Researchers Identify DEET-Detecting Receptors in Insects, Find Natural Substitutes for Chemical

Researchers at the University of California, Riverside, have discovered receptors in pests that detect DEET, a yellowish oil used in making insect-repellents.

They have also found three substitute chemicals that can mimic the effects of DEET without posing any toxicity risks. The new DEET-like chemicals can be used to fight diseases like malaria and West Nile Virus.

N, N-diethyl-m-toluamide, or DEET has been used to repel mosquitoes and ticks for more than 65 years now. However, experts weren't able to improve the chemical as DEET-receptors in insects remained unidentified over the years.

In the latest study, researchers identified three receptors that detect DEET.

The scientists examined all sensory neurons in insects to locate the receptors that were detecting DEET. They then conducted experiments on genetically-altered fruit flies (Drosophila melanogaster). These flies were designed in such a way that their DEET-detecting neurons glowed fluorescent green.

Researchers found that Ir40a receptors, which are present inside the sacculus, were responsible for detecting the chemical. Sacculus is located in the antenna of the insect and very few studies have described the function of this region.

"Until now, no one had a clue about which olfactory receptor insects used to avoid DEET. Without the receptors, it is impossible to apply modern technology to design new repellents to improve upon DEET," said Anandasankar Ray, an associate professor of entomology, lead author of the study.

The U.S. Army developed DEET in 1946 and it was registered for use by the general public in 1957. Currently, over 140 products containing DEET are in the market and a third of all people living in the U.S. use the chemical.

This study suggests that pretty soon we might see a newer range of cheap chemicals that can repel mosquitoes effectively.

Ray's lab screened nearly 500,000 compounds to find the ones that can be detected by olfactory receptors in pests. An algorithm developed by the team found 200 plant or animal-based compounds that could act as substitutes for the chemical. Of these, the team tested 10 compounds and found that eight of them could repel flies. Interestingly, three compounds are already approved by the U.S. Food and Drug Administration as food additives.

"All three compounds activated the same antennal cells in flies as DEET," Ray said in a news release.  "What's really encouraging is that some of these compounds may be affordable to produce in large quantities.  In the future, using this algorithm, we could find chemicals that activate DEET receptors but are substantially different, with far better properties than DEET. We could find truly novel repellants that have remarkable properties such as large spatial protection and long-term protection."

The study is published in the journal Nature.