Concurrent feline infectious peritonitis and toxoplasmosis in three cases

Concurrent feline infectious peritonitis and clinical toxoplasmosis was diagnosed in three cats. Definitive ante-mortem diagnosis was made by detecting intracellular feline Coronavirus antigen in macrophages using direct immunofluorescent staining and by identifying Toxoplasma gondii tachyzoites on cytological examination of peritoneal effusion (two cats) and bronchoalveolar lavage fluid (one cat). Concomitant illness or immunosuppression may have contributed to the development of systemic fulminant toxoplasmosis and feline infectious peritonitis in all three cases. Post-mortem histologic examination and immunohistochemistry for feline Coronavirus antigen and Toxoplasma gondii confirmed the diagnosis in all three cats. Severe granulomatous-necrotising rhinitis and vasculitis was present within the nasal cavity of one case. Immunohistochemistry demonstrated the presence of feline Coronavirus antigen in macrophages within these lesions. Nasal cavity involvement is an unusual manifestation of feline infectious peritonitis.