Abstract
Aedes albopictus (Skuse) is an invasive mosquito that has become an important vector of chikungunya and dengue viruses. Immature Ae. albopictus thrive in backyard household containers that require treatment with larvicides and when adult populations reach pest levels or disease transmission is ongoing, adulticiding is often required. To assess the feasibility of control of USA populations, we tested the susceptibility of Ae. albopictus to chemicals representing the main insecticide classes with different modes of action: organochlorines, organophosphates, carbamates, pyrethroids, insect growth regulators (IGR), naturalytes, and biolarvicides. We characterized a susceptible reference strain of Ae. albopictus, ATM95, and tested the susceptibility of eight USA populations to five adulticides and six larvicides. We found that USA populations are broadly susceptible to currently available larvicides and adulticides. Unexpectedly, however, we found significant resistance to dichlorodiphenyltrichloroethane (DDT) in two Florida populations and in a New Jersey population. We also found resistance to malathion, an organophosphate, in Florida and New Jersey and reduced susceptibility to the IGRs pyriproxyfen and methoprene. All populations tested were fully susceptible to pyrethroids. Biochemical assays revealed a significant up-regulation of GSTs in DDT-resistant populations in both larval and adult stages. Also, β-esterases were up-regulated in the populations with suspected resistance to malathion. Of note, we identified a previously unknown amino acid polymorphism (Phe → Leu) in domain III of the VGSC, in a location known to be associated with pyrethroid resistance in another container-inhabiting mosquito, Aedes aegypti L. The observed DDT resistance in populations from Florida may indicate multiple introductions of this species into the USA, possibly from tropical populations. In addition, the mechanisms underlying DDT resistance often result in pyrethroid resistance, which would undermine a remaining tool for the control of Ae. albopictus. Continued monitoring of the insecticide resistance status of this species is imperative.
Highlights
Aedes (Stegomyia) albopictus (Skuse), the Asian tiger mosquito, is an aggressive human- and day-biting species native to Asia that has recently expanded to at least 28 countries outside its native range, and occurs in all inhabitable continents [1]
Larval and adult bioassays Larval bioassays resulted in low resistant ratios (RRs) indicating that none of the eight USA populations of Ae. albopictus were resistant to the larvicides tested (Table 3)
Insecticides representing the major classes of insecticide (OC, OP, CA, PYR), bio-insecticides (Bti and spinosad), and insect growth regulators (IGR) were used in this study against larvae and adult mosquitoes following WHO protocols
Summary
Aedes (Stegomyia) albopictus (Skuse), the Asian tiger mosquito, is an aggressive human- and day-biting species native to Asia that has recently expanded to at least 28 countries outside its native range, and occurs in all inhabitable continents [1]. Detailed theoretical analyses indicate that the spread of Ae. albopictus may well continue into many more regions of the world [1,2,3]. This species is often considered mostly an urban nuisance, it was the principal dengue vector in Hawaii and other areas were Aedes aegypti L. populations have been controlled [4] and in the summer of 2013, an autochthonous case of dengue in Suffolk County, New York has been attributed to thriving populations of Ae. albopictus [5]. The European expansion of CHIKV would not have been possible without the prior invasion of that continent by Ae. albopictus [11]
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