Scientists Uncover DEET Receptors in Insects and Create Repellent Alternatives

The insect repellent, DEET, has long been known to be an effective way to keep mosquitoes and other pests at bay. Yet it's also been tagged as a chemical that's not necessarily healthy to be exposed to in large amounts. Now, though, researchers have uncovered DEET-detecting olfactory receptors that cause the repellency in insects. This could potentially allow scientists to develop alternatives to DEET in the future.

DEET was first introduced in the 1940s and has largely remained unchanged since then. This is largely because the receptor in insects for DEET was unknown. Capable of dissolving plastics and nylon, DEET has been reported to inhibit an enzyme in mammals that's important in the nervous system; this means that it could potentially cause problems for people in areas where it's used frequently.

In order to examine the receptors that detect DEET, the researchers turned to Drosophila melanogaster, the fruit fly. This insect was genetically engineered in such a way that neurons activated by DEET glowed a fluorescent green. This allowed them to better examine how the chemical impacted the insect.

"Until now, no one had a clue about which olfactory receptor insects used to avoid DEET," said Anandasankar Ray, one of the researchers, in a news release. "Without the receptors, it is impossible to apply modern technology to design new repellents to improve upon DEET."

What did they see? It turned out that receptors, called lr40a receptors, are responsible for detecting the DEET. These receptors line the inside of a poorly studied region of the antenna called the sacculus.

That's not all the scientists did, though. They then looked for substitutes for DEET. In all, the researchers screened half a million compounds against the DEET receptor to find substitutes. A computer algorithm the team developed identified which compounds are not only predicted to be strong repellents but also found naturally in fruits, plants or animals. In the end, the computer predicted nearly 200 natural DEET substitutes and of these, the scientists narrowed it down to four. Three of these have already been approved by the Food and Drug Administration as food additives.

"Our three compounds, which we tested rigorously in the lab, do not dissolve plastics," said Ray. "They are approved by the Food and Drug Administration for consumption as flavors or fragrances, and are already being used as flavoring agents in some foods. But now they can be applied to bed-nets, clothes, curtains--making them ward off insects."

The findings are huge when it comes to the future of insect repellent. They could lead to a new generation of cheap, affordable repellents that protect humans in places where malaria and other insect-borne diseases are a huge problem.

The findings are published in the journal Nature.