Temperature Influence on Insecticide Resistance in Aedes aegypti and Aedes albopictus Mosquitoes from South Texas

Aedes aegypti and Aedes albopictus are vectors for several emerging arboviruses including Zika, chikungunya and dengue. Both mosquitoes are found along the Rio Grande River in South Texas, along the border between Mexico and the United States of America. These mosquito species typically reside near human settlements. A preventative measure public health official use to help halt the spread of diseases is by controlling vector population with the use of insecticides, but as temperature vary, and with the constant exposure to commonly used insecticides, mosquitoes from South Texas may be developing a resistance to the insecticides. Resistance to insecticides may potentially vary in Ae. aegypti and Ae. albopictus mosquitoes as due to the variation in their rearing temperature. To test this, I examined the influence of exposing adult mosquitos of Ae. aegypti and Ae. albopictus following emergence to different temperatures on their susceptibility to different insecticides. I hypothesized that adults maintained at high temperatures would show decreased resistance to insecticides relative to lower temperatures. Colony mosquitoes were hatched, reared to adulthood, and then maintained in varying temperature regimes (22.58, 30.55 and 36˚C) that reflect seasonal temperatures in South Texas. Insecticide resistance to permethrin and deltamethrin was assessed using the Center for Disease Control and Prevention Bottle Bioassay method. Adult females were tested between 5 and 10 days after emergence. World Health Organization guidelines were used to classify the population as susceptible at the diagnostic time (DT) of 30 min and the overall time of 2 hours. Mosquitoes kept at different temperatures demonstrated differential susceptibility to insecticides. Low temperatures (22.58˚C) exposed mosquitoes had increased resistance to insecticides in both species, although specific insecticides varied in their efficacy. Susceptibility also varied between the mosquito species and insecticides at the mid and high temperature treatments. These results have important implications for public health officials to incorporate temperature in their decision-making process