Concurrent toxoplasmosis and feline infectious peritonitis in a cat

A 13-year-old, 4-kg, neutered male Maine coon presented with ascites. Toxoplasma gondii tachyzoites were seen within neutrophils and macrophages, and free within the abdominal fluid. At necropsy, many abdominal organs were positive for feline infectious peritonitis (FIP) antigens using immunohistochemical staining. This apparently is the first report of concurrent toxoplasmosis and FIP in a domestic cat.