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(Mosquito buzzing)

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(Swat)

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Gotcha.

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Mosquitos. I hate them.

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Don't you?

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That awful buzzing sound at night around your ears

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that drives you absolutely crazy?

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Knowing that she wants to stick a needle in your skin

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and suck out your blood? That's awful, right?

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In fact, there's only one good thing I can think of

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when it gets to mosquitos.

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When they fly into our bedroom at night,

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they prefer to bite my wife.

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But that's fascinating, right?

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Why does she receive more bites than I do?

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And the answer is smell, the smell of her body.

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And since we all smell different and produce chemicals

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on our skin that either attract or repel mosquitos,

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some of us are just more attractive than others.

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So my wife smells nicer than I do, or I just

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stink more than she does.

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Either way, mosquitos find us in the dark

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by sniffing us out. They smell us.

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And during my Ph.D, I wanted to know exactly

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what chemicals from our skin mosquitos used,

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African malarial mosquitos use to track us down at night.

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And there's a whole range of compounds that they do use.

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And this was not going to be an easy task.

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And therefore, we set up various experiments.

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Why did we set up these experiments?

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Because half the world's population runs the risk

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of contracting a killer disease like malaria

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through a simple mosquito bite.

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Every 30 seconds, somewhere on this planet,

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a child dies of malaria, and Paul Levy this morning,

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he was talking about the metaphor of the 727 crashing into the United States.

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Well, in Africa, we have the equivalent of seven jumbo 747s

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crashing every day.

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But perhaps if we can attract these mosquitos to traps,

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bait it with our smell, we may be able to stop transmission

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of disease.

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Now solving this puzzle was not an easy thing,

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because we produce hundreds of different chemicals on the skin,

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but we undertook some remarkable experiments

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that managed us to resolve this puzzle very quickly indeed.

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First, we observed that not all mosquito species

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bite on the same part of the body. Strange.

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So we set up an experiment

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whereby we put a naked volunteer in a large cage,

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and in that cage we released mosquitos

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to see where they were biting on the body of that person.

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And we found some remarkable differences.

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On the left here you see the bites

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by the Dutch malarial mosquito on this person.

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They had a very strong preference for biting on the face.

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In contrast, the African malarial mosquito

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had a very strong preference for biting the ankles and feet of this person,

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and that of course we should have known all along

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because they're called mosqui-toes, you see? (Laughter)

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That's right. (Applause)

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And so we started focusing on the smell of feet,

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on the smell of human feet,

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until we came across a remarkable statement in the literature

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that said that cheese smells after feet

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rather than the reverse. Think of it.

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And this triggered us to do a remarkable experiment.

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We tried, with a tiny little piece of Limburger cheese,

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which smells badly after feet,

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to attract African malaria mosquitos.

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And you know what? It worked.

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In fact, it worked so well that now we have a synthetic mixture

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of the aroma of Limburger cheese that we're using in Tanzania

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and has been shown there to be two to three times

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more attractive to mosquitos than humans.

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Limburg, be proud of your cheese,

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as it is now used in the fight against malaria.

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(Applause)

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That's the cheese, just to show you.

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My second story is remarkable as well.

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It's about man's best friend. It's about dogs.

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And I will show you

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how we can use dogs in the fight against malaria.

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One of the best ways of killing mosquitos

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is not to wait until they fly around like adults

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and bite people and transmit disease.

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It's to kill them when they're still in the water as larvae.

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Why? Because they are just like the CIA.

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In that pool of water, these larvae are concentrated.

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They're all together there. They are immobile.

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They can't escape from that water. They can't fly.

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And they're accessible. You can actually walk up

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to that pool and you can kill them there, right?

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So the problem that we face with this is that,

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throughout the landscape, all these pools of water

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with the larvae, they are scattered all over the place,

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which makes it very hard for an inspector like this

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to actually find all these breeding sites and treat them with insecticides.

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And last year we thought very, very hard,

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how can we resolve this problem? Until we realized

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that just like us, we have a unique smell,

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that mosquito larvae also have a very unique smell.

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And so we set up another crazy experiment,

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because we collected the smell of these larvae,

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put it on pieces of cloth, and then did something very remarkable.

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Here we have a bar with four holes,

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and we put the smell of these larvae in the left hole.

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Ooh, that was very quick.

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And then you see the dog. It's called Tweed. It's a border collie.

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He's examining these holes, and now he's got it already.

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He's going back to check the control holes again,

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but he's coming back to the first one,

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and now he's locking into that smell,

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which means that now we can use dogs

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with these inspectors to much better find

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the breeding sites of mosquitos in the field,

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and therefore have a much bigger impact on malaria.

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This lady is Ellen van der Zweep. She's one of the best dog-trainers in the world,

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and she believes that we can do a lot more.

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Since we also know that people that carry malaria parasites

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smell different compared to people that are uninfected,

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she's convinced that we can train dogs

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to find people that carry the parasite.

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That means that in a population where malaria

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has gone down all the way, and there's few people remaining with parasites,

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that the dogs can find these people,

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we can treat them with anti-malarial drugs, and give the final blow to malaria.

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Man's best friend in the fight against malaria.

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My third story is perhaps even more remarkable,

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and, I should say, has never been shown to the public until today.

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Yeah.

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It's a crazy story, but I believe it's perhaps the best

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and ultimate revenge against mosquitos ever.

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In fact, people have told me that now they will enjoy

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being bitten by mosquitos.

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And the question of course is, what would make someone

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enjoy being bitten by mosquitos?

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And the answer

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I have right here in my pocket,

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if I get it.

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It's a tablet, a simple tablet,

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and when I take it with water,

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it does miracles.

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Thank you.

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(Drinking)

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Now let me show you how this works.

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Here in this box I have a cage

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with several hundred hungry

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female mosquitos

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that I'm just about to release. (Laughter)

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Just kidding, just kidding.

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What I'm going to show you is I'm gonna stick my arm into it

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and I will show you how quickly they will bite.

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Here we go.

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Don't worry, I do this all the time in the lab.

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There we go. Okay.

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Now, on the video, on the video here,

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I'm going to show you exactly the same thing,

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except that what I'm showing you on the video

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happened one hour after I took the tablet.

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Have a look. That doesn't work. Okay. Sorry about that.

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I'm sticking in my arm, I'm giving them a big juicy

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blood meal, I'm shaking them off, and we follow them through time

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to see these mosquitos get very, very sick indeed,

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here shown in fast motion,

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and three hours later what we see at the bottom

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of the cage is dead mosquitos,

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very dead mosquitos, and I'm going to say, ladies and gentlemen,

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we have swapped the cards with mosquitos.

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They don't kill us. We kill them.

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(Applause)

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Now — (Laughter) —

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Maastricht, be prepared.

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Now think of what we can do with this.

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We can actually use this to contain outbreaks

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of mosquito-born diseases, of epidemics, right?

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And better still, imagine what would happen if,

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in a very large area, everyone would take these drugs,

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this drug, for just three weeks.

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That would give us an opportunity to actually eliminate

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malaria as a disease.

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So cheese, dogs and a pill to kill mosquitos.

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That's the kind of out-of-the-box science that I love doing,

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for the betterment of mankind,

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but especially for her, so that she can grow up

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in a world without malaria. Thank you. (Applause)