HEV prevalence in Indigenous and Non-Indigenous from the Brazilian Amazon Basin

Contributed by Jaqueline Mendes de Oliveira & Marcelo Alves Pinto

From the detection and characterization of hepatitis E virus (HEV)-genotype 3 (HEV-3), Paslahepevirus balayani species, in pig farms and the first report of an autochthonous, sporadic case of HEV-3 infection by our research group in Rio de Janeiro (2009-2010) (1,2), further studies showed the wide circulation of this zoonotic genotype among swine in Brazil. HEV genotypes 1 and 2, primarily transmitted by the faecal-oral route and directly correlated with the lack of potable water and sanitation access, have not been identified in Brazil until now.

In Southeast Asia, where hepatitis E is highly endemic, the use of river water for drinking and cooking is significantly associated with HEV-1 infection. Therefore, the anti-HEV prevalence in the riverine population is very high (40% to 60%) (3). In contrast, low anti-HEV rates (up to 4%) have been found in Brazilian riverine communities (4,5). Further studies in isolated and semi-isolated rural areas of the Eastern Brazilian Amazon, such as the Afro-descendant Quilombola´s communities, found a 1.6% anti-HEV prevalence. Regarding the traditional indigenous peoples from Brazil, HEV seroprevalence data are scarce. A recent study in the Apinajé indigenous community in the Brazilian Western Amazon reported a very low (0,19%) anti-HEV prevalence (6).

Considering the epidemiological pattern of HEV-3 infection in Brazil, which is highly prevalent among slaughtered and domestic pigs, zoonotically transmitted to humans, and frequently asymptomatic, cases of acute hepatitis E can be either underreported or misdiagnosed. Therefore, HEV seroprevalence in Brazil is quite variable among the five geographic regions, with the highest anti-HEV rates detected in rural and urban populations (including blood donors) from southeastern and southern regions (18% and 65%, respectively) (7–10). Such an epidemiological pattern is probably associated with regional dietary preference for pork meat and pork-derivative foodstuff.

Some seroprevalence studies focused on the overcrowded agricultural settlements of the Amazon Basin. For instance, a cross-sectional study was developed by Vitral and colleagues from our research group (11) in Ramal do Granada, Acre state, where poor housing conditions and lack of sanitary infrastructure are closely related to a high prevalence of enterically transmitted diseases. Indeed, we found a very high prevalence of hepatitis A virus (82.9%) and a moderate anti-HEV prevalence (12.9%; 95% CI, 9.5% to 16.2%). However, the anti-HEV prevalence in Acre rural settlers was considerably higher than those reported for other rural and riverine communities in the same region.

In our very recent study, Vasconcelos and Oliveira-Ferreira, with our collaboration (12), analyzed demographic and serological data from two cross-sectional studies conducted among non-indigenous inhabitants of urban and rural areas of Porto Velho, Rondônia state (2010–2011) and in a semi-isolated Amazonian indigenous community ¾ the Yanomami territory (2015). Among the 811 cryopreserved blood samples tested by two commercially available ELISA assays, the overall anti-HEV IgG detection rate was 6.78% (95%CI: 5.25–8.72). Either the Amazonian Yanomami indigenous or the non-indigenous inhabitants of Porto Velho, Rondônia, presented a low prevalence of anti-HEV IgG (2.8% and 3%, respectively). Interestingly, a considerably higher HEV seroprevalence (14.2%) was found in individuals living in a rural settlement near Porto Velho. Notably, the exploratory bivariate analysis indicated a higher likelihood of a positive anti-HEV IgG test for individuals who live in a rural settlement (aOR = 5.14; 95%CI 1.81–22.4) than those who live in an urban area.

Furthermore, we found that those born in the North region were less likely to have a positive anti-HEV IgG (OR= 0.45; 0.24–0.89) than those born in other geographic regions of Brazil. It is essential to consider that Acre and Rondônia’s agricultural settlements are mainly composed of migrants from the southern and southeastern regions of the country and, indeed, are not representative of the native inhabitants. Our findings corroborate those from a recent study among blood donors from Central Brazil (13). The authors observed that being born in South or Southeast Brazil was significantly associated (p < 0.001) with a higher risk of exposure to HEV.

Aiming to assess and compare HEV seroprevalence between indigenous and non-indigenous populations, this study evidenced distinct anti-HEV prevalence profiles between rural and urban areas of Rondônia and Amazon states. Our data corroborate other authors´ findings, showing that the prevalence of HEV in Brazil increases from North to South, independent of the cohort or study year. Therefore, further studies should be done to understand better the epidemiological pattern of HEV infection in rural and riverine populations of the Brazilian Amazon Basin. Besides, studies based on surface water and wastewater sampling should be conducted to evaluate the impact of illegal gold mining on the human, animal, and environmental health of the Yanomami and riverine population from the Amazon Basin.

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