Molecular detection and prevalence of porcine caliciviruses in eastern China from 2008 to 2009

Caliciviruses causing diarrhea have been reported in both industrial and developing countries, including China, in recent years. Porcine caliciviruses that are closely related to human sapoviruses (SaVs) and noroviruses (NoVs) have also been detected in swine, which has raised discussion about the animal reservoir and the potential risk for zoonotic transmission to humans. The objective of this work was to determine the frequency and age distribution of SaVs and NoVs in pigs and to characterize the strains prevalent in eastern China. A total of 904 stool samples from pigs of different ages were collected from eastern China from April 2008 to March 2009 and tested for both SaVs and NoVs using reverse transcription-polymerase chain reaction (RT–PCR). Our results indicate that 8 (0.9%) stool samples were positive for SaVs and 2 (0.2%) for NoVs. Phylogenetic analysis of partial sequences of the RNA-dependent RNA polymerase (RdRp) gene indicated that all of the SaV strains belonged to the GIII SaVs, while the two NoV strains belonged to the GII NoV genogroup. The 8 SaV strains were further divided into two clusters, which clustered closely with the Netherlands isolate (AY615804) and the Chinese strain (EU599212), respectively. The two NoV strains shared about 67.3–67.6% nucleotide homology with a human norovirus strain (DQ369797), the only NoV strain from mainland China available in GenBank. Moreover, our results suggest that SaV infections are more frequent in 0-1 month-old pigs than in older ones. In conclusion, the present study provides evidence that PoSaVs and PoNoVs exist in swine in eastern China.