Commonly Used Insect Repellents Hide Human Odors from Anopheles Mosquitoes

Ali Afify, Joshua F. Betz, Olena Riabinina, Chloé Lahondère, Christopher J. Potter

Research output: Contribution to journalArticle

Abstract

The mode of action for most mosquito repellents is unknown. This is primarily due to the difficulty in monitoring how the mosquito olfactory system responds to repellent odors. Here, we used the Q-system of binary expression to enable activity-dependent Ca2+ imaging in olfactory neurons of the African malaria mosquito Anopheles coluzzii. This system allows neuronal responses to common insect repellents to be directly visualized in living mosquitoes from all olfactory organs, including the antenna. The synthetic repellents N,N-diethyl-meta-toluamide (DEET) and IR3535 did not activate Anopheles odorant receptor co-receptor (Orco)-expressing olfactory receptor neurons (ORNs) at any concentration, and picaridin weakly activated ORNs only at high concentrations. In contrast, natural repellents (i.e. lemongrass oil and eugenol) strongly activated small numbers of ORNs in the Anopheles mosquito antennae at low concentrations. We determined that DEET, IR3535, and picaridin decrease the response of Orco-expressing ORNs when these repellents are physically mixed with activating human-derived odorants. We present evidence that synthetic repellents may primarily exert their olfactory mode of action by decreasing the amount of volatile odorants reaching ORNs. These results suggest that synthetic repellents disruptively change the chemical profile of host scent signatures on the skin surface, rendering humans invisible to Anopheles mosquitoes.

Original languageEnglish (US)
Pages (from-to)3669-3680.e5
JournalCurrent Biology
Volume29
Issue number21
DOIs
StatePublished - Nov 4 2019

Keywords

  • Anopheles
  • DEET
  • GCaMP6
  • QF2
  • calcium imaging
  • human odorants
  • malaria mosquito
  • masking
  • olfaction
  • repellents

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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