[Seasonal pattern and phylogenetic analysis with human isolates of genotype-IV hepatitis E virus in swine herds, eastern China].

Objective: To determine the seasonal prevalence of genotype-IV hepatitis E virus (HEV) in swine herds in Eastern China and explore the phylogenetic relationship between swine HEV and human HEV in the situation that zoonotic features of HEV had been confirmed.

Methods: From September 2007 to June 2008, a total of 1200 swine bile specimens were collected from three slaughter houses located in Zhejiang, Anhui and Jiangsu, the Eastern China, and detected for HEV RNA by using nested RT-PCR. The positive PCR products were sequenced. Then the swine HEV were phylogenetically determined with human HEV isolated in Eastern China.

Results: The positive rate for HEV RNA in swine herds was 4.5% totally. Significant differences of HEV detection were not observed among seasonal pattern (Sep - Oct: 6%, Dec - Jan: 4.33%, Mar - Apr: 4.33%, May - Jun: 3.33%) but in geographic distribution (Jiangsu: 6%, Anhui: 5%, Zhejiang: 2.5%). Regardless of isolation from different areas,swine and human genotype-IV HEV shared a high similarity. Phylogenetically, there were 80% - 100% and 96% - 100% identities within swine genotype-lV HEV at the nucleotide and amino acid levels respectively. Between swine HEV and human HEV, there were also similarities of 76% -99% and 95% - 100%. It was noted that some human and swine isolates were clustered with bootstrap values of > 90%.

Conclusion: Genotype-IV HEV is widely prevalent in swine herds in Eastern China and original common ancestor of evolution and transmission was implied. The sustaining prevalence within swine herds should have a probable influence on the epidemic situation of hepatitis E in human beings.