Abstract
Background:
Canine coronavirus (CCoV) is an important enteric virus of dogs and is widely distributed worldwide. The virus shows considerable genetic diversity and is classified into type I, type IIa, and type IIb genotypes. Although CCoV has been reported in various countries, information on its circulation and molecular characteristics in Japan remains limited.

Aim:
This study aimed to investigate the circulation and genetic characteristics of CCoV in domestic dogs in Japan between 2019 and 2020.

Methods:
Stool samples were collected from domestic dogs with or without diarrhea. Viral RNA was extracted from the samples and screened for CCoV by RT-PCR targeting the M gene. Positive samples were further analyzed by S gene-based RT-PCR to determine viral genotypes, including type I, type IIa, and type IIb CCoVs. Selected PCR products were sequenced, and phylogenetic analyses were performed to evaluate the genetic relationships between the detected strains and previously reported CCoVs.

Results:
CCoV RNA was detected in a subset of the analyzed samples. Genotyping analysis identified type I, type IIa, and type IIb CCoVs among the positive samples. Sequence and phylogenetic analyses showed that the detected strains clustered with previously reported CCoV lineages. These findings indicate that genetically diverse CCoVs are circulating in domestic dogs in Japan.

Conclusion:
This study demonstrates the circulation of CCoV in domestic dogs in Japan and provides updated molecular information on circulating strains. Although the samples were collected from limited regions and may not represent the nationwide situation, the results contribute to a better understanding of the molecular epidemiology and genetic diversity of CCoV in Japan.

Key words: Canine coronavirus; Domestic dogs; Molecular survey; Japan.