Health

Why are mosquitoes only attracted to some people?


is spread by mosquitoes in tropical areas around the world, and sometimes in subtropical areas such as the southeastern United States. It causes fever, rash and aches, sometimes bleeding and death.

More than 50 million cases of dengue occur annually and approximately 20,000 deathsmost are in children, according to the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (NIH).

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Zika is another mosquito-borne viral disease in the same family as dengue fever. Although Zika is not common to cause serious illness in adults, a recent outbreak in South America has caused severe birth defects in the unborn children of infected pregnant women. . Yellow fever, Japanese encephalitis, and West Nile are also members of this family of viruses.

These viruses need to continuously infect animal hosts as well as mosquitoes in order to spread. If either of these is missing — if all susceptible hosts are free of the virus or all mosquitoes die — the virus will disappear. For example, during the yellow fever outbreak in Philadelphia in 1793, the incoming fall frosts killed the local mosquitoes, and the outbreak ended.

In tropical climates where frost can’t be eliminated, mosquitoes are always present; The virus only needs a bite from an infected host to spread. The Zika virus and dengue fever seem to have evolved stealthily to increase morbidity.

Why do some people like mosquitoes more than others?

A team of researchers from UConn Health, Tsinghua University in Beijing, Institute of Infectious Diseases in Shenzhen, Ruili University Hospital and Chinese Medicine, Laboratory of Tropical and Subtropical Animal Viruses Tropical Yunnan, and the Chinese Center for Disease Control and Prevention, suspect that dengue and Zika may be manipulating the host in some way to attract mosquitoes. Both malaria and inflammation in general can change people’s scent. They think viral infections from dengue and Zika could do the same thing.

The team first tested whether mosquitoes showed a preference for infected mice. And indeed, when mosquitoes were given the choice of healthy mice or dengue-infected mice, the mosquitoes were more attracted to the dengue-infected mice.

They then analyzed the odor molecules on the skin of infected and healthy mice. They identified some of the more common molecules in infected animals and tested them individually. They applied them to clean mice and volunteers’ hands, and found that an odor molecule, acetophenone, that is particularly attractive to mosquitoes. Skin odorants collected from human dengue patients showed the same thing: more attractive to mosquitoes and produced more acetophenone.

Acetophenone is made by certain Bacillus bacteria that grow on human (and mouse) skin. The skin normally produces an antibacterial peptide to keep the Bacillus population in check. But it turned out that when mice were infected with dengue and Zika, they didn’t make as many antibacterial peptides, and the Bacillus bacteria grew faster.

“The virus can manipulate the microbiome of the host’s skin to attract more mosquitoes and spread faster!” Penghua Wang, an immunologist at UConn Health and one of the study authors. This finding could explain how the mosquito virus survives for such a long time.

Wang and co-authors also tested a potential preventive approach. They gave mice with dengue fever a vitamin A derivative, isotretinoin, which is known to increase the skin’s production of antibacterial peptides. Mice treated with isotretinoin secreted less acetophenone, reducing their attractiveness to mosquitoes and potentially reducing the risk of infecting others with the virus.

The next step, Wang said, is to analyze more patients with dengue and Zika to see if the link between skin odor and the general microbiome holds true under real-world conditions, and to see if isotretinoin reduce acetophenone production in the patient as well as in the patient. mouse.

Source: Eurekalert



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