Insecticide susceptibility tests of Anopheles minimus s.l., Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus in northern Thailand.

The susceptibility of Anopheles minimus s.l., Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus to insecticide in northern Thailand was monitored by using the WHO standard susceptibility test. One- to two-day old female mosquitos, which were reared from wild caught females or immature stages, were exposed to discriminating dosages of insecticides for recommended exposure periods, and the 24-hour mortality recorded. The results revealed that, in general, An. minimus s.l. was still susceptible to DDT and permethrin, except in some areas where a slight increase in tolerance to DDT was observed. Ae. aegypti and Ae. albopictus were both highly resistant to DDT, but in some areas the former was also resistant to permethrin and deltamethrin. Cx. quinquefasciatus was resistant to DDT and etofenprox, with a slight increase in tolerance to permethrin, deltamethrin, malathion and fenitrothion. No resistance to lambda-cyhalothrin was detected in any of the species studied.