Characterization of hepatitis E virus from sporadic hepatitis cases and sewage samples from Vellore, south India

Abstract

Background: Hepatitis E virus (HEV) is endemic in India and causes epidemics and sporadic cases. However, the exact transmission route for sporadic hepatitis E remains unclear. This study investigated HEV in sporadic hepatitis cases and sewage samples, as sewage is the major source of contamination of water in developing countries.

Methods: Monthly sampling and testing for HEV in sewage samples from Vellore, India was carried out for 1 year (November 2009-October 2010) and plasma and/or fecal samples from sporadic hepatitis cases presenting to a hospital in Vellore during 2006-2010 were tested for HEV RNA. A total of 144 raw sewage samples and 94 samples from sporadic hepatitis cases were tested for HEV RNA using RT-PCR.

Results: The prevalence of HEV RNA in sewage and sporadic cases was 55.6% and 9.6%, respectively. HEV strains isolated from sewage showed 94-100% nucleotide sequence similarity with the HEV strains isolated from the sporadic hepatitis cases. HEV RNA in sewage was identified more often during the summer (81.2%) than the monsoon season (14.5%) (p < 0.001).

Conclusion: This study indicates that sewage may be a source of contamination for sporadic hepatitis and also underscores the need for preventive measures to protect drinking water from sewage contamination, particularly in the summer. GENBANK ACCESSION NUMBERS: HEV strains isolated from this study were deposited in GenBank under accession numbers JF972766-JF972773, JN705651-JN705659 and JN705660-JN705662.

Keywords: Hepatitis E virus; India; RT PCR; Sewage; Sporadic hepatitis E; Transmission.

Figure 1

Phylogenetic dendrogram constructed by the neighbor-joining method based on the nucleotide sequence of the gene encoding the RNA dependent RNA polymerase from hepatitis E virus strains isolated from samples from sporadic cases and from sewage collected in Vellore, south India. Bootstrap values for 1000 pseudoreplicates are shown. Boxed sequences show the strains isolated from sewage in Vellore with high similarity to strains from sporadic cases in Vellore and Swedish nationals who were infected while travelling in India. Reference sequences from studies carried out in Sweden are shown with $ superscripts, sequences from Cuba with @ superscripts and sequences from the Vellore outbreak with # superscripts. GenBank reference sequences were also selected from other countries, Chad (AY204877) and Morocco (AY230202), and strains isolated from a Nepalese individual in Japan (AB533368), sewage from western India (AF398916), an outbreak in north India (JF414937) and an aymptomatic migrant in Italy (JX898218). Strains isolated from the current study have been deposited in GenBank with accession numbers: sewage samples: (%) VLSew1–VLSew8 (JF972766–JF972773); hospital samples: (ˆ) SHV1–SHV9 (JN705651–JN705659); and community samples: (&) SCV1–SCV3 (JN705660–JN705662).