Insecticide susceptibilityiresistance Status in Aedes agpti L. to insecticides

Abstract

Insecticides have been inadvertently used in vector control program for several years in Thailand. In this study, twenty two strains of Aedes aegypti adults and larvae from different locations were subjected to susceptibility tests against commonly used insecticides for vector control. Results showed that Ae. aegypti adults from almost locations were resistant to malathion and etofenprox, except for two strains from Thung Song and Meuang Surat Thani and one strain from Kosamphi which were found to manifest incipient resistance to malathion and etofenprox, respectively. All the test strains showed high level resistance to propoxur and permethrin. Various levels of deltamethrin susceptibilities were detected among the test Ae. aegypti strains. Fifty percent Knockdown Time (KT50) was detected in three synthetic pyrethroids (deltamethrin, etofenprox and permethrin). All the strains tested had prolonged knockdown time for both permethrin and etofenprox. Moderate KT50 was recorded from deltamethrin when compared with the susceptible strain, Bora from French Polynesia. Three strains of Ae. aegypti (Mueang Khon Kaen, Mueang Nong Khai and Kumphawapi strains) were found susceptible to deltamethrin.

The tests done on the last third stage larvae indicated strong susceptibilities of the strains to temephos, except for those that were collected from Kosamphi, Mueang Sukhothai and Wang Chao that showed incipient resistance. The results suggest that Ae. aegypti from Thailand can probably develop resistance to almost all insecticide class available in the market. Therefore, it is highly recommended that monitoring of insecticide resistance be made periodically to ensure efficacy of ongoing interventions. Through this study, the National Network for the Surveillance of the Insecticide Resistance in Thailand should be established.