Swine HEV infection in South India and phylogenetic analysis (1985-1999)

Hepatitis E is endemic in India. It was recently noted that although all the Indian human hepatitis E virus (HEV) isolates (1976-2001) were placed in genotype 1, the swine HEV recovered from western India (2000) belonged to genotype IV. This was in contrast to reports from the United States and Taiwan wherein both human and swine HEV belonged to the same genotype, i.e., genotypes III and IV, respectively. In order to validate these findings further, we retrospectively examined serum samples collected from pigs from southern India. Sequential serum samples from 45 (1985-1987) and 12 (1999) pigs from Karnataka state, south India, were screened for the presence of HEV RNA (nested PCR) and IgG-anti-HEV (ELISA). PCR products (Open Reading Frame-2 region) were sequenced and subjected to phylogenetic analysis. In this study, 42/45 (1985-1987) and 12/12 (1999) pigs showed seroconversion to IgG anti-HEV antibodies, with a mean age at seroconversion of 4.8 +/- 1.6 months. Four samples collected in 1999 and two samples collected during 1985 were HEV RNA positive. All swine HEV sequences clustered with genotype IV, demonstrating that swine HEV was prevalent among south Indian pigs for at least for 16 years and, similar to western India, belonged to genotype IV. Thus, genotype I and IV HEV continue to circulate in humans and pigs, respectively, from India. Whether swine HEV infects humans remains to be determined.