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