Chemical cocktail in skin summons disease-spreading mosquitoes: Scent serves as GPS for quick-to-bite disease vectors

Mosquitoes that spread Zika, dengue and yellow fever are guided toward their victims by a scent from human skin. The exact composition of that scent has not been identified until now.

A UC Riverside-led team discovered that the combination of carbon dioxide plus two chemicals, 2-ketoglutaric and lactic acids, elicits a scent that causes a mosquito to locate and land on its victim. This chemical cocktail also encourages probing, the use of piercing mouthparts to find blood.

This chemical mixture appears to specifically attract female Aedes aegypti mosquitoes, vectors of Zika as well as chikungunya, dengue, and yellow fever viruses. This mosquito originated in Africa, but has spread to tropical and subtropical regions worldwide, including the U.S.

This new research finding, and how the team discovered it, is detailed in the journal Scientific Reports. “Though others have identified compounds that attract mosquitoes, many of them don’t elicit a strong, rapid effect. This one does,” said Ring Cardé, UCR entomologist.

Mosquitoes use a variety of cues to locate their victims, including carbon dioxide, sight, temperature, and humidity. However, Cardé’s recent research shows skin odors are even more important for pinpointing a biting site.

“We demonstrated that mosquitoes land on visually indistinct targets imbued with these two odors, and these targets aren’t associated with heat or moisture,” Cardé said. “That leaves skin odor as the key guiding factor.”

Given the significance of odor in helping mosquitoes successfully feed on humans, Cardé wanted to discover the exact chemicals that make our scent so potent for the insects. Part of the equation, lactic acid, was identified as one chemical element in the odor cocktail as long ago as 1968.

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