Key Findings
A new study in the Journal of Experimental Biology reveals that mosquitoes can learn to associate the repellent Deet with the possibility of a blood meal, potentially altering their behavior.
The Study's Results
Under laboratory conditions, 60% of mosquitoes that had previously fed on warm blood while exposed to Deet subsequently attempted to bite when exposed to Deet alone. This rate was significantly higher than in control groups. In a separate test, nearly 60% of trained mosquitoes attempted to bite a researcher's Deet-treated hand, while untrained mosquitoes universally avoided it.
Understanding Deet and Its Use
Deet (N,N-diethyl-meta-toluamide) is a common insect repellent, recommended by the UK Health Security Agency at 50% concentration for protection against mosquitoes, which can transmit diseases such as dengue, malaria, and Zika. Previous studies observed reduced aversion to Deet after exposure, but the reason was unclear.
Expert Perspectives on the Findings
"The findings suggest a repellent's effect can be modified by experience, challenging the belief that repellents work solely through chemical properties."
— Prof. Claudio Lazzari, University of Tours, France
"While mosquitoes have learning abilities, the association with a strong repellent is remarkable and important to be aware of for the future."
— Dr. Nina Stanczyk, ETH Zürich
What This Means for the Public
Experts emphasize that the findings do not imply Deet loses effectiveness in normal use. The observed behavior change occurred under specific laboratory conditions designed to reveal the mechanism.
"It is unlikely mosquitoes would change their response under normal conditions, given varying repellents and the time between blood meals."
— Prof. Francesca Romana Dani, University of Florence
Dr. Stanczyk advises travelers to continue using repellents and to reapply as directed, noting that the risk of association is highest when the repellent wears off.