Summaryobjectives To report the prevalences of hepatitis B (HBV) and hepatitis D (HDV) infections in remote and more accessible Yanomami and Piaroa Venezuelan Amazonian Amerindian populations; to estimate incidence per susceptible.methods Clinico-epidemiological evaluation was carried out in 9 Piaroa villages. Blood samples were tested for HBV core antibody (anti-HBc), surface antigen (HBsAg) and HDV antibody (anti-HDV).Results were analysed using logistic regression, and estimates made of HBV forces of infection (FOI). Prevalences and FOI were also estimated for 4 Yanomami villages.results Mean Piaroa anti-HBc and HBsAg prevalences were 27.4% and 5.1%, respectively (up to 53% and 19% in the remote Autana region). Mean Yanomami anti-HBc and HBsAg prevalences were, respectively, 58.0% (range 43-70%) and 14.3% (31% in the village with highest HBsAg). No significant difference was found between sexes, with age and maternal HBsAg the only risk factors for HBV identified in multivariate regression of Piaroa data. Only 4 Piaroa and 2 Yanomami individuals were anti-HDV positive.conclusion Piaroa HBV prevalences were generally higher in remote villages than in less remote ones, with prevalences in Yanomami villages even higher. Anti-HBc prevalence was 47% in one Yanomami village with a history of HBV vaccination but no HBsAg cases were identified, suggestive of previously cleared or possibly transient infection or vaccine escape. Despite a past history of HDV epidemic outbreaks and HBsAg levels in some villages appearing sufficient to facilitate HDV transmission, anti-HDV prevalence was low; it remains to be established why no recent outbreaks have been reported.
BackgroundOccult hepatitis B infection (OBI) is characterized by the presence of hepatitis B virus (HBV) DNA in the absence of HBsAg in the serum of patients. The aim of this study was to characterize HBV infection among a Piaroa community, an Amerindian group which exhibits significant evidence of exposure to HBV but relatively low presence of HBsAg, and to explore the presence of OBI in this population.ResultsOf 150 sera, with 17% anti-HBc and 1.3% HBsAg prevalence, 70 were tested for the presence of HBV DNA. From these, 25 (36%) were found positive for HBV DNA by PCR in the core region. Two of these 25 sera were HBsAg positive, indicating an overt infection. Of the remaining 68 sera tested, 23 exhibited OBI. Of these, 13 were HBV DNA out of 25 anti-HBc positive (52%) and 10 HBV DNA positive, out of 43 anti-HBc negative (23%), with a statistical significance of p = 0.03. Viral DNA and HBsAg were present intermittently in follow up sera of 13 individuals. Sequence analysis in the core region of the amplified DNA products showed that all the strains belonged to HBV genotype F3. The OBI isolates displayed 96-100% nucleotide identity between them. One isolate exhibited the co-circulation of a wild type variant with a variant with a premature stop codon at the core protein, and a variant exhibiting a deletion of 28 amino acids.ConclusionsThe frequency of OBI found in this Amerindian group warrants further studies in other communities exhibiting different degrees of HBV exposure.
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