James Logan – TEDxLondon TRANSCRIPT
Malaria is still one of the biggest killers on the planet. Despite us making significant progress in the last 20 years, half the world’s population is still at risk from this disease.
In fact, every two minutes a child dies from Malaria. Our progress has undoubtedly stalled.
Now, we face many challenges when it comes to tackling Malaria. But one of the problems that we have is actually finding people who are infected with Malaria in the first place.
So for example, if people have some level of immunity to the disease, then they can develop an infection and become infectious and still pass it on, but not actually develop any symptoms. And that can be a big problem because how do you find those people — it’s like looking for a needle in a haystack.
Now, scientists have been trying to solve this problem for some years, but what I want to talk to you about today is that the solution to this problem may have been right under our noses this whole time.
That was a bit of a heavy start with lots of really important and serious statistics. So I want us all to just relax a little bit now, help me to relax a little bit as well.
So why don’t we all take a nice deep breath in. (Inhaling) Wow! And sigh.
Okay, I’m going to get blown away there. Okay, now I want you to do it again, but this time I want you to do it just through your nose, and I want you to really sense the environment around you.
And in fact, I want you to really smell the person who is sitting next to you, even if you don’t know them. I don’t care! Lean in. Get your nose right into their armpit. Stop being so British about it. Get your nose into the armpit, have a good old sniff. See what you can smell.
Now, each and every one of us would have had a very different sensory experience there. Some of us will have smelled something rather pleasant, perhaps somebody’s perfume.
But some of us might have smelled something a little bit less pleasant, perhaps — perhaps somebody’s bad breath or body odor. Maybe you even smelled your own body odor.
But there’s probably a good reason that some of us don’t like certain body smells. Throughout history, there had been many examples of diseases being associated with a smell.
So for example, typhoid apparently smells like baked brown bread. Well, that’s quite a nice smell, isn’t it? But it starts to get a little bit worse.
TB smells like stale beer, and yellow fever smells like the inside of a butcher shop, like raw meat. And in fact, when you look at the sort of words used to describe diseases, you tend to find these words: rotting, foul, putrid or pungent.
So it’s no surprise then, that smell and body odor gets a bit of a bad reputation. If I was to say to you: ‘You smell’, you’re going to take that not exactly as a compliment, are you?
But you do smell, you’ve just found that out, you do smell. It’s a scientific fact. I’d quite like to turn that on its head.
What if we could actually think about smell in a positive way? What if we could put it to good use? What if we could detect the chemicals that are given off by our bodies when we’re ill and use that to diagnose people?
Now, we’d need to develop good sensors that would allow us to do this. But it turns out that the world’s best sensors actually already exist. And they’re called ‘animals’.
Now, animals are built to smell. They live their everyday lives according to their nose. They sense the environments, which tells them really important information about how to stay alive, essentially.
Just imagine a mosquito. Imagine you’re a mosquito, and you’ve just flown in from outside and you’ve entered this room. You’re going to be entering a really complex world.
You’re going to be bombarded with smells from everywhere. We’ve just found out that we’re really smelly beasts. Each one of us is producing 500-600 different volatile chemicals. It’s not just one chemical like BO, lots and lots of chemicals.
But it’s not just you, it’s these seats you’re sitting on, the carpet, the glue that holds the carpet to the floor, the paint on the walls, the trees outside, everything around you is producing an odor, and it’s a really complex world that the mosquito has to fly through. And it has to find you within that really complex world.
And each and every one of you will know — C’mon, hands up, who always get bitten by mosquitoes? And hands up, who never get bitten? There’s always one or two really annoying people that never get bitten.
But the mosquito has a really hard job to find you, and that’s all to do with the way you smell. People who don’t attract mosquitoes smell repellent, and what we know is — I should clarify: repellent to mosquitoes, not to people.
And what we know now is that is actually controlled by our genes. But mosquitoes are able to do that because they have a highly sophisticated sense of smell, and they’re able to see through all this sort of odor sludge to find you, that individual, and bite you as a blood meal.
But what would happen if one of you was infected with malaria? Well, let’s just have a quick look at the malaria life cycle. So it’s quite complex, but basically what happens is: a mosquito has to bite somebody to become infected.
Once it bites an infected person, the parasites travel through the mouth part into the gut, and then bursts through the gut, creates cysts, and then the parasites replicate, and then they make a journey from the gut all the way to the salivary glands, where they are then injected back into another person when the mosquito bites because it injects saliva as it bites.
Then inside the human it goes through a whole other cycle, a whole other part of the life cycle. So it goes through a liver stage, changes shape and then comes out into the bloodstream again, and eventually that person will become infectious.
Now, one thing we know about the parasite world is that they are incredibly good at manipulating their hosts to enhance their own transmission, to make sure that they get passed onwards.
If this was to happen in the malaria system, it might make sense that it would be something to do with odor that they manipulate because odor is the key, odor’s the thing that links us between mosquitoes; that’s how they find us. This is what we call the malaria manipulation hypothesis. And it’s something that we’ve been working on over the last few years.
So one of the first things that we wanted to do in our study was to find out whether an infection with malaria actually makes you more attractive to mosquitoes or not.
So in Kenya with our colleagues, we designed an experiment where we had participants, children in Kenya, sleep inside tents. The odor from the tent was blown into a chamber which contained mosquitoes.
And the mosquitoes would behaviorally respond — they would fly towards or fly away from the odors depending on whether they liked them or not.
Now, some of the participants were infected with malaria and some of them were uninfected. But importantly, none of the children had any symptoms whatsoever.
Now, when we found and saw the results, it was really quite staggering. People who were infected with malaria were significantly more attractive than people who were uninfected.