Chemical cocktail in skin summons disease-spreading mosquitoes
Aedes aegyptii mosquito biting a person. Credit: CDC

Humans have a scent that guides mosquitoes toward their victims. Until now, the exact composition of that scent has not been determined.

The combination of carbon dioxide and two chemicals caused a mosquito to locate and land on its victim. The use of mouth parts to find blood is encouraged by this cocktail.

The chemical mixture seems to attract female Aedes aegypti mosquitoes, the main carriers of the Zika and chikungunya viruses. The mosquito originated in Africa and has spread around the world.

The journal Scientific Reports contains details of the new research finding. Many of the compounds that attract mosquitoes don't work quickly. Ring Cardé said that this one does.

Carbon dioxide, sight, temperature, and humidity are some of the things that mosquitoes use to find their victims. According to Cardé's research, skin odors are more important than ever for finding a biting site.

The mosquitoes land on targets that are not associated with heat or humidity. Skin odor is the main guiding factor.

Cardé wanted to find out the exact chemicals that make our scent so potent for mosquitoes. Lactic acid was one of the chemical elements in the odor cocktail as far back as 1968.

Carbon dioxide, ammonia, and other chemicals produced by humans attract these mosquitoes. According to Cardé, the other chemicals were not strong attractants.

Chemical cocktail in skin summons disease-spreading mosquitoes
A sock and glass beads used to trap human sweat scent for the mosquito research. Credit: Jan Bello/UCR

There was something undiscovered about the chemistry of the odors that attracted the mosquito. I wanted to make sure the blend was perfect.

The methods used to identify these chemicals wouldn't work for 2-ketoglutaric acid. This acid would not have been separated by gas chromatography.

"I think that these chemicals may not have been found before because of the complexity of the human odor profile and the minute amounts of these compounds present in sweat," said chemist Jan Bello, formerly of U CR and now with insect pest control company Provivi.

Cardé was looking for mosquito attractors when he turned to Bello. He filled his socks with glass beads and spent four hours walking around with them.

The beads felt like a massage, like squeezing stress balls full of sand, but with your feet. It would be uncomfortable after a while because they would get stuck in between your toes.

It was worth the hassle. The mosquitoes responded to the chemicals that were isolated from the sweat on the socks. The most active combination came out in this way.

Future studies will determine if the same compound is effective for any other mosquitoes and why people are bitten differently. No one knows why some mosquitoes are more attractive than others.

The research team is hopeful that their discovery can be used to kill disease-spreading mosquitoes.

We weren't sure if we would find these compounds, but at the end of the day, we're really happy we did. We had a hunch, but they don't always work out.

More information: Scientific Reports (2022). DOI: 10.1038/s41598-022-19254-w Journal information: Scientific Reports