Feline infectious peritonitis virus-associated rhinitis in a cat

CASE SUMMARY: This report describes a cat with initial respiratory signs prior to developing fulminant feline infectious peritonitis (FIP) after adoption from an animal shelter. Histologic examination of the tissues revealed typical lesions associated with FIP in the lung, liver, large intestine and small intestine. Histologic examination of the nasal cavity revealed pyogranulomatous rhinitis. Immunohistochemistry with monoclonal antibody FIPV3-70 targeting FIP antigen in macrophages confirmed FIP and molecular analysis identified a spike protein mutation (R793S) consistent with the presence of an FIP virus. Pathological changes, immunolabeling and molecular analysis provide evidence that respiratory infection by feline coronavirus is part of the spectrum of FIP-associated disease. RELEVANCE AND NOVEL INFORMATION: This report highlights nasal pathology associated with FIP through a combination of histopathology, immunohistochemistry and molecular characterization of the virus. Our work supports a little-appreciated role of the respiratory tract in FIP.