schistosomiasis /shis′təsōmī″əsis/ [Gk, schistos + soma + osis, condition] , a parasitic infection caused by a species of fluke of the genus Schistosoma. It is transmitted to humans, the definitive host, by contact with water containing the infective stage of the parasite, the cercaria. A single fluke may live in one part of the body, depositing eggs frequently, for up to 20 years. The eggs are irritating to mucous membrane, causing it to thicken and become papillomatous. Symptoms depend on the part of the body infected. Schistosoma may be found in the bladder, rectum, liver, lungs, spleen, intestines, and portal venous system. Pain, obstruction, dysfunction of the affected organ, and anemia may result. Diagnosis requires morphological identification of the ova or the parasite. Depending on the species, treatment may be with praziquantel, oxamniquine, or metrifonate. Prevention is more effective. Proper disposal of human urine and feces, chlorination of water, and eradication of the intermediate host, the freshwater snail Australorbis glabratus, are totally effective. Second only to malaria in the number of people affected, schistosomiasis is particularly prevalent in the tropics and in Asia. Also called bilharziasis. See also blood fluke, Schistosoma.
