Whole-genome analysis of bovine rotavirus species C isolates obtained in Yamagata, Japan, 2003–2010

An epidemic of diarrhoea in adult cows occurred at a total of 105 dairy farms in Yamagata Prefecture, Japan, between 2003 and 2010. Reverse transcription-PCR diagnostic tests revealed the presence of bovine rotavirus species C (RVCs) in samples from each of six farms (5.7 %). In this study, we determined the full-length nucleotide sequences of 11 RNA segments from six bovine RVC strains and investigated genetic diversity among them, including two bovine RVC strains identified in a previous study. Comparisons of all segmental nucleotide and the deduced amino acid sequences among bovine RVCs indicated high identities across all genes except for the VP4 gene. Phylogenetic analysis of each gene revealed that the six bovine RVCs belonged to a bovine cluster distinct from human and porcine RVCs. Bovine RVC strains could be clearly divided into two lineages of the VP4 genes. The nucleotide sequence identity for VP4 genes between lineage I and II was 83.7-84.8 %. Moreover, bovine RVC strains belonging to lineage I exhibited one amino acid deletion and three amino acid insertions, which differed for those strains belonging to lineage II. Our data suggest that multiple bovine RVCs originated from a common ancestor, but had different genetic backgrounds, not only in Yamagata Prefecture but also in the rest of Japan.