Uh Oh. Mosquitoes Learn to Ignore DEET

New study shows one species can develop a short-term adaptation (and bite you anyway)

Travelers take note: Your DEET-laden repellent may not actually protect against mosquitoes, according to new research from the London School of Hygiene and Tropical Medicine.

When scientists evaluated the response of Aedes aegypti, a type of mosquito known to carry yellow fever and dengue fever, to DEET, they found that the insects were able to to ignore the smell up to three hours after being exposed to the chemical. The findings were published in the journal PLOS ONE.

Although DEET repels most insects, previous studies by Dr. James Logan—Chief Scientific Officer for the Arthropod Control Product Test Centre—suggested that some flies and mosquitoes have a genetic adaptation in their odor receptors that makes them immune to the smell.

In the new study, Logan and his colleagues discovered a short-term, rather than genetic, adaptation. Their research showed that a brief exposure to DEET made some mosquitos less sensitive to the repellent. Up to three hours later, the presence of DEET still did not deter these insects.

The scientists believe the shift could be due to a decrease in sensitivity of the mosquito’s odor receptors after previous exposure. In other words, they were habituating to the repellent.

Still, Logan and his team aren’t ready to write off repellents all together.

“This doesn't mean that we should stop using repellents–on the contrary, DEET is a very good repellent, and is still recommended for use in high risk areas,” he said in an interview with the London School of Hygiene and Tropical Medicine. “However, we are keeping a close eye on how mosquitoes can overcome the repellent and ways in which we can combat this."

Via Gadling and the London School of Hygiene and Tropical Medicine.