Question: are you hoping to kill the parasite once in the body or before it gets into the body

An excellent question. A parasite like this lives inside us and lays eggs. We urinate out the eggs, which hatch in fresh water into a different form of the parasite. This infects snails, and when inside the snail, transforms into the parasite that infects us. It’s a cycle. It’s also *incredible* that this is possible – that the parasite can do this, and evade our immune system.

So when is it best to kill the parasite? Well, we could spray all the fresh water in Africa, but imagine how difficult that is? You’d be spraying a whole continent! You could kill all the snails, but again, there are a lot of them. How do you find them all? What about animals that rely on the snail for food? The alternative is to kill the parasite when it’s in the human. That’s easier because you give medicine to a person, and you immediately make the person better, and you can measure that. So it’s easier to kill the parasite when it’s inside the person. That means taking a drug. This works pretty well at the moment. There are side effects, but our new version of the drug helps with that.

But it’s a really interesting question you can ask about any parasite. With malaria, for example – do you kill the parasite when it’s in the human? Do you try to kill the mosquito? Or the parasite in the mosquito? It depends a little bit on what’s possible, but also whether there is a weak point anywhere. Maybe the parasite that is in the mosquito is vulnerable to some drug that’s easy to make. That makes that a good strategy. At the moment there’s a lot of work going on to read all the DNA in these parasites – what’s known as decoding the genome of the parasites. The hope is that by doing that, and understanding it, we can discover things in the molecular structure of the parasites that we can use against them – like a flaw in the design we can hit with a drug. That’s a pretty new area of science.