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(Mosquito buzzing)

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(Swat)

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Gotcha.

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Mosquitoes.

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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?

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That's awful, right?

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In fact, there's only one good thing
I can think of when it gets to mosquitoes.

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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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(Laughter)

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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,

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the smell of her body.

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And since we all smell different
and produce chemicals on our skin

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that either attract or repel mosquitoes,

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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 stink more than she does.

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Either way, mosquitoes find us in the dark
by sniffing us out. They smell us.

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And during my PhD,
I wanted to know exactly

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what chemicals from our skin
African malaria mosquitoes use

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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

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runs the risk 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,

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and Paul Levy this morning,
he was talking about the metaphor

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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 mosquitoes to traps,

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bait it with our smell,

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we may be able
to stop transmission 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.

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Strange.

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So we set up an experiment

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where we put a naked volunteer
in a large cage,

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(Laughter)

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and in that cage, we released mosquitoes

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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 malaria 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 malaria 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?

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(Laughter)

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That's right.

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(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.

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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 mosquitoes.

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And you know what? It worked.

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In fact, it worked so well

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that now we have a synthetic mixture
of the aroma of Limburger cheese

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that we're using in Tanzania

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and has been shown there

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to be two to three times
more attractive to mosquitoes 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 how we can use dogs
in the fight against malaria.

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One of the best ways of killing mosquitoes

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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?

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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.

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They can't fly.

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And they're accessible.

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You can actually walk up to that pool
and you can kill them there, right?

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So the problem that we face with this

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is that, throughout the landscape,
all these pools of water with the larvae,

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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,
how can we resolve this problem?

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Until we realized that just like us --
we have a unique smell --

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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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Oh, 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 with these inspectors

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to much better find the breeding sites
of mosquitoes 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.

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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
to find people that carry the parasite.

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That means that in a population
where malaria has gone down all the way

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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 antimalarial 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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(Audience cheers)

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Yeah.

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

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against mosquitoes ever.

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In fact, people have told me

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that now they will enjoy
being bitten by mosquitoes.

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And the question of course is,

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what would make someone
enjoy being bitten by mosquitoes?

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And the answer I have right here ...

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in my pocket --

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(Laughter)

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if I get it.

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It's a tablet.

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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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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 female mosquitoes ...

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(Laughter)

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that I'm just about to release.

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(Laughter)

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Just kidding, just kidding.

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(Laughter)

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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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There 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.

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OK.

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Now, on the video --

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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.

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That doesn't work.

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OK. Sorry about that.

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

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

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to see these mosquitoes
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 of the cage

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is dead mosquitoes ...

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very dead mosquitoes.

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And I'm going to say,
ladies and gentlemen,

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we have swapped the cards with mosquitoes.

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They don't kill us. We kill them.

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(Applause)

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Now --

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(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

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if, in a very large area, everyone would
take these drugs, for just three weeks.

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That would give us an opportunity

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to actually eliminate
malaria as a disease.

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So cheese, dogs and a pill
to kill mosquitoes.

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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,

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so that she can grow up
in a world without malaria.

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Thank you.

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(Applause)