Cattle-Derived Unsaturated Aldehydes Repel Biting Midges and Mosquitoes.

Area of Science:

• Entomology
• Chemical Ecology
• Vector Biology

Background:

• Host-derived repellents offer novel strategies for managing disease vectors and nuisance pests.
• Commercial repellents are often unavailable or ineffective against certain species, such as Culicoides biting midges.

Purpose of the Study:

• To identify novel host-derived volatile organic compounds (VOCs) that repel Culicoides nubeculosus.
• To evaluate the repellent efficacy of identified compounds against disease vector mosquitoes.

Main Methods:

• Revised criteria for identifying bioactive VOCs in cattle hair headspace odor.
• Gas chromatography-electroantennographic detection (GC-EAD) to assess antennal responses.
• Behavioral assays to evaluate repellent responses in Culicoides nubeculosus and mosquito species.

Main Results:

• Identified (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, and (E)-2-nonenal as differentially present in cattle odor and eliciting antennal responses in C. nubeculosus.
• A blend of these unsaturated aldehydes elicited a strong aversive response in C. nubeculosus.
• The blend demonstrated superior repellent activity against Aedes aegypti, Culex quinquefasciatus, and Anopheles coluzzii compared to commercial repellents.

Conclusions:

• A host-derived repellent odor blend of unsaturated aldehydes was identified.
• This blend effectively repels biting midges and disease vector mosquitoes, outperforming commercial repellents.
• The findings provide a new tool for integrated vector management strategies.