Schistosomiasis is a chronic, parasitic disease caused by blood flukes (trematode worms).
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 life-cycle. Others become trapped in body tissues, causing an immune reaction and progressive damage to organs and blood vessels.
In 2012, more than 42.1 million people were treated for schistosomiasis.
Schistosomiasis is found in 78 countries in tropical and sub-tropical areas, mostly in Africa. People are at risk of infection due to agricultural, domestic and recreational activities which expose them to infested water.
Symptoms of schistosomiasis are caused by the body’s reaction to the worms’ eggs, and not by the worms themselves.
Intestinal schistosomiasis can cause abdominal pain, diarrhoea, blood in the stool, liver and spleen enlargement, fluid in the peritoneal cavity and hypertension of the abdominal blood vessels.
Urogenital schistosomiasis causes blood in the urine, lesions and fibrosis of the bladder, ureter and genitals, kidney damage and sometimes bladder cancer. It can cause infertility.
In children, schistosomiasis can cause anaemia and stunting, reducing their learning abilities.
The control of schistosomiasis is based on regular, large-scale treatment of at-risk population groups, access to safe water, improved sanitation, hygiene education and snail control.