Mosquitoes can become attracted to insect repellant, study suggests

New research indicates that mosquitoes can learn to associate the insect repellent chemical Deet with the presence of a blood meal, potentially making the repellent attractive rather than deterrent under certain conditions. The study, conducted by researchers at the University of Tours, France, found that mosquitoes previously exposed to Deet while feeding on warm blood were more likely to attempt biting when later exposed to Deet alone. This suggests that mosquitoes’ responses to repellents can be influenced by experience, challenging the long-held belief that repellents work solely through their chemical properties. The experiments showed that about 60% of mosquitoes trained to associate Deet with feeding attempted to bite a Deet-treated surface or a researcher’s Deet-covered hand, compared to significantly lower rates among untrained mosquitoes. These findings were published in the Journal of Experimental Biology and highlight the mosquitoes’ capacity for associative learning, similar to Pavlovian conditioning. The researchers observed that mosquitoes initially trapped near warm blood treated with Deet repeatedly tried to bite despite the repellent’s presence, indicating a learned attraction. Experts in the field, including Dr. Nina Stanczyk of ETH Zürich, acknowledged the importance of the study in understanding mosquito behavior and repellent effectiveness. However, they stressed that the findings do not undermine the overall utility of Deet-based repellents, which remain a critical tool in preventing mosquito bites and the transmission of deadly diseases such as dengue, malaria, Zika, and Japanese encephalitis. Health authorities continue to recommend products containing up to 50% Deet as a first-line defense for travelers and residents in mosquito-prone regions. The study’s implications suggest that while Deet remains effective, mosquito learning and adaptation could influence future repellent development and usage strategies. Understanding how mosquitoes modify their behavior in response to repellents may help improve protective measures and reduce the risk of vector-borne diseases worldwide.