Behavioral responses to DDT and pyrethroids between Anopheles minimus species A and C, malaria vectors in Thailand.

Behavioral responses of two field populations of Anopheles minimus complex species A and C for contact and non-contact actions of chemicals were compared during and after exposure to operational field concentrations of DDT (2 g/m2), deltamethrin (0.02 g/m2), and lambdacyhalothrin (0.03 g/m2) using an excito-repellency escape chamber. The two populations were collected from the Mae Sot District in Tak Province (species A) and the Tri Yok District in Kanchanaburi Province (species C) in western Thailand. Female mosquitoes of both populations rapidly escaped from chambers after direct contact with DDT, deltamethrin, and lambdacyhalothrin. The non-contact repellency response to DDT and the two synthetic pyrethroids was pronounced with An. minimus species A; however, non-contact repellency was relatively weak with An. minimus species C, but remained significantly greater than the paired controls (P < 0.05). We conclude that strong contact irritancy was present in both test populations, whereas non-contact repellency also played a significant role in the escape response of An. minimus species A.