Transfluthrin enhances odorant receptor-mediated spatial repellency in Aedes aegypti.

Mosquito-borne diseases are an increasing global health challenge and vector-based interventions remain the most important methods for reducing the public health burden of most mosquito-borne diseases. Transfluthrin, a volatile pyrethroid insecticide, is used widely and effectively as an insecticide and as a repellent. In a recent study, we showed that at very low concentrations transfluthrin repels Aedes aegypti mosquitoes in a hand-in-cage assay without detectable stimulation of antennal olfactory responses. Furthermore, activation of sodium channels by transfluthrin enhances repellency by DEET, which has been reported to repel mosquitoes via odorant receptor (Or)-dependent and Or-independent mechanisms. However, whether activation of sodium channels by transfluthrin can serve as a general mechanism for synergizing the activities of other repellents remain unknown. In this study, we found that, in hand-in-cage assay, transfluthrin enhanced repellency by geranyl acetate and (E)-β-farnesene, which activate AaOr31. Such enhancement was not observed in AaOr31-knockout mosquitoes and dampened in a pyrethroid-resistant strain carrying two sodium channel mutations, which reduce the action of transfluthrin on sodium channels. In addition, transfluthrin also enhanced repellency by (-)-borneol, (±)-citronellal, camphor, and eucalyptol, which activate Or-mediated repellency. Our study has uncovered the ability of transfluthrin to enhance the repellency to a variety of mosquito repellents, beyond DEET, and provided experimental support for the emerging paradigm of synergistic interactions between repellency mediated by sodium channel activation and Or activation. These findings have potential implications in the development of more effective mosquito repellent mixtures.

Andreazza F ，Valbon W ，Dong K 《-》

Sodium channel activation underlies transfluthrin repellency in Aedes aegypti.

Andreazza F ，Valbon WR ，Wang Q ，Liu F ，Xu P ，Bandason E ，Chen M ，Wu S ，Smith LB ，Scott JG ，Jiang Y ，Jiang D ，Zhang A ，Oliveira EE ，Dong K ... -  《PLoS Neglected Tropical Diseases》

Bioallethrin activates specific olfactory sensory neurons and elicits spatial repellency in Aedes aegypti.

Use of pyrethroid insecticides is a pivotal strategy for mosquito control globally. Commonly known for their insecticidal activity by acting on voltage-gated sodium channels, pyrethroids, such as bioallethrin and transfluthrin, are used in mosquito coils, emanators and other vaporizers to repel mosquitoes and other biting arthropods. However, whether specific olfactory receptor neurons are activated by pyrethroids to trigger spatial repellency remains unknown. We used behavioral and electrophysiological approaches to elucidate the mechanism of bioallethrin repellency in Aedes aegypti, a major vector of dengue, yellow fever, Zika and chikungunya viruses. We found that bioallethrin elicits spatial (i.e. non-contact) repellency and activates a specific type of olfactory receptor neuron in mosquito antennae. Furthermore, bioallethrin repellency is significantly reduced in a mosquito mutant of Orco, an obligate olfactory co-receptor that is essential for the function of odorant receptors (Ors). These results indicate that activation of specific Or(s) by bioallethrin contributes to bioallethrin repellency. In addition, bioallethrin repellency was reduced in a pyrethroid-resistant strain that carries two mutations in the sodium channel gene that are responsible for knockdown resistance (kdr) to pyrethroids, indicating a role of activation of sodium channels in bioallethrin repellency. Results from this study show that bioallethrin repellency is likely to be the result of co-activation of Or(s) and sodium channels. These findings not only contribute to our understanding of the modes of action of volatile pyrethroids in spatial repellency, but also provide a framework for developing new repellents based on the dual-target mechanism revealed. © 2021 Society of Chemical Industry.

Valbon W ，Andreazza F ，Oliveira EE ，Liu F ，Feng B ，Hall M ，Klimavicz J ，Coats JR ，Dong K ... -  《-》

A dual-target molecular mechanism of pyrethrum repellency against mosquitoes.

Liu F ，Wang Q ，Xu P ，Andreazza F ，Valbon WR ，Bandason E ，Chen M ，Yan R ，Feng B ，Smith LB ，Scott JG ，Takamatsu G ，Ihara M ，Matsuda K ，Klimavicz J ，Coats J ，Oliveira EE ，Du Y ，Dong K ... -  《Nature Communications》

Pyrethroid-Derived Acids and Alcohols: Bioactivity and Synergistic Effects on Mosquito Repellency and Toxicity.

Yang L ，Richoux GM ，Norris EJ ，Cuba I ，Jiang S ，Coquerel Q ，Demares F ，Linthicum KJ ，Bloomquist JR ... -  《-》