Gorgas Memorial Institute of Tropical and Preventive Medicine, Middle America Research Unit, National Institute of Allergy and Infectious Diseases, Laboratory of Infectious Diseases, National Institutes of Health, Balboa Heights, Canal Zone
Previous studies of hepatitis B antigen (HBsAg) and antibody to it (anti-HBs) showed widely differing exposures between Panamanian Indian tribes. Cuna Indians living on islands appeared infrequently exposed to HBsAg; we found no one antigenemic and low age specific anti-HBs rates. In contrast, mainland dwelling Guaymi and Chocó Indians had a high prevalence of anti-HBs. We have now measured HBsAg by counterelectrophoresis and anti-HBs by radioimmunoassay in two Cuna Indian groups who live in the Darien forest. The prevalence of HBsAg among Darien Cuna was low, 3 positive of 239 tested, but 106 (44%) had anti-HBs. Darien Cuna thus evidenced greater exposure to HBsAg than island Cuna (8% had anti-HBs) and had an anti-HBs prevalence similar to the neighboring Chocó Indians (42%). The Guaymi Indians of western Panama had a lower frequency of anti-HBs (29%) than either Chocó or mainland Cuna but their frequency of chronic antigenemia was significantly greater. These data suggest that while exposure may be a function of village habitat, chronic antigenemia may reflect differences in host responses.
Present address: Department of Medicine and Epidemiology-International Health, University of Washington, Seattle, Washington 98195.
Present address: Scripps Clinic and Research Foundation, La Jolla, California 92037.