Mosquitoes smell and avoid the insect repellent DEET

Zainulabeuddin Syed, Walter S. Leal

Research output: Contribution to journalArticlepeer-review

216 Scopus citations

Abstract

The insect repellent DEET is effective against a variety of medically important pests, but its mode of action still draws considerable debate. The widely accepted hypothesis that DEET interferes with the detection of lactic acid has been challenged by demonstrated DEET-induced repellency in the absence of lactic acid. The most recent hypothesis suggests that DEET masks or jams the olfactory system by attenuating electrophysiological responses to 1-octen-3-ol. Our research shows that mosquitoes smell DEET directly and avoid it. We performed single-unit recordings from all functional ORNs on the antenna and maxillary palps of Culex quinquefasciatus and found an ORN in a short trichoid sensillum responding to DEET in a dose-dependent manner. The same ORN responded with higher sensitivity to terpenoid compounds. SPME and GC analysis showed that odorants were trapped in conventional stimulus cartridges upon addition of a DEET-impregnated filter paper strip thus leading to the observed reduced electrophysiological responses, as reported elsewhere. With a new stimulus delivery method releasing equal amounts of 1-octen-3-ol alone or in combination with DEET we found no difference in neuronal responses. When applied to human skin, DEET altered the chemical profile of emanations by a "fixative" effect that may also contribute to repellency. However, the main mode of action is the direct detection of DEET as indicated by the evidence that mosquitoes are endowed with DEET-detecting ORNs and corroborated by behavioral bioassays. In a sugar-feeding assay, both female and male mosquitoes avoided DEET. In addition, mosquitoes responding only to physical stimuli avoided DEET.

Original languageEnglish
Pages (from-to)13598-13603
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number36
DOIs
StatePublished - Sep 9 2008

Keywords

  • DEET mode of action
  • DEET-detecting neuron
  • Fixative effect of DEET
  • Mosquito olfaction
  • Surface-landing bioassay

ASJC Scopus subject areas

  • General

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