The soap you use could attract mosquitoes 1:08

(CNN) --

Anyone who has spent a summer afternoon swatting away mosquitoes, or a day scratching bites, will agree: Mosquitoes are the worst.

But the smells we humans produce are an important part of what attracts mosquitoes to us.


In a study published in May 2023, scientists helped determine the different body odor chemicals that attract these insects by building a testing area the size of an ice rink and introducing the odors of several people.

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Mosquitoes belong to the fly family and most of the time they feed on nectar.

However, females preparing to produce eggs need a meal with extra protein: blood.

At best, a bite will only leave you with a red, itchy bump.

But mosquito bites often turn deadly because of the parasites and viruses they transmit.

One of the most dangerous diseases is malaria.

Malaria is a blood-borne disease caused by microscopic parasites that settle in red blood cells.

When a mosquito bites a person infected with malaria, it inhales the parasite along with the blood.

After developing in the mosquito's stomach, the parasite "migrates to the salivary glands and is then spit back onto the skin of another human host when the mosquito returns to a blood meal," explains Dr. Conor McMeniman, associate professor of Microbiology. and Immunology at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Malaria Research Institute in Baltimore.

Malaria was eradicated in the United States in the last century thanks to window screens, air conditioning and improvements in drainage systems where aquatic mosquito larvae can grow, but the disease remains a danger to much of the world.

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"Malaria continues to cause more than 600,000 deaths a year, especially in children under 5 years of age, and also in pregnant women," says McMeniman, lead author of the new study published in the academic journal Current Biology.

"It inflicts a lot of suffering around the world, and part of the motivation for this study was to try to really understand how mosquitoes that transmit malaria find humans."

McMeniman, along with Bloomberg postdoctoral researchers and first authors of the study, Drs. Diego Giraldo and Stephanie Rankin-Turner, focused on

Anopheles gambiae

, a species of mosquito found in sub-Saharan Africa.

They partnered with the Macha Research Trust of Zambia, led by Dr. Edgar Simulundu, scientific director.

"We were very motivated to develop a system that would allow us to study the behavior of the African malaria mosquito in a habitat that mirrored its natural habitat in Africa," explains McMeniman.

The researchers also wanted to compare the olfactory preferences of mosquitoes between different humans, observe the insects' ability to track odors at distances of 20 meters and study them during their most active hours, between 10 at night and 2 in the morning. .

Researchers set up a screen the size of a skating rink to help understand how mosquitoes that transmit malaria find humans.

Credit: Julien Adam

To meet all these requirements, the researchers created a protected facility the size of a skating rink.

Around the perimeter of the facility were six tents with mosquito nets where study participants would sleep.

Air from the tents, containing the participants' characteristic breath and body odor, was pumped through long tubes to the main facility onto absorbent pads, heated and infused with carbon dioxide to mimic a sleeping human being.

Hundreds of mosquitoes in the main facility, measuring 20 by 20 meters, were then served a buffet of the smells of the sleeping subjects.

Infrared cameras followed the movement of the mosquitoes towards the different samples.

(The mosquitoes used in the study were not infected with malaria and could not reach sleeping humans.)

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Researchers discovered what many picnickers can attest: Some people attract more mosquitoes than others.

What's more, chemical analyzes of the stores' air revealed the odor-causing substances that did or did not attract mosquitoes.

The mosquitoes were most attracted to carboxylic acids in the air, including butyric acid, a compound present in "stinky" cheeses like Limburger.

These carboxylic acids are produced by bacteria on human skin and are not usually noticeable to us.

While the carboxylic acids attracted mosquitoes, another chemical called eucalyptol, present in plants, seemed to deter them.

The researchers suspected that a sample with a high concentration of eucalyptol could be related to the diet of one of the participants.

Simulundu said finding a correlation between chemicals present in different people's body odor and mosquitoes' attraction to those odors was "very interesting and exciting."

"This finding opens up approaches to develop lures or repellents that can be used in traps to alter the host-seeking behavior of mosquitoes, thereby controlling malaria vectors in regions where the disease is endemic," said Simulundu, co-author of the study.

Dr. Leslie Vosshall, a neurobiologist and vice president and chief scientific officer at the Howard Hughes Medical Institute, who was not involved in the study, was equally enthusiastic.

"I think it's a very interesting study," she said.

"It is the first time that an experiment of this type has been done on this scale outside the laboratory."

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Vosshall researches another species of mosquito that spreads dengue, Zika and chikungunya.

In a study published last year in the academic journal Cell, she and her colleagues discovered that this species of mosquito also seeks out the odor of carboxylic acids produced by bacteria on human skin.

The fact that these two different species respond to similar chemical signals is positive, she says, because it could make it easier to create mosquito repellents or traps in general.

The research may not have immediate consequences for avoiding insect bites at the next barbecue.

Vosshall noted that even scrubbing with unscented soap doesn't eliminate the natural odors that attract mosquitoes.

However, he noted that the new work "gives us some really good clues about what mosquitoes use to hunt us, and understanding what it is is essential for us to take the next steps."

-- Kate Golembiewski is a Chicago-based freelance science writer with a passion for zoology, thermodynamics, and death.

She hosts the comedy show "A Scientist Walks Into a Bar."

Editor's note:

This article was originally published in May 2023 and has been updated.

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