Present status of the insecticide susceptibility of Aedes mosquitoes in Thailand

[Abstract]The current method for interrupting dengue fever transmission is spraying insecticide in the area affected by the epidemic. In such cases, information about the insecticide susceptibility of the vector would allow an appropriate insecticide to be applied. It is also a key factor for control programs. Therefore, the insecticide susceptibility of Aedes aegypti and Ae.albopictus were investigated using the WHO susceptibility test kit. Adult mosquitoes or larvae collected from Bangkok, Phra Nakhon Si Ayutthaya, Chanthaburi, and Prachin Buri from 2008-2010 and reared in a laboratory were exposed to insecticide for 1 hour at discriminating diagnostic doses recommended by the WHO, and mortality was examined after 24 hour. In general, Ae.aegypti were tolerant or resistant to all insecticides except malathion. Their degrees of insecticide resistance ranged from high to low in Bangkok, Phra Nakhon Si Ayutthaya, Prachin Buri, and Chanthaburi, respectively. In the Bang Khae and Thung Khru districts of Bangkok, insecticide resistance increased each year. knock down resistance, which is related to pyrethroid resistance, was observed in Ae.aegypti. On the other hand, Ae.albopictus from Prachin Buri, Bangkok, and Phang-nga were able to tolerate DDT. However no Ae.albopictus that were tolerant/resistant to pyrethroid or malathion were found in this study.