Characterization of Pyrethroid Resistance Mechanisms in Aedes aegypti from the Florida Keys

The status of insecticide resistance in Aedes aegypti is of concern in areas where Aedes-borne arboviruses like chikungunya, dengue, and Zika occur. In recent years, outbreaks involving these arboviruses have occurred, for which vaccines do not exist; therefore, disease prevention is only through vector control and personal protection. Aedes aegypti are present on every inhabited island within the Florida Keys. The resistance status of Ae. aegypti in the Florida Keys was assessed to guide knowledge of the best choice of chemical for use during an outbreak. Mosquito eggs were collected using ovitraps placed on Key West, Stock Island, Vaca Key, Upper Matecumbe Key, Plantation Key, and Key Largo. Bottle bioassays were conducted at the Florida Keys Mosquito Control District using Biomist (R) 30+30 (Clarke Mosquito Control Products, Inc., Roselle, IL). Further bottle testing using malathion and permethrin occurred at the CDC, Fort Collins, CO, in addition to molecular and biochemical assays. Levels of resistance varied between islands with different underlying mechanisms present. Resistance was seen to Biomist (R) 30+30 but not to permethrin, indicating that piperonyl butoxide (PBO) or the inert ingredients may be involved in resistance. No study has been conducted to date examining the role of PBO in resistance. Key Largo was treated the most with adulticides and expressed the highest levels of alpha and beta esterases, oxidases, glutathione-S-transferases, and frequency of the V1016I knockdown mutation from all sites tested. Knowledge of localized resistance and underlying mechanisms helps in making rational decisions in selection of appropriate and effective insecticides. Control of mosquitoes is important because of their ability to spread disease, their impact on local economies, and the low tolerance of the public to high numbers of biting mosquitoes. In the absence of vaccines, vector control and/or personal protection remain the mainstays for the prevention of infection with pathogens transmitted by mosquitoes. Organized vector control programs and personal protection strategies rely on the use of insecticides to varying degrees. Vector

Automated summary

The study addresses insecticide resistance in Aedes aegypti in the Florida Keys, revealing varying levels of resistance across different islands with distinct underlying mechanisms. Resistance to Biomist (R) 30+30 was observed, while no resistance was seen to permethrin, indicating possible involvement of PBO or other inert ingredients in resistance. Understanding localized resistance helps in making informed decisions on insecticide selection.