Zika and dengue attract mosquitoes
Infection with the mosquito-bourne disease Dengue, or its relative the Zika virus, alters a person’s smell and makes them more attractive to mosquitoes, boosting the spread of the disease, a new study has found. The Chinese-based team have shown that when mice pick up a Dengue or Zika infection, the viruses temporarily alter their immune systems so that the spectrum of bacteria growing on the skin changes, altering the body odour. The change boosts the output of chemicals that mosquitoes use as a signal to find their next meal. Leslie Vosshall works on mosquito attraction at the Rockefeller University in New York. She gave Chris Smith her opinion on the new paper…
Leslie - What they show, which is what we have been looking for in our field for centuries, is an explanation for how viruses manipulate mosquitoes and humans to make it easier for mosquitoes to find humans. They infect mice with Zika or dengue and show that the virus changes the composition of the skin bacteria to make those animals much more attractive to mosquitoes. And so in a way, the virus is changing the composition of the body odour to lure mosquitoes, which makes it easier then for the virus to hop between mosquitoes and an animal host. This has huge implications for how viruses move back and forth between people and mosquitoes and provides a sort of an entry point to figure out how can we make this not happen.
Chris - How does the virus do that? How does it actually change the composition of the microbiome? What's going on?
Leslie - The virus has figured out how to interfere with the warfare between the microbiome and the human skin. What they're doing is manipulating this antimicrobial that would normally prune back the garden of bacteria. And then as a result, you get this huge increase in the microbiome and then the microbiome can increase the overall smelliness of the host.
Chris - And it's the smelliness that then attracts the mosquito?
Leslie - What they say is exactly that the virus playing with the composition of the skin microbiome is vastly increasing the smell. What I find remarkable is that it comes down to a single molecule. So you increase the amounts of acetophenone from the skin, and then that by itself is able to increase attraction.
Chris - Do we see other infections doing a similar sort of thing, or is this the first time we've really got a handle on how diseases can manipulate the way we smell and therefore our attractiveness to biting insects?
Leslie - What's amazing about the paper is that they didn't just leave it at dengue. They also showed that the same mechanism is happening for Zika, which was great; they doubled their work and doubled the impact. So there are many other RNA viruses that infect mosquitoes, and they haven't studied those here. It would be interesting to see if chikungunya or yellow fever has this effect. Going off of your question, there's a little bit of data showing people who are infected with malaria pathogens become much more attractive to mosquitoes.
Chris - And now we know that this happens, can we come in at the other end of the argument and say, well we know this is happening, it's making the mosquitoes want to bite people. Do we understand how it does that to the mosquito and are there prospects for being able to intervene in that process to stop mosquitoes being attracted by these substances and therefore break chains of transmission of these diseases?
Leslie - First of all, this paper is a tour de force of biology. What everybody wants to know is, okay, this is fine. It's great paper. How do I prevent myself from getting bitten? I don't wanna get bitten by mosquitoes. And so there is a bit of a message of hope in this paper. The logical chain would be as follows - acetophenone makes us more attractive to mosquitoes. The mechanism in the mosquito is that they pay attention to human body odour, they use that information to hunt. And so if acetophenone is a major signal that lures mosquitoes to us, what they say in the paper is of course, if you manipulate the host - the skin microbiome - to produce less of acetophenone, you should be less hunted by mosquitoes. And so, one possible application is that we have mechanisms, skin creams that will reduce the colonisation of bacteria that produces acetophenone for instance. It's difficult to manipulate the biology of the mosquito to change how they think about us. It's much easier to manipulate us, to manipulate our skin, to make us less smelly in ways that would attract mosquitoes to us.