Science Questions

Why do mosquitoes prefer some people?

Tue, 1st Mar 2016

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Question

Bronwyn Higgs asked:

Why do mosquitoes prefer certain people over others. When I enjoy a glass of wine on the back verandah with a friend - the mossies head straight for my wrists and ankles, while the leave my friend alone. Even when I cover myself in insect repellent, they buzz around searching for a bit of skin without the repellent. What have I got that is so attractive to these pesky insects?

Answer

Felicity Bedford put this question to Heather Ferguson, from Glasgow University...A mosquito biting a finger

Felicity - Some people, including me, seem to act as mosquito magnets.  I asked Heather Ferguson from Glasgow University whether mosi’s really do target me or if I’m just unlucky?

Heather - This is absolutely true.  We have very good evidence for a number of different mosquitoes, a number of different settings round the world so, if you think you're’ the one in the group that’s getting unfairly hammered by mosquitoes when you go out,  it’s probably true.

Felicity - Why is it mosquitoes find some people so much juicier than others?

Heather - Well that is an age old question and I think people have been thinking about this pretty much for as long as they’ve been getting bitten by mosquitoes.  And the short answer is we don’t actually have a precise understanding of why this happens.  It’s likely to be due to a complex mixture of environmental and genetic factors.  It’s a whole range of things including, for example, how much carbon dioxide you’re omitting when you breath.  Also it varies in response to different components of scent and odour that people will emit.

Felicity - This doesn’t sound like something we can do very much about.  Is it just a case of putting on some insect repellent?

Heather - Certainly repellent is really important and we would always advise people use it if they’re going to an area where they’re likely to be bitten.  But there’s a lot of other advantages to really researching this question and I think most noticeably, my collaborators in East Africa and other settings around the world have been making a lot of progress in trying to identify specific smells that attract mosquitoes, rather than repel them.

Felicity - That doesn’t sound like something I want to be doing…

Heather - Well it can be hard work but the payoff can be huge because this is something, if you can find an artificial odour that really is very attractive to mosquitoes, you might be able to use it for a trap.  So it is worth the effort.

Felicity - What kind of smells are we talking about here?

Heather - Some work that’s been done by a colleague of mine, a Dr Fredros Okumu who’s a Kenyan scientist.  He spent three or four years of his PhD working really, really hard amidst the most ghastly smells you can imagine.  Mixing different types of compounds at different concentrations, essentially always smelling as if he’d been locked up in a tent with a big rugby team, so really, really, smelly - sweat like odours.

Felicity - Oh, delightful!

Heather - But the payoff was enormous and he came up with a compound that, in some settings, can be about four times attractive to a malaria mosquito than an average person.  So this has now been taken forward with a large injection of funds from the Gates Foundation with idea being that in the future we might be able to have an odour-baited trap from malaria mosquitoes.

Felicity - Thanks Heather.  Short of finding a smelly rugby team to follow me around, I guess I’ll be stocking up on insect repellent for now.

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