Feline infectious peritonitis: a worldwide serosurvey.

Feline sera from 13 countries were assayed for coronavirus antibody, using a heterologous indirect immunofluorescence test. Significantly higher percentages of antibody carriers were obtained during testing randomly collected sera from mature males (greater than 1 year old) than in testing females of the same age. Antibodies were infrequently found in immature cats (less than 6 months old); at 1 year of age or older, a plateau was reached and little change in the percentage of seroconverted animals was observed. Differences were not detected between purebred cats vs mixed-breed cats or household vs stray cats. In animals showing clinical signs of feline infection peritonitis (FIP), antibodies were encountered with higher frequency than in clinically healthy cats. Significant differences in antibody incidence were found between countries, with a range between less than 10% and greater than 50% of seropositive individuals. Antibodies were detected in sera from an isolated cat population (Marion Island) and from wild-caught cheetahs (Acinonyx jubatus). The antibody specificity for FIP virus was confirmed by neutralization tests. The antibody pattern in randomly collected solitary cats, in catteries, and cats with clinical FIP showed characteristic differences in titer and incidence. The implications of these results for the epizootiology of FIP are discussed.