- Schistosomiasis is an acute and chronic disease caused by parasitic worms.
- People are infected during routine agricultural, domestic, occupational and recreational activities which expose them to infested water.
- Lack of hygiene and certain play habits of school-aged children such as swimming or fishing in infested water make them especially vulnerable to infection.
- Schistosomiasis control focuses on reducing disease through periodic, large-scale population treatment with praziquantel; a more comprehensive approach including potable water, adequate sanitation and snail control would also reduce transmission.
- At least 261 million people required preventive treatment for schistosomiasis in 2013.
- More than 40 million people were treated for schistosomiasis in 2013.
Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. At least 261 million people required preventive treatment in 2013. Preventive treatment, which should be repeated over a number of years, will reduce and prevent morbidity. Schistosomiasis transmission has been reported from 78 countries. However, preventive chemotherapy for schistosomiasis, where people and communities are targeted for large scale treatment, is only
required in 52 endemic countries with moderate to high transmission.
Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta containing parasite eggs which hatch in water.
People become infected when larval forms of the parasite – released by freshwater snails – penetrate the skin during contact with infested water.
In the body, the larvae develop into adult schistosomes. Adult worms live in the blood vessels where the females release eggs. Some of the eggs are passed out of the body in the faeces or urine to continue the parasite’s life-cycle. Others become trapped in body tissues, causing immune reactions and progressive damage to organs.
Schistosomiais is prevalent in tropical and sub-tropical areas, especially in poor communities without access to safe drinking water and adequate sanitation. It is estimated that at least 90% of those requiring treatment for schistosomiasis live in Africa.
There are two major forms of schistosomiasis – intestinal and urogenital – caused by five main species of blood fluke (see table).
Table: Parasite species and geographical distribution of schistosomiasis