Schistosomiasis
Schistosomiasis or Bilharziasis, widespread disease caused by the infestation of the human body by (flukes) commonly called blood flukes, of the genus Schistosoma. Blood flukes spend most of their life cycle in two hosts; the adult stage is spent in a mammal, usually humans, and the immature stages are spent in certain snails. Eggs discharged from the host hatch into larval forms in fresh water; from the water, the larvae, miracidia, invade the snail that acts as an intermediate host. The larval form of the parasite undergoes partial maturation in the snail, then escapes back into the water, as mature larvae called cercariae. At this stage they penetrate the skin of the host from the water and then migrate through the blood vessels to specific capillaries as maturation completes. There they remain and lay eggs.