Abstract
BackgroundVolatile pyrethroid insecticides, such as transfluthrin, have received increasing attention for their potent repellent activities in recent years for controlling human disease vectors. It has been long understood that pyrethroids kill insects by promoting activation and inhibiting inactivation of voltage-gated sodium channels. However, the mechanism of pyrethroid repellency remains poorly understood and controversial.Methodology/Principal findingsHere, we show that transfluthrin repels Aedes aegypti in a hand-in-cage assay at nonlethal concentrations as low as 1 ppm. Contrary to a previous report, transfluthrin does not elicit any electroantennogram (EAG) responses, indicating that it does not activate olfactory receptor neurons (ORNs). The 1S-cis isomer of transfluthrin, which does not activate sodium channels, does not elicit repellency. Mutations in the sodium channel gene that reduce the potency of transfluthrin on sodium channels decrease transfluthrin repellency but do not affect repellency by DEET. Furthermore, transfluthrin enhances DEET repellency.Conclusions/SignificanceThese results provide a surprising example that sodium channel activation alone is sufficient to potently repel mosquitoes. Our findings of sodium channel activation as the principal mechanism of transfluthrin repellency and potentiation of DEET repellency have broad implications in future development of a new generation of dual-target repellent formulations to more effectively repel a variety of human disease vectors.
Highlights
Pyrethroid insecticides are synthetic analogues of natural pyrethrins, which are major insecticidal components of the pyrethrum extract from the flowers of Chrysanthemum species [1]
We made two important discoveries in this study, showing that transfluthrin repellency is via activation of sodium channels and transfluthrin enhances DEET repellency
The insecticidal activity of pyrethroids is through their action on voltage-gated sodium channels, which are critical for electrical signaling in the nervous system
Summary
Pyrethroid insecticides are synthetic analogues of natural pyrethrins, which are major insecticidal components of the pyrethrum extract from the flowers of Chrysanthemum species [1]. Application of transfluthrin to hessian or sisal decorations/products, eave ribbons, eave-baffles and window screens offers a promising method of mosquito contact/bit prevention in both indoor or outdoor settings [11,13,14,16,17,18,19,20]. Volatile pyrethroid insecticides, such as transfluthrin, have received increasing attention for their potent repellent activities in recent years for controlling human disease vectors. The mechanism of pyrethroid repellency remains poorly understood and controversial
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