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TEDxMaastricht

Bart Knols: Cheese, dogs and a pill to kill mosquitoes and end malaria

April 2, 2012

We can use a mosquito's own instincts against her. At TEDxMaastricht speaker Bart Knols demos the imaginative solutions his team is developing to fight malaria -- including limburger cheese and a deadly pill. (Filmed at TEDxMaastricht.)

Bart Knols - Malariologist
Bart Knols is a doctor committed to killing mosquitoes and ending malaria. Full bio

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Double-click the English subtitles below to play the video.
(Mosquito buzzing)
00:15
(Swat)
00:25
Gotcha.
00:28
Mosquitos. I hate them.
00:31
Don't you?
00:35
That awful buzzing sound at night around your ears
00:36
that drives you absolutely crazy?
00:39
Knowing that she wants to stick a needle in your skin
00:42
and suck out your blood? That's awful, right?
00:44
In fact, there's only one good thing I can think of
00:48
when it gets to mosquitos.
00:51
When they fly into our bedroom at night,
00:54
they prefer to bite my wife.
00:57
But that's fascinating, right?
01:00
Why does she receive more bites than I do?
01:01
And the answer is smell, the smell of her body.
01:05
And since we all smell different and produce chemicals
01:10
on our skin that either attract or repel mosquitos,
01:12
some of us are just more attractive than others.
01:17
So my wife smells nicer than I do, or I just
01:20
stink more than she does.
01:23
Either way, mosquitos find us in the dark
01:26
by sniffing us out. They smell us.
01:30
And during my Ph.D, I wanted to know exactly
01:33
what chemicals from our skin mosquitos used,
01:35
African malarial mosquitos use to track us down at night.
01:38
And there's a whole range of compounds that they do use.
01:42
And this was not going to be an easy task.
01:45
And therefore, we set up various experiments.
01:48
Why did we set up these experiments?
01:52
Because half the world's population runs the risk
01:54
of contracting a killer disease like malaria
01:58
through a simple mosquito bite.
02:01
Every 30 seconds, somewhere on this planet,
02:04
a child dies of malaria, and Paul Levy this morning,
02:06
he was talking about the metaphor of the 727 crashing into the United States.
02:10
Well, in Africa, we have the equivalent of seven jumbo 747s
02:14
crashing every day.
02:19
But perhaps if we can attract these mosquitos to traps,
02:22
bait it with our smell, we may be able to stop transmission
02:25
of disease.
02:29
Now solving this puzzle was not an easy thing,
02:31
because we produce hundreds of different chemicals on the skin,
02:33
but we undertook some remarkable experiments
02:36
that managed us to resolve this puzzle very quickly indeed.
02:39
First, we observed that not all mosquito species
02:42
bite on the same part of the body. Strange.
02:46
So we set up an experiment
02:50
whereby we put a naked volunteer in a large cage,
02:51
and in that cage we released mosquitos
02:55
to see where they were biting on the body of that person.
02:58
And we found some remarkable differences.
03:01
On the left here you see the bites
03:04
by the Dutch malarial mosquito on this person.
03:06
They had a very strong preference for biting on the face.
03:09
In contrast, the African malarial mosquito
03:12
had a very strong preference for biting the ankles and feet of this person,
03:15
and that of course we should have known all along
03:20
because they're called mosqui-toes, you see? (Laughter)
03:23
That's right. (Applause)
03:27
And so we started focusing on the smell of feet,
03:31
on the smell of human feet,
03:36
until we came across a remarkable statement in the literature
03:38
that said that cheese smells after feet
03:41
rather than the reverse. Think of it.
03:45
And this triggered us to do a remarkable experiment.
03:49
We tried, with a tiny little piece of Limburger cheese,
03:51
which smells badly after feet,
03:56
to attract African malaria mosquitos.
03:58
And you know what? It worked.
04:01
In fact, it worked so well that now we have a synthetic mixture
04:04
of the aroma of Limburger cheese that we're using in Tanzania
04:09
and has been shown there to be two to three times
04:14
more attractive to mosquitos than humans.
04:16
Limburg, be proud of your cheese,
04:20
as it is now used in the fight against malaria.
04:23
(Applause)
04:26
That's the cheese, just to show you.
04:33
My second story is remarkable as well.
04:36
It's about man's best friend. It's about dogs.
04:39
And I will show you
04:43
how we can use dogs in the fight against malaria.
04:44
One of the best ways of killing mosquitos
04:47
is not to wait until they fly around like adults
04:51
and bite people and transmit disease.
04:54
It's to kill them when they're still in the water as larvae.
04:57
Why? Because they are just like the CIA.
05:01
In that pool of water, these larvae are concentrated.
05:05
They're all together there. They are immobile.
05:09
They can't escape from that water. They can't fly.
05:12
And they're accessible. You can actually walk up
05:15
to that pool and you can kill them there, right?
05:19
So the problem that we face with this is that,
05:23
throughout the landscape, all these pools of water
05:27
with the larvae, they are scattered all over the place,
05:30
which makes it very hard for an inspector like this
05:33
to actually find all these breeding sites and treat them with insecticides.
05:36
And last year we thought very, very hard,
05:40
how can we resolve this problem? Until we realized
05:42
that just like us, we have a unique smell,
05:46
that mosquito larvae also have a very unique smell.
05:49
And so we set up another crazy experiment,
05:53
because we collected the smell of these larvae,
05:55
put it on pieces of cloth, and then did something very remarkable.
05:57
Here we have a bar with four holes,
06:02
and we put the smell of these larvae in the left hole.
06:04
Ooh, that was very quick.
06:07
And then you see the dog. It's called Tweed. It's a border collie.
06:08
He's examining these holes, and now he's got it already.
06:11
He's going back to check the control holes again,
06:13
but he's coming back to the first one,
06:16
and now he's locking into that smell,
06:17
which means that now we can use dogs
06:20
with these inspectors to much better find
06:22
the breeding sites of mosquitos in the field,
06:25
and therefore have a much bigger impact on malaria.
06:27
This lady is Ellen van der Zweep. She's one of the best dog-trainers in the world,
06:30
and she believes that we can do a lot more.
06:34
Since we also know that people that carry malaria parasites
06:37
smell different compared to people that are uninfected,
06:40
she's convinced that we can train dogs
06:43
to find people that carry the parasite.
06:46
That means that in a population where malaria
06:49
has gone down all the way, and there's few people remaining with parasites,
06:51
that the dogs can find these people,
06:55
we can treat them with anti-malarial drugs, and give the final blow to malaria.
06:57
Man's best friend in the fight against malaria.
07:01
My third story is perhaps even more remarkable,
07:05
and, I should say, has never been shown to the public until today.
07:08
Yeah.
07:12
It's a crazy story, but I believe it's perhaps the best
07:15
and ultimate revenge against mosquitos ever.
07:18
In fact, people have told me that now they will enjoy
07:21
being bitten by mosquitos.
07:24
And the question of course is, what would make someone
07:27
enjoy being bitten by mosquitos?
07:30
And the answer
07:33
I have right here in my pocket,
07:34
if I get it.
07:38
It's a tablet, a simple tablet,
07:41
and when I take it with water,
07:44
it does miracles.
07:47
Thank you.
07:51
(Drinking)
07:55
Now let me show you how this works.
07:59
Here in this box I have a cage
08:03
with several hundred hungry
08:06
female mosquitos
08:11
that I'm just about to release. (Laughter)
08:15
Just kidding, just kidding.
08:19
What I'm going to show you is I'm gonna stick my arm into it
08:22
and I will show you how quickly they will bite.
08:25
Here we go.
08:28
Don't worry, I do this all the time in the lab.
08:30
There we go. Okay.
08:33
Now, on the video, on the video here,
08:37
I'm going to show you exactly the same thing,
08:42
except that what I'm showing you on the video
08:43
happened one hour after I took the tablet.
08:46
Have a look. That doesn't work. Okay. Sorry about that.
08:50
I'm sticking in my arm, I'm giving them a big juicy
08:54
blood meal, I'm shaking them off, and we follow them through time
08:57
to see these mosquitos get very, very sick indeed,
08:59
here shown in fast motion,
09:02
and three hours later what we see at the bottom
09:04
of the cage is dead mosquitos,
09:08
very dead mosquitos, and I'm going to say, ladies and gentlemen,
09:11
we have swapped the cards with mosquitos.
09:15
They don't kill us. We kill them.
09:17
(Applause)
09:22
Now — (Laughter) —
09:30
Maastricht, be prepared.
09:36
Now think of what we can do with this.
09:38
We can actually use this to contain outbreaks
09:40
of mosquito-born diseases, of epidemics, right?
09:42
And better still, imagine what would happen if,
09:45
in a very large area, everyone would take these drugs,
09:47
this drug, for just three weeks.
09:51
That would give us an opportunity to actually eliminate
09:53
malaria as a disease.
09:55
So cheese, dogs and a pill to kill mosquitos.
09:57
That's the kind of out-of-the-box science that I love doing,
10:01
for the betterment of mankind,
10:05
but especially for her, so that she can grow up
10:07
in a world without malaria. Thank you. (Applause)
10:10
Translator:Joseph Geni
Reviewer:Morton Bast

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Bart Knols - Malariologist
Bart Knols is a doctor committed to killing mosquitoes and ending malaria.

Why you should listen

Bart Knols is a malariologist with eleven years of experience managing large-scale research programs in East and Southern Africa. He’s worked at the United Nations (IAEA), served as a consultant for the World Health Organization, and acted as a Board Member of the UBS Bank Optimus Foundation in Switzerland. He has published over 140 peer-reviewed research articles and received the Ig Nobel Prize and an IAEA Special Service Award in 2006 and became a laureate of the Eijkman medal in 2007. He is currently the Managing Director at In2Care BV, Science Director & Managing Partner at Soper Strategies, and serves as Chair of the Advisory Board of the Dutch Malaria Foundation.

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