Hepatitis E virus (HEV) is an emerging zoonotic pathogen capable of both human-to-human and animal-to-human transmission. However, limited data are available regarding HEV infections in pigs in Heilongjiang Province, China. To investigate the prevalence of HEV in pigs in this region, liver samples from diseased or deceased pigs and fecal samples from healthy pigs were collected and analyzed. A total of 82 liver samples and 86 fecal samples were obtained from 13 farms and tested for HEV genotypes 3 and 4 using nested RT-PCR assays targeting the ORF2 gene. Samples with high viral loads were further subjected to direct sequencing and phylogenetic analysis. Overall, 32 samples tested positive for HEV RNA and were classified as genotype 3 or 4, with genotype 4 being the most prevalent. The identified subtypes included 3a, 4a, and 4d, among which subtype 4d was the most common. Phylogenetic analysis revealed that swine HEV genotype 3 (subtype 3a) and genotype 4 (subtypes 4a and 4d) clustered closely with reference sequences 3a/AB089824/JA10, 4a/JX9974449/NJ6, and 4d/JX997439/NJ5. These strains exhibited close genetic similarity to human HEV isolates previously reported in Tokyo, Japan, and eastern China. These findings indicate that HEV genotypes 3 and 4 are distributed in pig farms across Heilongjiang Province and suggest that zoonotic transmission between pigs and humans is frequent in China.

Keywords: genotype 3; genotype 4; hepatitis E virus; infection; pig farm.