Genetic diversity of porcine sapoviruses

Sapoviruses (SaVs) within the Caliciviridae family are an important cause of gastroenteritis in both humans and animals. Although the widespread occurrence of divergent human SaV strains has been reported, there have only been a few studies of porcine SaVs examining their genetic diversity. The aim of this study was to assess the genetic diversity of porcine SaVs in piglets with diarrhea in South Korea. Two hundred and thirty-seven fecal specimens from piglets with diarrhea were examined from 78 farms over a 2-year period from six provinces in South Korea. Overall, 69 (29.1%) of the samples from five provinces tested positive for porcine SaVs by either RT-PCR or nested PCR with the primer pairs specific to porcine SaVs. An analysis of the partial capsid gene (757bp) of 12 porcine SaVs detected from fecal samples showed genetic divergence, not only among the Korean porcine SaVs (67.7-99.1%), but also between Korean and American porcine SaVs (69.1-90.2%). Interestingly, one strain (Po/SaV/JN-MA113/05/Korea), formed a second porcine SaV/GIII genotype, and is tentatively called GIII/2. This strain had a 0.236-0.405 inter-cluster distance with the other strains in the same genogroup, which is comparable to the distances between the established GI and GII SaVs. Furthermore, two potential recombinant porcine SaVs were identified. In conclusion, porcine SaV infections are common in diarrheic piglets in South Korea. The infecting strains are genetically diverse, and include a newly recognized genotype and recombinant viruses within genogroup III.