Using direct immunofluorescence to detect coronaviruses in peritoneal in peritoneal and pleural effusions

Twenty‐one cases of feline infectious peritonitis (FIP) were diagnosed using a direct immunofluorescence test on cytocentrifuged pleural and peritoneal effusions from cats sampled in vivo (11 cases) and at necropsy (10 cases). A commercial fluorescent polyclonal antiserum of feline origin reacting with FIPV and cross reacting with transmissible gastroenteritis virus and canine coronavirus was used. Eleven cats with ascites of a different origin were used as negative controls. The direct immunofluorescence test was 97 per cent reliable (31 cases of 32) and can be used in routine diagnosis.