Schistosoma mansoni is a trematode flatworm, one of a number of species of schistosome causing the parasitic disease schistosomiasis, or Bilharzia. Schistosomiasis affects over 200 million people worldwide.

• Urinary schistosomiasis - parasites progressively damaging the bladder, ureters and kidneys.
• Intestinal schistosomiasis - parasites progressively enlarging the liver and spleen, damaging the intestine and causing hypertension of the abdominal blood vessels.

Drug treatment, snail control, improved sanitation and health education are being used to try and control schistosomiasis.