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Researchers are close to a better mosquito repellent

Tue., May 27, 2008

WASHINGTON – Researchers have identified seven possibilities for the next generation of mosquito repellent, some of which may work several times longer than the current standard-bearer, DEET. The next step: safety testing to make sure they’re not harmful.

While the new repellents aren’t likely to be available commercially for a few years, early tests on cloth were promising, with some chemicals repelling mosquitoes for as long as 73 days and many working for 40 to 50 days, compared to an average of 17.5 days with DEET, according to a study in today’s edition of Proceedings of the National Academy of Sciences.

Biting insects such as mosquitoes and ticks can spread diseases such as encephalitis, Lyme disease, Rocky Mountain spotted fever, malaria and dengue fever.

Several of the new chemicals “were just phenomenal,” said Ulrich R. Bernier, a research chemist at the Agriculture Department’s mosquito and fly research unit in Gainesville, Fla. “I was so surprised.”

Bernier, a co-author of the study, said he regularly receives new repellents from people and he ends up writing them back to say they don’t work.

In this case, researchers funded by the Defense Department set out to determine what makes repellents work, and then to use that information in finding more effective ways to chase away disease-carrying insects, Bernier explained in a telephone interview.

“We thought, can we do a better job of designing repellents?” Bernier said.

Using USDA data on hundreds of chemicals collected over 50 years, researchers led by Alan R. Katritzky of the University of Florida rated chemicals from “1” to “5” on ability to repel insects, and then focused on what the most effective ones – the 5s – had in common.

Focusing on a type of chemical known as N-acylpiperidines, they narrowed the study to 34 molecules – 23 that had never been tested before and 11 that had – Bernier explained.

From those, the 10 most effective were narrowed to seven, with eliminations based on concerns about toxicity and high cost to produce.

The tests were done on cloth treated with the chemicals and then placed on the arms of volunteers.

This summer, safety tests will begin on the seven, Bernier said, to make sure they are safe to use directly on the skin.

While the military is paying for the research, any success is expected to benefit the general public too.


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