The effect of increasing ambient temperature on the susceptibility of Aedes aegypti to permethrin: What’s global warming got to do with it?

Previous studies show that temperature directly affects the toxicity of insecticides to insects. Organophosphates exhibit a positive correlation between ambient temperature and mortality for many insect species. Carbamates exhibit a slightly negative correlation between ambient temperature and mortality. In contrast, pyrethroids are known to exhibit a distinctly negative correlation between increasing ambient temperature and mortality for many insect species. However, this relationship has not been systematically studied for adult mosquitoes. Therefore, we are examining the influence of temperature on the susceptibility of adult Aedes aegypti when exposed to permethrin. We are characterizing the median lethal concentration, LC50, for adult Ae. aegypti when exposed to eight concentrations of permethrin for 24 hours in bottle assays. In addition, we are determining the LC50 and dose-response curves for adult Ae. aegypti when exposed to the same concentrations at four temperatures (16, 23, 30, 34 ^oC) for 24 hours. Preliminary results show a negative correlation between temperature and mortality with temperatures between 16 ^oC and 30 ^oC and a positive correlation with temperatures from 30 ^oC to 34 ^oC 24 hours after exposure to permethrin. If mosquito populations are expanding in space and time because of increased temperatures due to climate warming, and at the same time they cannot be managed as effectively with pyrethroids, then this may pose considerable risk to public health.