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Schistosomiasis

Schistosomiasis is cause by the trematode worms from the genus Schistosoma within tropical and subtropical regions. Infections are most common in poor communities where access to safe water and adequate sanitation systems and is usually associated with rural communities where agriculture and fishing is common. In 2014 it was estimated that at least 258 million people require preventive chemotherapy for schistosomiasis.

 

Life Cycle
Transmission of schistosomiasis requires sources of fresh water with fresh water snails where the eggs hatch releasing miracidia. Once the miracidia are released they infect the fresh water snails where they developed and multiply into free-swimming cercariae which can penetrate the skin.

Once in the body the larvae develops into the adult schistosome where they can be found in the blood vessels around either the intestines or bladder where the females release eggs. The infections are separated into two groups, four species which cause intestinal schistosomiasis and one species responsible for urogenital schistosomiasis.

Symptoms
The symptoms caused by schistosomiasis are a result of the body’s response (immune reaction) to the eggs which can be trapped in the body’s tissue. Intestinal schistosomiasis can cause abdominal pain, diarrhoea and blood in the stool as well as enlargement of the liver in advanced cases. Urogential schistosomiasis classical presents with haematuria (blood in the urine) though in advanced cases fibrosis of the bladder and ureter and kidney damage can be seen.

Infections of schistosomiasis are treated with praziquantel which kills of the worms.