Hepatitis E virus infection among animals in northern India: an unlikely source of human disease

Hepatitis E virus (HEV) is a major cause of acute hepatitis in many developing countries. Based on data from nonendemic regions, an animal reservoir of HEV has been proposed; however, data from HEV-endemic regions are limited. We tested sera from 200 pigs, 98 chickens, 86 goats, 58 sheep and 30 buffaloes for anti-HEV IgG using two different enzyme immunoassays. Specificity of the detected antibodies was confirmed using inhibition assays. Stool specimens from 210 pigs, 94 piglets and 37 sheep were tested for HEV-RNA using nested amplification methods; the polymerase chain reaction products were sequenced and compared with known human and swine HEV sequences. Of the 200 swine sera, 193 and 195, respectively, tested positive in the two assays. All goat sera showed anti-HEV reactivity in both the assays. Inhibition studies confirmed the HEV specificity of antibodies detected in swine and goat sera using both the assays. Sera from sheep, buffalo and chickens also showed high rates of apparent reactivity, but inhibition studies were unable to confirm the specificity of reactions in these species. One faecal specimen showed amplification using Indian swine HEV-specific primers. The genomic sequence of the amplicon from this isolate had only 76-79% nucleotide and 93% amino acid homology with human HEV isolates reported from India and other parts of the world, and most closely resembled swine HEV isolates from other parts of India. Infection with HEV or a related agent is widespread among animals in northern India. However, the swine HEV in India differs genetically from human HEV isolates, indicating that pigs may not play an important role in the spread of human hepatitis E in endemic regions.