Experts have advised travellers to keep using Deet-based products despite findings that mosquitoes can learn to associate the chemical with a blood meal, potentially becoming attracted to it.
Study Reveals Mosquitoes Can Learn to Associate Deet with Food
Deet, or N,N-diethyl-meta-toluamide, is a widely used insect repellent recommended by the UK Health Security Agency in products containing 50% Deet to protect against mosquito bites. This protection is crucial as mosquitoes can transmit fatal diseases such as dengue, Japanese encephalitis, malaria, and Zika.
However, new research published in the Journal of Experimental Biology suggests that mosquitoes can learn to associate the presence of Deet with the possibility of a blood meal, similar to Pavlov's dogs learning to associate a bell with food. Professor Claudio Lazzari from the University of Tours, France, stated, "For a long time, it was believed that repellents worked solely because of their chemical properties... However, our findings suggest that the reaction can be modified by experience."
Experimental Findings
The researchers initially observed trapped mosquitoes attempting to bite a bag of warm blood they couldn't reach. Further investigation revealed that 60% of mosquitoes that fed when presented with warm blood alongside Deet subsequently showed biting attempts when exposed to Deet alone. In contrast, only 17% of untrained mosquitoes, 13% exposed to Deet alone, 17% that fed on warm blood without Deet, and 23% that fed on warm blood with non-simultaneous Deet exposure showed similar behavior.
In another test, nearly 60% of mosquitoes that previously fed on blood while exposed to Deet later attempted to bite a researcher's Deet-treated hand, while untrained mosquitoes universally preferred the untreated hand.
Expert Reactions
Dr. Nina Stanczyk of ETH Zürich, who has studied Deet's effectiveness, welcomed the research, noting, "Mosquitoes have been shown to have impressive learning abilities, but the fact they can associate such a strong repellent smell with their food and are then attracted to it afterwards is remarkable."
However, experts emphasize that these findings do not mean travellers should stop using Deet. Professor Lazzari clarified, "People should understand that Deet does not lose its effectiveness through normal use, but only under specific laboratory conditions." Professor Francesca Romana Dani from the University of Florence added that under normal conditions, mosquitoes are unlikely to change their response to Deet due to factors like different repellents encountered and the duration of memory.
Stanczyk advised travellers to continue using repellents confidently, stressing the importance of regular reapplication as per product instructions to ensure ongoing protection.
