# Updated Adulticide Susceptibility Status of Florida Populations of Aedes aegypti (Linnaeus, 1762)

## TL;DR

This study updates the insecticide resistance status of Aedes aegypti mosquitoes in Florida, showing continued resistance to pyrethroids.

## Contribution

The study provides updated, operationally relevant resistance data for Aedes aegypti in Florida using extensive bioassays.

## Key findings

- Aedes aegypti populations showed higher resistance to pyrethroids like sumithrin and deltamethrin.
- Organophosphate insecticides were found to be more effective against Aedes aegypti.
- Knockdown resistance was observed across all pyrethroid exposures, especially with etofenprox and sumithrin.

## Abstract

Insecticide resistance in Aedes aegypti (Linnaeus, 1762) poses a major challenge for vector control programs, undermining the effectiveness of chemical tools to mitigate both nuisance biting and the transmission of vector-borne diseases. Previous studies have documented widespread resistance to multiple adulticide active ingredients across Florida, particularly pyrethroids, along with high prevalence of knockdown resistance (kdr) mutations. Continued resistance monitoring is essential for guiding treatment decisions and detecting shifts in susceptibility over time. In collaboration with mosquito control programs across Florida, we assessed the susceptibility of 78 Ae. aegypti populations to up to six active ingredients, conducting 396 independent CDC bottle bioassays and calculating hazard ratios relative to a susceptible Ae. aegypti strain. For pyrethroids, 24 h post-exposure mortality was used to evaluate phenotypic recovery from knockdown. Hazard ratios revealed Ae. aegypti populations were more susceptible to organophosphate adulticide active ingredients, while the lowest hazard ratios, indicating higher resistance, were observed for sumithrin, deltamethrin, etofenprox, and permethrin, respectively. Evidence of knockdown resistance and recovery after 24 h was present across all pyrethroid exposures, with the highest levels following treatment with etofenprox and sumithrin. These findings confirm that pyrethroid resistance remains a significant barrier to Ae. aegypti control and provide updated, operationally relevant resistance data that can complement existing guidance and support evidence-based vector management strategies.