NAVLE Feline Infectious 6

Question 1

A 3-year-old indoor cat presents with pleural effusion, hyperglobulinemia (total protein 10.2 g/dL), and a pleural fluid albumin-to-globulin ratio of 0.3. FIP coronavirus PCR on the effusion is positive. Which additional finding would MOST strongly support effusive FIP over other causes of pleural effusion?

Accepted Answer

Serum alpha-1 acid glycoprotein (AGP) >1,500 µg/mL

Answer

Serum alpha-1 acid glycoprotein (AGP) >1,500 µg/mL has high sensitivity and specificity for FIP in cats with compatible clinical signs. While the Rivalta test is supportive of FIP-type effusion, it is not specific enough alone. High FCoV titers indicate exposure but not necessarily FIP (many healthy cats have high titers). Neutrophilic effusion with degenerate shift suggests bacterial pyothorax. AGP is an acute-phase protein markedly elevated in FIP and serves as one of the most diagnostically useful adjunct markers.

Question 2

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?

Accepted Answer

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

Answer

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 3

During a shelter outbreak investigation, 6 of 12 adult cats develop severe erosive stomatitis, limb edema, and pneumonia over 10 days with 2 fatalities. Kittens in the same ward are largely unaffected. Feline calicivirus (FCV) PCR is positive. Which strain characteristic BEST explains this outbreak pattern?

Accepted Answer

A recombinant FCV strain with enhanced tropism for endothelial cells causing virulent systemic FCV (VS-FCV)

Answer

Virulent systemic FCV (VS-FCV), also called hemorrhagic fever FCV, is characterized by endotheliotropism causing facial and limb edema, hemorrhagic diatheses, high fever, and mortality rates up to 67% in adult cats. Critically, VS-FCV preferentially affects adults because maternal antibodies from queens (who lack VS-FCV immunity) do NOT protect kittens against this antigenically distinct strain — however, adult cats with prior FCV immunity can still succumb because VS-FCV escapes neutralization by antibodies generated against classical FCV strains. The mortality pattern skewing toward adults is a hallmark of VS-FCV outbreaks.

Question 4

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?

Accepted Answer

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

Answer

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 5

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?

Accepted Answer

Waning humoral immunity below protective thresholds after 3 years combined with a high environmental viral load

Answer

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.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Feline Infectious 6