NAVLE Swine Medicine and Production — Questions and Answers
Question 1: A commercial sow farm reports a sudden increase in late-term abortions, stillbirths, and weak-born piglets across multiple farrowing rooms. Serology confirms Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). Which viral characteristic best explains the reproductive failure observed?
- PRRSV preferentially infects uterine endometrial cells, causing direct placental necrosis
- PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester (Correct answer)
- PRRSV crosses the placenta during early gestation and integrates into fetal DNA
- PRRSV causes reproductive failure exclusively through induction of hyperprogesteronemia
Correct answer: PRRSV infects porcine alveolar macrophages and spreads hematogenously to the fetoplacental unit during the last trimester
PRRSV targets porcine alveolar macrophages (PAMs) and monocyte-derived cells. During viremia — which is most consequential in the last trimester — virus crosses into the fetoplacental unit, causing fetal infection, death, and mummification. Early gestation infection rarely causes fetal loss; late gestation is the vulnerable window.
Question 2: A nursery pig presents with acute onset of polyarthritis, meningitis, and sudden death. Gram-positive cocci in pairs and short chains are isolated from CSF. What is the most likely causative organism?
- Erysipelothrix rhusiopathiae
- Streptococcus suis serotype 2 (Correct answer)
- Haemophilus parasuis
- Mycoplasma hyorhinis
Correct answer: Streptococcus suis serotype 2
Streptococcus suis serotype 2 is a leading cause of meningitis, polyarthritis, and septicemia in nursery and weanling pigs. It is a Gram-positive coccus in pairs/short chains. Erysipelothrix is Gram-positive but rod-shaped; Haemophilus parasuis (Glässer's disease) is Gram-negative; Mycoplasma lacks a cell wall.
Question 3: Postweaning multisystemic wasting syndrome (PMWS) associated with Porcine Circovirus type 2 (PCV2) is diagnosed in a 6-week-old pig. Which histologic lesion in lymph nodes is considered pathognomonic?
- Lymphoid hyperplasia with germinal center formation
- Lymphocytic vasculitis with fibrinoid necrosis
- Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies (Correct answer)
- Granulomatous lymphadenitis with central caseation
Correct answer: Lymphoid depletion with histiocytic replacement and intracytoplasmic basophilic inclusion bodies
PCV2-associated PMWS characteristically produces lymphoid depletion with replacement by histiocytes/macrophages that contain intracytoplasmic basophilic inclusion bodies (viral antigen). This combination is considered pathognomonic. Lymphoid hyperplasia is the opposite of what occurs.
Question 4: A gilt in a farrow-to-finish operation develops diamond-shaped, raised, red skin lesions over the trunk 2 days after moving to the breeding barn. The most appropriate treatment is:
- Florfenicol IM and supportive care
- Penicillin G IM, NSAIDs, and isolation (Correct answer)
- Ivermectin SC and topical antifungal
- Enrofloxacin IM and corticosteroids
Correct answer: Penicillin G IM, NSAIDs, and isolation
Diamond-shaped urticarial skin lesions (diamond skin disease) are classic for Erysipelothrix rhusiopathiae infection in pigs. Erysipelas responds well to penicillin G; NSAIDs reduce fever and inflammation. Corticosteroids are contraindicated in bacteremic animals; enrofloxacin has poor activity against Erysipelothrix.
Question 5: Which of the following is the recommended nutritional strategy to prevent osteochondrosis dissecans (OCD) in fast-growing market pigs?
- High-calcium, low-phosphorus diet to maximize bone density
- Restricting dietary lysine to slow growth rate
- Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate (Correct answer)
- Supplementing vitamin E and selenium to prevent oxidative cartilage damage
Correct answer: Ensuring Ca:P ratio of approximately 1.2:1 with adequate vitamin D and controlled growth rate
OCD in pigs is a developmental orthopedic disease linked to rapid growth, genetic selection for leanness, and mineral imbalances. A Ca:P ratio near 1.2:1 with adequate vitamin D3 and avoiding excess growth rate are the primary preventive strategies. Extreme calcium restriction or excess both impair endochondral ossification.
Question 6: Transmissible Gastroenteritis (TGE) and Porcine Epidemic Diarrhea (PED) cause clinically identical disease but differ in one key epidemiological feature. Which statement correctly distinguishes them?
- TGE is caused by a coronavirus while PED is caused by a rotavirus
- PED virus does not infect adult swine, while TGE virus affects all ages equally
- Both are coronaviruses, but TGE has largely been displaced in North America by PEDV since its 2013 emergence (Correct answer)
- TGE causes bloody diarrhea while PED causes watery white diarrhea with no blood
Correct answer: Both are coronaviruses, but TGE has largely been displaced in North America by PEDV since its 2013 emergence
Both TGE virus and PEDV (Porcine Epidemic Diarrhea Virus) are alpha-coronaviruses causing watery diarrhea with high mortality in neonates. A key epidemiological point: PEDV emerged explosively in North America in 2013 and has largely replaced TGE as the dominant enteric coronavirus. Both affect all ages, but neonatal mortality is highest. PED is not a rotavirus.
NAVLE Swine Medicine and Production
A commercial sow farm reports a sudden increase in late-term abortions, stillbirths, and weak-born piglets across multiple farrowing rooms.
Serology confirms Porcine Reproductive and Respiratory Syndrome Virus (PRRSV).
Which viral characteristic best explains the reproductive failure observed?