Male and female adult schistosomes live within blood vessels of the human intestines. The females release eggs that trespass the vessel walls and enter the intestinal lumen being eliminated with the human feces. When in water the egg releases a larva called miracidium that then swims to reach the snail that is the intermediate host.
Within the snail miracidia transform into cercariae, another kind of schistosome larva. The cercariae leave the snail and swim until penetrating through the human skin. In humans the cercaria gains the circulation infecting mainly the blood vessels of the intestines, liver or lungs and develops into the adult form of the parasite.   _{Your Comment}