Schistosomiasis is a disease caused by a parasitic flatworm that lives in freshwater. The worm (pictured) begins life as a tiny, free-swimming critter that infects a freshwater snail. Inside the snail, they develop into larvae – then decamp. Newly liberated, they seek out their next unsuspecting host, typically someone swimming in a river or lake. They burrow into the skin and migrate to the abdomen (taking a circuitous route via the lungs) to lay eggs. It’s the immune system’s vigorous reaction to these eggs that causes the disease, which can lead to kidney failure and bladder cancer. Lake Malawi, a popular tourist resort in East Africa, has an alarmingly high number of schistosome parasites – and the number of infected people is rising. A new study blames this on the surging human population around the lake, as well as on increasing agricultural land use and overfishing of snail-eating fish.
Written by Nick Kennedy
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