6.5 The epidemiology of hepatitis E virus and the relationship between infection in pigs and humans in a community of agricultural-food system in Nan, Thailand

摘要

Background: Several evidences suggest that pigs are reservoir of hepatitis E virus (HEV). No study in Thailand has been conducted to explore the transmission risks for HEV in pigs and humans. Aims: To define the burden of HEV in pigs and humans in Nan province, and evaluate the transmission of HEV among humans having direct or indirect contact with the pigs. Methods: The first study addressed the risks for HEV transmission between pigs in different sized farms, and possible risk factors among pigs in a cross-sectional study. We obtained sera and fecal samples from pigs to test for antibodies to HEV and HEV RNA. The second study addressed the association between occupational pig exposure to HEV infection among farmers and the general population in a cross-sectional study. All pig farmers from the first study were recruited in the second study. The comparison group resided in the same districts as the exposed group and the person must have had no history of occupational contact with any pigs. All participants were asked to give a blood specimen tested for HEV infection. Results: The first study found a 9.9% (87/879) seroprevalence of anti-HEV among pigs and 2.9% of pigs had HEV RNA positive fecal samples. All HEV sequences corresponded to genotype 3. Pigs raised on medium sized farms had higher anti-HEV seroprevalence than pigs raised on larger farms after controlling for other confounders. Better hygienic practices were used in larger farms compared with small or medium sized farms. The overall prevalence of anti-HEV was 23.0% (118/513) in the second study. There was no association between anti-HEV prevalence and direct exposure to pigs. Frequent consumption of organ meat ≥ 2 times per week was a significant risk factor for HEV seroprevalence, adjusted odds ratio (OR) 3.23, 95% confidence interval (CI) 1.15, 9.01. Conclusions: These studies establish that HEV is endemic among pig populations in Nan province. It appears that HEV infections in humans are acquired more frequently as a food-borne infection than by direct contact with pigs in this population.