PYRETHROID AND ORGANOPHOSPHATE SUSCEPTIBILITY STATUS OF AEDES AEGYPTI (LINNAEUS) AND AEDES ALBOPICTUS (SKUSE) IN PENANG, MALAYSIA

Abstract

Dengue is a serious problem in Malaysia, particularly in high-density urban communities. Many methods are used for mosquito control but the most important procedure usually includes chemical insecticides. Dengue control relies on insecticides to control the vectors, Aedes aegypti and Aedes albopictus. Using standard World Health Organization (WHO) adult bioassay tests, this study evaluated the susceptibility to lambda-cyhalothrin and pirimiphos-methyl of local populations of both species in a traditional community at Bagan Dalam, Penang, Malaysia. Unfed female mosquitoes aged 3-5 days post-emergence were exposed to WHO recommended dosages of insecticides over fixed time periods with results presented as knock-down time (KT₅₀) for each strain. The insecticide susceptible Vector Control Research Unit (VCRU) laboratory strains of both species were used as controls. Both species from Bagan Dalam were highly resistant to lambda-cyhalothrin with less than 10% mortality recorded 24 hours after exposure. However, both Ae. aegypti and Ae. albopictus from Bagan Dalam were susceptible to pirimiphos-methyl, showing 100% mortality recorded 24 hours after treatment. The results indicated that organophosphates such as pirimiphos-methyl might be used as an alternative to pyrethroid for dengue vector control in this highly dengue-prone area.