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

Gotcha! Mosquitoes! I hate them, don't you? That awful buzzing sound at night around your ears drives me 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. But that's fascinating, right? Why does she receive more bites than I do? The answer is smell—the smell of our body. 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. During my PhD, I wanted to know exactly what chemicals from our skin mosquitoes used. African malaria mosquitoes use these to track us down at night.

There's a whole range of compounds that they use, and this was not going to be an easy task. 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.

Paula Levy, this morning, was talking about the metaphor of the 77 crashing in the United States. Well, in Africa, we have the equivalent of seven jumbo 747s crashing every day. Perhaps if we can attract these mosquitoes to traps baited with our smell, we may be able to stop the transmission of disease.

Now, solving this puzzle was not easy because we produce hundreds of different chemicals on the skin. However, we undertook some remarkable experiments that allowed 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, right?

So we set up an experiment whereby we put a naked volunteer in a large cage and released mosquitoes to see where they were biting on that person’s body. We found some remarkable differences. On the left here, you see the bites by the Dutch malaria mosquito on this person. There's 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 mosquitoes! You see, that's right. And so, we started focusing 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! This triggered us to do a remarkable experiment: we tried a tiny little piece of Limburger cheese, which smells badly after feet, to attract African malaria mosquitoes.

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 it has been shown there to be 2 to 3 times more attractive to mosquitoes than humans. Limburg, be proud of your cheese, as it is now used in the fight against malaria!

Now, let me show you my second story; it’s remarkable as well. It's about man's best friend—it's about dogs. 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, transmitting disease. It's to kill them when they're still in the water, as larvae.

Why? Because they're just like the CIA! In that pool of water, these larvae are concentrated; they're all together, they are immobile, they can't escape from the water, they can't fly, and they are accessible. You can actually walk up to that pool and kill them right there.

So the problem we face is that throughout the landscape, all these pools are filled with larvae. They're scattered all over the place, which makes it very hard for an inspector to actually find all these breeding sites and treat them with insecticides. Last year, we thought very, very hard about how we could resolve this problem until we realized that just like us, mosquito larvae also have a very unique smell.

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. Whoo! That was very quick!

Then you see the dog—its name is Tweet. It's a border collie, and he's examining these holes. Now he's got it all ready! 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. This means we can use dogs with these inspectors to find the breeding sites of mosquitoes in the field much better, and therefore have a much bigger impact on malaria.

This lady is Alan from Gooseway. 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 who carry malaria parasites smell different compared to people who are uninfected.

She's convinced that we can train dogs to find people that carry the parasite. That means that in the population where malaria has gone down all the way and only a few people remain with parasites, the dogs can find these people. We can treat them with anti-malarial drugs and give a 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 it has never been shown to the public until today. 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.

The question, of course, is what would make someone enjoy being bitten by mosquitoes? The answer? I have it right here in my pocket. If I get it, it’s a tongueless 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 that I'm just about to release. Just kidding! What I'm going to show you is I’m going to 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. Okay, now on the video here, I'm going to show you exactly the same thing, except that what I’m showing you in the video happened one hour after I took the tablet. Have a look!

Okay, sorry about that. I'm sticky getting my arm in. 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.

Three hours later, what we see on the bottom of the cage is dead mosquitoes—very dead mosquitoes. I’m going to say, ladies and gentlemen, we have swapped the cards with mosquitoes! They don’t kill us—we kill them.

Now—Maslak vp prayers! Now think of what we can do with this. We can actually use this to contain outbreaks of mosquito-borne diseases—of epidemics! Right? And better still, imagine what would happen if in a very large area everyone took this drug 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!