Prevalence of canine coronavirus (CCoV) in dog in Japan: detection of CCoV RNA and retrospective serological analysis

TAKANO, Tomomi; YAMASHITA, Saya; MURATA-OHKUBO, Michiko; SATOH, Kumi; DOKI, Tomoyoshi; HOHDATSU, Tsutomu

The presence of CCoV-I-infected dogs was confirmed in 2007 in Japan and 2002 in Italy [11, 12] , suggesting that CCoV-I-infected dogs were already present earlier than 2007 in Japan. Thus, using canine sera collected between 1998 and 2006, the presence of anti-CCoV-I antibody earlier than 2007 was investigated employing the neutralizing antibody test. However, in the absence of CCoV-I laboratory strain, we used FCoV-I that shares high sequence homology in the S protein with CCoV-I. Neutralizing anti-FCoV-I antibodies were detected in serum samples from dogs in Japan. It was assumed that the neutralizing anti-FCoV-I antibody-positive dogs had been: i) infected with CCoV-I showing high-level genetic homology with FCoV-I or ii) infected with FCoV-I. It is also strongly suggested that CCoV-I-infected dogs and FCoV-I-infected dogs were mixed in the dogs from which sera were collected. However, regarding ii), to our knowledge, infection of a dog with FCoV has not been reported. In any case, it was clarified that 77.7% of dogs in Japan possess antibodies against FCoV-I and/or CCoV-I. It is suggested that FCoV-I and/or CCoV-I are widely prevalent in dogs in Japan since 1998. To closely investigate CCoV-I or FCoV-I infection in dogs, it is necessary to perform similar tests using both CCoV-I and FCoV-I. However, no assay detecting only anti-CCoV-I antibodies is available. Development of a method to detect anti-CCoV-I antibodies is desired.