Swine HEV infection in south India and phylogenetic analysis (1985–1999)

Abstract

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 I, 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.

Host Immune Status and Response to Hepatitis E Virus Infection

“…In developing countries in Asia and Africa, where HEV-1 predominates, human infections with HEV-3 and HEV-4 are rarely reported, and no large outbreaks have been attributed to these strains. However, HEV-3 and HEV-4 have been confirmed sporadically in local populations, in travelers to these regions (119,144), and in resident animal populations and locally obtained meat (107,108,114,161,162).…”

“…However, genotype 1a/1c coinfections were documented in 2 people hospitalized in Kathmandu, Nepal (255,256). While HEV-4 has been amplified from serum, liver, and stool samples from swine in India (107,114,161,162,257), there have been no reports of human coinfection with both HEV-1 and -4. Differences in primary exposure routes (contaminated water for HEV-1 and -2 versus direct contact with infected animals or undercooked meat for HEV-3 and -4) may explain why no such coinfections have been reported.…”

In Vitro and In Vivo Mutational Analysis of the 3′-Terminal Regions of Hepatitis E Virus Genomes and Replicons

“…Serological prevalence data suggest that HEV might be endemic in industrialized countries as well, although it rarely causes disease in these countries (reviewed in references 7, 19, and 29). Antibodies to HEV (anti-HEV) have also been detected in a wide variety of animals, and HEV has been found in swine (2,10,12,25,33), deer (35), and chickens (11,14); these findings raise the possibility that HEV may be a zoonosis (22). HEV strains infecting mammals differ at the nucleotide level by as much as 27%, whereas the avian strain differs from the mammalian strains by up to 50%.…”

Distribution and Propagation of Hepatitis E Virus in Experimentally Infected Swine

“…These circumstances imply the possibility of iatrogenic transmission of HEV through contaminated blood transfusion; however, the precise distribution and proliferation of HEV in patients remains poorly understood. Naturally and experimental infection of HEV genotypes 1, 3 and 4 in Pigs have been reported in several countries, including Japan [22][23][24][25][26][27]. However, there is no experimental animal model to understand the distribution and multiplication of this virus.…”