Unraveling insecticide resistance patterns in Illinois West Nile virus vectors

Mosquitoes are major disease vectors, making them a significant public health concern worldwide. Currently, the most effective way to control them is with the use of insecticides. However, insecticide use can easily lead to the development of resistance. Monitoring mosquito susceptibility to insecticides is vital for informed decisions during an outbreak. Culex pipiens and Culex restuans are common mosquito species found in Illinois and primary vectors of West Nile virus. To better understand the levels of insecticide resistance of Culex populations, egg collections were made throughout the state from 2018-2020. Collected eggs were reared under standardized laboratory conditions and adults were tested for insecticide resistance using the CDC’s bottle bioassay protocol. Results from the bottle assays indicate variable resistance rates in Illinois. This variation in resistance appears to be driven by population differences in rates of knockdown resistance (kdr) mutations and metabolic resistance mechanisms.