CLINICAL FILARIAL DISEASE IN 2 ETHNIC ENDEMIC COMMUNITIES OF ORISSA, INDIA

To evaluate the possible role of ethnicity in susceptibility to filari al infection, a comparative study of the prevalence of filarial infect ion was initiated in an endemic village inhabited by two ethnic popula tions of mainlanders and tribals. An age and sex matched sampled popul ation of 591 mainlanders and 106 tribals was studied by detailed clini cal and parasitological (60 mm(3) blood) examinations. Sera collected from both population groups (26 each) matched for clinical stage of in fection were analysed for humoral immune responses such as antifilaria l IgG, circulating filarial antigen and immune complex level. The over all prevalences of clinical disease and infection in both mainlanders (34.18 and 14.4%) and tribals (25.47 and 17.9%) were comparable. Howev er, both annual average adenolymphangitic attack rate (1.77 year(-1)) and the prevalence of chronic filarial disease (22.6%) amongst tribals were significantly lower. No true elephantiasis was observed in triba ls. No significant difference was observed in their humoral immune res ponse, although the antifilarial antibody of IgG class in all stages o f filarial infection was lower in tribals than in mainlanders. The res ults did not reveal any difference in susceptibility to filarial infec tion in the ethnic groups. The paucity of progressive lesions observed in tribals possibly reflects a difference in the anatomy of lymphatic s or genetic or immunoregulatory mechanisms, that needs further study.