Exposure to Deet Makes Some Mosquitoes Less Sensitive to Repellent

A new study reveals that mosquitoes ignore the smell of the insect repellent Deet after getting exposed to it for a brief period of time.

Deet is a strong repellent that was first developed by the U.S. military. Most insects are repelled by Deet. However, there have been concerns that the repellent is losing its effectiveness and some mosquitoes are becoming insensitive to its smell.

To study the effects of the repellent on the insects, a team of researchers from the London School of Hygiene & Tropical Medicine, U.K., tested the response of Aedes aegypti mosquitoes by luring them with a human arm covered in Deet.

Aedes aegypti mosquitoes bite during the day and are capable of transmitting dengue fever. The research team noticed that the mosquitoes were initially deterred by the substance for a few hours. But the insects later became less sensitive to the repellent. They found that the mosquitoes' insensitivity to the smell could be correlated to a decrease in the sensitivity of odor receptors on the mosquito's antennae after they were exposed to the substance for some time.

"We think that the mosquitoes are habituating to the repellent, similar to a phenomenon seen with the human sense of smell also. However, the human olfactory system is very different from a mosquito's, so the mechanism involved in this case is likely to be very different," explains researcher James Logan, from the London School of Hygiene & Tropical Medicine.

Earlier studies by Logan's research group have already shown that some flies and mosquitoes carry a genetic change in their odor receptors that make them insensitive to the repellent's smell. But this new study uncovers responses in mosquitoes to temporary olfactory changes that were taking place.

Logan insists that it is very important to understand both permanent genetic changes and short-term changes in the insects' odor receptors, reports BBC.

The researcher and his colleagues stressed that their findings should not stop people from using Deet, as it is a very good substance and recommended to be used in high risk areas. The team hopes the study will help scientists who are trying to develop new, effective versions of the mosquito repellent.

The findings of the study are published in the journal PLOS ONE.