry products under the Federal Meat Inspection Act?

USDA APHIS
FDA
USDA FSIS (Correct answer)
CDC

Correct answer: USDA FSIS

The USDA Food Safety and Inspection Service (FSIS) is mandated to inspect meat, poultry, and egg products under federal law.

Question 119: A dairy herd is diagnosed with Brucella abortus. Which federal program mandates testing and slaughter of reactor animals in the US?

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

Correct answer: Brucellosis Eradication Program

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

Question 120: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?

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

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 121: A radiograph of a 3-year-old Quarter Horse reveals periarticular bone proliferation and subchondral bone lucency at the distal interphalangeal joint with a linear radiolucent defect extending from the articular surface of the distal phalanx. This finding is MOST consistent with:

Septic pedal osteitis
Subchondral bone cyst (osseous cyst-like lesion) (Correct answer)
Keratoma
Palmar/plantar process fracture of the distal phalanx

Correct answer: Subchondral bone cyst (osseous cyst-like lesion)

Osseous cyst-like lesions (subchondral bone cysts) of the distal phalanx in horses appear as radiolucent defects communicating with the articular surface, typically at the distal interphalangeal joint. The periarticular new bone production and the subchondral lucency with articular communication are hallmark findings. Palmar/plantar process fractures are linear lucencies at the palmar/plantar aspect of P3 not centered on the articular surface. Keratoma is a space-occupying soft tissue lesion within the hoof capsule causing focal pressure remodeling of the solar margin. Septic pedal osteitis produces irregular lysis without the discrete cyst-like architecture.

Question 122: A feedlot veterinarian is investigating a cluster of sudden deaths in newly arrived stocker cattle (500–700 lb) that had been on feed for 8–14 days. Gross necropsy findings include: marked rumen distension with frothy ingesta, marked pulmonary edema and emphysema, hepatic lipidosis, and no evidence of blackleg or other clostridial lesions. Histopathology shows acute tubular necrosis in the kidneys. Which diagnosis BEST unifies these pathologic findings, and what is the most likely predisposing management factor?

Polioencephalomalacia secondary to high-sulfur water; the renal lesions reflect concurrent dehydration-associated prerenal azotemia
Grain overload (ruminal acidosis) with secondary mycotoxin-related hepatonephropathy; predisposed by rapid ration step-up exceeding rumen adaptation capacity (Correct answer)
Urea toxicosis from excessive non-protein nitrogen (NPN) supplementation; frothy rumen contents reflect ammonia-driven disruption of rumen microflora and gas production
Acute interstitial pneumonia (fog fever / atypical interstitial pneumonia) caused by L-tryptophan→3-methylindole conversion; predisposed by abrupt lush pasture access after a period of nutritional restriction

Correct answer: Grain overload (ruminal acidosis) with secondary mycotoxin-related hepatonephropathy; predisposed by rapid ration step-up exceeding rumen adaptation capacity

The combination of frothy rumen distension, pulmonary edema/emphysema, hepatic lipidosis, and acute tubular necrosis in feedlot cattle 8–14 days post-arrival that died suddenly is the classic picture of grain overload (acute rumen acidosis) with systemic sequelae. Rapid fermentation of excessive starch produces lactic acid, driving pH below 5.5, which causes rumenitis, systemic acidemia, endotoxemia, hepatic lipid accumulation (from mobilization during the metabolic crisis), and renal tubular injury from circulating toxins and hemodynamic compromise. The frothy rumen content is distinct from frothy bloat—here it reflects disrupted motility and gas trapping from acidic pH. Predisposing factor: an aggressive ration step-up that exceeds rumen papillae adaptation. Fog fever occurs in pastured cattle moved to lush grass, not feedlot receiving. Polioencephalomalacia would show cerebrocortical necrosis histologically. Urea toxicosis causes tetany, cerebral edema, and bloat but not the hepatorenal pattern seen here.

Question 123: 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?

Atipamezole IV
Naloxone full dose IV
Glycopyrrolate IV to treat bradycardia without reversing opioid (Correct answer)
Flumazenil 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 124: A 6-year-old Standardbred pacer presents with hindlimb lameness localized to the hock. Radiographs reveal periarticular osteophytes at the distal intertarsal and tarsometatarsal joints. The MOST appropriate treatment is:

Neurectomy of the tibial nerve
Intra-articular corticosteroids into the affected low-motion joints (Correct answer)
Cunean tenectomy alone
Arthroscopic joint lavage of the tarsocrural joint

Correct answer: Intra-articular corticosteroids into the affected low-motion joints

Bone spavin (osteoarthritis of the low-motion hock joints) is treated with intra-articular corticosteroid injections into the distal intertarsal and tarsometatarsal joints to reduce inflammation and pain.

Question 125: A cat presents with bilateral anterior uveitis. FIP testing is negative. Which other infectious agent should be high on the differential list?

Feline panleukopenia virus
Feline calicivirus
Toxoplasma gondii (Correct answer)
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 126: On a lateral thoracic radiograph, 'sternal contact' of the heart is increased in which cardiac condition?

Pulmonary hypertension
Pericardial effusion
Left atrial enlargement
Right ventricular enlargement (Correct answer)

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 127: A 7-year-old Golden Retriever presents with polyuria, polydipsia, and a pendulous abdomen. Urinalysis reveals isosthenuria (USG 1.008) and glucosuria with a normal blood glucose of 95 mg/dL. Abdominal ultrasound shows bilateral adrenomegaly. Which mechanism best explains the glucosuria in this patient?

Primary renal glucosuria due to SGLT2 transporter mutation
Concurrent diabetes mellitus with stress-induced blood glucose normalization at time of sampling
Occult postprandial hyperglycemia exceeding the renal threshold transiently
Renal tubular dysfunction secondary to hypercortisolism causing a Fanconi-like syndrome (Correct answer)

Correct answer: Renal tubular dysfunction secondary to hypercortisolism causing a Fanconi-like syndrome

Hyperadrenocorticism (Cushing's syndrome) can cause proximal renal tubular dysfunction resembling Fanconi syndrome, leading to glucosuria, aminoaciduria, and phosphaturia despite normoglycemia. The bilateral adrenomegaly, classic clinical signs, and isosthenuria all point to pituitary-dependent hyperadrenocorticism. The glucosuria here is not due to hyperglycemia exceeding the renal threshold but rather impaired tubular reabsorption. Primary renal glucosuria from SGLT2 mutations is rare in dogs, and the clinical picture does not support transient hyperglycemia or stress normalization.

Question 128: 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?

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

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 129: 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?

Atropine 0.04 mg/kg IV + epinephrine 0.01 mg/kg IV (Correct answer)
Epinephrine 0.01 mg/kg IV alone
Vasopressin 0.4 units/kg IV + atropine 0.02 mg/kg IV
Dopamine CRI at 5 µg/kg/min

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 130: 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 131: Which epidemiological measure best quantifies the additional risk of disease attributable to a specific exposure?

Relative risk
Attributable risk (risk difference) (Correct answer)
Odds ratio
Incidence rate

Correct answer: Attributable risk (risk difference)

Attributable risk (risk difference) measures the excess disease burden among the exposed group that is directly attributable to the exposure.

Question 132: 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?

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

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 133: 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?

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

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 134: 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?

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)
Cull all cows with linear score ≥5 at current lactation stage to rapidly reduce the high-SCC reservoir
Add post-milking teat dipping with an iodine-based barrier dip to reduce the 8%/month new infection rate
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 135: The Hazard Analysis Critical Control Point (HACCP) system was originally developed to ensure food safety for which population?

Commercial airline passengers
Military personnel in field operations
Hospitalized immunocompromised patients
NASA astronauts (Correct answer)

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 136: During fluoroscopic esophagram in a 2-year-old German Shepherd, liquid barium rapidly opacifies the esophagus but you observe persistent, focal retention of barium in a fusiform dilation of the esophagus at the level of the heart base. The esophagus proximal and distal to this region is normal in caliber. Manometric data (if available) would MOST likely show which of the following?

Failure of lower esophageal sphincter relaxation (achalasia-like) (Correct answer)
Absent peristalsis throughout the entire esophagus
Reduced amplitude contractions in the caudal esophageal segment only
Normal esophageal peristalsis with elevated resting lower esophageal sphincter pressure

Correct answer: Failure of lower esophageal sphincter relaxation (achalasia-like)

Focal, persistent barium retention in a fusiform dilation at the heart base, with normal esophageal caliber proximal and distal, is the classic fluoroscopic appearance of a vascular ring anomaly—specifically persistent right aortic arch (PRAA) with entrapment of the esophagus. However, in an adult dog with acquired focal heart-base dilation, the most likely diagnosis is a functional obstruction analogous to achalasia (failure of the lower esophageal sphincter or distal esophageal segment to relax). This would produce failure of LES relaxation on manometry. True idiopathic megaesophagus shows absent peristalsis throughout the entire esophagus (choice B), not focal dilation. Choices C and D do not correspond to a mechanism that produces focal fusiform retention.

Question 137: During a foreign animal disease investigation, a herd of cattle on a Midwestern farm is confirmed positive for Foot-and-Mouth Disease (FMD). The index farm is 12 km from an international port. Under the USDA APHIS FAD PReP protocols, which of the following best describes the immediate zoning structure established?

A 10-km Quarantine Zone with uniform restrictions throughout, pending further case confirmation
A 3-km Protection Zone surrounded by a 10-km Surveillance Zone
A 3-km Infected Zone surrounded by a 7-km Buffer Zone and a 10-km Surveillance Zone
A 10-km Control Area subdivided into an inner Infected Zone and an outer Buffer Zone, embedded within a Surveillance Zone extending to 10 km beyond the Control Area (Correct answer)

Correct answer: A 10-km Control Area subdivided into an inner Infected Zone and an outer Buffer Zone, embedded within a Surveillance Zone extending to 10 km beyond the Control Area

Under USDA APHIS FAD PReP Secure Beef Supply and FMD response plans, the standard zoning architecture establishes a Control Area (typically 10 km radius) subdivided into an inner Infected Zone (roughly 3 km) and an outer Buffer Zone. This Control Area is then embedded within a broader Surveillance Zone extending an additional 10 km beyond the Control Area perimeter. Uniform quarantine across the entire zone without subdivision does not reflect the tiered, risk-stratified approach required by APHIS protocols.

Question 138: A 6-year-old cat is referred for evaluation of refractory hypertension (BP consistently >200 mmHg systolic) unresponsive to amlodipine at 0.625 mg/cat PO q24h. Serum aldosterone is markedly elevated. Abdominal CT reveals a 1.2 cm unilateral adrenal mass. Which diagnosis best explains this clinical picture, and what is the definitive treatment?

Primary hyperaldosteronism (Conn's syndrome); adrenalectomy or medical management with spironolactone (Correct answer)
Adrenal carcinoma with ectopic ACTH secretion; palliative mitotane
Pheochromocytoma; adrenalectomy after pre-operative alpha-blockade with phenoxybenzamine
Adrenal-dependent hyperadrenocorticism; trilostane therapy

Correct answer: Primary hyperaldosteronism (Conn's syndrome); adrenalectomy or medical management with spironolactone

Feline primary hyperaldosteronism (Conn's syndrome) is an underrecognized cause of refractory systemic hypertension in cats. It results from autonomous aldosterone secretion (usually by an adrenal adenoma or carcinoma), causing sodium retention, hypokalemia, and pressure-resistant hypertension. Markedly elevated aldosterone with a unilateral adrenal mass is the classic presentation. Definitive treatment is unilateral adrenalectomy; medical management with the mineralocorticoid antagonist spironolactone ± potassium supplementation is used when surgery is not feasible. Pheochromocytoma causes catecholamine excess (not aldosterone excess) and would require phenoxybenzamine pre-operatively. Hyperadrenocorticism does not typically cause marked aldosterone elevation.

Question 139: A 10-year-old Warmblood shows grade 3/5 forelimb lameness that worsens on the lunge circle with the affected limb on the inside. Lameness is abolished by an abaxial sesamoid nerve block. The NEXT most appropriate diagnostic step is:

Low 4-point nerve block
Radiographs of the pastern
MRI of the foot
Intra-articular anesthesia of the fetlock joint (Correct answer)

Correct answer: Intra-articular anesthesia of the fetlock joint

After an abaxial sesamoid block confirms pain distal to the fetlock, intra-articular anesthesia of the fetlock joint helps differentiate fetlock joint pathology from other sources in that region.

Question 140: A 4-year-old Border Collie presents with episodic muscle tremors, hypersalivation, and mydriasis after being on a rural property. Organophosphate toxicosis is suspected. What is the mechanism and antidote?

Sodium channel blockade; lipid emulsion therapy
Nicotinic receptor blockade; atropine
GABA antagonism; diazepam
Acetylcholinesterase inhibition; atropine and pralidoxime (Correct answer)

Correct answer: Acetylcholinesterase inhibition; atropine and pralidoxime

Organophosphates irreversibly inhibit acetylcholinesterase causing acetylcholine accumulation; atropine blocks muscarinic effects while pralidoxime reactivates the enzyme if given early.

Question 141: 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?

Milbemycin oxime + spinosad (Trifexis)
Selamectin + lufenuron
Ivermectin + ketoconazole (Correct answer)
Doramectin + doxycycline

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 142: 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?

A gas-filled and distended gallbladder (emphysematous cholecystitis).
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.
Generalized loss of serosal detail throughout the entire abdomen.

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 143: 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 144: A 4-year-old male intact Labrador Retriever is presented for acute collapse. ECG shows a ventricular rate of 280 bpm with wide, bizarre QRS complexes and no discernible P waves. Blood pressure is 60/40 mmHg. The dog ate a large meal 3 hours ago and the owner notes intermittent exercise intolerance for 2 months. Cardiac troponin I is markedly elevated. What is the MOST likely underlying diagnosis driving this arrhythmia?

Arrhythmogenic right ventricular cardiomyopathy (ARVC) (Correct answer)
Dilated cardiomyopathy with secondary ventricular tachycardia
Gastric dilatation-volvulus with vagally-mediated arrhythmia
Hypokalemia-induced ventricular tachycardia following dietary indiscretion

Correct answer: Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heritable cardiomyopathy particularly prevalent in Boxers but also documented in Labrador Retrievers. It is characterized by fibrofatty replacement of right ventricular myocardium and a propensity for sustained ventricular tachycardia and sudden death, often without concurrent structural dilation. The elevated troponin I reflects myocardial injury, the history of exercise intolerance suggests a chronic underlying process, and the arrhythmia morphology is consistent with a right ventricular origin. Dilated cardiomyopathy typically shows systolic dysfunction on echo; GDV arrhythmias are usually less organized; hypokalemia alone rarely causes rates this high with this degree of hemodynamic compromise.

Question 145: 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?

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

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 146: 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)
Methylprednisolone acetate
Platelet-rich plasma (PRP)

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 147: A veterinary public health officer receives a report of a ranch hand who developed cutaneous anthrax after handling a cow carcass. Soil samples from the pasture confirm Bacillus anthracis spores at 4 × 10⁴ CFU/gram at depths up to 15 cm. Which regulatory authority and specific action is the MOST appropriate immediate response under U.S. law?

Notify OSHA under 29 CFR 1910.1030 (bloodborne pathogens standard) and require the ranch to implement an exposure control plan
Notify USDA-APHIS and state animal health officials; impose a state-level quarantine, vaccinate remaining animals with Sterne strain vaccine, and safely dispose of the carcass by deep burial or incineration on-site (Correct answer)
Notify CDC and initiate a select-agent registration audit of the farm under 42 CFR Part 73
Notify USDA-APHIS and condemn the herd under the Animal Health Protection Act; request EPA Superfund designation for soil remediation

Correct answer: Notify USDA-APHIS and state animal health officials; impose a state-level quarantine, vaccinate remaining animals with Sterne strain vaccine, and safely dispose of the carcass by deep burial or incineration on-site

Anthrax is a state-regulated foreign animal disease reportable condition in most U.S. states. The immediate veterinary public health response involves notifying USDA-APHIS and state animal health officials, imposing quarantine to prevent movement of potentially exposed animals, vaccinating the surviving herd with the licensed Sterne 34F2 strain (the only USDA-licensed veterinary anthrax vaccine), and disposing of the carcass by on-site deep burial (≥6 feet with lime) or incineration — never necropsy or movement off-site, as opening the carcass sporulates the organism. EPA Superfund is not applicable here; CDC select-agent regulations apply to laboratories, not farms with natural anthrax; OSHA bloodborne pathogens standard does not cover B. anthracis (a Category A bioterrorism agent covered separately).

Question 148: 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
Cervical vertebral stenotic myelopathy (Wobbler syndrome) (Correct answer)
Equine protozoal myeloencephalitis (EPM)
Equine herpesvirus myeloencephalopathy

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 149: 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?

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

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 150: A state veterinarian is investigating a cluster of human Salmonella Typhimurium infections epidemiologically linked to a small organic poultry farm. Whole-genome sequencing reveals the human isolates share a 5-SNP difference from the flock isolates. What is the most appropriate interpretation of this genomic finding?

WGS data alone is sufficient to close the outbreak investigation without further epidemiological correlation
The isolates are highly likely to share a common source, as 5 SNPs is within the expected evolutionary divergence during transmission (Correct answer)
The isolates are unlikely to share a common source because a 5-SNP difference exceeds outbreak thresholds
The isolates are definitively from different sources and the investigation should be redirected

Correct answer: The isolates are highly likely to share a common source, as 5 SNPs is within the expected evolutionary divergence during transmission

Whole-genome sequencing outbreak thresholds vary by organism, but for Salmonella, isolates within 5–10 SNPs are generally considered closely related and consistent with a common source. Evolutionary divergence occurs during host adaptation and transmission chains. WGS must always be interpreted alongside epidemiological data — it supports but does not independently confirm or close an investigation. A 5-SNP difference does not exclude a common source.

Question 151: On CT of the nasal cavity in a dog with nasal discharge, which finding most strongly suggests fungal rhinitis (Aspergillus) rather than nasal neoplasia?

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

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 152: A horse develops laminitis after prolonged use of which drug class?

Tetracyclines
Opioids
Corticosteroids (Correct answer)
Aminoglycosides

Correct answer: Corticosteroids

Prolonged corticosteroid use in horses can lead to laminitis due to alterations in digital blood flow and carbohydrate metabolism.

Question 153: A 6-month-old intact female Border Collie is presented with a 2-week history of progressive hindlimb ataxia, hypermetria, and intention tremors. The puppy was purchased from a farm where the dam was fed a selenium-deficient diet during gestation. Cerebrospinal fluid analysis is unremarkable. Which diagnosis is most consistent with these findings?

Canine distemper virus–induced cerebellar hypoplasia
Neonatal selenium deficiency–related cerebellar hypoplasia
Neuroaxonal dystrophy (NAD) specific to Border Collies (Correct answer)
Hereditary ataxia due to RAB3GAP1 mutation

Correct answer: Neuroaxonal dystrophy (NAD) specific to Border Collies

Neuroaxonal dystrophy (NAD) is a hereditary neurodegenerative condition recognized in Border Collies caused by mutations in the PLA2G6 gene. It presents in young dogs (typically 2–6 months) with progressive cerebellar signs including ataxia, hypermetria, and intention tremors. CSF is often normal. While selenium deficiency can cause white muscle disease (skeletal and cardiac muscle necrosis) in young animals, it does not cause cerebellar hypoplasia in dogs. Canine distemper causes cerebellar hypoplasia in neonatal infection but would typically have other systemic signs. The breed-specific hereditary condition is the most accurate diagnosis here.

Question 154: A veterinary public health officer is reviewing a HACCP plan for a federally inspected poultry slaughter establishment. The establishment proposes a single critical control point (CCP) — post-chill chlorinated water immersion at 50 ppm — for Salmonella control. Which of the following is the most accurate assessment of this plan's adequacy under current USDA-FSIS regulations?

The plan is inadequate; FSIS requires pathogen reduction performance standards for Salmonella that must be validated with microbial testing data, and a single post-chill intervention without upstream interventions (ante-mortem, scalding, defeathering CCPs) is unlikely to meet the Salmonella performance standard for broilers (Correct answer)
The plan is adequate but only if the establishment also maintains an antimicrobial resistance monitoring program under the National Antimicrobial Resistance Monitoring System (NARMS)
The plan is adequate; 50 ppm chlorine post-chill is an FSIS-approved intervention that satisfies all Salmonella performance standards when properly monitored
The plan is inadequate solely because FSIS prohibits chlorine concentrations above 20 ppm in immersion chillers under the Federal Food, Drug, and Cosmetic Act

Correct answer: The plan is inadequate; FSIS requires pathogen reduction performance standards for Salmonella that must be validated with microbial testing data, and a single post-chill intervention without upstream interventions (ante-mortem, scalding, defeathering CCPs) is unlikely to meet the Salmonella performance standard for broilers

FSIS mandates Salmonella performance standards (9 CFR Part 381) requiring establishments to demonstrate through microbial sampling that their process consistently produces product meeting the standard. A HACCP plan must be validated — meaning the establishment must show the CCP actually achieves the food safety objective. A single post-chill CCP is generally insufficient because a multi-hurdle approach (scalding temperature, inside-outside bird washer, antimicrobial rinses at multiple points) is needed to achieve meaningful log reductions. FSIS allows chlorine up to 20 ppm in water that contacts carcasses for human consumption without rinsing, but chiller water at higher concentrations with rinsing is managed under different tolerances — the regulatory limit issue is real but secondary to the validation inadequacy. NARMS participation is voluntary.

Question 155: 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?

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
High-protein diet increases cecal ammonia concentrations, causing direct mucosal necrosis and secondary Escherichia coli bacteremia

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 156: Which method is used to calculate the attack rate during a foodborne illness outbreak investigation?

Number ill / number exposed × 100 (Correct answer)
Number ill / total population × 100
Number new cases / population at risk × 100
Number exposed / number ill × 100

Correct answer: Number ill / number exposed × 100

Attack rate = (number of ill persons / number exposed) × 100, measuring the proportion of exposed individuals who became ill.

Question 157: A 9-month-old blue and gold macaw is presented for evaluation of a suspected choanal atresia. Rhinoscopy confirms a membranous occlusion of the right choana. While planning surgical correction, you are asked about the embryological origin of the choana. Which statement is correct, and which surgical approach carries the highest risk of iatrogenic ophthalmic injury in psittacines?

The choana is formed by fusion of the nasal conchae; palatal incision risks the palatine artery exclusively
The choana arises from fusion of the secondary palate; rhinotomy via the dorsal beak base risks the infraorbital sinus and lacrimal duct
The choana is derived from the primary palate; transoral choanal perforation with a rigid probe carries the highest risk to the globe due to the diverticulum of the infraorbital sinus extending caudal to the eye (Correct answer)
The choana arises from Rathke's pouch; endoscopic transnasal dilation poses the greatest risk to the optic chiasm

Correct answer: The choana is derived from the primary palate; transoral choanal perforation with a rigid probe carries the highest risk to the globe due to the diverticulum of the infraorbital sinus extending caudal to the eye

In psittacines, the choana arises from the primary palate (not the secondary palate as in mammals). The most commonly used surgical approach — transoral perforation of the choanal membrane using a rigid probe or dilator — carries significant risk of injury to the globe because the infraorbital sinus in parrots has a large caudal diverticulum that extends caudal and lateral to the orbit; blind perforation can penetrate this sinus and continue into orbital contents. Rathke's pouch is the embryological origin of the adenohypophysis, not the choana.

Question 158: A 7-year-old cat presents with icterus, anemia, and splenomegaly. Blood smear shows intraerythrocytic organisms. Which organism is most likely responsible?

Cytauxzoon felis
Bartonella henselae
Babesia felis
Mycoplasma haemofelis (Correct answer)

Correct answer: Mycoplasma haemofelis

Mycoplasma haemofelis (formerly Haemobartonella felis) is the most common cause of feline infectious anemia, attaching to the surface of red blood cells.

Question 159: Which NSAID is FDA-approved for long-term pain management in cats in the United States?

Robenacoxib (Correct answer)
Ketoprofen
Meloxicam
Grapiprant

Correct answer: Robenacoxib

Robenacoxib (Onsior) is the only NSAID approved for longer-term use in cats in the US; meloxicam is approved for single-dose injection only.

Question 160: A beef producer wants to improve weaning weights and post-weaning growth. Which management practice during the preconditioning period (45-60 days post-weaning) has the GREATEST impact on feedlot health outcomes?

Administering growth implants immediately at weaning
Keeping calves on the cow for 9 months before weaning
Providing ad libitum grain access from birth
Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale (Correct answer)

Correct answer: Completing vaccination series, weaning, castration, and dehorning at least 45 days before sale

Preconditioning programs that complete the BRD vaccination series, castration, and dehorning at least 45 days before sale reduce feedlot morbidity and mortality by allowing stress recovery and vaccine immune response maturation.

Question 161: 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?

Alpha-2 adrenergic agonist (e.g., detomidine)
Calcium channel blocker (e.g., diltiazem) (Correct answer)
Opioid agonist (e.g., butorphanol)
Cardiac glycoside (e.g., digoxin)

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 162: 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?

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

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 163: A dog's abdominal ultrasound reveals a splenic mass with a 'target' or 'bull's-eye' lesion appearance (hypoechoic halo around a hyperechoic center). This pattern is most associated with:

Splenic hematoma
Splenic abscess
Nodular hyperplasia
Metastatic neoplasia (Correct answer)

Correct answer: Metastatic neoplasia

A target or bull's-eye lesion pattern in the spleen is classically associated with metastatic disease, where a necrotic center is surrounded by viable tumor tissue.

Question 164: A 4 kg cat requires ketamine for induction. Which statement about ketamine in cats is most accurate?

It significantly depresses cardiovascular function
It is hepatically metabolized to active metabolites that extend sedation
It provides excellent visceral analgesia alone
It must be combined with a benzodiazepine or alpha-2 agonist to prevent seizure-like muscle rigidity (Correct answer)

Correct answer: It must be combined with a benzodiazepine or alpha-2 agonist to prevent seizure-like muscle rigidity

Ketamine alone causes muscle hypertonicity and vocalization; co-administration of diazepam or medetomidine produces smooth induction.

Question 165: A 5-year-old spayed female Border Collie presents with a 6-week history of progressive right forelimb lameness. Radiographs show a permeative lytic lesion at the distal radius with cortical destruction and a Codman's triangle. Fine-needle aspirate cytology reveals large polygonal cells with marked anisokaryosis. You initiate staging workup. Which finding would MOST significantly worsen the prognosis compared to the baseline expected survival with standard of care?

Regional axillary lymph node enlargement confirmed as metastatic on aspirate (Correct answer)
Bone scintigraphy showing increased uptake at the ipsilateral scapula
Serum alkaline phosphatase (ALP) > 110 IU/L
Pulmonary nodules >1 cm visible on thoracic CT but not plain radiographs

Correct answer: Regional axillary lymph node enlargement confirmed as metastatic on aspirate

Regional lymph node metastasis (confirmed histologically or cytologically) is a well-established negative prognostic indicator in canine appendicular osteosarcoma and upstages the disease. It is associated with significantly shortened survival times compared to dogs without nodal metastasis, even with amputation and chemotherapy. Elevated ALP is a negative prognostic factor but is common and does not change staging definitively. Pulmonary nodules detected only on CT but not radiographs are of uncertain significance and may be inflammatory. Skip metastasis to the scapula (detected by scintigraphy) suggests polyostotic disease, which is poor, but confirmed nodal spread is the most clearly documented survival-shortening finding listed.

Question 166: 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
Isoflurane
Halothane (Correct answer)

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 167: Which drug is the antidote for acetaminophen toxicity in cats?

Vitamin K1
Atropine
Activated charcoal alone
N-acetylcysteine (NAC) (Correct answer)

Correct answer: N-acetylcysteine (NAC)

N-acetylcysteine replenishes glutathione stores, allowing detoxification of the toxic acetaminophen metabolite NAPQI and is the primary antidote for acetaminophen toxicity.

Question 168: 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
Pleural effusion
Cardiomegaly (Correct answer)
Pneumothorax

Correct answer: Cardiomegaly

A cardiac silhouette exceeding 75% of thoracic width on the VD view is consistent with cardiomegaly.

Question 169: In avian anatomy, the proventriculus is best described as which of the following?

The muscular gizzard that grinds food
The avian equivalent of the small intestine
The glandular stomach that secretes HCl and pepsin (Correct answer)
A food storage pouch along the esophagus

Correct answer: The glandular stomach that secretes HCl and pepsin

The proventriculus is the glandular (true) stomach of birds that secretes hydrochloric acid and digestive enzymes before food enters the ventriculus.

Question 170: A cat is presented for suspected oleander (Nerium oleander) ingestion. What is the primary mechanism of toxicity?

Muscarinic cholinergic receptor agonism
Competitive inhibition of vitamin K epoxide reductase
Inhibition of Na+/K+-ATPase causing cardiac glycoside toxidrome (Correct answer)
Cyanide-like inhibition of cellular cytochrome oxidase

Correct answer: Inhibition of Na+/K+-ATPase causing cardiac glycoside toxidrome

Oleandrin and neriine in oleander inhibit Na+/K+-ATPase, causing hyperkalemia, bradyarrhythmias, and AV block similar to digoxin toxicity.

Question 171: Botulism outbreaks associated with commercially processed foods typically involve which form of Clostridium botulinum toxin production?

Preformed toxin ingestion from improperly processed low-acid canned foods (Correct answer)
Wound botulism from contaminated soil
Intestinal toxicoinfection in infants consuming spores
Iatrogenic botulism from therapeutic injections

Correct answer: Preformed toxin ingestion from improperly processed low-acid canned foods

Foodborne botulism typically results from ingestion of preformed toxin in low-acid, anaerobic environments created by improper canning processes.

Question 172: A ferret presents with progressive hind limb weakness, muscle wasting, and hypoglycemia. Blood glucose is 45 mg/dL. The most likely diagnosis is:

Lymphoma
Aleutian disease
Insulinoma (Correct answer)
Adrenal gland disease

Correct answer: Insulinoma

Insulinoma is the most common pancreatic tumor in ferrets and classically causes episodic hypoglycemia with hind limb weakness.

Question 173: 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?

Spironolactone
Pimobendan (Correct answer)
Enalapril
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 174: 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)
Alfaxalone (3 mg/kg IV bolus)
Tiletamine-zolazepam (2 mg/kg IV)

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 175: Weakness, despair, lethargy, ptyalism, and posterior paresis are symptoms that a 5-year-old ferret exhibits. The patient's owner reports that these symptoms frequently appear every morning before feeding and typically subside after the meal. The symptoms have recently gotten worse and lasted longer. Which of the subsequent diagnoses is most likely?

Adrenal cortical neoplasia
Lymphoma
Insulinoma (Correct answer)
Pancreatic exocrine adenocarcinoma

Correct answer: Insulinoma

The ferret's symptoms of weakness, despair, lethargy, ptyalism, and posterior paresis, which frequently appear before feeding and resolve after a meal, are classic signs of hypoglycemia. This pattern is highly characteristic of an insulinoma, a tumor of the pancreatic beta cells that secretes excessive insulin, leading to dangerously low blood glucose levels. The worsening and prolonged duration of symptoms indicate disease progression.

Question 176: Which feline coronavirus (FCoV) mutation is classically associated with the transition from enteric infection to feline infectious peritonitis (FIP)?

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

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 177: 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?

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

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 178: A producer wants to reduce the risk of hardware disease (traumatic reticuloperitonitis) in his dairy herd. What is the most cost-effective preventive measure?

Vaccinating with Clostridium perfringens toxoid
Installing metal detectors on TMR feeders only
Feeding chopped hay to slow rumen contractions
Administering rumen magnets to all cows (Correct answer)

Correct answer: Administering rumen magnets to all cows

A permanent ceramic or bar magnet placed in the reticulum captures ingested ferrous metal objects, preventing them from penetrating the reticulum wall.

Question 179: When performing a dental nerve block using the infraorbital approach in a dog, which nerve is primarily desensitized?

Maxillary nerve branches supplying upper premolars and incisors (Correct answer)
Inferior alveolar nerve
Lingual nerve
Mental nerve

Correct answer: Maxillary nerve branches supplying upper premolars and incisors

The infraorbital nerve block desensitizes the upper incisors, canine, and premolars ipsilaterally by blocking the maxillary nerve at the infraorbital foramen.

Question 180: 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?

VS-FCV outbreaks are caused by FCV recombination with feline coronavirus, creating a chimeric virus not covered by monovalent 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 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 181: 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?

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

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

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

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 183: When evaluating a horse for subtle hindlimb lameness, which surface is MOST useful for accentuating the gait abnormality?

Firm, level asphalt surface
Grass pasture
Rubber-matted stall aisle
Soft, deep sand arena (Correct answer)

Correct answer: Soft, deep sand arena

A soft, deep surface increases concussion and proprioceptive demands on the hindlimb, accentuating subtle lameness signs that may not be visible on a firmer surface.

Question 184: During exploratory laparotomy for colic, the surgeon identifies a section of small intestine that is dark purple-black in color with no palpable pulse in the mesenteric vasculature after 10 minutes of warm saline lavage. What is the appropriate surgical decision?

Apply topical papaverine to improve perfusion
Pack the abdomen and stage the surgery
Perform resection and anastomosis of the non-viable segment (Correct answer)
Replace the intestine and close; reassess in 24 hours

Correct answer: Perform resection and anastomosis of the non-viable segment

Non-viable intestine (no color change, no mesenteric pulse after warming) must be resected with end-to-end or side-to-side anastomosis to prevent endotoxemia and peritonitis.

Question 185: 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
Reduce the methimazole dose by 50% and add prednisolone to manage the immune-mediated reaction
Discontinue methimazole immediately and transition to radioactive iodine (I-131) or surgical thyroidectomy after stabilization (Correct answer)
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 186: 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?

Right dorsal colitis from prolonged COX-1 inhibition in the hindgut
Bone marrow suppression from camelid sensitivity to NSAIDs
Nephrotoxicity worsened by the llama's slower drug elimination half-life (Correct answer)
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 187: A 12-year-old Thoroughbred mare undergoes an emergency exploratory celiotomy for a large colon volvulus. Which of the following is the most common post-operative complication that can significantly impact morbidity and mortality in the immediate post-surgical period?

Laminitis
Post-operative ileus (POI) (Correct answer)
Adhesion formation
Incisional infection

Correct answer: Post-operative ileus (POI)

Post-operative ileus (POI), characterized by a lack of normal intestinal motility, is a very common and serious complication following equine colic surgery, particularly after procedures involving the small intestine or significant large colon manipulation. It can lead to gastric reflux, pain, and endotoxemia, and is a leading cause of post-operative death or euthanasia. While incisional infections, laminitis, and adhesions are also significant complications, POI is a more immediate and frequent life-threatening concern in the first few days post-surgery.

Question 188: 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?

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

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 189: On thoracic radiographs of a dog, which cardiac silhouette finding is most consistent with left atrial enlargement?

Rounding of the right heart border
Loss of the caudal waist on the ventrodorsal view
Increased sternal contact length
Elevation of the trachea at the carina (Correct answer)

Correct answer: Elevation of the trachea at the carina

Left atrial enlargement causes dorsal displacement and elevation of the trachea at the carina (mainstem bronchi splaying) on lateral radiographs.

Question 190: 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?

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

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

60°F to 180°F (16°C to 82°C)
32°F to 40°F (0°C to 4°C)
40°F to 140°F (4°C to 60°C) (Correct answer)
50°F to 165°F (10°C to 74°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 192: A 10-year-old spayed DSH cat presents with polyuria, polydipsia, and a serum sodium of 168 mEq/L. Urine specific gravity is 1.008. ADH administration fails to concentrate urine. Which diagnosis and underlying mechanism best explains this presentation?

Psychogenic polydipsia causing medullary washout and secondary renal concentrating defect
Hyperosmolar hypernatremia from pure water deficit with intact ADH axis
Nephrogenic diabetes insipidus due to renal tubular unresponsiveness to ADH (Correct answer)
Central diabetes insipidus due to hypothalamic ADH deficiency

Correct answer: Nephrogenic diabetes insipidus due to renal tubular unresponsiveness to ADH

Failure to concentrate urine after exogenous ADH administration confirms nephrogenic diabetes insipidus (NDI) — the renal tubules are unresponsive to ADH despite its presence. Central DI would respond to ADH administration with urine concentration. Psychogenic polydipsia causes medullary washout but typically responds partially to ADH. The hypernatremia here results from water loss exceeding intake, not pure water deficit with intact concentrating ability.

Question 193: 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?

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

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 194: CT of the abdomen in a 5-year-old intact male dog reveals a retroperitoneal mass cranial to the kidney with heterogeneous contrast enhancement and central necrosis. The ipsilateral kidney is displaced ventrally. No primary tumor is identified. The MOST likely diagnosis is:

Adrenocortical carcinoma
Retroperitoneal liposarcoma
Renal cell carcinoma
Paraganglioma (extra-adrenal pheochromocytoma) (Correct answer)

Correct answer: Paraganglioma (extra-adrenal pheochromocytoma)

Extra-adrenal paragangliomas (extra-adrenal pheochromocytomas) arise from chromaffin cells along the aorta and adjacent sympathetic ganglia, most commonly in the retroperitoneum cranial to or between the kidneys. On CT, they appear as large, heterogeneously enhancing masses with central necrosis that displace adjacent structures. Their location separate from the adrenal gland distinguishes them from adrenocortical carcinoma. Renal cell carcinoma would originate within the renal parenchyma. Retroperitoneal liposarcoma would contain macroscopic fat attenuation on CT. The intact male status and retroperitoneal location cranial to the kidney are classic for paraganglioma in dogs.

Question 195: Which ultrasonographic finding is MOST consistent with gastric dilatation-volvulus (GDV) versus simple dilatation in a dog?

Thickening of the gastric wall with loss of wall layering
Inability to obtain gastric images due to gas artifact
Uniform gastric distension with fluid content
Compartmentalization of the stomach into two gas-filled regions on the right lateral view (Correct answer)

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 196: A herd of cattle in the Texas panhandle develops polioencephalomalacia (PEM). The most common cause in feedlot cattle on high-sulfur diets is deficiency or antagonism of which vitamin?

Vitamin A
Thiamine (Vitamin B1) (Correct answer)
Vitamin E
Niacin

Correct answer: Thiamine (Vitamin B1)

High dietary sulfur promotes ruminal H2S production, which inhibits thiamine-dependent enzymes and causes cerebrocortical necrosis (polioencephalomalacia).

Question 197: 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?

Presence or absence of deep pain perception (Correct answer)
Degree of spinal cord swelling on MRI
Body weight of the patient
Duration of clinical signs before surgery

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 198: A 7-year-old FIV-positive cat is being treated for Cryptococcus neoformans meningoencephalitis with fluconazole. After 8 weeks, the cat shows neurological deterioration despite antigen titers decreasing. What is the MOST likely explanation for this paradoxical worsening?

Secondary Toxoplasma gondii co-infection causing immune-mediated encephalitis
Immune reconstitution inflammatory syndrome (IRIS) triggered by partial immune recovery on antifungal therapy (Correct answer)
Cerebral cryptococcoma formation requiring surgical debulking
Fluconazole resistance has developed and liposomal amphotericin B should be substituted immediately

Correct answer: Immune reconstitution inflammatory syndrome (IRIS) triggered by partial immune recovery on antifungal therapy

Immune reconstitution inflammatory syndrome (IRIS) is recognized in FIV-positive cats undergoing antifungal treatment, analogous to HIV patients. As antifungal therapy reduces fungal burden, even partial immune recovery in an FIV-affected cat can trigger a dysregulated inflammatory response to residual fungal antigens in the CNS, causing paradoxical worsening despite falling titers. This is managed with short-course immunomodulation (prednisolone), not antifungal escalation. Fluconazole resistance is rare in Cryptococcus and would present with rising titers, not falling ones.

Question 199: A 4-year-old Quarter Horse undergoes emergency surgery for a right dorsal colon displacement (right dorsal displacement of the large colon). Intraoperatively, the pelvic flexure is exteriorized and the colon is repositioned. Postoperatively on day 3, the horse develops profuse watery diarrhea, hypoproteinemia, and peripheral edema. Repeat gastric reflux yields 8 liters. Which complication best explains this clinical picture?

Enterocolitis caused by Salmonella spp. secondary to colonic ischemia-reperfusion injury
Proximal enteritis (duodenitis-proximal jejunitis) with concurrent colonic dysfunction
Right dorsal colitis secondary to perioperative NSAID toxicity (Correct answer)
Recurrence of the large colon displacement with secondary ileus

Correct answer: Right dorsal colitis secondary to perioperative NSAID toxicity

Right dorsal colitis (RDC) is a well-recognized sequela of excessive NSAID administration (particularly phenylbutazone) in the perioperative period. It causes focal ulceration and inflammation of the right dorsal colon, leading to protein-losing enteropathy (hypoproteinemia, edema) and diarrhea. The concurrent large-volume gastric reflux results from ileus secondary to the colonic inflammation. While Salmonella is possible, the clinical context of recent intensive NSAID therapy for colic surgery makes RDC the most likely diagnosis.

Question 200: FIP has no known treatment.

False
True (Correct answer)

Correct answer: True

Historically, Feline Infectious Peritonitis (FIP) was considered an untreatable and universally fatal disease. While new antiviral drugs have emerged, at the time this question was likely formulated, there was no widely recognized or approved 'cure' or treatment. The statement reflects the historical understanding and the challenge of FIP treatment.

Question 201: On a lateral thoracic radiograph of a dog, which structure should be used to assess left atrial enlargement?

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

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 202: A beef cow has been in second-stage labor for 90 minutes with no calf produced. Vaginal examination reveals a calf in dorsal longitudinal presentation with both forelimbs retained. Which corrective manipulation should be performed?

Apply traction immediately to the visible head to deliver the calf
Administer oxytocin 20 IU IV to increase uterine contractions
Repel the head, extend and cup each forelimb in turn, then reposition in anterior presentation before applying traction (Correct answer)
Perform fetotomy of the head to relieve obstruction

Correct answer: Repel the head, extend and cup each forelimb in turn, then reposition in anterior presentation before applying traction

Retained forelimbs (head-only presentation) must be corrected before traction to avoid traumatic brachial plexus injury and uterine laceration. The calf is repelled cranially (pushed back into the uterus) to create space, each forelimb is cupped and brought into extension one at a time, then traction is applied with the calf in normal anterior presentation. Traction on the head alone risks elbow lock and maternal injury.

Question 203: A cattle producer wants to treat a cow with bacterial pneumonia. Which beta-lactam antibiotic has an approved long-acting formulation for cattle?

Ceftiofur (Correct answer)
Amoxicillin
Penicillin G procaine
Ampicillin

Correct answer: Ceftiofur

Ceftiofur (as ceftiofur crystalline free acid) has a long-acting formulation approved in cattle that provides therapeutic concentrations for several days.

Question 204: Which breed is most predisposed to developing dilated cardiomyopathy (DCM) and typically presents with atrial fibrillation as its most common arrhythmia?

Doberman Pinscher
Irish Wolfhound (Correct answer)
Boxer
Cavalier King Charles Spaniel

Correct answer: Irish Wolfhound

Irish Wolfhounds have a very high prevalence of DCM and, due to their large atrial mass, are particularly prone to atrial fibrillation as a complicating arrhythmia.

Question 205: Which anesthetic agent is considered safest for induction in chelonians due to minimal cardiovascular depression?

Ketamine alone
Propofol
Alfaxalone (Correct answer)
Tiletamine-zolazepam

Correct answer: Alfaxalone

Alfaxalone provides smooth induction with less cardiovascular and respiratory depression compared to propofol and is preferred in chelonians.

Question 206: Which fungal organism causes 'yellow fungus disease' (invasive necrotizing mycosis) in bearded dragons?

Fusarium solani
Aspergillus fumigatus
Nannizziopsis guarroi (Correct answer)
Candida albicans

Correct answer: Nannizziopsis guarroi

Nannizziopsis guarroi causes yellow fungus disease in bearded dragons, producing invasive, necrotizing cutaneous lesions that are often fatal.

Question 207: A 7-year-old, neutered male Golden Retriever is presented with a chief complaint of weight gain, lethargy, and a 'rat tail' (alopecia on the tail). Physical examination reveals a dull coat, truncal alopecia, and mild obesity. Which of the following clinicopathologic abnormalities would be most supportive of a diagnosis of hypothyroidism?

Increased ALT and ALKP
Low BUN and creatinine
Hyperglycemia
Hypercholesterolemia (Correct answer)

Correct answer: Hypercholesterolemia

The clinical signs described are classic for canine hypothyroidism. Due to the decreased metabolic rate associated with hypothyroidism, hypercholesterolemia is a very common finding on a serum biochemistry panel, present in about 75% of cases. While a mild, non-regenerative anemia may also be seen, hypercholesterolemia is the most consistent biochemical abnormality.

Question 208: A 6-year-old male neutered Domestic Shorthair cat is evaluated for a 6-month history of weight loss despite polyphagia, intermittent vomiting, and hyperactivity. T4 is 7.8 µg/dL (reference: 0.8–4.0). You initiate methimazole therapy. Four weeks later, the owner reports the cat is less active and has developed facial pruritus and excoriations. Repeat T4 is now 1.2 µg/dL. Creatinine has risen from 1.2 to 3.8 mg/dL. Which pathophysiological explanation BEST accounts for the creatinine increase?

Dehydration secondary to decreased water intake now that polydipsia has resolved
Reduced muscle mass from prolonged hyperthyroid catabolism causing decreased creatinine production masking true GFR
Unmasking of pre-existing chronic kidney disease as hyperthyroidism-driven hyperfiltration is corrected (Correct answer)
Methimazole-induced immune-mediated glomerulonephritis

Correct answer: Unmasking of pre-existing chronic kidney disease as hyperthyroidism-driven hyperfiltration is corrected

Hyperthyroidism increases cardiac output and renal blood flow, creating a state of hyperfiltration that artificially elevates GFR and masks underlying chronic kidney disease (CKD). When hyperthyroidism is treated and T4 normalizes, renal perfusion returns to baseline, revealing the true (and reduced) GFR. This is a well-recognized clinical phenomenon in cats—treating hyperthyroidism can unmask occult CKD, and creatinine rising post-treatment reflects true underlying renal insufficiency, not treatment-induced nephrotoxicity. Methimazole can rarely cause immune-mediated glomerulonephritis, but the facial excoriations here represent a common idiosyncratic skin reaction to methimazole, not nephritis. The timing and magnitude of creatinine rise best fits unmasking rather than dehydration or muscle wasting.

Question 209: On thoracic radiographs of a cat, you identify a soft tissue opacity causing ventral displacement of the trachea at the thoracic inlet and dorsal displacement of the thoracic esophagus. The opacity silhouettes with the cranial cardiac border. Which structure most likely accounts for this pattern?

Branchial arch remnant
Thymic lymphoma (Correct answer)
Ectopic thyroid carcinoma
Cranial mediastinal cyst

Correct answer: Thymic lymphoma

In cats, cranial mediastinal masses that ventral-displace the trachea and dorsal-displace the esophagus while silhouetting with the cranial cardiac silhouette are classically thymic lymphoma. This is the most common cranial mediastinal mass in cats and frequently causes pleural effusion. Ectopic thyroid carcinoma is much rarer and tends to be more cranially positioned at the thoracic inlet. Cranial mediastinal cysts are uncommon and typically incidental; they would not show the described displacement pattern to the same degree. Branchial arch remnants are cervical, not thoracic.

Question 210: 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)
Most splenic masses in dogs are benign hematomas
Splenectomy is contraindicated until coagulopathy is corrected
Fine needle aspirate is diagnostic in the majority of splenic masses

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 211: A 10-year-old DSH cat presents with polyuria, polydipsia, and a serum fructosamine of 285 µmol/L (reference: 190–365). Blood glucose is 14.2 mmol/L. Which interpretation is most accurate?

Fructosamine is unreliable in cats with concurrent hemolytic anemia and should be repeated
A fructosamine of 285 µmol/L is diagnostic for hyperthyroidism-induced insulin resistance
The fructosamine confirms sustained hyperglycemia consistent with diabetes mellitus
The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM (Correct answer)

Correct answer: The fructosamine is within normal range, suggesting stress hyperglycemia rather than DM

Feline fructosamine reflects average glycemic control over 1–3 weeks. A value of 285 µmol/L falls within the normal reference range (190–365 µmol/L), indicating the hyperglycemia is likely transient (stress-induced) rather than sustained DM. Stress hyperglycemia is common in cats; fructosamine helps differentiate it from true DM. A fructosamine >400 µmol/L typically confirms DM. The other options misapply the reference values or attribute the finding incorrectly.

Question 212: A 3-year-old intact female rabbit is anesthetized for an ovariohysterectomy. Forty minutes into maintenance on 2.5% isoflurane, the rabbit becomes apneic with no response to a sternal rub. SpO2 drops to 82%. Which factor is MOST responsible for this rabbit's increased anesthetic risk compared to dogs and cats?

Rabbits lack µ-opioid receptors, making premedication protocols less effective
Rabbits have a higher requirement for isoflurane (MAC ~2.05%) than most domestic species
Rabbits metabolize inhalant agents 3× faster due to their high surface-area-to-volume ratio
Rabbits have obligate nasal breathing and a relatively small thoracic cavity with diaphragm-dependent ventilation (Correct answer)

Correct answer: Rabbits have obligate nasal breathing and a relatively small thoracic cavity with diaphragm-dependent ventilation

Rabbits are obligate nasal breathers with a diaphragm-dependent respiratory pattern and a relatively large abdominal visceral mass that restricts diaphragmatic excursion in dorsal recumbency. They have a narrow thoracic cavity relative to body size, poor respiratory reserve, and a highly sensitive respiratory center that is easily depressed by inhalants. These anatomical features make apnea common at surgical planes of anesthesia and make ventilatory support mandatory. The rabbit MAC for isoflurane (~2.05%) is indeed slightly higher than in dogs (~1.28%) and cats (~1.63%), but this alone doesn't cause apnea at 2.5%. Rabbits do have µ-opioid receptors. While high metabolic rate is real, it does not cause apnea.

Question 213: A dog presents with acute onset of right-sided head tilt, nystagmus with the fast phase to the left, and rolling. MRI is normal. The most likely diagnosis is:

Cerebellar stroke
Brainstem neoplasia
Idiopathic vestibular syndrome (Correct answer)
Otitis interna

Correct answer: Idiopathic vestibular syndrome

Idiopathic (geriatric) vestibular syndrome presents with acute severe peripheral vestibular signs and a normal MRI, and typically resolves spontaneously within 72 hours to 2 weeks.

Question 214: Acetaminophen (paracetamol) toxicity in cats primarily causes which two clinical findings?

Methemoglobinemia and hepatic necrosis (Correct answer)
Coagulopathy and thrombocytopenia
Acute renal failure and hypertension
Hypocalcemia and seizures

Correct answer: Methemoglobinemia and hepatic necrosis

Cats lack sufficient glucuronyl transferase to conjugate acetaminophen, leading to methemoglobinemia (muddy mucous membranes) and hepatic necrosis.

Question 215: A cat with confirmed FeLV infection is most likely to develop which neoplastic condition?

Multicentric lymphoma (Correct answer)
Hepatocellular carcinoma
Mast cell tumor
Mammary adenocarcinoma

Correct answer: Multicentric lymphoma

FeLV strongly predisposes cats to multicentric lymphoma, particularly T-cell lymphoma in young cats.

Question 216: A 5-year-old intact male ferret presents with bilateral symmetric alopecia starting at the tail base and progressing cranially, mild pruritus, and a swollen vulva-like perineal swelling. The owner reports the ferret has been increasingly lethargic over the past month. Serum estradiol is markedly elevated. Which underlying cause is most likely?

Functional ovarian remnant from incomplete gonadectomy
Adrenal cortical disease causing excess sex hormone production (Correct answer)
Exogenous estrogen exposure from a housemate cat on transdermal estradiol therapy
Sertoli cell tumor producing excess estrogen

Correct answer: Adrenal cortical disease causing excess sex hormone production

Adrenal gland disease (hyperadrenocorticism in ferrets) is the most common cause of bilaterally symmetric alopecia, pruritus, elevated sex hormones, and signs of hyperestrogenism (including vulvar swelling in spayed females OR perineal gland swelling in males) in ferrets. Ferret adrenal disease is distinct from Cushing's disease in dogs — it involves excess androgen and estrogen production (primarily), not cortisol. Early spay/neuter, a standard US practice, is a major predisposing factor. A Sertoli cell tumor is possible in intact male ferrets, but this ferret's presentation with bilateral symmetric alopecia AND a perineal swelling (often mistaken for a vulva) is classic for adrenal disease. Exogenous estrogen exposure and ovarian remnant are far less likely in this context.

Question 217: 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?

Tick vector transmission
Venereal transmission from infected bulls
Ingestion of oocysts from dog feces (horizontal)
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 218: What is the gold standard diagnostic test for confirming wet (effusive) FIP?

Abdominal ultrasound showing mesenteric lymphadenopathy
Serum coronavirus antibody titer >1:3200
Complete blood count showing lymphopenia
Effusion fluid RT-PCR for FCoV with immunostaining of macrophages (Correct answer)

Correct answer: Effusion fluid RT-PCR for FCoV with immunostaining of macrophages

Immunostaining for FCoV antigen within macrophages in effusion fluid or tissue biopsy is the gold standard for definitive FIP diagnosis.

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

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

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: Lily (Lilium spp.) ingestion in cats primarily targets which organ system?

Cardiovascular system
Hepatic system
Central nervous system
Renal system (Correct answer)

Correct answer: Renal system

True lily ingestion in cats causes acute renal failure due to nephrotoxic steroidal glycosides; even small amounts can be fatal.

Question 221: A 6-year-old Hanoverian dressage horse presents for evaluation of progressive bilateral forelimb lameness, worse on the right. Flexion tests mildly positive distally. Nerve blocks: palmar digital nerve block negative bilaterally; abaxial sesamoid block positive right (80% improvement), equivocal left. MRI of the right foot reveals diffuse signal hyperintensity on STIR sequences within the deep digital flexor tendon (DDFT) at the level of the navicular bone, with fibre disruption along the dorsal border. Which MRI finding in the DDFT would indicate a significantly worse prognosis, warranting immediate discussion of career-ending probability with the owner?

Focal signal hyperintensity limited to the medial lobe of the DDFT without dorsal border involvement
Diffuse T2 hyperintensity of the DDFT at the pastern level without navicular bone contact
Moderate increased signal on T1-weighted sequences at the musculotendinous junction
Full-thickness sagittal split of the DDFT visible on transverse sequences combined with navicular bone remodeling (Correct answer)

Correct answer: Full-thickness sagittal split of the DDFT visible on transverse sequences combined with navicular bone remodeling

A full-thickness sagittal split of the DDFT on transverse MRI sequences, particularly when combined with navicular bone remodeling (reflecting chronicity and mechanical overload), carries a significantly worse prognosis for return to athletic function. This lesion represents complete disruption of the central fibers with likely adhesion formation to the navicular fibrocartilage, severely compromising the tendon's ability to heal functionally. Focal lobe lesions without full-thickness extension or isolated hyperintensity at the musculotendinous junction are associated with more favorable outcomes. Combined DDFT splitting with bony changes is consistently the highest-risk MRI pattern in peer-reviewed equine foot imaging literature.

Question 222: During exploratory laparotomy on a 4-year-old Border Collie for suspected intestinal foreign body, you discover a 6 cm segment of jejunum that is dark purple-black, lacks peristalsis, and does not bleed when cut. The mesenteric vessels to this segment appear grossly intact. You resect the segment. Intraoperatively, which suture pattern for the jejunojejunostomy anastomosis has been shown to produce the LEAST luminal narrowing in small-diameter bowel?

Single-layer inverting Connell pattern
Two-layer inverting pattern using Cushing followed by Lembert
Single-layer simple interrupted appositional pattern (Correct answer)
Single-layer continuous Gambee pattern

Correct answer: Single-layer simple interrupted appositional pattern

Single-layer simple interrupted appositional (end-to-end) anastomosis produces the least luminal narrowing because it avoids the inversion of tissue that inherently reduces the anastomotic diameter. Two-layer inverting patterns and continuous inverting patterns (Connell) reduce lumen diameter by folding tissue inward, which is particularly problematic in the small-bore jejunum of dogs. The Gambee pattern is a modified appositional pattern that also reduces inversion, but simple interrupted appositional remains the gold standard for minimizing stricture in veterinary small intestinal surgery. Healing strength and leak rates are comparable or superior for single-layer appositional techniques.

Question 223: 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)
Paramyxovirus-associated hepatocellular carcinoma — submit serology for Ferlavirus antibodies
Nutritional secondary hyperparathyroidism — measure ionized calcium and PTH levels
Hepatic lipidosis — obtain a liver biopsy via endoscopy to confirm lipid vacuolation

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

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

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 225: 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?

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)
CNS should be targeted first with intramammary therapy because they represent the largest numerical contributor to the elevated BTSCC
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 226: In a spayed female ferret presenting with vulvar swelling, which disease is the most likely diagnosis?

Diabetes mellitus
Insulinoma
Ovarian remnant syndrome
Adrenal gland disease (Correct answer)

Correct answer: Adrenal gland disease

Adrenal gland disease in ferrets causes excess sex hormone secretion from adrenocortical tissue, leading to vulvar swelling even in spayed females.

Question 227: A 12-year-old cat diagnosed with hyperthyroidism is started on oral methimazole. Within the first three weeks of treatment, the owner reports the cat is scratching its face and neck incessantly, causing excoriations. Which of the following is the most appropriate action?

Switch to the transdermal formulation of methimazole.
Decrease the dose of methimazole by half and recheck in one week.
Add a glucocorticoid to the treatment regimen to control the pruritus.
Discontinue methimazole and discuss alternative treatments like radioiodine (I-131) therapy. (Correct answer)

Correct answer: Discontinue methimazole and discuss alternative treatments like radioiodine (I-131) therapy.

Severe facial pruritus and excoriation is an uncommon but serious idiosyncratic adverse reaction to methimazole in cats. It is considered an immunologic reaction and will not resolve by lowering the dose and is likely to recur with any formulation of the drug, including transdermal. The appropriate response is to stop the drug immediately and manage the pruritus. An alternative therapy for hyperthyroidism, such as radioiodine (I-131) or a prescription diet, must be chosen as the cat cannot tolerate methimazole.

Question 228: During anesthesia of a horse, you notice the mean arterial pressure drops to 55 mmHg. After adjusting vaporizer settings, which drug is most appropriate to improve cardiac output?

Vasopressin
Atropine
Epinephrine
Dobutamine (Correct answer)

Correct answer: Dobutamine

Dobutamine is a positive inotrope that increases cardiac output and improves perfusion pressure in anesthetized horses with inhalant-induced hypotension.

Question 229: Tritrichomonas foetus causes large-bowel diarrhea in cats. Which drug is currently recommended for treatment despite limited efficacy data?

Metronidazole
Sulfadimethoxine
Ronidazole (Correct answer)
Fenbendazole

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 230: 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?

Subtotal corpectomy with polymethylmethacrylate stabilization
Foraminotomy to decompress nerve roots bilaterally
Ventral stabilization using a Bagby basket (cervical vertebral interbody fusion) (Correct answer)
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 231: Which local anesthetic has the highest risk of causing methemoglobinemia in cats?

Benzocaine (Correct answer)
Bupivacaine
Lidocaine
Ropivacaine

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

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

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 233: A 7-year-old Thoroughbred presents with acute-onset, severe left forelimb lameness following a race. Radiographs reveal a complete, non-displaced sagittal fracture of the proximal phalanx. Intraoperative lag screw fixation is planned. Which cortex should the lag screw thread engage to achieve interfragmentary compression?

Both cortices with equal thread engagement to distribute load
The far cortex only, with the near cortex overdrilled to gliding hole diameter (Correct answer)
The far cortex with a washer placed under the screw head at the near cortex
The near cortex only, leaving the far cortex unthreaded

Correct answer: The far cortex only, with the near cortex overdrilled to gliding hole diameter

Lag screw technique requires overdrilling the near (glide) cortex to the outer thread diameter so it does not engage, while the thread bites only the far cortex. As the screw head seats against the near cortex, it pulls the far fragment toward the head, generating interfragmentary compression. Engaging both cortices or the near cortex alone negates the compression mechanism.

Question 234: A dairy producer wants to monitor transition cow health. Which single blood test best predicts subclinical ketosis in fresh cows?

Urine acetone dipstick color change
Serum beta-hydroxybutyrate (BHB) ≥1.2 mmol/L (Correct answer)
Blood glucose <2.5 mmol/L
Serum NEFA >0.4 mEq/L at dry-off only

Correct answer: Serum beta-hydroxybutyrate (BHB) ≥1.2 mmol/L

Serum BHB ≥1.2 mmol/L (1.0–1.4 mmol/L threshold range) measured in the first 2 weeks postpartum is the gold standard for diagnosing subclinical ketosis.

Question 235: A dog receives an overdose of acepromazine. Which statement about acepromazine reversal is correct?

Flumazenil fully reverses phenothiazine effects
Reversal can be achieved with atipamezole
Naloxone effectively reverses acepromazine sedation
There is no specific reversal agent; treatment is supportive (Correct answer)

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 236: A dog is prescribed phenobarbital for seizure control. Which of the following is the most important monitoring parameter for long-term therapy?

Urinalysis
Complete blood count
Serum electrolytes
Serum bile acids and liver enzymes (Correct answer)

Correct answer: Serum bile acids and liver enzymes

Phenobarbital induces hepatic enzymes and can cause hepatotoxicity with long-term use, so serum bile acids and liver enzymes must be monitored regularly.

Question 237: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?

Acepromazine (Correct answer)
Butorphanol
Midazolam
Dexmedetomidine

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 238: Which drug class is contraindicated in cats with urethral obstruction due to risk of worsening urethral tone?

Non-depolarizing neuromuscular blockers
Opioid agonists (Correct answer)
Benzodiazepines
Alpha-1 adrenergic antagonists

Correct answer: Opioid agonists

Pure opioid agonists (e.g., morphine) increase urethral sphincter tone in cats and can worsen urinary obstruction.

Question 239: A 6-year-old horse is presented with a history of spontaneous, severe epistaxis (nosebleed) from the right nostril. Endoscopic examination reveals a large, diphtheritic membrane on the dorsal aspect of the right guttural pouch, overlying the internal carotid artery. What is the most definitive treatment to prevent a fatal hemorrhage in this horse?

Long-term systemic antifungal therapy
Daily lavage of the guttural pouch with povidone-iodine
Transarterial coil embolization of the affected artery (Correct answer)
Surgical removal of the fungal plaque

Correct answer: Transarterial coil embolization of the affected artery

Guttural pouch mycosis with erosion of a major artery, such as the internal carotid, is a life-threatening emergency due to the risk of fatal hemorrhage. The most effective and definitive treatment to prevent bleeding is to occlude blood flow to the affected arterial segment. Transarterial coil embolization is the preferred method to achieve this. While medical management with antifungal drugs is part of the overall treatment to resolve the infection, it does not address the immediate risk of catastrophic bleeding.

Question 240: 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?

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

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 241: In a dairy herd investigation of reproductive failure, you find a 28% first-service conception rate and multiple cows with endometritis diagnosed via cytology (>18% PMNs at 21–33 days post-partum). Mycoplasma bovigenitalium is cultured from uterine swabs of several affected cows. Which of the following is MOST accurate regarding treatment of this herd?

Mycoplasma species lack a cell wall and are therefore intrinsically resistant to all beta-lactam antibiotics; systemic fluoroquinolones or tetracyclines are more appropriate, but treatment success is poor (Correct answer)
Ceftiofur intrauterine infusion is effective because third-generation cephalosporins have broad-spectrum gram-negative coverage including Mycoplasma
Intrauterine infusion of oxytetracycline is the treatment of choice because Mycoplasma lacks a cell wall and oxytetracycline penetrates uterine secretions well
Prostaglandin F2α administered at diagnosis will resolve mycoplasma endometritis by inducing luteolysis and restoring estrous cyclicity

Correct answer: Mycoplasma species lack a cell wall and are therefore intrinsically resistant to all beta-lactam antibiotics; systemic fluoroquinolones or tetracyclines are more appropriate, but treatment success is poor

Mycoplasma spp. lack a peptidoglycan cell wall, which confers intrinsic resistance to all beta-lactam antibiotics (penicillins, cephalosporins, and carbapenems) regardless of generation or spectrum (rules out A and C). Drugs targeting cell wall synthesis have no activity against cell-wall-free organisms. Tetracyclines and fluoroquinolones have in vitro activity, but clinical treatment success for Mycoplasma genital infections in cattle is notoriously poor, often requiring culling of chronically infected animals and biosecurity measures. Prostaglandin (D) supports uterine clearance in bacterial endometritis but does not address Mycoplasma specifically and is not curative.

Question 242: A 10-year-old Labrador Retriever is being managed for degenerative joint disease with long-term meloxicam. The owner reports the dog has developed polyuria and polydipsia over the past 6 weeks. Serum creatinine is 2.4 mg/dL (baseline 1.0 mg/dL), BUN 52 mg/dL, phosphorus 6.8 mg/dL, and urine specific gravity 1.014. Blood pressure is 178/112 mmHg. Which combination of interventions is most appropriate as the FIRST priority?

Continue meloxicam with renal-protective dose, initiate benazepril, and begin phosphate restriction
Discontinue meloxicam, initiate amlodipine, begin phosphate binder therapy, and start subcutaneous fluids (Correct answer)
Reduce meloxicam dose by 50%, initiate enalapril, and restrict dietary protein
Discontinue meloxicam, initiate amlodipine, and recheck creatinine in 2 weeks before starting additional therapies

Correct answer: Discontinue meloxicam, initiate amlodipine, begin phosphate binder therapy, and start subcutaneous fluids

This dog has IRIS Stage 2–3 CKD with concurrent hypertension and hyperphosphatemia. The NSAID must be discontinued immediately as it contributes to renal vasoconstriction and worsening CKD. Hypertension at this level (>160 mmHg systolic) requires immediate treatment with amlodipine (first-line antihypertensive in dogs). Hyperphosphatemia above 6 mg/dL in CKD warrants phosphate binder initiation. Subcutaneous fluids support renal perfusion. Waiting to address hypertension or hyperphosphatemia would allow ongoing target organ damage.

Question 243: 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?

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

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 244: Ovine Progressive Pneumonia (OPP) caused by Maedi-Visna virus is best controlled in a flock through which strategy?

Annual vaccination with killed-virus OPP vaccine
Prophylactic long-term tetracycline administration in feed
Parenteral ivermectin to eliminate the arthropod vector
Test-and-cull seropositive animals combined with separating lambs from seropositive ewes at birth (Correct answer)

Correct answer: Test-and-cull seropositive animals combined with separating lambs from seropositive ewes at birth

Maedi-Visna/OPP is a lentiviral infection with no vaccine or cure. Control relies on identifying seropositive animals via AGID or ELISA and removing them, combined with preventing transmission to lambs via infected colostrum/milk by separating and heat-treating or discarding colostrum. There is no arthropod vector; it is spread by close contact and milk.

Question 245: A 10-year-old spayed female Cocker Spaniel presents with a 2-month history of progressive exercise intolerance, ascites, and jugular venous distension. Echocardiography reveals a thickened, immobile tricuspid valve with moderate tricuspid regurgitation, a mildly dilated right atrium, and paradoxical septal motion. The left heart is structurally normal. B-type natriuretic peptide (BNP) is markedly elevated. Which echocardiographic finding is MOST pathognomonic for tricuspid valve dysplasia (TVD) rather than acquired myxomatous tricuspid degeneration (secondary to right-sided CHF)?

Tricuspid valve leaflets that are thickened, shortened, and tethered to the ventricular wall with abnormal chordae tendineae insertion (Correct answer)
Right atrial enlargement disproportionate to the degree of tricuspid regurgitation
Paradoxical interventricular septal motion indicating right ventricular volume overload
Moderate-to-severe tricuspid regurgitation on color Doppler imaging

Correct answer: Tricuspid valve leaflets that are thickened, shortened, and tethered to the ventricular wall with abnormal chordae tendineae insertion

Tricuspid valve dysplasia (TVD) is a congenital malformation characterized by structural abnormalities of the valve apparatus itself: shortened, thickened, or dysplastic leaflets; direct attachment (tethering) of leaflet tissue to the papillary muscles or ventricular wall; malformed or absent chordae tendineae; and abnormal papillary muscle architecture. These anatomical features are distinguishable on echocardiography from acquired myxomatous degeneration, which causes nodular thickening at the leaflet tips and prolapse without tethering. Paradoxical septal motion, tricuspid regurgitation by Doppler, and right atrial enlargement can all occur in either condition and are therefore not pathognomonic. The tethering/dysplastic valve apparatus is specific to TVD.

Question 246: What is the recommended minimum colostrum quality (Brix refractometer reading) indicating adequate IgG concentration for feeding to neonatal calves?

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

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 247: 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?

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

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 248: 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?

Fecal-oral transmission of Escherichia coli O157:H7 via raw milk; FDA under the Grade A Pasteurized Milk Ordinance (PMO) (Correct answer)
Direct contact transmission of Salmonella Typhimurium; CDC under the Public Health Service Act
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 249: 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.
Vaccinating all adult animals annually with a modified-live virus (MLV) vaccine.
Treating all clinically ill animals with supportive care and antibiotics.

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

Fentanyl
Morphine
Hydromorphone
Buprenorphine (Correct answer)

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 251: Which vaccine-preventable feline disease is caused by a parvovirus and requires only biannual boosters in adult cats after the initial series?

Feline leukemia virus
Feline panleukopenia (Correct answer)
Feline herpesvirus-1
Feline calicivirus

Correct answer: Feline panleukopenia

Feline panleukopenia virus (FPV) vaccines provide long-lasting immunity; AAFP guidelines recommend triennial or less frequent boosters in low-risk adult cats after initial series.

Question 252: A 5-year-old Poodle presents with acute collapse, pale mucous membranes, and distended abdomen. Ultrasound reveals a large hepatic mass with free abdominal fluid. Which tumor is most commonly associated with hemoabdomen in dogs?

Lymphoma
Hepatocellular carcinoma
Hemangiosarcoma (Correct answer)
Mast cell tumor

Correct answer: Hemangiosarcoma

Hemangiosarcoma of the spleen or liver is the most common cause of spontaneous hemoabdomen in dogs due to its highly vascular and fragile nature.

Question 253: A green iguana is presented with metabolic bone disease. Which nutritional deficiency is most commonly responsible?

Vitamin E deficiency
Phosphorus deficiency
Calcium deficiency and/or inadequate UV-B exposure (Correct answer)
Vitamin A 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 254: A 'string of pearls' sign on abdominal radiographs of a cat refers to:

Gas within the portal vasculature
Multiple uroliths in the ureter
Small gas bubbles trapped between intestinal folds indicating ileus (Correct answer)
Mineralization of lymph nodes in the mesentery

Correct answer: Small gas bubbles trapped between intestinal folds indicating ileus

The 'string of pearls' sign describes small gas bubbles trapped between the valvulae conniventes in paralytic ileus, indicating functional obstruction.

Question 255: During a herd health visit to a 300-cow cow-calf operation, you review the spring vaccination protocol. Calves receive modified-live virus (MLV) BVDV vaccine at branding (approximately 3 months of age). Several producers in the region report that calves vaccinated with MLV-BVDV at this age occasionally fail to seroconvert. Which mechanism BEST explains this vaccine failure in the context of herd health?

CD8+ T-cell immaturity at 3 months of age prevents development of cytotoxic memory
Colostral maternal antibody interference neutralizing vaccine virus before an immune response is mounted (Correct answer)
BVDV Type 2 strains in the MLV vaccine are poorly immunogenic in calves under 6 months
Concurrent PI (persistently infected) calves shedding wild-type BVDV that overcompetes with vaccine virus

Correct answer: Colostral maternal antibody interference neutralizing vaccine virus before an immune response is mounted

Maternal antibody interference is the classic and most well-documented explanation for MLV-BVDV vaccine failure at branding age. Calves acquire passive immunity through colostrum, and maternally derived antibodies (MDA) to BVDV can persist for 3–6 months or longer depending on colostrum quality and dam titer. These MDAs neutralize the attenuated vaccine virus before the calf's own immune system can mount a primary response, resulting in seronegative calves despite vaccination. This is why some protocols recommend delaying BVDV vaccination until weaning (~6–7 months) or using killed vaccine initially. PI calves shedding high-titer wild-type BVDV can cause immunotolerance in herd-mates but do not mechanistically interfere with vaccine virus the same way MDA does.

Question 256: Which of the following correctly describes 'first-pass metabolism'?

Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation (Correct answer)
The initial drug distribution phase immediately after IV injection
Metabolism occurring in the GI lumen before absorption
Drug elimination by the kidneys after IV administration

Correct answer: Hepatic metabolism that reduces bioavailability of orally administered drugs before reaching systemic circulation

First-pass metabolism refers to the hepatic biotransformation of an orally administered drug as it passes through the portal circulation before reaching systemic circulation, reducing bioavailability.

Question 257: On ultrasound of the urinary bladder, a non-shadowing, gravity-dependent echogenic material that shifts with patient repositioning is MOST consistent with:

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

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 258: 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 259: What is the significance of 'air bronchograms' on thoracic radiographs?

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

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 260: A 3-year-old spayed female cat presents in acute hepatic failure. The owner reports giving the cat an 'herbal flea remedy' containing pennyroyal oil topically two days ago. Serum chemistry reveals markedly elevated ALT, total bilirubin of 7.2 mg/dL, and prolonged PT. Which toxic mechanism best explains pennyroyal oil's hepatotoxicity in this patient?

Pulegone is bioactivated by CYP2E1 to a reactive electrophile (menthofuran and its epoxide) that depletes glutathione and causes covalent protein adducts (Correct answer)
Pennyroyal's monoterpene ketones directly inhibit mitochondrial complex I, causing ATP depletion and hepatocyte necrosis
Cats cannot N-acetylate pulegone, allowing it to accumulate as a free radical that causes zone 3 hepatic necrosis via lipid peroxidation
Pulegone undergoes β-oxidation in feline hepatocytes, generating microvesicular steatosis through medium-chain acyl-CoA dehydrogenase inhibition

Correct answer: Pulegone is bioactivated by CYP2E1 to a reactive electrophile (menthofuran and its epoxide) that depletes glutathione and causes covalent protein adducts

Pennyroyal oil is rich in pulegone, which undergoes hepatic bioactivation via CYP2E1 (and to a lesser extent CYP1A2) to form menthofuran and its reactive electrophilic epoxide intermediate. These metabolites rapidly deplete hepatic glutathione stores and form covalent adducts with cellular proteins, causing centrilobular (zone 3) hepatocellular necrosis. Cats are especially vulnerable because of their pre-existing deficiency in multiple conjugation pathways, reducing their capacity to detoxify reactive intermediates. N-acetylation deficiency is a known feline limitation but is not the primary mechanism here. Treatment parallels acetaminophen toxicosis: N-acetylcysteine (NAC) to replenish glutathione, along with supportive care.

Question 261: 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:

Duration of clinical signs before surgery
Presence or absence of deep pain perception in the pelvic limbs (Correct answer)
Severity of disc extrusion on MRI (Grasso scale grade)
Age of the patient at time of 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 262: A 1-year-old male intact German Shepherd presents with bilateral cryptorchidism. The owner wants the dog neutered. Which statement is most accurate?

Both retained and descended testicles must be removed (Correct answer)
Orchiopexy should be performed to reposition retained testicles
Cryptorchid testicles are sterile and pose no health risk
Only the scrotal testicle needs to be removed

Correct answer: Both retained and descended testicles must be removed

Retained testicles have a 13-14 times higher risk of developing Sertoli cell tumors and testicular torsion, so both must be removed during neutering.

Question 263: 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?

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

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 264: On abdominal ultrasound of a 6-year-old intact female Rottweiler, the adrenal glands are both enlarged (left: 1.8 cm, right: 2.1 cm in maximum width) with rounded poles and heterogeneous echogenicity. ACTH stimulation test is equivocal. Urine cortisol:creatinine ratio is elevated on two samples. Low-dose dexamethasone suppression test (LDDST) shows failure to suppress. Which additional imaging finding would MOST strongly support pituitary-dependent hyperadrenocorticism (PDH) over adrenal-dependent hyperadrenocorticism (ADH)?

A unilateral adrenal mass >2 cm with contralateral adrenal atrophy
Adrenal mineralisation on CT with loss of normal architecture
A pituitary mass >6 mm on contrast-enhanced MRI (pituitary macroadenoma) (Correct answer)
Bilateral adrenal enlargement with preserved corticomedullary ratio on CT

Correct answer: A pituitary mass >6 mm on contrast-enhanced MRI (pituitary macroadenoma)

A pituitary macroadenoma (>6 mm) on contrast-enhanced MRI is the most definitive imaging finding confirming PDH, as it directly identifies the source of excess ACTH. Bilateral adrenal enlargement is consistent with PDH but does not distinguish it from other bilateral adrenal diseases. Preserved corticomedullary ratio supports hyperplasia (PDH) but is not definitive. Unilateral adrenal mass >2 cm with contralateral atrophy is the classic finding for ADH (functional adrenal cortical tumor), not PDH. Adrenal mineralization can occur in both functional and non-functional masses.

Question 265: A cat anesthetized with isoflurane develops bradycardia (HR 70 bpm). What is the MOST appropriate first step before administering any drug?

Administer atropine IV immediately
Lighten anesthetic depth and reassess all parameters (Correct answer)
Begin a dopamine CRI
Increase the oxygen flow rate

Correct answer: Lighten anesthetic depth and reassess all parameters

Before administering any drug, the appropriate first response is to lighten anesthetic depth and assess all parameters, as anesthetic-induced vagal tone and excessive depth are common reversible causes of bradycardia.

Question 266: A 1,200-head commercial feedlot is experiencing an increased rate of liver condemnations at slaughter (18% vs. the target <10%). Rumen pH monitoring via rumenocentesis on 12 randomly selected cattle 6 hours post-feeding shows a mean rumen pH of 5.8 with 4 animals below 5.5. The current ration uses dry-rolled corn at 85% of dry matter. Which management change will MOST directly address the primary pathophysiological mechanism driving the liver condemnation rate?

Increase dietary roughage inclusion from 5% to 12% to buffer rumen pH
Switch from dry-rolled to high-moisture corn to slow starch fermentation rate
Add virginiamycin at 17 g/ton to suppress lactic acid-producing Streptococcus bovis
Add monensin at 200–360 mg/head/day to shift ruminal fermentation toward propionate (Correct answer)

Correct answer: Add monensin at 200–360 mg/head/day to shift ruminal fermentation toward propionate

Liver abscesses (the primary cause of liver condemnations in feedlots) result from rumenitis → rumen wall ulceration → bacteremia with Fusobacterium necrophorum seeding the liver. Subacute rumen acidosis (SARA, pH 5.5–5.8) is the driver of rumenitis. Monensin, an ionophore, shifts fermentation away from butyrate/propionate ratios that damage the rumen epithelium, reduces lactic acid accumulation, and directly reduces liver abscess rates by ~50% — the most validated single intervention. High-moisture corn actually ferments more rapidly than dry-rolled corn, potentially worsening acidosis. Increasing roughage helps buffer pH but is less targeted and reduces energy density. Virginiamycin specifically targets acute lactic acidosis (Streptococcus bovis/Lactobacillus), which is not the predominant concern here given pH values in the SARA range rather than <5.0.

Question 267: A cat is prescribed methimazole for hyperthyroidism. Which adverse effect is most commonly reported in the first 1–3 months of therapy?

Bone marrow aplasia
Peripheral neuropathy
Facial pruritus and excoriation (Correct answer)
Hepatotoxicity

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 268: A veterinarian prescribes enrofloxacin 5 mg/kg IV once daily for a 6-year-old cat with bacteremia. On day 3, the owner calls reporting the cat is bumping into objects and appears disoriented. Fundic examination reveals multifocal areas of retinal degeneration. What pharmacokinetic property of fluoroquinolones in cats most directly explains this toxicity?

Cats have a high volume of distribution for enrofloxacin, concentrating it in ocular tissues at doses safe in other species
Cats have reduced hepatic CYP1A2 activity, leading to accumulation of the parent compound (Correct answer)
Enrofloxacin's metabolic conversion to ciprofloxacin is prolonged in cats, producing toxic peak plasma levels
Cats lack sufficient glucuronidation capacity, causing enrofloxacin to accumulate in retinal photoreceptors

Correct answer: Cats have reduced hepatic CYP1A2 activity, leading to accumulation of the parent compound

Cats have markedly reduced hepatic CYP1A2 (cytochrome P450 1A2) activity compared to dogs and humans. Enrofloxacin is primarily metabolized by CYP1A2 to ciprofloxacin. With impaired metabolism, the parent compound (enrofloxacin) accumulates to high plasma concentrations. Enrofloxacin — more so than ciprofloxacin — is directly retinotoxic in cats, causing acute retinal degeneration and blindness, especially at doses ≥5 mg/kg/day IV. The AVMA-recommended feline dose is ≤2.5 mg/kg/day to reduce this risk. Glucuronidation deficiency in cats is real but pertains to other drug classes (e.g., acetaminophen, aspirin), not fluoroquinolone toxicity.

Question 269: On CT myelography of a dog, an 'intramedullary' lesion is characterized by:

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

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 270: Feline infectious peritonitis (FIP) wet form is characterized by accumulation of effusion. Which laboratory finding is most consistent with FIP effusion?

Hemorrhagic effusion with high RBC count
Low protein (<2.5 g/dL) transudate
High protein (>3.5 g/dL) with low cellularity and low albumin:globulin ratio (Correct answer)
High protein (>3.5 g/dL) with low cellularity and high albumin:globulin ratio

Correct answer: High protein (>3.5 g/dL) with low cellularity and low albumin:globulin ratio

FIP effusion is a high-protein (>3.5 g/dL) modified transudate with low cellularity and a low albumin:globulin ratio (<0.4), reflecting the vasculitis-driven protein leak.

Question 271: A 4-year-old Labrador Retriever is presented for episodic weakness and collapse after exercise. The owner reports the dog recovers within 10–20 minutes of rest. On examination, the dog is normal between episodes. Serum chemistry and CBC are unremarkable. An ECG during an induced episode shows a wide complex tachycardia at 280 bpm. Which breed-specific genetic mutation is most directly responsible for this presentation?

MDR1 (ABCB1) gene mutation causing P-glycoprotein deficiency
Pyruvate kinase (PK) deficiency causing compensatory erythrocytosis
Dynamin 1 (DNM1) gene mutation causing exercise-induced collapse (Correct answer)
Phosphofructokinase (PFK) deficiency causing hemolytic anemia with exertion

Correct answer: Dynamin 1 (DNM1) gene mutation causing exercise-induced collapse

Exercise-Induced Collapse (EIC) in Labrador Retrievers is caused by an autosomal recessive mutation in the Dynamin 1 (DNM1) gene, which encodes a GTPase critical for synaptic vesicle recycling. During intense exercise, the dysfunctional DNM1 leads to failure of neuromuscular transmission, resulting in collapse. The wide-complex tachycardia during the episode represents a ventricular arrhythmia secondary to the collapse event, not a primary cardiac disease. MDR1 mutations cause drug sensitivity. PFK deficiency causes hemolytic episodes with exercise but shows marked regenerative anemia. PK deficiency causes chronic hemolytic anemia.

Question 272: A 6-year-old Doberman Pinscher is being treated for dilated cardiomyopathy with digoxin. The dog develops acute renal failure secondary to a urinary obstruction. Which pharmacokinetic change requires the MOST urgent dose adjustment?

Reduced renal clearance causing digoxin accumulation and toxicity (Correct answer)
Enhanced protein binding reducing free drug concentration
Decreased hepatic first-pass metabolism increasing bioavailability
Increased volume of distribution due to fluid redistribution

Correct answer: Reduced renal clearance causing digoxin accumulation and toxicity

Digoxin is primarily eliminated by renal excretion (60-75% unchanged in urine). Acute renal failure dramatically reduces digoxin clearance, causing drug accumulation and a narrow therapeutic index means toxicity (arrhythmias, GI signs, neurological effects) develops rapidly. Dose reduction or extended dosing intervals are mandatory. Digoxin has minimal hepatic first-pass effect, and renal failure typically decreases (not increases) protein binding and volume of distribution.

Question 273: 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?

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

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 274: 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?

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

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

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

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 276: A 10-year-old Soft Coated Wheaten Terrier with a 2-year history of protein-losing nephropathy (PLN) and concurrent protein-losing enteropathy (PLE) is being managed medically. Current medications include enalapril, low-dose aspirin, and a hydrolyzed protein diet. Today's labs: albumin 1.4 g/dL, BUN 58 mg/dL, creatinine 2.8 mg/dL (IRIS CKD Stage 3), urine protein:creatinine (UPC) 6.2, cholesterol 480 mg/dL. The owner asks about adding immunosuppression. Which of the following statements regarding treatment is most accurate for this specific breed and presentation?

Prednisolone at immunosuppressive doses is the treatment of choice because immune-complex GN in Wheatens responds reliably to corticosteroids
Mycophenolate mofetil is the first-line immunosuppressant and should be started at full dose immediately
Immunosuppression is absolutely contraindicated with a creatinine of 2.8 mg/dL and IRIS Stage 3 CKD
Cyclosporine is relatively contraindicated in Wheaten Terriers with concurrent CKD due to nephrotoxicity risk, and mycophenolate is preferred (Correct answer)

Correct answer: Cyclosporine is relatively contraindicated in Wheaten Terriers with concurrent CKD due to nephrotoxicity risk, and mycophenolate is preferred

Soft Coated Wheaten Terriers have a breed-specific immune-complex membranoproliferative glomerulonephritis (MPGN) that is often refractory to corticosteroids and may worsen with prednisone (increased proteinuria, hypertension, accelerated GFR decline). The current IRIS and ACVIM consensus guidelines for immune-complex GN in this breed favor mycophenolate mofetil (MMF) over cyclosporine, as cyclosporine has direct nephrotoxic effects via afferent arteriolar vasoconstriction that can be particularly harmful in a dog with established CKD. MMF is initiated at 10–20 mg/kg PO BID with dose adjustments for renal function. Immunosuppression is not absolutely contraindicated in CKD if the underlying immune process is driving the nephropathy — treating the cause may slow progression.

Question 277: A veterinarian is performing a herd reproductive evaluation. Which metric best represents overall reproductive efficiency in a beef cow-calf operation?

Pregnancy rate per estrous cycle (PR/EC)
Conception rate to first service
Bull-to-cow ratio during the breeding season
Percentage of cows pregnant by 90 days post-calving (21-day pregnancy rate) (Correct answer)

Correct answer: Percentage of cows pregnant by 90 days post-calving (21-day pregnancy rate)

The percentage of cows pregnant by 90 days post-calving (equivalent to a 90-day breeding season) measures overall reproductive efficiency by accounting for both conception rate and submission rate.

Question 278: A lesion causing ipsilateral hemiparesis, ipsilateral facial paralysis (CN VII), and ipsilateral loss of the menace response with intact vision best localizes to which neuroanatomical site?

Ipsilateral C1-C5 spinal cord segment
Ipsilateral cerebellum (cerebellar hemisphere)
Contralateral cerebral cortex (forebrain)
Ipsilateral brainstem (pons/medulla) (Correct answer)

Correct answer: Ipsilateral brainstem (pons/medulla)

Cranial nerve VII (facial) nucleus is located in the pons. A lesion in the ipsilateral pons/medulla causes ipsilateral CN VII palsy (facial paralysis), ipsilateral hemiparesis (UMN, because corticospinal tracts haven't crossed yet at this level), and ipsilateral menace loss (cerebellar/pontine relay for menace). A forebrain lesion would cause contralateral deficits. Cerebellar lesions cause ataxia, not weakness or CN VII signs.

Question 279: 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)
Superficial bacterial pyoderma
Pemphigus foliaceus
Mast cell tumor with epidermal reaction

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 280: Which route of buprenorphine administration has been shown to achieve effective plasma concentrations in cats via the oral mucosa?

Intranasal
Transdermal patch
Transmucosally (OTM — oral transmucosal) (Correct answer)
Subcutaneous injection only

Correct answer: Transmucosally (OTM — oral transmucosal)

Buprenorphine is highly bioavailable when applied to the oral mucosa of cats (OTM) due to the alkaline feline oral pH facilitating absorption.

Question 281: A horse presents with a positive flexion test of the distal limb and lameness that is abolished by a palmar digital nerve block. Which structure is MOST likely affected?

Coffin joint
Pastern joint
Navicular bone or navicular bursa (Correct answer)
Digital flexor tendon sheath

Correct answer: Navicular bone or navicular bursa

A palmar digital nerve block desensitizes the navicular region, and a positive distal limb flexion test implicates the navicular apparatus as the primary source of pain.

Question 282: A dog is presented with acute onset of non-ambulatory tetraparesis following a traumatic event. Spinal radiographs reveal atlantoaxial subluxation. What is the definitive treatment of choice?

Cervical splinting with a neck brace
Corticosteroid therapy
Strict cage rest alone
Surgical stabilization of the atlantoaxial joint (Correct answer)

Correct answer: Surgical stabilization of the atlantoaxial joint

Surgical stabilization via ventral fixation or dorsal wiring provides definitive correction of atlantoaxial subluxation, which otherwise risks life-threatening spinal cord compression.

Question 283: A 3-year-old intact male cat presents with acute onset of pelvic limb paralysis, cold limbs below the stifle, absent femoral pulses bilaterally, and cyanotic nail beds. The most likely diagnosis is:

Fibrocartilaginous embolism (FCE) of the thoracolumbar spinal cord
Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy (Correct answer)
Traumatic spinal cord injury with T3-L3 myelopathy
Botulism with flaccid tetraplegia

Correct answer: Aortic thromboembolism (ATE) secondary to hypertrophic cardiomyopathy

Aortic thromboembolism in cats classically presents as the 'SAD' triad: Sudden onset, Asymmetric or bilateral pelvic limb paresis/paralysis, and Devastating pain. Cold, paralyzed limbs with absent femoral pulses and cyanotic nail beds (ischemia distal to the thrombus at the aortic trifurcation) are pathognomonic. Most cases have underlying hypertrophic cardiomyopathy. FCE is painless; spinal trauma has a history of injury.

Question 284: Which preanesthetic agent has the LEAST cardiovascular depression and is therefore most appropriate in critically ill or hemodynamically unstable patients?

Acepromazine
Midazolam (Correct answer)
Medetomidine
Xylazine

Correct answer: Midazolam

Midazolam and other benzodiazepines have minimal cardiovascular effects, making them preferred preanesthetic agents for critically ill, geriatric, or hemodynamically compromised patients.

Question 285: A horse presents with acute onset of severe bilateral forelimb lameness, leaning back on the hindlimbs, and bounding digital pulses. The MOST likely diagnosis is:

Laminitis (Correct answer)
Bilateral navicular bursitis
Bilateral coffin joint sepsis
Equine protozoal myeloencephalitis (EPM)

Correct answer: Laminitis

Acute laminitis classically presents with bilateral forelimb pain causing a characteristic saw-horse stance, bounding digital pulses, and reluctance to walk.

Question 286: A 450-cow dairy herd has a bulk tank somatic cell count (BTSCC) persistently between 350,000–420,000 cells/mL despite standard mastitis control measures. Pathogen culture of composite milk from cows with SCC >200,000 cells/mL reveals 68% Streptococcus agalactiae. Which intervention would most rapidly reduce the BTSCC in this contagious mastitis scenario?

Segregate all Streptococcus agalactiae-positive cows, milk them last, and cull chronically infected animals over the next 6 months
Initiate blitz therapy: treat all culture-positive cows simultaneously with intramammary penicillin while they remain in the milking herd (Correct answer)
Switch to a pre- and post-dip iodine teat disinfection protocol and retest in 90 days
Implement selective dry cow therapy based on pre-dry-off SCC and culture results

Correct answer: Initiate blitz therapy: treat all culture-positive cows simultaneously with intramammary penicillin while they remain in the milking herd

Streptococcus agalactiae is an obligate intramammary pathogen exquisitely sensitive to penicillin. Blitz therapy—treating all infected cows simultaneously with intramammary penicillin (with or without systemic support) while they remain in the milking string—achieves rapid, herd-level cure rates exceeding 90% and can dramatically reduce BTSCC within a single lactation. Selective dry cow therapy is effective for long-term control but does not treat cows currently in lactation. Segregation and milking-last slow transmission but do not cure existing infections. Improved teat disinfection addresses environmental or contagious spread prevention but does not eliminate existing infections.

Question 287: During arthroscopic surgery of the tarsocrural joint in a horse, you identify an osteochondral fragment at the distal intermediate ridge of the tibia (DIRT lesion). Intraoperatively you notice the synovial membrane is markedly hypertrophied and there is significant fibrillation of the adjacent cartilage beyond the fragment margin. Which prognostic factor most significantly worsens the long-term athletic outcome after fragment removal in this scenario?

Duration of lameness prior to surgery
Size of the original osteochondral fragment
Patient age at time of surgery
Presence of concurrent cartilage fibrillation extending beyond the lesion (Correct answer)

Correct answer: Presence of concurrent cartilage fibrillation extending beyond the lesion

While fragment size and age are considered, extensive cartilage fibrillation beyond the OCD lesion margin indicates generalized articular cartilage degeneration that will progress independently of fragment removal. This diffuse cartilage damage is the strongest negative prognostic indicator for return to full athletic function, as fragment removal alone cannot address the surrounding degenerative process.

Question 288: When performing musculoskeletal ultrasound in a dog, a tendon appears hyperechoic with a fibrillar pattern when the beam is perpendicular, but becomes hypoechoic when the transducer is angled. This phenomenon is called:

Shadowing artifact
Anisotropy (Correct answer)
Refraction
Enhancement

Correct answer: Anisotropy

Anisotropy is the property of tendons and ligaments whereby echogenicity changes dramatically with beam angle relative to fiber orientation.

Question 289: A 3-year-old intact male dog presents with a draining tract near the anus with recurrent abscesses. Probing reveals a communication with the rectum. What is this condition?

Rectal prolapse
Perineal hernia
Anal sac impaction
Perianal fistula (anal furunculosis) (Correct answer)

Correct answer: Perianal fistula (anal furunculosis)

Perianal fistulas (anal furunculosis) are chronic inflammatory tunneling tracts around the anus communicating with the rectum, most commonly seen in German Shepherds.

Question 290: 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 an FIV vaccination (Fel-O-Vax FIV) within the past 4 years (Correct answer)
The cat received a blood transfusion from an FIV-positive donor 2 weeks ago
The cat has concurrent FeLV viremia causing cross-reactive antibody production
The cat is a kitten under 6 months with maternally derived antibodies from an FIV-positive queen

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 291: A 6-year-old Bernese Mountain Dog presents with progressive exercise intolerance and a 3-week history of ascites. Physical exam reveals jugular venous distension, muffled heart sounds, and hepatomegaly. Echocardiography demonstrates a large pericardial effusion. Pericardiocentesis is performed, yielding 600 mL of serosanguineous fluid. Cytology of the fluid is non-diagnostic. Which of the following is the most common underlying etiology in this breed and age group, and what is the most appropriate long-term management?

Idiopathic pericardial effusion; recommend subtotal pericardiectomy after two recurrences
Mesothelioma; recommend intracavitary cisplatin after pericardiectomy
Right atrial hemangiosarcoma; recommend pericardiectomy plus doxorubicin-based chemotherapy (Correct answer)
Aortic body (chemodectoma) tumor; recommend palliative pericardiectomy with guarded prognosis

Correct answer: Right atrial hemangiosarcoma; recommend pericardiectomy plus doxorubicin-based chemotherapy

In large and giant breeds, particularly Bernese Mountain Dogs, Golden Retrievers, and German Shepherds, right atrial hemangiosarcoma (HSA) is the most common cause of pericardial effusion. Idiopathic pericardial effusion is more common in medium breeds. Aortic body tumors (chemodectoma) are more common in brachycephalic breeds. Hemangiosarcoma carries a very poor prognosis; median survival with pericardiectomy alone is approximately 4 months. Doxorubicin-based chemotherapy (e.g., VAC protocol) is the standard of care adjunct, extending median survival to approximately 4–6 months. Non-diagnostic cytology is typical of HSA, as these tumors shed poorly and hemorrhagic effusions mask neoplastic cells.

Question 292: 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?

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

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 293: A veterinarian is performing a complete blood count on a red-tailed hawk (Buteo jamaicensis) and notices large, round, pale-staining intracytoplasmic inclusions within erythrocytes, affecting approximately 15% of cells. The bird is mildly lethargic but otherwise clinically stable. Which of the following is the MOST accurate statement regarding this finding?

This is Haemoproteus sp. and is considered non-pathogenic in raptors; treatment is unnecessary
This is Leucocytozoon sp., which is transmitted by blackflies and can cause fatal anemia in accipiters (Correct answer)
These inclusions represent viral intranuclear inclusions displaced to the cytoplasm during erythrocyte maturation
This is Plasmodium sp., which is the primary avian malaria parasite requiring immediate chloroquine treatment

Correct answer: This is Leucocytozoon sp., which is transmitted by blackflies and can cause fatal anemia in accipiters

The large, round intracytoplasmic inclusions in erythrocytes of a raptor are most consistent with Leucocytozoon sp. gametocytes. Unlike Haemoproteus (which has halter-shaped gametocytes in erythrocytes and is generally non-pathogenic), Leucocytozoon can cause severe hemolytic anemia, particularly in accipiters (Accipiter spp.) and young birds. It is transmitted by Simulium (blackflies) and Culicoides. Plasmodium produces smaller, irregular inclusions with hemozoin pigment granules. Leucocytozoon gametocytes are large enough to distort the host cell, which helps distinguish them.

Question 294: A beef cow herd experiences a cluster of late-term abortions (7–9 months gestation) over 3 weeks. Fetuses show autolysis with placentitis. Serologic titers for Neospora caninum are elevated in affected cows but not in non-aborted herdmates. Which epidemiologic pattern best supports transient epidemic neosporosis rather than endemic neosporosis in this herd?

Affected cows have daughters with high seropositivity, suggesting vertical transmission is the dominant route of introduction
Abortion rate is 2–3% annually and steadily increases each year as new heifers enter the breeding herd
Abortions occur in cows of all ages with no clustering by age cohort and seroprevalence is uniformly distributed across the herd
Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared (Correct answer)

Correct answer: Abortions are concentrated in first-calf heifers and 2-year-olds with a rapid onset and high attack rate, while older cows are largely spared

Epidemic (point-source) neosporosis typically results from a sudden environmental exposure—such as contamination of feed or water with dog feces containing Neospora oocysts. This produces a high attack rate concentrated in a short time window and often disproportionately affects naive younger animals that lack any prior immunity. Endemic neosporosis, by contrast, is maintained by vertical (transplacental) transmission and tends to show a steady low-level abortion rate (1–3%) distributed across all age groups with seropositive dams producing seropositive offspring over successive years.

Question 295: 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:

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

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 296: A 12-year-old horse with recurrent uveitis undergoes a vitrectomy under general anesthesia. Thirty minutes into the procedure, the surgeon reports the eye is extremely firm (increased intraocular pressure). Which anesthetic agent, if used, is MOST likely responsible for this finding?

Ketamine administered as a constant rate infusion (Correct answer)
Romifidine given as premedication 45 minutes prior
Butorphanol used as part of a balanced analgesia protocol
Medetomidine administered during induction

Correct answer: Ketamine administered as a constant rate infusion

Ketamine elevates intraocular pressure (IOP) by increasing extraocular muscle tone and by inducing nystagmus and blepharospasm, which mechanically compress the globe. This effect is clinically significant in ophthalmic surgery where a firm eye impairs surgical access and can cause expulsive hemorrhage or vitreous prolapse. Alpha-2 agonists like romifidine and medetomidine actually decrease IOP through reduced aqueous humor production and systemic blood pressure, making them preferable adjuncts in ophthalmic cases. Butorphanol has no clinically meaningful effect on IOP. Ketamine CRIs are therefore avoided or used with extreme caution in intraocular surgical procedures.

Question 297: 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
Addison's disease
Pheochromocytoma
Hyperaldosteronism (Conn's syndrome) (Correct answer)

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 298: 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?

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

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 299: 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?

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
The antimicrobial selected for metaphylaxis should be a different class from the anticipated treatment antimicrobial to preserve treatment options (Correct answer)

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 300: 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?

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

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 301: 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 302: In avian medicine, which drug is contraindicated in pigeons and doves due to severe toxicity?

Metronidazole
Enrofloxacin
Doxycycline
Fenbendazole at high doses (Correct answer)

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 303: An 11-year-old Cocker Spaniel with mitral valve disease is now in CHF (NYHA functional class III). Which combination of drugs is considered standard of care per the ACVIM 2019 consensus guidelines for dogs with CHF?

Amlodipine + furosemide + atenolol
Furosemide + atenolol + digoxin
Pimobendan + digoxin + spironolactone
Furosemide + pimobendan + enalapril (Correct answer)

Correct answer: Furosemide + pimobendan + enalapril

The ACVIM 2019 consensus recommends furosemide, pimobendan, and an ACE inhibitor as the core triple therapy for dogs in CHF due to myxomatous mitral valve disease.

Question 304: A 10-year-old Quarter Horse presents with a chronic, intermittent, bilateral forelimb lameness that worsens on hard surfaces. The horse points the affected feet and shows a shortened cranial phase of the stride. Hoof tester application across the heels elicits a painful response. A palmar digital nerve block significantly improves the lameness. Which of the following is the most likely diagnosis?

Coffin joint septic arthritis
Sole abscess
Navicular syndrome (Correct answer)
Laminitis

Correct answer: Navicular syndrome

Navicular syndrome is a chronic degenerative condition affecting the navicular bone and associated soft tissue structures in the heel of the foot. The clinical signs described—chronic bilateral forelimb lameness, pointing, pain on hoof testers over the heel, and improvement with a palmar digital nerve block—are all classic indicators of this condition. While other conditions can cause heel pain, the chronicity and bilateral nature strongly suggest navicular syndrome.

Question 305: Which of the following organisms is most frequently present in feline pyometra?

Streptococcus pyogenes
Pseudomonas aeruginosa
Escherichia coli (Correct answer)
Staphylococcus aureus

Correct answer: Escherichia coli

Escherichia coli (E. coli) is by far the most common bacterial isolate found in cases of feline pyometra, as well as canine pyometra. This bacterium typically ascends from the lower reproductive tract or urinary tract into the uterus, especially under the influence of progesterone, which makes the uterus more susceptible to infection.

Question 306: A 10-year-old diabetic cat is scheduled for dental extraction. Which inhalant anesthetic is preferred due to its lower solubility and faster recovery profile?

Enflurane
Sevoflurane (Correct answer)
Isoflurane
Halothane

Correct answer: Sevoflurane

Sevoflurane has the lowest blood-gas partition coefficient among commonly used veterinary inhalants, resulting in the fastest induction and recovery.

Question 307: 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?

Octreotide SC injections are the first-line treatment of choice due to superior efficacy over prednisone in ferrets
Frequent high-protein, low-carbohydrate meals alone are sufficient medical management for insulinoma without pharmacologic intervention
Prednisone at 0.5–1 mg/kg PO BID is the preferred first-line medical management for insulinoma in ferrets
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)

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 308: 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?

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)
Canine parvovirus type 2c (CPV-2c) infection, which is not cross-neutralized by antibodies induced by FPV inactivated vaccines
Cold-chain failure during vaccine storage causing loss of adjuvant efficacy without affecting antigen content

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 309: 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?

ACTH stimulation test (Correct answer)
Endogenous ACTH concentration
Abdominal ultrasound
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 310: An 8-year-old Dachshund presents with acute onset of severe back pain and inability to ambulate. MRI confirms acute thoracolumbar IVDD at T12-13. Deep pain perception is absent. Within what time frame should surgical decompression ideally occur to maximize neurological recovery?

Within 4 hours
Within 24 hours
Within 6 hours
Within 48 hours (Correct answer)

Correct answer: Within 48 hours

Surgical decompression within 48 hours of loss of deep pain perception is associated with the best neurological outcomes in acute IVDD.

Question 311: A horse presents with sudden onset severe hindlimb lameness and a palpable defect in the middle gluteal muscle. The horse had been exercising at speed just before onset. What is the most likely diagnosis?

Femoral nerve paralysis
Fibrotic myopathy of the semimembranosus
Exertional rhabdomyolysis with muscle tear (tying-up) (Correct answer)
Sacroiliac subluxation

Correct answer: Exertional rhabdomyolysis with muscle tear (tying-up)

Acute muscle tear of the gluteal region with a palpable defect following high-intensity exercise is consistent with exertional rhabdomyolysis severe enough to cause myofibrillar disruption.

Question 312: Which serum biomarker is most specific for acute pancreatitis diagnosis in cats?

Serum trypsin-like immunoreactivity (fTLI)
Serum lipase
Feline pancreatic lipase immunoreactivity (fPLI/Spec fPL) (Correct answer)
Serum amylase

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 313: A veterinarian recommends a Selective Dry Cow Therapy (SDCT) program instead of blanket dry cow therapy. What is the PRIMARY advantage of SDCT?

It prevents new environmental mastitis infections during the dry period
It reduces antibiotic use by treating only cows with existing infections or high SCC (Correct answer)
It increases milk production in the subsequent lactation
It eliminates the need for teat sealants at dry-off

Correct answer: It reduces antibiotic use by treating only cows with existing infections or high SCC

SDCT reduces antimicrobial use by reserving intramammary antibiotic tubes for cows with evidence of infection, supporting antibiotic stewardship while maintaining udder health outcomes in low-SCC cows.

Question 314: Which federal regulation requires interstate shipment of livestock to be accompanied by a Certificate of Veterinary Inspection (CVI)?

Animal Health Protection Act (Correct answer)
Animal Welfare Act
Federal Meat Inspection Act
Virus-Serum-Toxin 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 315: Metabolic bone disease (MBD) in captive reptiles is most commonly caused by which combination of factors?

Bacterial osteomyelitis secondary to trauma
Calcium/phosphorus imbalance and UV-B light deficiency (Correct answer)
Hyperthyroidism
Excess vitamin D3 supplementation

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 316: A 9-year-old cat with chronic kidney disease (CKD, IRIS Stage 3) and osteoarthritis requires long-term analgesia. Buprenorphine has provided insufficient pain control. Which analgesic option presents the HIGHEST risk of acute-on-chronic kidney injury in this patient and should be strictly avoided?

Low-dose ketamine CRI (0.1–0.2 mg/kg/hr) during hospitalization
Meloxicam 0.1 mg/kg PO q24h as long-term maintenance (Correct answer)
Robenacoxib 1 mg/kg PO q24h for ≤3 days
Gabapentin 5 mg/kg PO q12h

Correct answer: Meloxicam 0.1 mg/kg PO q24h as long-term maintenance

NSAIDs inhibit prostaglandin synthesis via COX enzymes. Prostaglandins are critical for maintaining afferent arteriolar dilation and glomerular filtration pressure in cats with CKD, where compensatory renal hemodynamics are already stressed. Long-term meloxicam use in CKD cats (especially IRIS Stage 3–4) poses a high risk of further reducing GFR and precipitating acute decompensation. While robenacoxib is also an NSAID, the short-course limitation (≤3 days) and its preferential local tissue distribution reduce systemic renal risk in CKD compared to chronic meloxicam. Gabapentin is renally excreted but is generally considered safe with dose adjustment in CKD, and low-dose ketamine CRI does not depend on prostaglandin-mediated renal perfusion. Chronic NSAID use in IRIS Stage 3+ CKD is contraindicated in cats.

Question 317: On ultrasound of the urinary bladder, a dependent hyperechoic layer with acoustic shadowing that moves when the patient is repositioned most likely represents:

Transitional cell carcinoma
Bladder wall thickening
Uroliths (bladder stones) (Correct answer)
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 318: A 35 kg Labrador Retriever is receiving a morphine CRI at 0.1 mg/kg/hr post-orthopedic surgery. Six hours postoperatively, the dog is dysphoric, vocalizing, scratching at the face, and mildly ataxic, with a heart rate of 58 bpm. The MOST appropriate next step is:

Increase the morphine CRI to 0.2 mg/kg/hr to deepen analgesia
Administer low-dose naloxone 0.002 mg/kg IV and reassess pain score (Correct answer)
Switch to a fentanyl CRI and add acepromazine 0.02 mg/kg for sedation
Administer naloxone 0.04 mg/kg IV to reverse opioid toxicity

Correct answer: Administer low-dose naloxone 0.002 mg/kg IV and reassess pain score

The clinical picture—dysphoria, facial scratching (opioid-induced pruritus), ataxia, and bradycardia—represents morphine-induced side effects rather than undertreated pain. Full reversal with a standard naloxone dose (0.04 mg/kg) would eliminate analgesia, causing acute pain rebound. Low-dose naloxone (0.001–0.004 mg/kg IV) selectively reverses side effects such as dysphoria, pruritus, and excessive sedation while largely preserving analgesic efficacy. Increasing the CRI would worsen the side effect profile. Acepromazine can deepen sedation but does not address the underlying opioid-mediated dysphoria and may mask neurologic deterioration.

Question 319: A 12-year-old Warmblood sport horse presents with subtle right forelimb lameness that worsens significantly after palmar digital nerve blocks but does not improve with abaxial sesamoid blocks. Radiographs of the foot are unremarkable. Which diagnosis best explains this paradoxical worsening?

Deep digital flexor tendon tear proximal to the pastern
Neurectomy effect unmasking proximal limb pain (Correct answer)
Collateral desmitis of the distal interphalangeal joint
Navicular syndrome with concurrent palmar foot pain

Correct answer: Neurectomy effect unmasking proximal limb pain

Paradoxical worsening after a distal nerve block occurs when the blocked region was providing some compensatory proprioceptive input or the horse was guarding against distal pain in a way that partially stabilized a more proximal lesion. By abolishing the distal pain signal, the proximal pathology (which the abaxial sesamoid block does not reach) becomes the dominant pain source and lameness worsens. This 'unmasking' phenomenon is a recognized pitfall in sequential perineural diagnostic analgesia.

Question 320: A 6-year-old neutered male Dalmatian presents with recurrent urolithiasis. Stones have previously been typed as urate uroliths. The owner reports the dog is fed a standard commercial diet. Which of the following explains why Dalmatians are predisposed to urate urolithiasis compared to other breeds, even when consuming the same dietary purine levels?

Dalmatians overexpress xanthine oxidase in the liver, producing excess uric acid from purine catabolism that overwhelms normal uricase activity
Dalmatians have a hepatic uricase enzyme that converts uric acid to allantoin at a slower rate than other breeds due to a missense mutation in the SLC2A9 gene
Dalmatians have a defect in the renal proximal tubular transporter URAT1 (encoded by SLC22A12) that impairs uric acid reabsorption, combined with reduced hepatic uricase activity (Correct answer)
Dalmatians lack hepatic uricase entirely due to an autosomal recessive mutation in the uricase gene, making them physiologically similar to humans

Correct answer: Dalmatians have a defect in the renal proximal tubular transporter URAT1 (encoded by SLC22A12) that impairs uric acid reabsorption, combined with reduced hepatic uricase activity

Dalmatians have a dual defect: (1) reduced hepatic uricase activity compared to other dogs (they do have uricase, unlike humans, but at lower functional levels), and (2) a defect in renal tubular uric acid reabsorption mediated by the SLC22A12/URAT1 transporter. This combination results in higher serum uric acid concentrations and markedly elevated urinary uric acid excretion. The SLC2A9 mutation seen in humans causes hypouricemia by increasing renal uric acid excretion, which is a different mechanism. Dalmatians are not uricase-null (option B describes humans), and xanthine oxidase overexpression (option D) is not the established mechanism.

Question 321: 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?

Endogenous ACTH concentration measurement
No further testing is needed; the 8-hour suppression pattern is diagnostic for pituitary-dependent hyperadrenocorticism (PDH) (Correct answer)
High-dose dexamethasone suppression test (HDDST) to confirm PDH vs. ADH
Adrenal ultrasonography to rule out adrenal-dependent hyperadrenocorticism

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 322: A ventrodorsal thoracic radiograph of a 4-year-old Maine Coon cat shows a 'reverse D' or 'D-shaped' cardiac silhouette with straightening of the right heart border, tracheal deviation to the left, and post-stenotic dilation of the main pulmonary artery. Echocardiography confirms pulmonic stenosis. Which radiographic measurement, if applied, would MOST accurately quantify cardiac enlargement in this cat?

Cardiothoracic ratio on the VD view
Vertebral Heart Score (VHS) using lateral projection (Correct answer)
Vertebral Left Atrial Score (VLAS) on lateral projection
Right heart-to-thoracic ratio on the VD view

Correct answer: Vertebral Heart Score (VHS) using lateral projection

The Vertebral Heart Score (VHS), measured on the lateral projection, is the validated, species-specific method for quantifying cardiac enlargement in cats (normal ≤ 8.0 vertebrae). It accounts for thoracic conformation variability and is the standard reference used in feline cardiology publications. The cardiothoracic ratio is unreliable in cats due to their narrow, deep thorax. VLAS specifically quantifies left atrial size and is used for HOCM monitoring — not right-sided disease. A right heart-to-thoracic ratio is not a validated feline-specific metric. In pulmonic stenosis, the VHS captures the overall right heart enlargement on the lateral view.

Question 323: 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)
Negative contrast cystogram
Excretory urogram
Positive contrast cystogram

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

Hyponatremia and hyperkalemia (Correct answer)
Hypercalcemia and hyperphosphatemia
Hypernatremia and hypokalemia
Hypomagnesemia and hypochloremia

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

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

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 326: 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:

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

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 327: A 4-year-old Labrador Retriever is presented for acute vomiting and hematemesis 36 hours after accidental ingestion of ibuprofen. BUN is 85 mg/dL, creatinine is 6.2 mg/dL, and urinalysis shows glucosuria with isosthenuria. Renal biopsy reveals necrosis of the medullary thick ascending limb. Which mechanism BEST explains this specific distribution of renal injury?

Inhibition of thromboxane A2 causing glomerular thrombosis
Direct tubular toxicity of ibuprofen metabolites concentrated in the cortical proximal tubules
Systemic hypoperfusion causing cortical ischemia
Inhibition of prostaglandin-mediated vasodilation in the renal medulla leading to hypoxic necrosis (Correct answer)

Correct answer: Inhibition of prostaglandin-mediated vasodilation in the renal medulla leading to hypoxic necrosis

NSAIDs inhibit cyclooxygenase, blocking prostaglandin synthesis. In the renal medulla, prostaglandins (particularly PGE2 and PGI2) are critical for maintaining vasodilation against the high medullary osmotic gradient and countercurrent vasoconstrictive environment. The medullary thick ascending limb (mTAL) is metabolically active yet receives relatively hypoxic blood, making it uniquely dependent on prostaglandin-mediated vasodilation. NSAID inhibition causes vasoconstriction and medullary ischemia, selectively damaging the mTAL. This differs from the cortical proximal tubule injury seen with aminoglycosides.

Question 328: Feline panleukopenia virus (FPV) primarily targets which tissue due to its requirement for rapidly dividing cells?

Renal tubular epithelium
Intestinal crypt epithelium (Correct answer)
Pulmonary alveolar cells
Hepatocytes

Correct answer: Intestinal crypt epithelium

FPV targets rapidly dividing intestinal crypt cells, leading to villous collapse, malabsorption, and severe hemorrhagic enteritis.

Question 329: A geriatric cat with known HCM develops signs of congestive heart failure with pulmonary edema. Which diuretic is the cornerstone of initial CHF management?

Torsemide
Hydrochlorothiazide
Spironolactone
Furosemide (Correct answer)

Correct answer: Furosemide

Furosemide (a loop diuretic) is the cornerstone of acute and chronic CHF management in cats with HCM-associated pulmonary edema.

Question 330: Which finding on effusion fluid analysis is most consistent with FIP rather than cardiac or neoplastic effusion?

Hemorrhagic effusion with numerous erythrocytes
Exudate with low protein and low cell count
Transudate with protein <25 g/L
Straw-colored viscous exudate with protein >35 g/L and low cell count (Correct answer)

Correct answer: Straw-colored viscous exudate with protein >35 g/L and low cell count

FIP effusion is typically a viscous, straw-colored exudate with high protein (>35 g/L) but surprisingly low cell counts, yielding a high Rivalta test result.

Question 331: A 12-year-old Quarter Horse mare presents with a 48-hour history of weight shifting, bilateral forelimb lameness, and divergent hoof rings. Digital pulses are bounding in all four feet. Radiographs reveal a 12-degree rotation of P3 with a 6 mm sole depth in the left front foot. Which statement regarding prognosis and management is most accurate?

Coffin bone rotation beyond 10 degrees is an absolute indication for euthanasia regardless of sole depth
A sole depth ≥5 mm after rotation carries a favorable prognosis; corrective shoeing alone is sufficient treatment
The combination of >11.5-degree rotation AND <6 mm sole depth defines a negative prognosis threshold; this case is borderline and surgical options such as deep digital flexor tenotomy should be considered (Correct answer)
Venography is contraindicated in chronic laminitis cases with rotation due to risk of increased lamellar ischemia

Correct answer: The combination of >11.5-degree rotation AND <6 mm sole depth defines a negative prognosis threshold; this case is borderline and surgical options such as deep digital flexor tenotomy should be considered

The critical prognostic thresholds in equine laminitis are rotation >11.5 degrees AND sole depth <6 mm simultaneously — this combination correlates strongly with poor outcome. This mare sits right at these thresholds (12-degree rotation, 6 mm sole depth), making her prognosis guarded and warranting serious consideration of deep digital flexor tenotomy (DDFT tenotomy) to relieve pull on the distal phalanx. Sole depth ≥5 mm is actually a relatively negative threshold, not favorable. Rotation alone beyond 10 degrees is not an absolute euthanasia criterion. Venography is actually valuable in these cases to assess lamellar blood flow and guide prognosis.

Question 332: A chinchilla presents with drooling, difficulty eating, and sharp molar spurs on oral exam. This condition is best described as:

Slobbers (dental malocclusion) (Correct answer)
Oral candidiasis
Stomatitis
Cheek pouch impaction

Correct answer: Slobbers (dental malocclusion)

Dental malocclusion in chinchillas, commonly called 'slobbers,' results from molar spurs that lacerate the tongue and cause hypersalivation.

Question 333: 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?

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
Predictable accumulation of diazepam's active metabolite desmethyldiazepam due to impaired feline glucuronidation
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 334: A 10-year-old DSH cat presents with polyuria, polydipsia, and a palpable ventral neck mass. Serum T4 is 8.2 µg/dL (normal 0.8–4.0). Which cardiac abnormality is most commonly associated with this condition?

Restrictive cardiomyopathy
Hypertrophic cardiomyopathy (Correct answer)
Pericardial effusion
Dilated cardiomyopathy

Correct answer: Hypertrophic cardiomyopathy

Hyperthyroidism in cats most commonly causes hypertrophic cardiomyopathy due to the chronotropic and inotropic effects of excess thyroid hormone.

Question 335: A dog undergoes hindlimb amputation. Which regional anesthetic technique would provide the MOST comprehensive perioperative analgesia for this procedure?

Wound soaker catheter only
Intrapleural bupivacaine instillation
Lumbosacral epidural with morphine and lidocaine (Correct answer)
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 336: Which of the following is the most accurate description of a 'chip fracture' at the dorsal aspect of the proximal interphalangeal joint in a performance horse?

A stress fracture of the palmar cortex of the middle phalanx
An osteochondral fragment typically arising from the dorsal proximal rim of the middle phalanx (Correct answer)
A traumatic fracture of the extensor process of the distal phalanx
A subchondral cystic lesion within the proximal interphalangeal joint

Correct answer: An osteochondral fragment typically arising from the dorsal proximal rim of the middle phalanx

Dorsal chip fractures at the pastern joint are osteochondral fragments typically arising from the dorsal proximal rim of the middle phalanx, removed arthroscopically.

Question 337: A 9-year-old DSH cat is diagnosed with oral squamous cell carcinoma and the oncologist considers platinum-based chemotherapy. A technician asks whether cisplatin can be dose-reduced for safer use in this cat. Which statement most accurately describes cisplatin use in cats?

Cisplatin is absolutely contraindicated in cats because it causes fatal pulmonary edema and pleural effusion regardless of dose (Correct answer)
Cisplatin is safe in cats when combined with ondansetron pretreatment to blunt the acute cytokine-mediated response
Cisplatin can be used safely in cats at doses 50% lower than those used in dogs with aggressive IV fluid diuresis
Cisplatin toxicity in cats manifests primarily as nephrotoxicity and peripheral neuropathy, identical to other species

Correct answer: Cisplatin is absolutely contraindicated in cats because it causes fatal pulmonary edema and pleural effusion regardless of dose

Cisplatin is absolutely contraindicated in cats at any dose. Unlike dogs and humans where the primary toxicities are nephrotoxicity and myelosuppression, cats develop fatal acute pulmonary edema and pleural effusion within hours to days of cisplatin administration due to species-specific capillary permeability responses. No dose reduction or supportive care protocol makes cisplatin safe in this species. Carboplatin is the preferred platinum-based alternative for feline oncology patients.

Question 338: Organophosphate toxicity in animals is treated with which combination of drugs?

Physostigmine and diazepam
Pralidoxime (2-PAM) alone
Atropine and pralidoxime (2-PAM) (Correct answer)
Naloxone and flumazenil

Correct answer: Atropine and pralidoxime (2-PAM)

Atropine blocks muscarinic signs of organophosphate toxicity while pralidoxime reactivates acetylcholinesterase if given early before 'aging' of the enzyme occurs.

Question 339: A cat develops bradycardia and hypotension following topical application of an ophthalmic timolol solution. What is the mechanism of this adverse effect?

Direct myocardial toxicity of the benzalkonium chloride preservative
Systemic absorption of the beta-blocker through the nasolacrimal duct (Correct answer)
Activation of the oculocardiac reflex by the drops
Alpha-1 agonist activity at cardiac receptors

Correct answer: Systemic absorption of the beta-blocker through the nasolacrimal duct

Timolol is absorbed systemically via the nasolacrimal duct in cats, exerting beta-1 blockade effects on heart rate and blood pressure.

Question 340: A 7-year-old intact male Shetland Sheepdog presents with bilateral symmetric alopecia, hyperpigmentation, and a 'rat tail' appearance. Serum chemistry reveals hypercholesterolemia and mild elevations in ALP. An ACTH stimulation test is normal. Which additional diagnostic test is most appropriate to confirm the suspected diagnosis?

GnRH stimulation test measuring testosterone and estradiol (Correct answer)
Low-dose dexamethasone suppression test
Urine cortisol:creatinine ratio
TSH stimulation test with bovine TSH

Correct answer: GnRH stimulation test measuring testosterone and estradiol

The clinical picture — bilateral flank alopecia, hyperpigmentation, and 'rat tail' in an intact male — is classic for sex hormone-related alopecia (hyperandrogenism or adrenal sex hormone excess). A normal ACTH stimulation test rules out typical hyperadrenocorticism. A GnRH stimulation test measures testosterone and estradiol pre- and post-stimulation to identify testicular or adrenal sex hormone overproduction, which is the key next step. Castration is both diagnostic and therapeutic in many such cases.

Question 341: A 12-year-old Miniature Schnauzer presents with hypercalcemia (Ca 14.2 mg/dL), weight loss, and peripheral lymphadenopathy. Which test is most useful to differentiate hypercalcemia of malignancy from primary hyperparathyroidism?

Ionized calcium
Urinary calcium:creatinine ratio
PTH and PTHrP assay (Correct answer)
Serum phosphorus

Correct answer: PTH and PTHrP assay

Measuring both PTH (elevated in hyperparathyroidism) and PTHrP (elevated in humoral hypercalcemia of malignancy) is the most direct way to distinguish these causes.

Question 342: 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:

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

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 343: 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:

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

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 344: A dog receiving long-term phenobarbital therapy for epilepsy requires treatment with metronidazole for anaerobic infection. The metronidazole dose used is 60 mg/kg/day (an inadvertent overdose). Three days later the dog shows acute onset vertical nystagmus, intention tremors, and ataxia. What is the MOST accurate explanation for why phenobarbital may have worsened the neurotoxicity risk in this case?

Phenobarbital induces hepatic CYP450 enzymes, reducing metronidazole clearance and elevating plasma concentrations (Correct answer)
Phenobarbital depletes hepatic glutathione stores, impairing metronidazole detoxification
Phenobarbital competes with metronidazole at GABA-A receptors, paradoxically disinhibiting cerebellar circuits
Phenobarbital upregulates CYP450 enzymes, accelerating metronidazole metabolism to its toxic hydroxyl metabolite

Correct answer: Phenobarbital induces hepatic CYP450 enzymes, reducing metronidazole clearance and elevating plasma concentrations

Phenobarbital is a potent inducer of hepatic cytochrome P450 enzymes (particularly CYP2B and CYP3A). Paradoxically, while enzyme induction generally accelerates drug metabolism, metronidazole's primary metabolic pathway through CYP2C/3A becomes saturated or altered in the context of enzyme induction, and critically, some studies indicate phenobarbital reduces metronidazole clearance in dogs, raising plasma levels. Metronidazole neurotoxicity (cerebellar signs — nystagmus, ataxia, intention tremors) is concentration-dependent. While the overdose is the primary driver here, concurrent CYP450 induction by phenobarbital can paradoxically impair metronidazole clearance rather than enhance it in dogs, worsening accumulation. The safe dose of metronidazole in dogs on phenobarbital is ≤30 mg/kg/day.

Question 345: Feline infectious peritonitis dry (non-effusive) form most commonly causes granulomatous lesions in which anatomical sites?

Lungs and pleural cavity
Joints and synovium
Eyes, CNS, and abdominal organs (Correct answer)
Skin and ear canal

Correct answer: Eyes, CNS, and abdominal organs

Dry FIP granulomas typically affect the eyes (uveitis), CNS (ataxia, seizures), and abdominal organs (kidney, mesenteric lymph nodes).

Question 346: On a lateral skull radiograph of a rabbit, you observe bilateral tympanic bullae with significantly increased opacity and thickened walls. The petrous temporal bones appear sclerotic. This pattern is MOST consistent with:

Thymoma with paraneoplastic vestibular syndrome
Otitis media/interna with secondary bulla osteitis (Correct answer)
Encephalitozoon cuniculi granulomatous encephalitis
Cervical lymphoma compressing the vestibulocochlear nerve

Correct answer: Otitis media/interna with secondary bulla osteitis

In rabbits, bilateral tympanic bulla opacification with wall thickening and petrous bone sclerosis on skull radiographs is diagnostic of chronic otitis media/interna with bulla osteitis. Pasteurella multocida is the most common causative agent. This imaging triad—bulla opacity, bulla wall thickening, and petrosal sclerosis—represents chronic inflammatory and reactive bone change. Encephalitozoon cuniculi causes neurological signs but does not produce radiographic bulla changes. Thymoma is a thoracic disease. Cervical lymphoma would not produce intraosseous bulla changes visible radiographically.

Question 347: Xylitol ingestion in cats compared to dogs is best described as:

Non-toxic; cats do not absorb xylitol from the GI tract
Less understood; cats appear more resistant to xylitol-induced hypoglycemia than dogs (Correct answer)
Equally dangerous, causing hypoglycemia and hepatic failure
More dangerous, causing acute renal failure in addition to hypoglycemia

Correct answer: Less understood; cats appear more resistant to xylitol-induced hypoglycemia than dogs

Current evidence suggests cats are less susceptible to xylitol-induced hypoglycemia than dogs, though caution is still warranted and monitoring is recommended.

Question 348: A 5-year-old Cocker Spaniel presents with acute lethargy, pale mucous membranes, and icterus. A complete blood count reveals a severe regenerative anemia (HCT 15%) with marked spherocytosis and autoagglutination. Which of the following is the most likely diagnosis?

Von Willebrand's disease
Zinc toxicity
Babesiosis
Immune-Mediated Hemolytic Anemia (IMHA) (Correct answer)

Correct answer: Immune-Mediated Hemolytic Anemia (IMHA)

The combination of severe regenerative anemia, spherocytosis, and autoagglutination is pathognomonic for Immune-Mediated Hemolytic Anemia (IMHA). Spherocytes are red blood cells that have lost their biconcave shape due to partial phagocytosis, a hallmark of extravascular hemolysis in IMHA. Autoagglutination is the macroscopic clumping of red blood cells due to antibody coating. While other conditions can cause anemia, this specific combination of findings points strongly to an immune-mediated process.

Question 349: 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?

Administer sodium bicarbonate IV
Increase fresh gas flow rate
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 350: When treating a reptile patient, why is it essential to maintain the animal within its preferred optimal temperature zone (POTZ)?

POTZ is important only for feeding, not medical treatment
Temperature has no effect on antibiotic efficacy in reptiles
POTZ only affects reproductive behavior, not clinical outcomes
Reptiles are ectotherms, so immune function and drug metabolism depend on environmental temperature (Correct answer)

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 351: How would you handle FIP with ocular involvement?

Topical antibiotics (2'bacterial infections)
Topical pilocarpine
Glycopyrrolate
Topical steroids and atropine (Correct answer)

Correct answer: Topical steroids and atropine

Ocular involvement in FIP often manifests as uveitis, causing inflammation, pain, and vision impairment. Topical steroids (e.g., prednisolone acetate) are used to reduce inflammation, while topical atropine is used to relieve ciliary spasm, dilate the pupil, and prevent synechia formation. This combination effectively manages the pain and complications associated with FIP-related uveitis.

Question 352: 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?

Cervical disc disease
Radial nerve paralysis
Brachial plexus avulsion (Correct answer)
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 353: 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 provides analgesia primarily through κ-opioid receptor agonism in the periaqueductal gray
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

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 354: 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 carcinoma — aggressive treatment warranted
Metastatic carcinoma — full staging required
Nodular hyperplasia — no treatment required
Hepatocellular adenoma (hepatoma) — typically benign, wide surgical excision curative (Correct answer)

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 355: 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?

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

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 356: Kinematic gait analysis of a Warmblood dressage horse reveals a decreased protraction arc of the right forelimb with a shortened cranial phase of the stride but a normal caudal phase. Flexion tests are equivocal. Diagnostic analgesia of the coffin and pastern joints is negative. Which anatomical structure's pathology BEST explains decreased protraction with preserved caudal phase?

Subscapular bursitis limiting scapulohumeral joint extension
Superficial digital flexor tendon adhesion at the fetlock annular ligament
Medial palmar intercarpal ligament desmitis restricting carpal flexion
Infraspinatus muscle contracture limiting shoulder abduction and cranial advancement (Correct answer)

Correct answer: Infraspinatus muscle contracture limiting shoulder abduction and cranial advancement

Infraspinatus muscle contracture or fibrotic myopathy produces a characteristic limitation of shoulder abduction and external rotation, mechanically restricting cranial limb advancement (protraction). Because the caudal phase depends primarily on the stay apparatus and caudal muscle groups — which are unaffected — the stride has a normal push-off but a clipped cranial arc. This is distinct from elbow or carpal lesions and from foot pain. Diagnosis is confirmed by palpation of a firm, fibrous infraspinatus body, asymmetric shoulder abduction, and circumduction gait. It is an under-recognized cause of 'subtle' forelimb gait asymmetry in sport horses.

Question 357: A cat receiving repeated or prolonged propofol infusions is at risk for which unique hematologic complication?

Disseminated intravascular coagulation
Aplastic anemia
Thrombocytopenia
Heinz body anemia (Correct answer)

Correct answer: Heinz body anemia

Cats lack efficient glucuronidation and are sensitive to the phenolic compounds in propofol, which can cause oxidative damage to hemoglobin and formation of Heinz bodies, leading to hemolytic anemia.

Question 358: A cat with chronic diarrhea is found to shed feline coronavirus on fecal PCR. The cat is otherwise healthy. What is the most appropriate management?

Immediately begin GS-441524 treatment
Isolate permanently from all other cats
Monitor clinically; most cats clear enteric FCoV shedding without developing FIP (Correct answer)
Administer prednisolone to prevent FIP development

Correct answer: Monitor clinically; most cats clear enteric FCoV shedding without developing FIP

Most cats shed enteric FCoV transiently without progressing to FIP; monitoring clinical status is appropriate rather than immediate treatment.

Question 359: When calculating the economic impact of mastitis in a dairy herd, which production loss component is typically the largest?

Premature culling costs
Antibiotic treatment costs
Veterinary labor and diagnostic fees
Reduced milk production (discarded milk + production drop) (Correct answer)

Correct answer: Reduced milk production (discarded milk + production drop)

Reduced milk yield accounts for approximately 60–70% of total mastitis costs; clinical and subclinical cases each cow produces significantly less milk throughout the lactation.

Question 360: A 6-year-old Rottweiler presents with acute vomiting and melena. Gastroscopy reveals a deep ulcer in the antrum. Which drug class is most effective at preventing NSAID-induced gastrointestinal ulcers in dogs?

H2-receptor antagonists
Sucralfate
Proton pump inhibitors (Correct answer)
Bismuth subsalicylate

Correct answer: Proton pump inhibitors

Proton pump inhibitors (e.g., omeprazole) provide the most potent and sustained acid suppression and are superior to H2 blockers for preventing and treating GI ulcers.

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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