New Study Reveals Surprising Insights About Deet and Mosquitoes
Widely recognized as an effective deterrent for mosquito bites, Deet may actually become appealing to these insects if they learn to associate it with feeding, according to new research.
Deet, or N,N-diethyl-meta-toluamide, is commonly found in bug repellents, with the UK Health Security Agency recommending products containing 50% Deet as the top choice for protection against mosquitoes. This protection is crucial since mosquito bites can transmit severe diseases like dengue, Japanese encephalitis, malaria, and Zika in various regions.
Interestingly, a recent study suggests that, much like Pavlov’s dogs learned to connect a bell with food, mosquitoes can also learn that the presence of Deet signals the potential for a blood meal.
Professor Claudio Lazzari from the University of Tours in France remarked that for years, it was assumed that repellents operated purely due to their chemical properties, either by being toxic or unpleasant to mosquitoes or by interfering with their ability to detect humans. However, he notes that their findings indicate that experiences can alter this reaction, representing a noteworthy shift in our comprehension of how repellents work.
Previous studies hinted that mosquitoes appeared less deterred by Deet after initial exposure, but the reasons behind this had remained unclear. In their research, documented in the Journal of Experimental Biology, the team first noted that trapped mosquitoes would attempt to bite a bag filled with warm blood that was just out of reach.
Upon further analysis, they discovered that about 60% of mosquitoes that fed while exposed to Deet later exhibited biting behavior when presented with Deet alone. This was notably more than the 17% of insects with no prior training, 13% that had initially been exposed to Deet alone, and 17% that had fed on warm blood without prior exposure to Deet.
In another experiment, nearly 60% of mosquitoes that had previously fed while near Deet tried to bite a researcher’s Deet-treated hand, contrasting sharply with the untrained mosquitoes that tried to bite the untreated hand.
Dr. Nina Stanczyk from ETH Zürich, who has investigated Deet’s effectiveness, expressed support for the findings. She highlighted how impressive it is that mosquitoes can link a strong repellent scent to food, suggesting this is something we should be mindful of moving forward.
However, experts are quick to reassure travelers not to abandon Deet. Lazzari emphasized that Deet remains effective under normal conditions, losing efficacy only in specific laboratory setups designed to showcase its effects on mosquitoes.
Professor Francesca Romana Dani, an entomologist at the University of Florence who did not participate in the study, pointed out that it’s improbable for mosquitoes to alter their response to Deet based on past experiences, especially since they may encounter various repellents during different feeding sessions.
She added that even though a mosquito can take multiple blood meals, these occur every few days, making it important to assess the duration of memory related to a prior meal influenced by Deet exposure.
Stanczyk reiterated that travelers should continue using repellents confidently. “The authors mentioned that it was tough to get mosquitoes to feed for the first time in the presence of Deet, and the highest risk of forming an association is when the repellent begins to fade,” she said. “So, the key takeaway for travelers is to reapply repellent regularly as per the product instructions.”
