Molecular detection and genetic characterization of kobuviruses in fecal samples collected from diarrheic cattle in Korea.

Kobuviruses are small, non-enveloped viruses with single-stranded, positive-sense genomic RNA, belonging to the family Picornaviridae, a highly diverse family of important pathogens of humans and animals. In spite of discovery of bovine kobuvirus was first reported in 2003, which is several years ago, information about the virus is lacking. In this study, we first identified bovine kobuviruses from Korean diarrheic cattle by RT-PCR using the generic kobuvirus primers with subsequent cloning and sequencing, and reported genetic characterization of Korean bovine kobuviruses by phylogenetic analysis. Among 62 diarrheic fecal samples collected from 36 cattle farms in 2008-2010 in Korea, 16 (25.8%) samples and 13 (36.1%) farms were positive for kobuvirus, and this indicated that kobuvirus infections are endemic in diarrheic cattle in Korea. The rates of evolutionary substitution of kobuvirus and age of MRCA of Korean kobuvirus were estimated on the basis of temporal information of the sequences by divergence analysis. Phylogenetic analysis showed that six strains except CPF4293 belonged to bovine kobuviruses and formed the exclusive branch with other bovine kobuvirus reference strains; The CPF4293 strain, however, was especially close to porcine kobuviruses rather than to any other kobuviruses, and showed the close genetic relationship with porcine kobuvirus strains isolated in 2009 in Japan, even though it was originated from bovine fecal sample. These data raise questions as to whether interspecies transmission of porcine kobuvirus to cattle may occur in nature.