CHANGING PREVALENCE OF HEPATITIS-B VIRUS IN URBANIZED AUSTRALIAN ABORIGINES

Serological surveys of desert or rural Australian Aboriginal settlemen ts report up to 85% positivity for hepatitis B virus (HBV) markers. We report the results of two cross-sectional HBV surveys carried out 5 y ears apart in the bi-racial town of Condobolin, New South Wales (popul ation 3086; 14% Aborigines). In 1983-84, none of the 310 non-Aborigine s tested were hepatitis B surface antigen (HBsAg) positive but 7.2% we re positive for hepatitis B core antibody (anti-HBc). Among Aboriginal subjects, 57.6% had detectable HBV markers and 16.9% were HBsAg posit ive. In 1987-88, no non-Aborigines were HBsAg positive and only 1% (of 422 individuals) had anti-core antibodies. In contrast, 36% of Aborig inal subjects had HBV markers and 6% were HBsAg positive. No significa nt difference in detectable HBV markers was found among 98 Aborigines who were included in both surveys. Migration was the main factor influ encing the HBV prevalence between the two surveys. Clustering of HBsAg carriers occurred within households and the likely mode of infection was intrafamilial horizontal childhood transmission. There was a signi ficant association between HBV markers and tattooing in Aborigines (P < 0.02). Overall, HBV markers were less frequent in this population th an in other desert or rural Aboriginal populations surveyed. The preva lence of HBV infection in non-Aboriginal households was not significan tly different from that in the Australian Caucasian population.