Characterization Of Sodium Channel Mutations In The Dengue Vector Mosquitoesaedesaegyptiandaedesalbopictuswithin The Context Of Ongoingwolbachiareleases In Kuala Lumpur, Malaysia

Simple Summary Mosquitoes,Aedes aegyptiandAe. albopictusare vectors of dengue and must be controlled to prevent and contain outbreaks of this disease. Control by insecticide application is common and pyrethroid insecticides provide rapid knockdown of mosquitoes combined with relatively low mammalian toxicity. However, resistance to pyrethroids and other chemicals is causing problems for mosquito control around the world. In Malaysia, an alternative method of dengue reduction is employed which comprises releases ofAe. aegyptimosquitoes infected with a bacterium,Wolbachia, found naturally in other insects.Wolbachiaturns the mosquitoes into incompetent vectors so they do not transmit the disease.Wolbachiamosquitoes are reared in the laboratory before release and must be able to survive in the field where they will encounter insecticides. Our study demonstrates benefits of crossing laboratory mosquitoes to those from the field over generations, so that the mosquito lines acquire field resistance characteristics (mutations in the sodium channel gene). We demonstrate that resistance mutations provide a survival advantage toWolbachia Ae. aegyptimosquitoes, which must be maintained in laboratory lines by regular backcrossing. We also describe appearance of a sodium channel mutation in MalaysianAe. albopictuswhich may indicate that pyrethroid resistance is increasing in this species. Specific sodium channel gene mutations confer target site resistance to pyrethroid insecticides in mosquitoes and other insects. InAedesmosquito species, multiple mutations that contribute to resistance vary in their importance around the world. Here, we characterize voltage sensitive sodium channel (Vssc) mutations in populations ofAedesaegyptifrom Kuala Lumpur, Malaysia, and look at their persistence in populations affected by ongoingWolbachiareleases (a dengue control measure). We also describe aVsscmutation inAedesalbopictus(F1534L) found for the first time in Malaysia. We show that there are three predominantVsschaplotypes inAedesaegyptiin this region, which all persist with regular backcrossing, thereby maintaining the original genetic composition of the populations. We identify changes in genotype frequency in closed populations ofAe.aegyptimaintained for multiple generations in laboratory culture, suggesting different fitness costs associated with the genotypes, some of which may be associated with the sex of the mosquito. Following population replacement ofAe.aegyptibyWolbachiain the target area, however, we find that theVsscmutations have persisted at pre-release levels. Mosquitoes in two genotype classes demonstrate a type I pyrethroid resistance advantage over wildtype mosquitoes when exposed to 0.25% permethrin. This resistance advantage is even more pronounced with a type II pyrethroid, deltamethrin (0.03%). The results point to the importance of these mutations in pyrethroid resistance in mosquito populations and the need for regular backcrossing with male mosquitoes from the field to maintain similarity of genetic background and population integrity duringWolbachiareleases.