A new study published in the Journal of Experimental Biology suggests that mosquitoes can actually learn to be attracted to DEET, a common ingredient used in insect repellents.
DEET, also known by its chemical name, N-diethyl-meta-toluamide, is widely used around the world to protect people from mosquito bites.
The UK Health Security Agency recommends repellents containing 50% DEET as one of the best ways to prevent mosquito bites.
The new research, led by behavioural physiologist Prof Dr Claudio Lazzari from the University of Tours in France, found that mosquitoes can be trained to connect the smell of DEET with getting a blood meal.
“For a long time, it was believed that repellents worked solely because of their chemical properties, either by being toxic or unpleasant to mosquitoes and driving them away, or by blocking their ability to detect humans.
“However, our findings suggest that the reaction can be modified by experience,” says Prof Lazzari.
“We believe this represents a significant change in our understanding of repellents.”
In the experiment, mosquitoes were first kept in a container linked to two chambers: one with clean air and the other with DEET.
At first, the insects were allowed to feed on warm artificial blood while exposed only to clean air.
Later, researchers introduced DEET while the mosquitoes were feeding, training them to associate the smell with food.
To test the results, trained and untrained mosquitoes were placed in small tubes.
One end had a person’s untreated hand, while the other had a hand sprayed with DEET repellent.
The trained mosquitoes tried to bite the DEET-covered hand, while the untrained mosquitoes avoided it.
The researchers found that nearly 60% of mosquitoes trained with blood and DEET tried to reach and bite the DEET-treated hand.
Meanwhile, untrained mosquitoes preferred the untreated hand instead.
“Mosquitoes have been shown to have impressive learning abilities, but the fact that they can associate such a strong repellent smell with their food and are then attracted to it afterwards is remarkable, and important for us to be aware of for the future,” Prof Lazzari says.
However, experts stressed that these findings do not mean people should stop using DEET-based repellents.
They explained that DEET still works effectively in normal use. – dpa
