Schistosomiasis

Diseases of liver, gastrointestinal tract and bladder caused by schistosomes, trematode worms that parasitize people. Infection is from infested water. There are three main species of these trematode worms (flukes) —Schistosoma haematobium, S. japonicum, and S. mansoni — that cause disease in humans. The larval forms of the parasite live in freshwater snails. The cercaria (form of the parasite) is liberated from the snail burrow into skin, transforms to the schistosomulum stage, and migrates to the urinary tract (S. haematobium), liver or intestine (S. japonicum, S.mansoni) where the adult worms develop. Eggs are shed into the urinary tract or the intestine and hatch to form miracidia (yet another form of the parasite) which then infect snails, completing the life cycle of the parasite. Adult schistosome worms can cause very serious tissue damage. Some schistosomes which cannot live within man nonetheless cause swimmer’s itch. Schistosomiasis is also called bilharzia after the shortlived German physician Theodor Bilharz (1825-1862).
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Infection with a species of Schistosoma; manifestations of this often chronic and debilitating disease vary with the infecting species but depend in large measure upon tissue reaction (granulation and fibrosis) to the eggs deposited in venules and in the hepatic portals, the latter resulting in portal hypertension and esophageal varices, as well as liver damage leading to cirrhosis. See tropical diseases, under disease. SEE ALSO: schistosomal dermatitis, Symmers clay pipestem fibrosis. SYN: bilharziasis, bilharziosis, hemic distomiasis, snail fever.
- Asiatic s. SYN: s. japonica.
- bladder s. SYN: s. haematobium.
- cutaneous s. japonica SYN: s. japonica.
- ectopic s. a clinical form of s. that occurs outside of the normal site of parasitism (mesenteric vein or hepatic portals); may result from accidental blood-borne transport of schistosome eggs or, rarely, adult worms, to various unusual sites such as the skin, brain, or spinal cord.
- s. haematobium infection with Schistosoma haematobium, the eggs of which invade the urinary tract, causing cystitis and hematuria, and possibly an increased likelihood of bladder cancer. SYN: bladder s., Egyptian hematuria, endemic hematuria, urinary s..
- S. intercalatum infection with Schistosoma intercalatum; occurs only in West Africa; few symptoms reported and no cases of hepatic fibrosis known.
- intestinal s. SYN: s. mansoni.
- s. japonica, Japanese s. infection with Schistosoma japonicum, characterized by dysenteric symptoms, painful enlargement of the liver and spleen, dropsy, urticaria, and progressive anemia. SYN: Asiatic s., cutaneous s. japonica, kabure itch, kabure, Katayama syndrome, Kinkiang fever, Oriental s., rice itch, urticarial fever, Yangtze Valley fever.
- Manson s. SYN: s. mansoni.
- s. mansoni infection with Schistosoma mansoni, the eggs of which invade the wall of the large intestine and the liver, causing irritation, inflammation, and ultimately fibrosis. SYN: intestinal s., Manson disease, Manson s..
- s. mekongi infection with Schistosoma mekongi, which chiefly afflicts children in the Mekong delta, where it was discovered; the disease is similar to s. japonica.
- Oriental s. SYN: s. japonica.
- pulmonary s. pulmonary manifestations of infection with Schistosoma, usually Schistosoma mansoni, occurring when schistosomals, which form in the skin from the cercariae which have entered from infected water, migrate via the bloodstream to the lungs, en route to the gastrointestinal tract and the portal vein; symptoms are usually limited to cough.
- urinary s. SYN: s. haematobium.

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schis·to·so·mi·a·sis .shis-tə-sō-'mī-ə-səs, .skis- n, pl -a·ses -.sēz infestation with or disease caused by schistosomes specif a severe endemic disease of humans in much of Africa and parts of Asia and So. America that is caused by any of three trematode worms of the genus Schistosoma (S. haematobium, S. mansoni, and S. japonicum) which multiply in snail intermediate hosts and are disseminated into freshwaters as furcocercous cercariae that bore into the body when it is in contact with infested water, migrate through the tissues to the visceral venous plexuses (as of the bladder or intestine) where they attain maturity, and cause much of their injury through hemorrhage and damage to tissues resulting from the passage of the usu. spiny eggs to the intestine and bladder whence they pass out to start a new cycle of infection in snail hosts called also bilharzia, bilharziasis, snail fever compare SWIMMER'S ITCH

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n.
a tropical disease caused by blood flukes of the genus Schistosoma. Eggs present in the stools or urine of infected people undergo part of their larval development within freshwater snails living in water contaminated with human sewage. The disease is contracted when cercaria larvae, released from the snails, penetrate the skin of anyone bathing in infected water. Adult flukes eventually settle in the blood vessels of the intestine (S. mansoni and S. japonicum) or the bladder (S. haematobium); the release of their spiked eggs causes anaemia, inflammation, and the formation of scar tissue. Additional intestinal symptoms are diarrhoea, dysentery, enlargement of the spleen and liver, and cirrhosis of the liver. If the bladder is affected, blood is passed in the urine and cystitis and cancer of the bladder may develop. The disease is treated with praziquantel.

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schis·to·so·mi·a·sis (shis″-) (skis″to-so-miґə-sis) infection with flukes of the genus Schistosoma; called also bilharziasis and bilharziosis.

Schistosomiasis. Colon biopsy specimen showing a schistosome egg granuloma.


Medical dictionary. 2011.

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