To solve the age-old question of why mosquitoes eat some people alive but spare others, scientists built a large, inflatable platform in Zambia and let half a dozen people sleeping in nearby tents smell them. They discovered that malaria-carrying mosquitoes, like those that carry yellow fever, are attracted to specific chemicals on human skin.
They identified a lucky individual whose unique body odor seemed relatively unappealing and opened a new avenue in the search for ways to prevent bites.
At close range, mosquitoes use visual cues and body heat to locate their prey. But when they’re out of sight—a few dozen feet away—they’re thought to track carbon dioxide and other chemicals in body odor and breath. It is the right mix of active research environments that mosquitoes find most compelling.
Experiments on mosquitoes are usually conducted in relatively small boxes or wind tunnels, free from the aromatic cacophony of the real outdoors. But such experiments tend to mimic mosquito decisions at close range. So scientists built a massive new platform to reach the needs of mosquitoes in the wild.
“I like to think of mosquitoes as the world’s largest mosquito repellent,” said Connor McMeniman, assistant professor of molecular microbiology and immunology at the Johns Hopkins Malaria Research Institute, who led the study. In the magazine Current biology.
How do mosquitoes choose their targets?
Mosquitoes are the deadliest predators of humans, carrying diseases such as malaria, yellow fever and dengue fever that kill more than half a million people each year.
Anopheles gambiae, one of the malaria-carrying species, is a particularly dangerous predator. They are different. Assumptions How far Mosquitoes flyBut they tend to run less than half a mile a day, he says A study From West Africa. They typically feed around midnight, flying into the eaves of people’s open houses. 2,000 people die from malaria every year in Zambia.
Scientists built an outdoor test area the size of two tennis courts, or 2,000 times larger than a typical lab setup, to learn how these mosquitoes attack their sleeping victims. They let the mosquitoes into their open-air lab. Then the researchers did everything they could to satisfy the right feeling.
At stations scattered around the arena, air-conditioning ducts offered hugs to various people sleeping in nearby tents. At each station, there are hot plates heated to human body temperature next to piped aromas alongside carbon dioxide burners.
With an infrared camera, scientists saw which hot plates were mosquito discos. They found that heat and carbon dioxide are not enough to attract insects without the additional smell of human body.
“This study adds a lot,” said Leslie Vosshall, a neurobiologist and chief science officer at the Howard Hughes Medical Institute, who recently found that skin chemistry is a magnet for the different species of mosquitoes that carry yellow fever.
“This is a different mosquito — a very important mosquito,” Vosshall said of Anopheles gambiae. “This mosquito kills orders of magnitude of people… It’s a true top predator of humans.”
The research shows that the mosquitoes are particularly attuned to the sebum secretions that produce skin and protect it from microbes. Chemical compounds called carboxylic acids are a strong draw — both in the new study and in Vosshall’s work with Ades Egypt.
But in the new study, an individual was relatively unpleasant, the researchers. Their signature scent is unusually low in carboxylic acids and high in eucalyptus, a substance found in many plants, and diet may play a role, McMenamin said.
What’s next for mosquito researchers?
Now that the researchers have shown that their test site works, they are planning a much larger experiment pitting 120 sleepers against each other to see who is more resistant to mosquitoes. .
They hope to understand what chemical combination makes one person more or less attractive than others. They also study how things like diet or the microorganisms on people’s skin – the skin microbiome – influence their attractiveness. McMeniman also dreams of building a similar facility in the United States to test mosquito species that spread disease and spoil backyard barbecues.
Insights from such experiments could lead mosquitoes to rehabilitate themselves, perhaps by finding ways to alter skin chemistry or hide, making them less attractive to humans.
But the quest to explain why mosquitoes prefer some people over others may not be an easy answer. Previous experiments have shown that pregnant women are more likely to attract mosquitoes. Drinking alcohol attracts mosquitoes. Using certain types of soap, even those scented with chemicals known to repel mosquitoes, paradoxically increases the attractiveness of humans to mosquitoes.
“The most important thing for mosquitoes is not the type of chemical in abundance, but those chemical interactions and relative abundances,” said Clement Vinauger, assistant professor of biochemistry at Virginia Tech. He soon Four commonly used soaps were tested And while three people added to their attractiveness to Aedes aegypti mosquitoes, one—a native coconut and vanilla body wash—seemed to decrease it, perhaps because mosquitoes don’t like coconut oil.
“The short answer is it’s a complex problem,” Vinauger said.