Efficacy and Influence of Consumer-Based Household Aerosol Insecticides against Aedes Aegypti in the Context of Highly Pyrethroid-Resistant Communities Open Access

Gray, Lyndsey (2017)

Permanent URL: https://etd.library.emory.edu/concern/etds/5t34sk06t?locale=en


Efficacy and Influence of Consumer-Based Household Aerosol Insecticides against Aedes Aegypti in the Context of Highly Pyrethroid-Resistant Communities

Background: The Aedes aegypti mosquito constitutes a major, international public health concern due to its role in transmitting viral diseases, such as yellow fever, dengue, Mayaro, chikungunya, and Zika virus. As such, there is an immediate need for effective vector control strategies. Unfortunately, widespread use of pyrethroid-based insecticides has led to increased selective pressure for insecticide-resistant Ae. aegypti. Missing from the literature, though, is how household insecticide products may contribute towards insecticide knock-down resistance. This study seeks to characterize how use of commercial aerosolized insecticides leads to differential mortality and genetic selection for insecticide-resistant Ae. aegypti mosquitoes in Mérida, Mexico.

Methods: We surveyed 150 homes across three communities of Mérida to determine prevalent aerosol insecticide products and application techniques to design two semi-field experiments, which examined differential mortality rates among susceptible and pyrethroid-resistant Ae. aegypti mosquitoes after exposure to aerial and surface spraying. All mosquitoes were analyzed through real-time PCR to determine presence of I1016 point mutations of the sodium channel para genes.

Results: Two commercial aerosolized insecticides, Raid Casa y Jardín and Baygon Ultra Verde, were selected for use in subsequent experimental trials. In aerial spray trials, all three resistant colonies had lower mortality rates than the control, but, in comparison to the susceptible strain, relative odds reduction for mortality was highest for San Lorenzo (OR: 0.04, 95%CI: 0.01, 0.23). Kaplan-Meier curves also indicated high knock-down rates for resistant mosquitoes in the aerial spray trials that did not result in mortality. Residual trials showed a significant increased hazard for mortality for Ae. aegypti mosquitoes exposed to Baygon Ultra Verde rather than Raid Casa y Jardín in surface spray trials (HR: 3.11, 95%CI: 2.47, 3.93). Kaplan-Meier survival curves indicated high survival for mosquitoes from resistant colonies in the residual trials in comparison to susceptible Ae. aegypti. I1016 homozygous mutant genotype conferred the greatest resistance (OR: 0.06, 95%CI: 0.03, 0.12). While I1016 allele frequency differed significantly by survival phenotype in the aerial spray trials (all p-values <0.05), they did not for residual spray trials.

Discussion: This study reports strong Ae. aegypti pyrethroid resistance selection driven by commercial aerosolized insecticides. In order for mosquito-control programs to successfully manage pyrethroid resistance in Ae. aegypti, they must account for and integrate individual-level mosquito management strategies.

Table of Contents

Table of Contents

Introduction 1

Methods 5

Study Area 5

Survey Design and Execution 6

Experimental Design 6

Statistical Analyses 9

Genetic Analyses 11

Results 12

Survey Data 12

Aerial Spray Trials 13

Surface Spray Trials 15

Genetic Analyses 17

Discussion 17

Appendix 1: Tables and figures 23

References 34

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