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Mosquitoes and human diseases: understanding how they smell we can save lives



It is not yet known how effective mosquitoes that can bite can track us, but this is important because they not only make us itchy. They also carry dangerous diseases such as Zika virus, dengue fever, West Nile virus and malaria, which can be fatal.

In fact, stopping these nasty insects in their tracks can save up to 500,000 lives per year due to these diseases.

Caroline Lindy McBride, assistant professor of ecology and evolutionary biology at the Princeton School of Neuroscience, said: “In every case, mosquitoes have evolved to bite. This happens only two or three times. New Jersey graduate School.

This is why she wants to understand how they find and target humans.

Mosquitoes can smell us

McBride said: “Most mosquitoes choose what they want to bite based on smell.”

; His laboratory focuses on the evolution of Aedes aegypti mosquitoes, which have evolved specifically to bite humans.

Only female mosquitoes suck blood because they need eggs to lay eggs. The key question is to understand how a potentially disease-carrying female mosquito can sniff out a person and ignore other warm-blooded animals.

Shown here are the female mosquitoes of the African subspecies Aedes aegypti formosus that bite humans (left) and the global invasive subspecies Aedes aegypti aegypti that bites humans (right).

Christopher Porter, associate professor of neuroscience at the Center for Sensory Biology at Johns Hopkins University, said that once people know this, they can create more effective insect repellents (or baits to lure mosquitoes away from humans) to save life.

If scientists can control their sense of smell, “we can really control what these mosquitoes are doing.” Porter studied another human-specific malaria-carrying mosquito, Anopheles.

Our smell is complicated

This is not an easy question to answer, because the smell of any animal is made up of hundreds of compounds mixed together in a specific ratio.

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McBride said: “The actual chemicals found in human odors are basically the same as those found in animal odors. This is the only thing that is unique in the proportion and relative abundance of these compounds in the human mixture.”

Every time a hungry female mosquito flies by, it performs complex chemical mathematical operations in its tiny brain to figure out what is a human, what is a dog, and what is a flower.

Smell library

“In order to investigate, we decided to record neural activity in women’s brains while exposing them to natural human and animal odor extracts,” Zhilei Zhao, a graduate student in the McBride laboratory, described the laboratory’s work on Twitter. Wrote in the post. Zhao wrote that it took four years to develop “necessary genetic reagents, odor delivery systems and analytical methods.”
(From left) Postdoctoral researchers Noah Rose and Gilbert Bianquinche of Princeton University investigate the larvae of Aedes aegypti in a tree hole near Kedougou, Senegal. More than half of the world's population lives in areas where Aedes aegypti exists.

McBride’s laboratory team created a database of the chemical composition of animal odors. Jessica Zung, a graduate student in McBride’s lab, said: “The data set does not actually exist, so we decided to collect it ourselves.”

So far, Zung has collected odor samples from about 40 different animals (including guinea pigs, rats, quail, etc.).

A common compound stands out

Comparing some of these samples with 16 human samples, some problems were found. Zong said that Decanal is a simple, common compound that is especially abundant in human skin.

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In nature, ubiquitous in humans, de water comes from another more complex compound. Zung looked through the archives to find research from the 1970s (most of which were to find a cure for acne), which detailed how lignin, a component of the skin’s natural oils, was broken down and what was left can water. This acid (as its name suggests) is only found in humans. This may be the cause of high levels of de water, which helps mosquitoes smell our odor, but more research is needed.

Understanding what the mosquitoes smell is only part of the story; it is also important to understand how they work. In order to understand exactly how mosquitoes use this feeling, scientists have bred genetically modified Aedes aegypti so that we can cut their tiny heads and place them under a fancy microscope and observe how they are exposed to humans and animals. The firing of neurons during smell, McBride said.

The research team already knows that mosquitoes have about 60 different types of neurons that can sense smells, so when they look at the insect’s brain, they think they might see a lot of activity. But it is surprisingly quiet, which means that the signal may be very simple, with only two types of neurons.

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McBride said of this work: “One type of neuron responds very strongly to both humans and animals. The other type of neuron responds strongly to both humans and animals, but it responds more strongly to humans than to animals. The response is much stronger.” Therefore, just compare the mosquito’s brain with only two types of neurons.

This kind of research has only been possible since the detailed study of mosquito brains came out, and this kind of technology has only recently appeared. Porter said: “Traditionally, it is difficult to study this at the current level.”

Examples of rapid development

Incredibly, mosquitoes targeting humans have evolved to be able to do this in the last 5,000 years, so this is “a truly amazing example of rapid evolution,” McBride said.

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Aedes aegypti (also known as “yellow fever mosquitoes”) also carry dengue fever, Zika virus and chikungunya. McBride said that this creature originated in Africa and may have reached the southern United States, the current range of Central and South America, via slave ships in the 1600s.

These diseases cause thousands of deaths and illnesses every year, which is why mosquitoes are called “the deadliest animal in the world” by the US Centers for Disease Control and Prevention. Both McBride and Porter hope that their work can be used by others who work in mosquito repellents and attractants to prevent disease.

It’s easy to keep them away

As for insider knowledge on how to prevent herself from being bitten in her own backyard, McBride said she uses a fan.

“Let the air blow where you are sitting outside, above the barbecue, or under the table where you bite.” She said that this is not to say that you are emitting a smell to get the mosquitoes out of the track.

McBride said this is simply because these deadly creatures are “not great aviators.”

A former geologist Starre Vartan She is a science journalist and dog runner who lives on a small island in Puget Sound near Seattle. No matter where she goes, she still picks up rocks.




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