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Davis, California

Monday, June 5, 2023

New research may lead to advancements in mosquito and disease control

Mosquitoes bite; it’s no revelation. But amid new research, scientists now know what entices them to do so – blame it on the nonanal.

Pronounced “nawn-uh-nawl,” it is a chemical naturally produced in humans and acts as the dominant odor that attracts blood-feeding Culex mosquitoes, according to a study recently published by UC Davis entomology professor Walter Leal and postdoctoral researcher Zain Syed, in the Proceedings of the National Academy of Sciences.

To humans, nonanal smells like roses. To Culex mosquitoes, it smells like lunch.

“Before, we knew that mosquitoes were attracted to carbon dioxide,” Leal said. “But this is the first time anyone has shown they’re attracted to nonanal.”

It’s true that mosquito bites can be irritating. But much more importantly, they can transmit diseases such as West Nile virus, malaria and dengue fever, making the study a significant development in the progress toward mosquito and disease control, researchers say.

“Leal and Syed have identified a human odor that is detected with great sensitivity by the antennae of mosquitoes that transmit West Nile virus,” said Yale University professor John Carlson, a leading scientist in insect olfaction in a press release. “In addition to its scientific interest, the study may have important practical applications in the control of these mosquitoes and the diseases they carry.”

Infected mosquitoes, which become carriers of the virus after they feed on infected birds, most commonly spread West Nile virus to humans and other animals.

Since 1999, there have been 1,147 deaths from West Nile virus in the United States and 23 deaths in 2009 thus far, according to the U.S. Centers for Disease Control.

Currently, mosquitoes are largely controlled with pesticides, Leal said.

“But now that the effects of nonanal are better understood, we may be able to develop ways to direct and control mosquitoes with attraction instead of deterrents. Pesticides can be centralized instead of being spread everywhere.”

After testing hundreds of naturally produced chemicals from humans and birds, the researchers determined the specificity and sensitivity of those compounds to the mosquitoes’ antennae.

Leal and Syed then found that nonanal acts synergistically with carbon dioxide to increase trap captures by more than 50 percent, compared to mosquito traps with carbon dioxide alone, according to a press release.

Though this research makes significant strides toward mosquito control, researchers still do not understand the effects of nonanal concentration on attraction or the reasons why mosquitoes are more attracted to some humans compared to others.

Leal says there is still work to be done.

“This research will have significant implications,” Leal said. “But there are many steps that take a long time. Labs here at Davis are working on them.”

DAVID LAVINE can be reached at features@theaggie.org.