Pyrethrins elicit olfactory response and spatial repellency in Aedes albopictus

Area of Science:

• Entomology
• Chemical Ecology
• Neuroscience

Background:

• Pyrethrum, derived from Chrysanthemum flowers, is a known botanical insecticide and repellent.
• Its insecticidal properties stem from six pyrethrin esters, which target voltage-gated sodium channels in insects.
• While pyrethrum's repellent use against mosquitoes is centuries old, the underlying mechanism remained unclear.

Purpose of the Study:

• To investigate the mechanism of pyrethrum-induced spatial repellency in Aedes albopictus.
• To identify specific pyrethrin compounds responsible for mosquito repellency.
• To explore the activation of olfactory receptors by pyrethrum components.

Main Methods:

• Electroantennogram (EAG) recordings were used to measure olfactory responses to pyrethrum vapor.
• Isolation of individual pyrethrin esters from pyrethrum extract.
• Behavioral assays to assess spatial repellency induced by specific pyrethrin compounds.

Main Results:

• Pyrethrum vapor induced dose-dependent EAG responses in Aedes albopictus antennae.
• Five of the six isolated pyrethrin esters elicited EAG responses.
• Pyrethrins I and II, cinerin II, and jasmolin II were found to induce spatial repellency, while cinerin I and jasmolin I did not.

Conclusions:

• Four pyrethrin compounds (pyrethrins I and II, cinerin II, jasmolin II) activate olfactory-receptor neurons and spatial repellency in Aedes albopictus.
• This research lays the groundwork for structure-function studies of pyrethrins and their olfactory receptors.
• Findings support the development of novel, effective mosquito repellents to combat vector-borne diseases.