Diagnostic Doses of Two Pyrethroids Currently Used for Control of Aedes aegypti L. (Diptera: Culicidae), a Vector of Dengue

Abstract

Determining the diagnostic dose is crucial in evaluating the susceptibility of a mosquito population to certain insecticides. Presently, the diagnostic doses of only two pyrethroids (permethrin and λ-cyhalothrin) have been published for monitoring insecticide susceptibility of Aedes aegypti. Therefore, the objective of this study was to establish the diagnostic doses for two synthetic pyrethroids—bifenthrin and α-cypermethrin—currently used in dengue vector control, using the United State Department of Agriculture (USDA) standard strain of Aedes aegypti. These diagnostic doses were subsequently used to evaluate the susceptibility status in fi eld collected specimens of Ae. aegypti. Based on the baseline susceptibility levels, all three fi eld strains demonstrated varying levels of physiological resistance to each compound. Strong resistance to bifenthrin was seen in one strain from Nong Khai resulting in 14.14% mortality whereas complete mortality (100%) was observed in the USDA standard strain when exposed to the established diagnostic doses of these two synthetic pyrethroids. These diagnostic doses could be applied for monitoring the susceptibility status in mosquito populations across Thailand.