Identification and molecular characterization of porcine kobuvirus in U. S. swine.

Porcine kobuvirus has been associated with piglet diarrhea in Asia and Europe, but there are no reports of its presence in the U.S. swine farms. We screened intestinal contents from 114 diarrheic pigs and fecal samples from 46 apparently healthy pigs to determine the presence of kobuvirus by reverse transcription-polymerase chain reaction using 3D (RNA polymerase) region primers (amplicon size 216 bp). The samples from ill pigs came from 15 different U.S. states, while those from healthy pigs were obtained from three different farms in Minnesota. Twenty-five (21.9 %) pigs with diarrhea and ten (21.7 %) healthy pigs were positive for kobuvirus. All strains from diarrheic pigs were further typed by means of VP1 region primers (amplicon size 811 bp). Phylogenetic analysis revealed that all porcine kobuvirus strains had 93.1-96.5 % nucleotide identity with NLD45 strain from the Netherlands and BRA24 strain from Brazil in the 3D region. In the VP1 region, only 86.7-88.5 % homology was found with the T247 strain from Japan and 85.8-87.4 % homology with WUH1 strain from China. All 25 kobuvirus positive pigs had mixed infection with transmissible gastroenteritis virus and/or rotavirus (groups A, B, or C). Pigs less than 4 weeks of age showed higher prevalence of kobuvirus than the older pigs. The results of this preliminary study indicate that porcine kobuvirus is present in both healthy and diarrheic pigs in the U.S. and that further studies are needed to determine its role in gastrointestinal infections of pigs.