Analysis of spike and accessory 3c genes mutations of less virulent and FIP-associated feline coronaviruses in Beijing, China.

Mutations in S and 3c genes of feline coronavirus (FCoV) have been associated with the development of feline infectious peritonitis (FIP). In the present study, FCoV S and 3c genes mutations were analyzed in healthy and FIP cats. M1058L mutation was found in 13.64% (3/22) feces from FIP cats, but not in feces from healthy cats (0/39). The intact 3c gene was found in feces from both healthy cats (19/19) and FIP cats (12/12). All parenteral samples from FIP cats carried one or more of the M1058L mutation, S1060A mutation and mutated 3c gene. FCoV reverse-transcriptase polymerase chain reaction (RT-PCR) of parenteral samples (including ascites, pleural effusions and tissue) is recommended as the gold standard for clinical diagnosis of FIP rather than detection of the M1058L mutation, but when cats have severe gastrointestinal symptoms and lesions, detection of the M1058L mutation in feces may be helpful in diagnosing FIP.