Emerging insecticide resistance is a problem for vector control, especially in disease endemic areas.Resistance is not desirable from a control perspective because it is associated with a higher cost in order to achieve a comparable level of control, and control failure results in disease resurgence. It is important to identify and characterize developing resistance in terms of extent and mechanisms so that future control strategies can be optimized. Pyrethroid resistance has previously been documented in Puerto Rican populations of Aedes aegypti mosquitoes. In this study, resistance to three insecticides was determined for susceptible (Orlando - ORL) and resistant (Puerto Rico - PR) strains of Aedes aegypti. The insecticides used were technical permethrin (95.85%), etofenprox (96.8%), and propoxur (99.9%).Groups of 10 female mosquitoes were topically dosed on the thorax in triplicate using acetone as a solvent. Mortality was assessed for each dose replicate at 24hr to determine the number of dead or obviously impaired mosquitoes, characterized by twitching and erratic or upside-down flight. Dose response curves and probit regression analyses were generated for each chemical and pair of mosquito strains (ORL and PR).Resistance ratios were calculated using the LD50 values.As expected, there was a higher resistance ratio for both permethrin (221.9) and for etofenprox (941.7), as pyrethroid resistance has previously been documented in Puerto Rican mosquito populations. Although the resistance ratio for propoxur was not large (6.4), it is higher than the 2-4 fold increase expected from vigor tolerance found when comparing wild populations of mosquitoes to laboratory strains. Future work will investigate the possible mechanisms that underlie this observed resistance including the examination of insecticide penetration, metabolism and altered target sites in vector mosquitoes.

Resistance of Puerto Rican <i>Aedes aegypti</i> to permethrin, etofenprox, and propoxur by LD<sub>50</sub> estimation

248th National Meeting (2014)

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Resistance of Puerto Rican Aedes aegypti to permethrin, etofenprox, and propoxur by LD50 estimation

Resistance of Puerto Rican Aedes aegypti to permethrin, etofenprox, and propoxur by LD₅₀ estimation