Prevalence survey of filariasis in two villages in Chingleput district of Tamil Nadu.

A baseline survey of filariasis was conducted in two endemic villages in Chingleput district of Tamil Nadu, to obtain the prevalence rate of microfilaraemia and that of clinical filarial disease along with its various clinical patterns. Of the 2921 dejure population registered, in 2735 a comprehensive clinical examination for filariasis was carried out by a physician. In 2658 persons of those clinically examined, night blood samples were collected by finger prick. The results of the survey confirmed that the two village were highly endemic for filariasis, the prevalence rates of clinical disease and microfilaraemia being 20 and 12 per cent respectively. The endemicity rate was 31 per cent. Nocturnally periodic Wuchereria bancrofti was the only species identified. The major manifestations of clinical disease were lymphadenitis in the acute phase, hydrocele and oedema of the lower limbs in the chronic phase and involvement of the lower limbs in the elephantiasis phase. Among males with disease in the chronic phase, genital involvement was more than that of the lower limbs. The distributions of the patients by age in the three phases, although overlapping, suggested that the disease generally progressed with age from acute to chronic to elephantiasis phase. The microfilarial rate among persons with clinical disease was lower as compared to that among persons without disease. An entomological survey of one of the villages showed that Culex quinquefasciatus was the vector with high infection and infectivity rates.