Assessment of Insecticide Resistance to Organophosphates and Pyrethroids in Aedes aegypti

Abstract

Aedes aegypti is the primary vector of pathogens such as Zika, dengue, yellow fever and chikungunya viruses, making mosquito control for this species a vital part of protecting public health. Pesticides used to control the infestation of adult mosquitoes that transmit disease, also known as adulticides, prevent the onset and spread of vector-borne disease outbreaks. It is essential to conduct mosquito surveillance and to determine the insecticide resistance status for populations before adulticiding. Only the most effective insecticides should be used to avoid financial loss and ineffective control of mosquitoes. Pyrethroids and organophosphates are the most commonly used insecticides for mosquito control. Permethrin (a pyrethroid) accounts for 25% of all insecticides used throughout the world, and thus pyrethroid resistant mosquito populations are of public health concern. Here, the efficacy of active ingredients (AIs) (permethrin [pyrethroid], chlorpyrifos [organophosphate]), formulated products (Mosquitomist[trademark] [contains chlorpyrifos], Biomist[copyright] [contains permethrin]), and synergists (piperonyl butoxide, diethyl maleate, s-s-s-tributyl phosphorotrithioate) were evaluated for controlling two populations (pyrethroid resistant and susceptible) of Ae. aegypti in a laboratory setting. We show that Mosquitomist[trademark] performed best against the pyrethroid resistant population with a mortality rate of 100% at the diagnostic time. The addition of synergists to AIs did not increase the efficacy against the pyrethroid resistant mosquito population. This resistance to synergists may due to the mechanism of action working to enable this population of mosquitoes to be pyrethroid resistant. Further research is needed to discover how mechanisms of resistance may impact synergist effectiveness.