Susceptibility status of vectors of Japanese encephalitis to insecticides in south Arcot and Tirunelveli districts of Tamil Nadu.

Villages in South Arcot and Tirunelveli districts with high incidence of Japanese Encephalitis were selected for the study of insecticidal resistance to vectors. Culex vishnui and Anopheles hyrcanus group were found to be resistant to DDT (4 per cent for 60 min. exposure) and dieldrin (0.4 per cent for 60 min. exposure) but susceptible to Malathion (5 per cent for 60 min. exposure). So far, this is perhaps the first report of Anopheles hyrcanus group resistant to DDT and dieldrin to be reported from this area. The resistance may be due to extensive use of DDT and HCH for agricultural purposes.

Control of bancroftian filariasis by diethylcarbamazine medicated common salt in Karaikal, Pondicherry, India.

A trial of diethylcarbamazine (DEC) mixed in crystal common salt at a concentration of 0.15 to 0.2 per cent was carried out for 46 months (1982 to 1986) in Karaikal town and five commune panchayats of Pondicherry for control of bancroftian filariasis. Comparison of pre and post trial surveys showed 97.6 per cent reduction of microfilaria rate. No microfilaria or disease case was found in less than 5 years age group in the post trial survey. There was about 72 per cent reduction of disease rate. In the post trial substantial reduction of disease manifestation was found in 40 years and below age groups. Vector Culex quinquefasciatus density, filaria infection and infectivity rates were monitored only in Karaikal town. Infective vector mosquitoes were found in 1982 and 1983 only but afterwards no infective mosquito was encountered.