Oni, Ayodele Oluropo; (1996) Genotypes of hepatitis B and C viruses in Nigeria. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

A small scale epidemiological survey of hepatitis B and C virus infection amongst healthy adult blood donors and children of pre-school age in Nigeria was carried out using various serological markers of hepatitis B virus (HBsAg, anti-HBs, HBeAg, anti-HBe), and hepatitis C virus infection (anti-HCV ELISA and RIBA tests). Between 10 and 11 % of the adults, and 16% of the children were HBsAg positive. A viraemia rate of 23.8% was found among the HBsAg positive adults, and 25% among the HBsAg positive children. Evidence of past exposure (anti-HBs) among adult blood donors was 41.24%. The subtype of HBV present in Nigeria was determined by amplifying and sequencing HBV DNA, encoding the antigenic determinant a and surrounding region. Two subtypes of HBV are present in Nigeria, adw & ayw. The subtype ayw was in the majority (7/10 of HBV sequenced). A multiple infection with both subtypes of HBV was found in one donor, another donor was infected with both wild type and a variant of ayw. HBV DNA encoding the pre-core and part of the core region of 7 donors was sequenced. One donor was infected with a precore mutant and another was infected with a further variant of HBV. The prevalence of anti-HCV detected by a second generation ELISA was 8% (16/200) of the adult donors, but most of them were negative on supplementary testing. None of the children tested was anti-HCV positive. 25% (4/16) of the anti-HCV positive sera were RIBA test positive and 12.5% (2/16) were indeterminate. Four RIBA positive samples and one negative were HCV-RNA positive, thus 31.25% (5/16) of the ELISA-positive sera were HCV RNA positive by reverse transcriptase polymerase chain reaction (RT-PCR). Three regions of HCV were sequenced, the 5'untranslated region (5'UTR), core and NS5. At least two HCV genotypes are present in Nigeria, type 1 and type 4. Phylogenetic analysis and pairwise comparison confirmed two new subtypes which were provisionally designated 1d and 4i.

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