Adult Schistosoma is found in the blood vessels of the bladder of humans. Schistosoma is a parasitic flatworm that causes a disease called schistosomiasis, which is transmitted by contact with contaminated water. When the larvae of the Schistosoma parasite penetrate the skin of a human host, they migrate to the veins in the abdominal area and then to the blood vessels of the bladder, where they develop into adult worms. These adult worms lay their eggs, which are passed out of the body in the urine, leading to a host of symptoms associated with schistosomiasis.