Quantification of permethrin resistance andkdralleles in Florida strains ofAedes aegypti(L.) andAedes albopictus(Skuse)

Estep, Alden S.; Sanscrainte, Neil D.; Waits, Christy M.; Bernard, Sarah J.; Lloyd, Aaron; Lucas, Keira J.; Buckner, Eva A.; Vaidyanathan, Rajeev; Morreale, Rachel; Conti, Lisa; Becnel, James J.

doi:10.1101/365171

“…While other mechanisms related to the outcome of resistance in this and related species have been identified(16), variation in resistance status in the Ae. aegypti populations studied here is highly correlated with frequencies of these mutations, as was shown in Estep et al2018(18), where the authors found a Pearson correlation coefficient of 0.905 between frequencies of the IICC genotype and the permethrin resistance ratio (3).…”

supporting

confidence: 83%

“…The data used in this study were collected as part of a statewide insecticide resistance monitoring effort that is described in detail in Estep et al 2018 (18). The frequencies of kdr genotypes were determined for Ae.…”

Section: Methodsmentioning

confidence: 99%

Spatial variation in the frequency of knockdown resistance genotypes in Florida Aedes aegypti populations

Mundis

¹

,

Estep

²

,

Waits

³

et al. 2020

Preprint

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Background The development of insecticide resistance in disease-vectoring mosquito species can lead to vector control failure and disease resurgence. However, insecticide applications remain an essential public health intervention. In Florida, insecticide resistance in Aedes aegypti , an anthropophilic mosquito species capable of transmitting dengue, chikungunya, and Zika virus, is a major concern. Understanding the location, scale, and driving factors of insecticide resistance can enhance the ability of vector control organizations to target populations effectively. Methods We used previously collected data on frequencies of mutations that confer resistance to commonly used pyrethroid insecticides in Aedes aegypti specimens from 62 sites distributed across 18 counties in Florida. To determine the scale of clustering for the most resistant variant, we used a Ripley’s K function. We also used a spatial scanning statistic technique to identify the locations of clusters where higher than expected frequencies of susceptible or resistant mosquitoes occurred. We then tested for associations between landscape, demographic, and insecticide-use factors using a beta regression modelling approach and evaluated the effect of spatial lag and spatial error terms on overall explanatory power of these models. Results The scale at which maximum clustering of the most resistant variant occurs is approximately 20 kilometers. We identified statistically significant clusters of genotypes associated with resistancein several coastal cities, although some of these clusters were near significant clusters of susceptible mosquitoes, indicating selection pressures vary at the local scale. Vegetation density, distance from roads, and pyrethroid-use by vector control districts were consistently significant predictors of knockdown resistance genotype frequency in the top-performing beta regression models, although pyrethroid-use surprisingly had a negatively associated with resistance. The incorporation of spatial lags resulted in improvements to the fit and explanatory power of the models, indicating an underlying diffusion process likely explains some of the spatial patterns observed. Conclusions The genetic mutations that confer resistance to pyrethroids in Aedes aegpyti mosquitoes in Florida exhibit spatial autocorrelation and patterns that can be partially explained by landscape and insecticide-use factors. Further work at local scales should be able to identify the mechanisms by which these variables influence selection for alleles associated with resistance.

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“…The first mutation at codon 1016 results in a change from a valine (V) to an isoleucine (I) (17), while the second mutation at codon 1534 results in a change from a phenylalanine (F) to a cysteine (C). The frequency of individuals with the homozygous mutant variant at both sites (IICC) has a strong positive correlation with pyrethroid resistance in tested populations and can be used to estimate on-theground resistance (18,19). Mosquitoes that are heterozygous at both sites typically exhibit limited resistance to pyrethroids (20).…”

Section: Introductionmentioning

confidence: 99%

Spatial variation in the frequency of knockdown resistance genotypes in Florida Aedes aegypti populations

Mundis

¹

,

Estep

²

,

Waits

³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Background The development of insecticide resistance in disease-vectoring mosquito species can lead to vector control failure and disease resurgence. However, insecticide applications remain an essential public health intervention. In Florida, insecticide resistance in Aedes aegypti , an anthropophilic mosquito species capable of transmitting dengue, chikungunya, and Zika virus, is a major concern. Understanding the location, scale, and driving factors of insecticide resistance can enhance the ability of vector control organizations to target populations effectively. Methods We used previously collected data on frequencies of mutations that confer resistance to commonly used pyrethroid insecticides in Aedes aegypti specimens from 62 sites distributed across 18 counties in Florida. To determine the scale of clustering for the most resistant variant, we used a Ripley’s K function. We also used a spatial scanning statistic technique to identify the locations of clusters where higher than expected frequencies of susceptible or resistant mosquitoes occurred. We then tested for associations between landscape, demographic, and insecticide-use factors using a beta regression modelling approach and evaluated the effect of spatial lag and spatial error terms on overall explanatory power of these models. Results The scale at which maximum clustering of the most resistant variant occurs is approximately 20 kilometers. We identified statistically significant clusters of genotypes associated with resistancein several coastal cities, although some of these clusters were near significant clusters of susceptible mosquitoes, indicating selection pressures vary at the local scale. Vegetation density, distance from roads, and pyrethroid-use by vector control districts were consistently significant predictors of knockdown resistance genotype frequency in the top-performing beta regression models, although pyrethroid-use surprisingly had a negatively associated with resistance. The incorporation of spatial lags resulted in improvements to the fit and explanatory power of the models, indicating an underlying diffusion process likely explains some of the spatial patterns observed. Conclusions The genetic mutations that confer resistance to pyrethroids in Aedes aegpyti mosquitoes in Florida exhibit spatial autocorrelation and patterns that can be partially explained by landscape and insecticide-use factors. Further work at local scales should be able to identify the mechanisms by which these variables influence selection for alleles associated with resistance.

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“…A case in point was the 2016 Zika outbreak in Miami‐Dade County that was in part due to insecticide resistance in Ae. aegypti populations (Estep et al 2018) and made it harder to control mosquitoes. New and alternative control strategies are needed to address this problem.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of boric acid as toxic sugar bait against resistant Aedes aegypti mosquitoes

Pearson

¹

,

Blore

²

,

Efstathion

³

et al. 2020

Journal of Vector Ecology

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Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.

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Quantification of permethrin resistance andkdralleles in Florida strains ofAedes aegypti(L.) andAedes albopictus(Skuse)

Cited by 29 publications

References 31 publications

Spatial variation in the frequency of knockdown resistance genotypes in Florida Aedes aegypti populations

Spatial variation in the frequency of knockdown resistance genotypes in Florida Aedes aegypti populations

Spatial variation in the frequency of knockdown resistance genotypes in Florida Aedes aegypti populations

Evaluation of boric acid as toxic sugar bait against resistant Aedes aegypti mosquitoes

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