Hepatitis B, C and D virus prevalence in children and adults in Mbeya Region, Tanzania: Results from a cohort study 2002-2009

Introduction: sub-Saharan Africa bears a high prevalence for hepatitis B virus (HBV) infection. This analysis aims at elucidating the exposure to HBV across different age groups in Mbeya Region in Tanzania and determines prevalences of hepatitis C (HCV) and hepatitis delta antigen (HDV) infections. Methods: plasma samples from children and adults with defined HIV status were analysed for HBV, HCV and HDV markers. Results: hepatitis B (HBs)-antigen positivity was 8.3% (3/36) in the 0 to 5 years age group, 13.3% (8/60) in the 6 to 7 years, 17.2% (10/58) in the 8 to 14 years and 13.3% (8/60) in the 15 to 18 years age groups. In adults 5.0% of samples were HBs-antigen positive. Overall, 17.1% were HIV-1 positive. Adults infected with HIV-1 were significantly more often HBs-antigen positive (7.5%) than HIV-1 negative adults (4.5%; p<0.05). A serological sub-study including 174 adults showed that both total anti-HBs and total anti-HBc positivity increased with age in HBs-antigen negative participants. Across all age groups, HCV antibodies were found in 9 individuals, HDV antibodies in 3 individuals. Conclusion: children presented a high prevalence of HBs-antigen carriers, with lower levels in the younger children. Among adults, the overall prevalence of HBs-antigen was lower than in children, either corresponding to clearance of HBV over time or due to a die-off effect. HBs-antigen positive adults had higher frequencies of anti-HBc-and anti-HBe-antibodies, indicating better immunological control of HBV infection than children. This supports claims that HBV infections in Africa are mostly acquired in childhood and to a large extent cleared again by adulthood. One in 20 adults remains chronically infected, emphasising the importance of HBV vaccination strategies.