Schistosomiasis: progress report 2001–2011, strategic plan 2012–2020
Overview
Schistosomiasis remains a major public health problem with almost 240 million people, and more than 90% of them living in sub-Saharan Africa, requiring preventive chemotherapy. Schistosomiasis in humans results from infection with parasitic blood flukes of the genus Schistosoma. Six species of schistosomes cause infection in humans. While the disease is now predominantly in Africa, it also occurs in the Americas, the Eastern Mediterranean region, the Southeast Asian region and the Western Pacific.
Infection is acquired when parasitic larvae penetrate the skin of people exposed to infested freshwater. Early infection may be characterized by dermatitis. Followed by a systemic acute phase caused by the migration of the juvenile worms through the circulatory system. In later phases, parasite eggs from adult worms cause penetrate the mucosa of the urogenital tract and the intestine. In such organs, acute inflammation progressively becomes chronic, and hyperaemia, abnormal growths such as polyps and internal haemorrhage are gradually replaced by fibrosis and thickening of the tissues. Bladder cancer is a late-stage consequence of S. haematobium infection, while embolization of eggs from the intestine to the liver through the portal system is typical of infection with the other Schistosoma spp., and is responsible for progressive liver fibrosis, portal hypertension and ascites.
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