Study Reveals Mosquitoes Can Learn to Like DEET, Challenge to Insect Repellents

Mosquitoes may be able to learn to associate the smell of DEET, one of the most powerful insect repellents available, with food and potentially become attracted to it, according to a study published in the Journal of Experimental Biology.

The research indicates that while DEET is designed to keep insects away, certain conditions can lead mosquitoes to associate the chemical scent with a reward, such as blood or sugar.

The study was a collaboration between Claudio Lazzari at the University of Tours in France and Clément Vinauger, an associate professor at Virginia Tech within the Department of Biochemistry in the College of Agriculture and Life Sciences.

Researchers focused their study on the yellow fever mosquito, Aedes aegypti. This species is known for spreading chikungunya, yellow fever, Zika, and dengue fever, affecting tens of millions of people annually.

To test the mosquitoes’ ability to learn, the team used Pavlovian conditioning. In this process, mosquitoes were restrained behind fabric mesh with a bag of warm blood placed just out of their reach.

Once the insects began to feed on the blood, the researchers introduced the scent of DEET. After repeating this process four times, more than 60% of the mosquitoes attempted to feed when they were presented with the smell of DEET alone.

The team further tested this behavior by offering mosquitoes a choice between two human hands: one that was untreated and one coated with normal concentrations of DEET.

While untrained mosquitoes avoided the hand treated with DEET, the trained mosquitoes were drawn toward it.

The researchers also observed that mosquitoes could form this same association if sugar was used as the reward instead of blood.

Vinauger, who is also an affiliate of the Fralin Life Sciences Institute’s Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, noted that this finding challenges the traditional understanding of how repellents function.

The prevailing assumption has been that DEET works through chemistry—either by smelling unpleasant to mosquitoes or by preventing them from detecting the scent of humans.

However, this study suggests that the brain of a mosquito can rewrite its response to the chemical based on its experiences.

“If someone applies DEET and the concentration fades over time, but a mosquito still manages to feed, the insect may begin associating that smell with a reward,” Clément Vinauger

Despite these findings, Vinauger stated that people should not stop using DEET, as it remains highly effective, particularly in regions where mosquito-borne diseases are common.

The study does suggest that the timing and concentration of the repellent are more critical than previously thought.

Vinauger suggested that rather than applying a large amount of repellent at once, users may find it more effective to reapply regularly to ensure the protection remains active and continuous.

He also noted that clothing treated with DEET could present specific challenges, as the concentration of the chemical in the fabric tends to decline over time.

This research builds upon Vinauger’s previous work on mosquito behavior, which began during his PhD in Lazzari’s lab and continued during his time as a postdoctoral researcher at the University of Washington.

His prior experiments demonstrated that mosquitoes can remember and avoid hosts that swat at them, use a combination of vision and smell to track humans, and respond differently to various body soaps.

At Virginia Tech, Vinauger’s lab continues to study how mosquitoes process sensory information to adapt to their environments and locate hosts.

Vinauger believes that understanding these behavioral and neural mechanisms is essential for public health, especially as insecticide resistance increases and Aedes aegypti moves into new geographic regions.

He described the ability of mosquitoes to keep outsmarting our control strategies as a primary reason why researchers must understand the insects at the behavioral, neural, and molecular levels.