— The mystery of how DEET repels mosquitoes and other bugs, has been solved by UC Riverside researchers.

Anandasankar "Anand" Ray, an associate professor of entomology at UC Riverside.— UC Riverside
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The scientists have found the exact target in the pests that causes DEET aversion. Using that knowledge, they have identified three chemicals which also repel mosquitoes, but don't dissolve plastics or pose toxicity risks, like DEET can.

Moreover, the chemicals are already approved for other uses, and so can be quickly incorporated into repellents against mosquitoes and other bugs. They're also cheaper than DEET, said Anandasankar "Anand" Ray, an associate professor of entomology, who led the research.

More and better repellents are needed to fight mosquito-borne diseases. Malaria kills 1.2 million people worldwide each year. Dengue, West Nile virus and yellow fever are also major public health risks in many countries.

The study was published Wednesday in the scientific journal Nature. An earlier study by Ray and colleagues on blocking mosquitoes from sensing their prey was published in Nature in 2011.

Ray and colleagues discovered the olfactory receptors that detect the presence of DEET. Called Ir40a receptors, they line the inside of a part of the antenna called the sacculus. The team then screened 500,000 chemicals with a computer algorithm for predicted activity against the receptors. They found nearly 200 potential DEET substitutes, then tested 10 of the most promising for repellent activity.

Eight of these 10 strongly repelled flies, and four of those tested on Aedes mosquitos also repelled them.

Of the four, three are food additives already approved by the U.S. Food and Drug Administration.

“All three compounds activated the same antennal cells in flies as DEET,” Ray said in a UCR press release. “What’s really encouraging is that some of these compounds may be affordable to produce in large quantities.
