How DEET repels the world’s ‘most deadly animal’

"Mosquitoes are considered the most deadly animals on the planet, but unfortunately, not everyone who needs this repellent can afford to use it, and not all who can afford it can use it due to its undesirable properties such as an unpleasant odor," says Walter Leal. (Credit: iStockphoto)

Scientists have discovered just how DEET repels mosquitoes.

They also have identified a plant defensive compound that might mimic DEET, a discovery that could pave the way for better and more affordable insect repellents.

More than 200 million people worldwide use DEET, developed by scientists at the US Department of Agriculture and patented by the US Army in 1946.

“Mosquitoes are considered the most deadly animals on the planet, but unfortunately, not everyone who needs this repellent can afford to use it, and not all who can afford it can use it due to its undesirable properties such as an unpleasant odor,” says lead author Professor Walter Leal of the molecular and cellular biology department.

“Vector-borne diseases are major health problems for travelers and people living in endemic regions,” Leal says. “Among the most notorious vectors are mosquitoes that transmit the protozoan parasites causing malaria and viruses that cause infections, such as dengue, yellow fever, chikungunya, and encephalitis.”

How mosquitoes smell

Mosquitoes detect scents with olfactory receptors on their antennae. The researchers examined two families of olfactory receptors of the southern house mosquito, Culex quinquefasciatus, which transmits diseases such as West Nile virus.

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One receptor group, “ionotropic receptors,” normally detects acids, bases, and other water-soluble compounds. The researchers discovered, however, that a receptor from the odorant receptor group is directly activated by DEET.

They also detected a link between DEET and the compound methyl jasmonate, suggesting that DEET might work by mimicking a defensive chemical found in plants.

Dan Strickman, senior program officer for vector control at the Bill and Melinda Gates Foundation’s Global Health Program, says, “We are at a very exciting time for research on insect repellents.” (The Gates Foundation was not involved in the study.)

“For decades, the field concentrated on screening compounds for activity, with little or no understanding of how chemicals interacted with mosquitoes to discourage biting. Use of modern techniques that combine molecular biology, biochemistry, and physiology has generated evidence on how mosquitoes perceive odors,” Strickman says.

Findings from the study appear in the Proceedings of the National Academy of Sciences.

Mosquito researcher Anthony Cornel, an associate professor with the UC Davis entomology and nematology department and based at the Kearney Agricultural Research and Extension Center, Parlier, provided mosquitoes that allowed the Leal lab to duplicate his mosquito colony at UC Davis. Richard Benton of the University of Lausanne, Switzerland, shared his flies, Drosophila plasmids, which are also part of the research.

The National Institute of Allergy and Infectious Diseases of the National Institutes of Health supported the work.

Source: UC Davis