Prevalence of four different subgenotypes of genotype 4 hepatitis E virus among swine in the Shanghai area of China

BACKGROUND Hepatitis E virus (HEV) is a zoonotic pathogen of which swine was reported as major reservoirs. HEV has been divided into 4 different genotypes according to phylogenetic analysis. Recent reports showed that genotype 4 HEV is freely transmitted between humans and swine in eastern China, including Shanghai area. This paper investigated the recent infection status of HEV among swine population of Shanghai area in China. METHODS 480 swine faecal specimens were collected from 23 farms which distribute all over Shanghai from September to November, 2007 and tested for the presence of HEV RNA by the polymerase chain reaction (PCR). RESULTS Our results showed that 26.1% (6/23) of the swine farms were positive for HEV RNA and the positive rate of the six farms were ranged from 9.1% to 33.3%. The HEV RNA positive rate for total samples were 5% (24/480). The resulted positive band specific for HEV was sequenced and sequence analysis indicated that all of these isolates belonged to genotype 4 HEV. Phylogenetic analysis showed that the 24 isolates clustered into 4 distinct subgroups, sharing 83.3-89.7% inter-subgroup and 97-99% intra-subgroup identities. More over, isolates in three of the four subgroups closely clustered with previous identified strains, sharing up high to 97% identity with them. CONCLUSION These results suggested that there were 4 different subgenotypes of HEV prevalent in Shanghai, and some of them may not be indigenous to Shanghai but introduced from other geographic regions.