Insecticide-induced behavioral responses in two populations of Anopheles maculatus and Anopheles sawadwongporni, malaria vectors in Thailand.

Behavioral responses of 2 wild-caught populations of Anopheles maculatus (Theobald) and Anopheles sawadwongporni Rattanarithikul and Green to operational field doses of DDT (2 g/m2) and permethrin (0.5 g/m2) were characterized using an excito-repellency test system. Both test populations, collected from animal quarters at Ban Pu Teuy, Sai Yok District, Kanchanaburi Province, western Thailand, were found completely susceptible to DDT and permethrin. Specimens from 2 test populations quickly escaped from direct contact with treated surfaces from 2 insecticides compared with paired controls. Noncontact repellency response to DDT was significantly pronounced in An. sawadwongporni (P < 0.05) and comparatively weak in An. maculatus, but it was statistically greater than individually paired controls (P < 0.05). We conclude that contact irritancy is a major behavioral response of both field populations when exposed directly to DDT and permethrin, whereas noncontact repellency to DDT also produced a significant escape response in An. sawadwongporni.