SYNTHETIC INSECTICIDES SUSCEPTIBLE OF AEDES AEGYPTI IN THE AREAS OF LOWER NORTHERN PART OF THAILAND

Abstract

The objective of this study was to explore the sensitivity of Aedes aegypti to different synthetic insecticides. Mosquito larvae were gathered from main six districts within three main representative provinces Including Muang and Noen Maprang districts (Phitsanulok), Muang and Thung Saliam districts (Sukhothai) and Muang and Nam Pat districts (Uttaradit) in the lower northern part of Thailand. After all mosquitoes were bred and raised under the laboratory condition until becoming adults, susceptibility test according to the standard method of the World Health Organization was performed. It was revealed that Ae. aegypti obtained from every area demonstrated resistance to Alpha-cypermethrin 0.03%, Lambda-cyhalothrin 0.03%. Meanwhile, Ae. aegypti began to develop incipient resistance to Deltamethrin 0.15% in almost all areas except Ae. aegypti gathered from Muang Uttaradit that was susceptible to Deltamethrin 0.15% accounting for 100% of mortality rate. Based on the probit analysis (KT₅₀ and KT₉₅) after exposure, the mean KT₅₀ and KT₉₅ of Ae. aegypti exposed to Alpha-cypermethrin 0.03% were the lowest in Thung Saliam districts (Sukhothai) (69.20 minutes) and Noen Maprang (Phitsanulok) (109.99 minutes). For Lambda-cyhalothrin 0.03%, the mean KT₅₀ and KT₉₅ of Ae. aegypti were the lowest in Thung Saliam districts (Sukhothai) (69.30 minutes) and Muang (Uttaradit) (98.69 minutes). Whereas, Ae. aegypti gained from Nam Pat (Uttaradit) illustrated the lowest mean KT₅₀ and KT₉₅ of the treated mosquitoes (Deltamethrin 0.15%) of 22.31 and 51.64 minutes, respectively. Nonetheless, the use of chemicals should be considered when it is necessary and it should be correctly chosen according to academic principles. The sensitivity test of Aedes mosquitoes should be continuously performed. All obtained results could be the basic information for decision making to use chemicals safely and efficiently.