P-1 - Expanded Monitoring of Insecticide Resistance and Follow-up Bioassays in Aedes aegypti Collected in Southern Puerto Rico in 2019 and 2023.

Abstract: Abstract

Aedes aegypti is the primary vector for dengue, chikungunya, and Zika viruses. The use of insecticides remains an important tool to control Ae. aegypti; however, the development of resistance in this species in Puerto Rico has brought new challenges for control and the need for continuous monitoring. In 2019, we investigated the insecticide resistance profiles of mosquitoes collected in the communities of La Margarita, Playa, Villodas, and Arboleda in southern Puerto Rico and reported high levels of resistance against the pyrethroids permethrin, sumethrin, bifenthrin, and deltamethrin. We detected resistance against the organophosphate malathion with mortality ranging from 23-93% at diagnostic time. However, we saw 100% mortality at 120min indicating a weaker mechanism of resistance for this organophosphate. In 2023, we reassessed resistance to these same insecticides and added bioassays for pyrethrum and transfluthrin. For permethrin, sumethrin, bifenthrin, and deltamethrin mosquitoes from those same communities remained resistant to the pyrethroids ranging from 0-3% mortality for permethrin, 0-36% for bifenthrin, and 0-20% for deltamethrin. We observed no mortality in any community when challenged with sumethrin. We saw increased resistance to malathion which ranged from 2-20% mortality in 2023, but again 100% mortality was observed at 120min. For pyrethrum, mortality across the four populations ranged from 0-9%. In two communities, Villodas and Arboleda mortality after exposure to transfluthrin was 34% and 22%, respectively. These findings highlight the importance of frequent monitoring of insecticide resistance and the need to identify sources of exposure that drive and maintain resistance in Puerto Rico Ae. aegypti populations.