Pathological findings in a cat with cryptococcosis and feline immunodeficiency virus infection

Area of Science:

• Veterinary Pathology
• Mycology
• Immunology

Background:

• Systemic fungal infections can be severe in immunocompromised animals.
• Feline immunodeficiency virus (FIV) compromises the immune system, increasing susceptibility to opportunistic infections like cryptococcosis.

Purpose of the Study:

• To document the pathological, immunocytochemical, and ultrastructural findings of systemic cryptococcosis in a cat with concurrent FIV infection.
• To characterize the inflammatory response and the location of Cryptococcus yeasts within tissues.

Main Methods:

• Gross examination of affected organs.
• Histopathological analysis of lymph nodes, brain, lung, kidney, and eye.
• Immunocytochemistry using anti-CD3 antibodies.
• Electron microscopy to visualize fungal yeasts and cellular interactions.

Main Results:

• Major gross findings included lymphadenopathy and leptomeningeal cloudiness.
• Cryptococcus yeasts were abundant in lymph nodes, brain, and lungs, with lesser amounts in kidneys and eyes.
• Inflammatory reactions ranged from mononuclear to granulomatous, varying by organ.
• Electron microscopy revealed yeasts primarily within phagocytic cells.
• Immunocytochemistry identified CD3+ T-cells within the inflammatory infiltrates.

Conclusions:

• Concurrent FIV infection likely contributed to the severity and dissemination of cryptococcosis.
• The findings highlight the importance of considering opportunistic fungal infections in immunocompromised felines.
• Understanding the host-pathogen interaction, including phagocytosis of yeasts, is crucial for managing cryptococcosis.