BCSE BCSE - Basic and Clinical Sciences Examination Veterinary Microbiology and Infectious Diseases Questions and Answers 4 — Questions and Answers
Question 1: Which fungal organism is the causative agent of blastomycosis in dogs and is endemic to the Mississippi and Ohio River valleys?
- Histoplasma capsulatum
- Blastomyces dermatitidis (Correct answer)
- Coccidioides immitis
- Cryptococcus neoformans
Correct answer: Blastomyces dermatitidis
Blastomyces dermatitidis is the dimorphic fungus causing blastomycosis, endemic to river valleys of the central and eastern United States.
Question 2: A horse presents with mucopurulent nasal discharge and submandibular lymphadenopathy. Culture yields a beta-hemolytic Streptococcus with a Lancefield group C antigen. What is the most likely diagnosis?
- Strangles caused by Streptococcus equi subsp. equi (Correct answer)
- Pneumonia caused by Streptococcus pneumoniae
- Strangles caused by Streptococcus equi subsp. zooepidemicus
- Pigeon fever caused by Corynebacterium pseudotuberculosis
Correct answer: Strangles caused by Streptococcus equi subsp. equi
Streptococcus equi subsp. equi (group C Streptococcus) is the obligate pathogen causing classic strangles with abscessation of submandibular lymph nodes in horses.
Question 3: Which of the following viruses uses reverse transcriptase and integrates a DNA provirus into the host genome, causing immunodeficiency in cats?
- Feline herpesvirus-1
- Feline leukemia virus
- Feline calicivirus
- Feline immunodeficiency virus (Correct answer)
Correct answer: Feline immunodeficiency virus
Feline immunodeficiency virus (FIV) is a lentivirus (retrovirus) that uses reverse transcriptase and integrates as a provirus, causing progressive CD4+ T-cell depletion.
Question 4: Sarcocystis neurona is the primary causative agent of equine protozoal myeloencephalitis (EPM). What is the definitive host of this organism?
- White-tailed deer
- Opossum (Didelphis virginiana) (Correct answer)
- Raccoon
- Armadillo
Correct answer: Opossum (Didelphis virginiana)
The Virginia opossum (Didelphis virginiana) is the definitive host of Sarcocystis neurona, shedding sporocysts in its feces that contaminate horse feed and water.
Question 5: A cow is found dead with a bloated carcass that rapidly decomposes. Impression smears reveal large, boxcar-shaped Gram-positive rods. Which organism is most likely responsible?
- Clostridium chauvoei
- Bacillus anthracis (Correct answer)
- Clostridium novyi
- Clostridium perfringens type D
Correct answer: Bacillus anthracis
Bacillus anthracis produces large, boxcar-shaped, non-hemolytic Gram-positive rods with a distinctive square-ended appearance and causes rapid death and bloating in ruminants.
Question 6: Which Ehrlichia species primarily infects granulocytes and is transmitted by Ixodes scapularis in dogs and humans in the northeastern United States?
- Ehrlichia canis
- Anaplasma phagocytophilum (Correct answer)
- Ehrlichia ewingii
- Anaplasma platys
Correct answer: Anaplasma phagocytophilum
Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) infects granulocytes and is transmitted by Ixodes scapularis, causing granulocytic anaplasmosis.
Question 7: A dog presents with rapidly progressive hemorrhagic gastroenteritis and high mortality in a shelter setting. PCR confirms Canine parvovirus type 2. Which cell populations are preferentially targeted?
- Mature hepatocytes and Kupffer cells
- Rapidly dividing cells including intestinal crypt epithelium and lymphoid tissue (Correct answer)
- Neurons of the cerebral cortex and brainstem
- Mature erythrocytes and megakaryocytes
Correct answer: Rapidly dividing cells including intestinal crypt epithelium and lymphoid tissue
Canine parvovirus type 2 targets rapidly dividing cells, primarily intestinal crypt epithelium and lymphoid tissues, leading to hemorrhagic enteritis and leukopenia.
BCSE BCSE - Basic and Clinical Sciences Examination Veterinary Microbiology and Infectious Diseases Questions and Answers 4
Which fungal organism is the causative agent of blastomycosis in dogs and is endemic to the Mississippi and Ohio River valleys?