Just like malaria, schistosomiasis is caused by a tiny parasite that's transmitted to humans via an animal host known as a vector. The vector, in this case though, is not a mosquito but a snail. Yeah, just try there. So, let's have a look. Yeah, that looks like one. So that snail could infect up to 100 people over a period of a couple of months. And that's the problem. It's the kind of scale of individuals and numbers which gives this disease such a roothold in these environments. It's quite incredible. Well, it's funny first, let we know we're all standing here in waders just wearing gloves, protecting ourselves from this rather benign looking snail while, behind us. Mums are collecting water to bathe their kids in. Everyone's gonna be drinking the water and washing its. That's quite right. The parasite has evolved to live half of its life in the snail and half in the people it infects.


如疟疾一样，血吸虫病是由微小的寄生虫引发的。它会经由一种叫带菌体的动物寄主，传播到人体之中。在此情况下，带菌体不是蚊子而是蜗牛。 试试捞那边 我们来看一看 这里有一只 这只蜗牛会在短短几个月中，传染100人之多。这就是问题所在。此地人群的分布广而密集，让这种疾病根植于环境中。 真不可思议 我们正站在这里，穿着防水靴，戴着手套，保护自己，不会被这个毫不起眼的蜗牛感染。但在身后，妈妈在打水给孩子们洗澡，所有人都会饮用湖水，都会在这里洗涮 -没错 这种寄生虫已逐渐进化，既可存活在蜗牛中，也可依赖它所感染的人体生存。