What makes a mosquito want to take a bite out of you?
We know that mosquitoes are more attracted to the odor of mice infected with the parasite that carries malaria than to the aroma of healthy mice.
And that raises a tantalizing question in scientific minds: What about mosquito-borne viruses, like dengue and Zika — two dangerous diseases prevalent in the tropics and subtropics? (Dengue can lead to hemorrhagic fever, vomiting, and abdominal pain, while Zika can cause congenital abnormalities in developing fetuses and newborns.)
Both viruses rely on mosquitoes to shuttle them between people. So would a person infected by dengue or Zika also seem extra delicious to the bug's quivering, odor-sensing antennae?
If the answer is yes, it would shed light on how these viruses accomplish their job of transmission — of moving from one organism to another.
If an infected person draws in mosquitoes due to their odor, "I mean, the infection just increase[s] the chance to be located by a mosquito," says Penghua Wang, an immunologist with University of Connecticut Health.
That's what Wang and his team tried to figure out in a series of experiments described in a new study published in today's edition of Cell. They blew air over two cohorts of mice — one infected with either dengue or Zika, the other not — and the mosquitoes flocked to the odor wafting off the infected mice.
"These two viruses can alter a person's body odor to be more attractive to mosquitoes," Wang concludes. They do so by changing the skin's microbiome to get the bacteria to produce an aroma that — if you're a mosquito — is just intoxicating. When Wang learned of the results, he says, "I felt very excited. I said, 'Oh, wow, this is going to be [a] big thing.' "
Noushin Emami, an infectious disease biologist at the University of Greenwich in London not involved in the research, points out that mice and people are different organisms.
"There's a lot of things in our body [that are] different from [the] mice body," she says, suggesting the study's applicability to humans needs to be affirmed. It's worth noting, however, that as part of this study the researchers did notice the mosquitoes were similarly attracted to the odor of people with dengue as well — a promising avenue of future work.
Emami is intrigued by the prospect. In fact, she says that the ability of viruses to arrange a complicated dance across multiple species — the mammal that gets infected, the mosquito that transports the pathogen and the microbiome that beckons the bugs — reminds Emami of a theatrical production. "Everything works together. We have very nice players like actors, until you understand the end story — it's going to be disease, it's going to be sickness."
The findings from the new study also suggested a possible remedy. After giving the infected mice an oral vitamin A supplement, which reverted their microbiome to a healthier state, the interest of the mosquitoes waned.
And that may offer a clue as to why dengue and Zika spread in certain regions. Wang says that vitamin A deficiency is common in low- and middle-income countries, especially where mosquito-transmitted diseases like these two viruses are prevalent. He hopes future research will investigate whether an extra boost of dietary vitamin A might decrease the chances that a vulnerable individual will get that disease-spreading mosquito bite.