Dengue fever and Zika virus make humans more attractive to mosquitoes | Chemistry

Mosquito-borne diseases kill hundreds of thousands of people each year.Due to malaria 600,000 dead A year, it’s most famous.However, about 4 billion people live in high-risk areas Dengue fever A fever infection that kills about 40,000 people each year.And at least an individual 86 countries Infected with Jika virus. Cases are rarely fatal, but they are associated with severe birth defects. Scientists studying such diseases are now investigating whether the virus can fine-tune human physiology for their benefit, and if so, how they do it. I am.

That quest led Gongchen, Tsinghua University-Peking University Joint Center for Life Sciences Microbiologist, tests whether humans infected with dengue fever and Zika virus are more attractive to mosquitoes.their New research Released today cell Reveal that mosquitoes will become more attracted to hosts infected with both Flavivirus, West Nile fever and the same family illness and yellow fever. Their results show that the chemicals produced by the bacteria on the skin are responsible for this increased attraction to insects. Chen wrote in an email that his team’s findings “can inform actual public health strategies for controlling mosquito-borne flavivirus viral diseases such as dengue and Zika fever.” ..

In the first part of their multi-step study, Chen’s team found two types of mosquitoes. Egyptian temple When Aedes albopictus, Was more attracted to Zika virus or dengue-infected mice than uninfected mice. They put the mosquitoes in a plastic box connected by a tube and in two other boxes, one on each side. These side chambers were piped with air from a container near mice that were uninfected or infected with Zika or dengue fever.

Scientists released 60 mosquitoes into a central room and carefully observed their movements over the course of a week. Initially, the same number of mosquitoes were in each side box. But by the fourth day, scientists noticed a clear pattern. About 70% of mosquitoes were in boxes connected to infected mice, while only 30% were in boxes connected to uninfected mice. However, after adding a deodorizer to prevent odorous chemicals from entering the box, the mosquitoes no longer showed preference when they repeated the experiment. Scientists have concluded that the viral infection changes the odor of mice, making them more attractive to mosquitoes.

To test whether humans become more attractive to mosquitoes when infected, Chen’s team recruited both dengue patients and uninfected participants. The researchers wiped their armpits to collect body odor chemicals, holding a piece of paper containing the odorous compound in one hand and untreated paper in the other. Using the same method as before, mosquitoes could choose from both hands. Like mice, mosquitoes showed the strongest attraction to the odor of humans infected with dengue fever.

To determine which specific compounds are altered by a flavivirus infection, scientists have isolated chemicals released into the atmosphere by infected and uninfected mice. Twenty compounds were different between mice infected with Zika or dengue compared to uninfected mice. Next, researchers tested whether each of these compounds could cause nerve impulses from the antennae of mosquitoes to the brain. This shows that mosquitoes can detect chemicals.

A compound called acetophenone was the prime suspect because it caused the strongest electrical response in mosquito antenna tests. Acetophenone was released more into the atmosphere by mice infected with Zika or dengue compared to uninfected mice. Patients with human dengue also showed higher levels of acetophenone release than uninfected participants.

Acetophenone was also the only chemical that showed a clear attraction when mosquitoes were applied to the skin of mice. When acetophenone was applied to one hand and both hands were placed in a chamber connected to the mosquito cage, the mosquitoes swarmed towards the chemical-laden hand.

Previous studies have found evidence of increased mosquito attraction in humans infected with mosquito-borne diseases, but this study was the first study to clearly identify a particular chemical as the reason for this attraction. There is one. “I think the highlight of this study is that they discovered this acetophenone and very clearly found this effect in both mice and humans,” said Niels Verhulst, a vector entomologist at the University of Zurich. increase. Parasitology Institute Those who were not involved in this study.

Researchers were still wondering why acetophenone emissions increased after the virus was infected. Since acetophenone is a common bacterial waste product, researchers thought that acetophenone could be produced by the bacteria that inhabit the skin. They found that they chose to kill bacteria from the skin of some mice and fly towards uninfected mice as often as mosquito-infected mice. Mice lacking skin bacteria produced very little acetophenone.

Scientists dig deeper.They found that infected mice have more Bacillus Bacteria than uninfected mice.when Bacillus Bacteria have been added to the skin of mice, making them more attractive to mosquitoes. Bacillus Bacteria also produced the highest acetophenone release of all skin bacteria tested.

In summary, the results of this study show that dengue or Zika infections Bacillus Bacteria attach to the skin, increasing acetophenone excretion and increasing mosquito attraction.according to Julian Martinez, An evolutionary biologist at the MRC-University of Glasgow Virus Research Center who was not involved in this study, and it is very rare that each step in this pathway is very clearly understood. “Parasitic worms often evolve ways to manipulate the host to increase infection, and we know many examples of this in the animal kingdom,” he says, “but most. If so, we have no clue about the mechanism. “

Understanding this mosquito attraction mechanism is an important step forward, but Verhulst predicts that it is not the only function.Based on previous research, he has other bacteria Bacillus It may also be involved in attracting mosquitoes. “If you think about skin bacteria that attract mosquitoes, four or five studies show that. Staphylococcus It plays a role, “he says. Chen also states that compounds other than acetophenone may also be involved in increasing the attractiveness of infected host mosquitoes.

Chen’s research team is currently looking at ways to apply their findings to reduce the spread of dengue and related viruses. They are considering treating patients with dengue fever with medications that reduce acetophenone excretion.A common acne drug called isotretinoin is known to increase the production of antibacterial proteins that are particularly effective in killing. Bacillus Bacteria. When isotretinoin is administered to infected mice, Bacillus The load has decreased and the attractiveness of mosquitoes has decreased. However, given that most of this work was done in mice, more research is needed on humans. Chen also states that isotretinoin has potentially serious neurological side effects, so his team is investigating safer alternative therapies.

Other potential applications of these findings may include more effective mosquito trap designs and faster testing for dengue or Zika infections. Health care professionals may be able to determine the status of an infection by measuring the release of acetophenone from the skin. “This is much faster than taking a blood sample and testing it,” says Verhulst.

The research team also plans to take a closer look at the mosquitoes themselves. Chen now wants to find a gene that allows mosquitoes to detect acetophenone. If these can be turned off, the vector will be less likely to be attracted to infected humans and the virus may be less likely to spread.

Of course, Martinez also points out that accurate predictions of how mosquitoes behave can depend on how the virus affects mosquitoes. “If you want to understand the epidemiology of a virus, you need to look at every different step in its life cycle,” he says. So when it’s in humans, and when it’s in mosquitoes. “