BCSE - Basic and Clinical Sciences Examination Veterinary Microbiology and Infectious Diseases Questions and Answers Flashcards

Bovine viral diarrhea virus (BVDV) infection during which gestational window produces persistently infected (PI) calves?

Answer: Days 40–125 of gestation

PI calves result from fetal infection between approximately days 40 and 125, before immune competence develops, causing immunologic tolerance to the virus.

Which organism is the primary cause of contagious equine metritis (CEM) in mares?

Answer: Taylorella equigenitalis

Taylorella equigenitalis is a fastidious Gram-negative coccobacillus that causes CEM, a reportable venereal disease of horses in the US.

The 'gold standard' for diagnosing rabies in animals involves which laboratory technique on which tissue?

Answer: Direct fluorescent antibody (DFA) test on fresh brain tissue (brainstem/cerebellum)

The DFA test on unfixed brain tissue, particularly the brainstem and cerebellum, is the CDC-approved gold standard for animal rabies diagnosis.

Which mechanism allows methicillin-resistant Staphylococcus aureus (MRSA) to resist beta-lactam antibiotics?

Answer: Production of an altered penicillin-binding protein (PBP2a) encoded by the mecA gene

MRSA carries the mecA gene encoding PBP2a, a transpeptidase with very low affinity for all beta-lactam antibiotics, conferring broad resistance.

Aspergillus fumigatus nasal granulomas in dogs are best diagnosed by which combination?

Answer: Rhinoscopy with visualization of plaques plus fungal culture or cytology confirming Aspergillus

Definitive diagnosis of nasal aspergillosis requires rhinoscopic visualization of characteristic white fungal plaques combined with cytology or culture confirmation.

Which RNA virus causes foot-and-mouth disease (FMD), and why is it significant to the US livestock industry?

Answer: Aphthovirus (Picornaviridae); FMD is a foreign animal disease that would cause massive trade embargoes if introduced

FMD is caused by Aphthovirus (family Picornaviridae) and is a reportable foreign animal disease whose introduction would immediately halt US livestock exports.