Molecular epidemiology of bovine toroviruses circulating in South Korea.

The prevalence of the bovine torovirus (BToV) and its genetic characterization have been reported in North America, Europe and Japan. Therefore, this study examined the prevalence and genetic diversity of the BToV in a total of 645 diarrheic fecal samples from 629 Korean native beef calf herds using RT-PCR and nested PCR with the primer pairs specific to a part of the BToV membrane (M) gene. Overall, 19 (2.9%) out of 645 diarrheic samples from 19 herds (6.9%) tested positive for BToVs by either RT-PCR or nested PCR. A comparison of the nucleotide (nt) and amino acid (aa) sequences of a part of the BToV M gene (409bp) among the BToVs showed the Korean BToVs to have comparatively higher sequence homology to the Japanese and Dutch BToVs than to the American and Italian BToVs. Generally, the Korean BToV strains clustered with the Japanese and Dutch BToV strains. However, the American and Italian BToV strains clustered on a separate major branch, suggesting that these are more distantly related to other known BToV strains. These results suggest that the BToV infections are sporadic in diarrheic calves in South Korea, and the Korean BToV strains are more closely related to the Japanese and Dutch BToVs than to the American and Italian BToVs.

Molecular characterization of novel G5 bovine rotavirus strains.

Group A rotaviruses are a major cause of acute gastroenteritis in young children as well as many domestic animals. The rotavirus genome is composed of 11 segments of double-stranded RNA and can undergo genetic reassortment during mixed infections, leading to progeny viruses with novel or atypical phenotypes. The aim of this study was to determine if the bovine group A rotavirus strains KJ44 and KJ75, isolated from clinically infected calves, share genetic features with viruses obtained from heterologous species. All 11 genes sequences of the KJ44 and KJ75 strains were sequenced and analyzed. The KJ44 VP4 had 91.7% to 96.3% deduced amino acid identity to the bovine related P[1] strain, whereas the KJ75 strain was most closely related to the bovine related P[5] strain (91.9% to 96.9% amino acid identity). Both KJ44 and KJ75 strains also contained the bovine related VP3 gene. The remaining 9 segments were closely related to porcine group A rotaviruses. The KJ44 and KJ75 strains showed high amino acid identity to the G5 rotaviruses, sharing 90.4% to 99.0% identity. In addition, these strains belonged to the NSP4 genotype B, which is typical of porcine rotaviruses and subgroup I, with the closest relationship to the porcine JL-94 strain. These results strongly suggest that bovine rotavirus strains with the G5 genotype occur in nature as a novel G genotype in cattle as a result of a natural reassortment between bovine and porcine strains.