Quantification of permethrin resistance andkdralleles in Florida strains ofAedes aegypti(L.) andAedes albopictus(Skuse)
Authors: Estep Alden S. , Sanscrainte Neil D. , Waits Christy M. , Bernard Sarah J. , Lloyd Aaron M. , Lucas Keira J. , Buckner Eva A. , Vaidyanathan Rajeev , Morreale Rachel , Conti Lisa A. , Becnel James J. 
Published: July 2018

Recent outbreaks of locally transmitted dengue and Zika viruses in Florida have placed more emphasis on the importance of integrated vector management plans forAedes aegypti(L.) andAedes albopictusSkuse. Adulticiding, primarily with pyrethroids, can be the best option available for the immediate control of potentially arbovirus-infected mosquitoes during outbreak situations. While pyrethroid resistance is common inAe. aegyptiworldwide and testing is recommended by CDC and WHO, resistance to this class of products has not been widely examined or quantified in Florida. To address this information gap, we performed the first study to quantify both pyrethroid resistance and genetic markers of pyrethroid resistance inAe. aegyptiandAe. albopictusstrains in Florida. Using direct topical application, we examined 21Ae. aegyptistrains from 9 counties and found permethrin resistance (resistance ratio (RR)=6-61-fold) in all strains when compared to the susceptible ORL1952 control strain. Permethrin resistance in five strains ofAe. albopictuswas very low (RR<1.6) even when collected from the same containers producing resistantAe. aegypti. Characterization of two sodium channelkdralleles associated with pyrethroid-resistance showed widespread distribution in 62 strains ofAe. aegypti. The 1534 phenylalanine to cysteine (F1534C) single nucleotide polymorphism SNP was fixed or nearly fixed in all strains regardless of RR. We observed much more variation in the 1016 valine to isoleucine (V1016I) allele and observed that increasing frequency of the homozygous V1016I allele correlates strongly with increased RR (Pearson corr= 0.905). In agreement with previous studies, we observed a very low frequency of threekdrgenotypes, IIFF, VIFF, and IIFC. In this study, we provide a statewide examination of pyrethroid resistance, and demonstrate that permethrin resistance and the genetic markers for resistance are widely present in FLAe. aegypti. Resistance testing should be included in an effective management program.

Author Summary

Aedes aegyptiandAedes albopictuscan vector a variety of arboviruses that cause diseases and are thus a public health concern. Pyrethroid insecticide resistance is common inAedes aegyptiin many locations worldwide and can adversely affect vector control operations. However, the resistance status of these vectors in Florida is largely unreported and recent local transmission of dengue and Zika viruses has made this information critical for effective control operations. In this study, we showed that permethrin resistance and two common SNPs of the voltage gated sodium channel (V1016I and F1534C) previously associated with pyrethroid resistance were widely present in FloridaAedes aegyptistrains. We also observed a strong correlation between the IICC genotype and RR as determined by topical application, which suggests, as have others, thatkdrfrequency may be a useful indicator of resistance inAedes aegypti.