Are mosquitoes biting you more than other mosquitoes these days?There may be an answer to this study on mice

Mosquitoes are the deadliest animals in the world. More than one million deaths a year are caused by mosquito-borne diseases such as malaria, yellow fever, dengue fever, Zika fever and chikungunya fever.

The way mosquitoes seek out and feed their hosts is an important element of how the virus circulates in nature. Mosquitoes spread the disease by acting as carriers of viruses and other pathogens. A mosquito that bites a person infected with the virus can acquire the virus and infect the next person.

For immunologists and infectious disease researchers like me, a better understanding of how the virus interacts with the host may offer new strategies for the prevention and treatment of mosquito-borne diseases. not. In our recently published study, my colleagues and I found that some viruses make a person’s body odor more attractive to mosquitoes and allow more bites to spread. I discovered that it could be connected.

The virus changes the odor of the host and attracts mosquitoes

Mosquitoes identify potential hosts through a variety of sensory cues, such as body temperature and carbon dioxide released from breathing. Smell also plays a role. Previous laboratory studies have shown that malaria-infected mice change their scent, making them more attractive to mosquitoes. With this in mind, my colleagues and I asked if other mosquito-borne viruses such as dengue and Zika could also change a person’s scent and make them more attractive to mosquitoes. And I wondered if there was a way to prevent these changes.

To investigate this, mice infected with dengue or Zika virus, uninfected mice, and mosquitoes were placed in one of the three arms of the glass chamber. It was found that when air was blown into the mouse chamber and the odor was directed at the mosquitoes, more mosquitoes flew toward the infected mice than at the uninfected mice.

Carbon dioxide was excluded as the reason why mosquitoes were attracted to infected mice. This is because deer-infected mice emit less carbon dioxide than non-infected mice, whereas dengue-infected mice did not change their emission levels. Similarly, if mosquitoes did not distinguish between elevated and normal mice, they ruled out temperature as a potential attractive factor.

Next, we evaluated the role of body odor in increasing the attraction of mosquitoes to infected mice. After placing a filter in the glass chamber to prevent mouse odors from reaching the mosquitoes, we found that the number of mosquitoes flying towards infected and uninfected mice was comparable. This suggests that the smell of infected mice attracted mosquitoes.

To identify the odor, 20 gaseous compounds were isolated from the scent emitted by infected mice. Of these, three were found that stimulated a significant response to the antennae of mosquitoes. When these three compounds were applied to healthy mouse skin and human volunteer hands, only one acetophenone attracted more mosquitoes compared to controls. Infected mice were found to produce 10 times more acetophenone than uninfected mice.

Similarly, odors collected from the armpits of dengue patients were found to contain more acetophenone than odors from healthy people. When applying the scent of a dengue patient on the one hand and the scent of a healthy person on the other, the mosquitoes were consistently attracted to the scent of dengue.

These findings mean that dengue and Zika virus can increase the amount of acetophenone produced and released by the host, making it even more attractive to mosquitoes. When uninfected mosquitoes bite these attractive hosts, they can bite others and spread the virus further.

How the virus increases acetophenone production

Next, I wanted to find out how the virus increases the amount of acetophenone that attracts mosquitoes produced by the host. Acetophenone is a commonly used chemical perfume fragrance and is also a metabolic by-product commonly produced by certain bacteria that inhabit the skin and intestines of both humans and mice. So I wondered if it had something to do with the changing types of bacteria on the skin.

To test this idea, we removed skin or intestinal bacteria before exposing infected mice to mosquitoes. Moss was more attracted to infected mice depleted of gut microbiota than to uninfected mice, but less to infected mice depleted of skin bacteria. These results suggest that skin microbes are an essential source of acetophenone.

Comparing the skin bacterial composition of infected and non-infected mice, it was found that the common type of bacillus, Bacillus, is the major acetophenone-producing bacterium, and the number of infected mice has increased significantly. This meant that dengue fever and Zika virus could alter the host’s odor by altering the microbial flora of the skin.

Reduce odors that attract mosquitoes

Finally, I wondered if there was a way to prevent this odor change.

One potential option was found when observing reduced levels of molecules that fight key microorganisms produced by infected mouse skin cells. This is called RELMα. This suggests that dengue and Zika virus suppress the production of this molecule, making mice more vulnerable to infection.

Vitamin A and its related compounds are known to strongly promote the production of RELMα. Therefore, infected mice were given a vitamin A derivative for several days, the amount of RELMα and Bacillus bacteria present in the skin was measured, and the mice were exposed to mosquitoes.

Infected mice treated with vitamin A derivatives were found to be able to return RELMα levels to levels in non-infected mice and reduce the amount of Bacillus in the skin. Mosquitoes were also less attracted to these treated infected mice than uninfected mice.

Our next step is to reproduce these results for people and ultimately apply what we have learned to patients. Vitamin A deficiency is common in developing countries. This is especially true in sub-Saharan Africa and Southeast Asia, where mosquito-borne viral diseases are widespread. The next step is to investigate whether vitamin A or its derivatives from the diet can reduce the attraction of mosquitoes to people infected with Zika or dengue and then reduce mosquito-borne diseases in the long run. That is.

Summary

• Mosquitoes identify potential hosts through a variety of sensory cues, such as body temperature and carbon dioxide released from breathing.

• Previous laboratory studies have shown that malaria-infected mice change their scent, making them more attractive to mosquitoes.

• Dengue and Zika virus can increase the amount of acetophenone produced and released by the host, making it even more attractive to mosquitoes.

Penghua Wang, Associate Professor of Immunology, University of Connecticut, Storrs, USA

This article will be republished from conversation Under a Creative Commons license.