Isolation of feline syncytia-forming virus from oropharyngeal swab samples and buffy coat cells.

Thirteen of 40 female cats were found to be chronically infected with feline syncytia-forming virus (FeSFV). Attempts to isolate the virus from these cats by conventional methods were not successful. However, virus was isolated from oropharyngeal swab samples and buffy coat cells. A new method was used involving inoculation of actively dividing Crandell feline kidney cell cultures. Cultures were trypsinized 3 days after inoculation and, as a result, cytopathic effect was amplified and ability to detect the virus was enhanced. The FeSFV was detected in 93% (92/88) of the oropharyngeal swab samples and 100% (14/14) of the buffy coat cell specimens. Feline sera were tested by immunodiffusion for precipitating antibody against FeSFV antigen. There was 100% correlation between viral infection and the presence of precipitating antibody. Virus and antibody persisted in infected cats for the duration of this study (8 months for 5 of the infected cats). Urolithiasis was observed in 15 of 28 male cats. Although a direct relationship between FeSFV infection and urolithiasis was not established, most of these male cats (20 of 21) had antibody to FeSFV.