Comparative epidemiological studies on lymphatic filariasis, between tribal and non-tribal populations of Bankura district, West Bengal, India.

There is little information on the epidemiology of lymphatic filariasis, caused by infection with Wuchereria bancrofti, in West Bengal. That which is known mostly relates to Calcutta and its suburbs, and there have been few studies on the disease among the tribal populations of the state. The present study was designed to compare the epidemiology of filariasis in tribal and non-tribal populations living in Bankura district. Blood samples were collected at night from 2076 tribal and 4985 non-tribal subjects and checked, microscopically, for microfilariae (mff). Each subject was also examined clinically, for any manifestations of the disease. The results revealed that the tribal subjects had not only lower prevalences of microfilaraemia (3.17% v. 8.86%) and of symptomatic filariasis (5.92% v. 13.74%) than the non-tribal, but also less intense infections (with mean counts for the microfilaraemics of 6.50 v. 13.55 mff/20 microliters blood). Filariasis endemicity, measured as the percentage of subjects with microfilaraemia and/or disease, was therefore much lower among the tribal subjects (8.95%) than the non-tribal (22.12%).