Epidemic of Equine Coronavirus at Obihiro Racecourse, Hokkaido, Japan in 2012

Equine coronavirus (ECoV) outbreaks have occurred three times at Obihiro Racecourse in Hokkaido, Japan. The third ECoV outbreak occurred between late February and early April 2012. The main clinical signs of affected horses were anorexia, pyrexia and leucopenia; gastrointestinal disease was observed in about 10% of affected horses. Two ECoV strains were isolated from diarrheal samples. All paired sera (9/9) collected from febrile horses showed seroconversion by neutralization test. Sequence and phylogenetic analysis of the ECoV isolated showed that putative amino acid sequences in S and N genes were highly conserved among ECoV strains. In contrast, sequences of the region coding 4.7kDa non-structural protein (p4.7) differed among the strains. Because of the diversity of the p4.7 region, this region should be useful for epidemiological investigation of ECoV.