Insecticide Resistance Surveillance of a Zika Virus Vector, Aedes albopictus, in the State of Illinois

The extent to which populations of two vector species in Illinois, the Asian tiger mosquito, Aedes albopictus, and the northern house mosquito, Culex pipiens, remain sensitive to two commonly-used insecticides (permethrin and malathion) was investigated using a series of CDC bottle assays.For Ae. albopictus, 6 colonies were established from collections in central and southern Illinois, while for Cx. pipiens eggs were collected in the North Shore of Cook County.The results suggest that the time until death occurred was longer in several of the more southern field populations for Ae. albopictus than that of a sensitive reference strain, for both malathion and permethrin at the recommended diagnostic dose. At a lower concentration of malathion,however,field populations appeared more sensitive than the reference strain.Further work will be required to confirm whether these conflicting results reflect environmental noise or a true genetic difference in the sensitivity status of these populations.The time until death occurred was also longer in field-collected Cx. pipiens than that of a sensitive reference strainwhen exposed to three different concentrations of permethrin. The results of this initial insecticide resistance survey thus suggest that insecticide sensitivity varies among populations. Confirmation of and expansion on these results, through additional bioassays, inclusion of additional populations across Illinois, elucidation of the physiological mechanisms involved, and investigations performed over time will be required to develop a thorough understanding of the threat to public health associated with potentially increasing levels of resistance in IL mosquito populations.