According to a mice study, these microbes might make you more attractive to mosquitoes

According to a mice study, these microbes might make you more attractive to mosquitoes ...

Mosquitoes are the world's deadliest animal. Over 1 million deaths are reported per year due to mosquito-borne illnesses, including malaria, yellow fever, dengue fever, Zika, and chikungunya illness.

Mosquitoes are important components of how viruses and other pathogens are transmitted in nature. A mosquito that bites a person infected with a virus can acquire the virus and pass it onto the next person it bites.

A better understanding of how a virus interacts with a host might offer new approaches to preventing and treating mosquito-borne illnesses, according to immunologists and infectious disease researchers like me.

My colleagues and I discovered that certain viruses can alter a person's body odor to make him more attractive to mosquitoes, leading to more bites that enable a virus to spread.

Viruses alter host scents in order to attract mosquitoes.

Through different sensory cues, mosquitoes identify a potential host, such as your body temperature and the carbon dioxide released from your breath.

Odors also play a role. Previous lab research has shown that malaria-infected mice have altered smells that make them more attractive to mosquitoes.

My colleagues and I questioned whether other mosquito-borne illnesses, such as dengue and Zika, might be able to alter a person's scent to attract mosquitoes, and if there is a way to prevent such changes.

To investigate this, we placed mice infected with the Dengue or Zika virus, uninfected mice, and mosquitoes in one of three arms of a glass chamber. When we applied airflow through the mouse chambers to funnel their odors toward the mosquitoes, we found that more mosquitoes preferred to fly toward the infected mice than uninfected mice.

Carbon dioxide was ruled out as a reason for the mosquitoes' attraction to the infected mice, because while Zika-infected mice emitted less carbon dioxide than uninfected mice, dengue-infected mice did not alter emission levels.

When mosquitoes did not differentiate between mice with elevated or normal body temperatures, we excluded body temperature as a potential attractive factor.

Then, we examined the role of body smells in mosquitoes' increased attraction to infected mice.

We found that the number of mosquitoes that flew towards infected and uninfected mice was comparable.

This suggests that there was something about the infected mice's odors that drew mosquitoes toward them.

We isolated 20 different gaseous chemical compounds from the infected mice's scent, three of which appeared to stimulate a significant response in mosquito antennae.

Only one, acetophenone, attracted more mosquitoes than the control when we applied these three compounds to healthy mice and human volunteers.

Similarly, we discovered that dengue fever patients' armpits contained more acetophenone than those from healthy individuals.

mosquitoes were consistently attracted to the hand with dengue fever odors when we applied the volunteer's odor on the other hand.

These findings suggest that the dengue and Zika viruses are capable of increasing the amount of acetophenone their hosts produce and emit, making them even more attractive to mosquitoes. When uninfected mosquitoes bite these attractive hosts, they may bite other people and spread the virus even further.

How do viruses increase acetophenone production?

Next, we wanted to know how viruses were increasing the amount of mosquito-attracting acetophenone their hosts produced.

Acetophenone, a chemical commonly used as a fragrance in perfumes, is also a metabolic byproduct of certain bacteria that live on the skin and in the intestines of both humans and mice. So we wondered if it had something to do with changes in the type of bacteria on the skin.

Before exposing infected mice to mosquitoes, we removed the skin or intestinal fungus from them.

Although mosquitoes were still more attracted to infected mice with depleted intestinal bacteria than to uninfected mice, they were also significantly less attracted to infected mice with depleted skin bacteria.

These results demonstrate that skin microbes are a critical source of acetophenone.

When we compared the skin bacteria compositions of infected and uninfected mice, we found that a common rod-shaped bacteria, Bacillus, was a major acetophenone producer and had significantly increased numbers on infected mice.

This meant that the Dengue and Zika viruses were able to alter their host's odor by altering the skin's microbiome.

Reducing mosquito-attracting odors

Final, we wanted to know if there was a way to prevent this odor change.

When we observed that infected mice had decreased levels of an important microbe-fighting protein called RELM, we concluded that the dengue and Zika viruses suppressed this enzyme, making the mice more susceptible to infection.

Vitamin A and its related chemical compounds are known to significantly increase RELM production. So we fed a vitamin A derivative to infected mice over the course of a few days, measured the amount of RELM and Bacillus bacteria present on their skin, and exposed them to mosquitoes.

Infected mice treated with the vitamin A derivative were able to restore their RELM levels to levels of uninfected mice, as well as reduce the amount of Bacillus bacteria on their skin. Mosquitoes were also no more attracted to these treated, uninfected mice.

Our next step is to replicate these findings in animals and eventually apply what we learned to patients. Vitamin A deficiencies are common in developing countries, particularly in sub-Saharan Africa and Southeast Asia, where mosquito-transmitted viral diseases are prevalent.

Our next steps are to investigate whether dietary vitamin A or its derivatives may reduce mosquito attraction to people infected with Zika and dengue, and thus reduce mosquito-borne diseases in the long run.

Penghua Wang, University of Connecticut's assistant professor of immunology.

This article has been republished from The Conversation under a Creative Commons license. Read the original article here.

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