Insecticide susceptibility status of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti in Panaji, Goa.

Adult and larval insecticidal tests conducted in Panaji, Goa, revealed that adults of An. stephensi were resistant to DDT (4.0%), dieldrin (0.4%) and malathion (5.0%). The larvae of An. stephensi were also resistant to DDT (2.5 mg/l) and malathion (3.125 mg/l). Cx. quinquefasciatus adults were resistant to DDT, dieldrin, malathion and fenitrothion (1.0%), and larvae were highly resistant to DDT but showed low resistance to malathion and fenitrothion (0.125 mg/I). Adults of Ae. aegypti were resistant to DDT and dieldrin and the larvae showed resistance to DDT but good susceptibility to fenitrothion and complete susceptibility to malathion. The triple resistance of An. stephensi to DDT, dieldrin and malathion is intriguing as malathion has never been used in the health sector in Goa. A very limited use of malathion was done in the agricultural sector in Chandor area, which is 50 km away from the study area.