Bilharzia is a parasitic disease caused by a flatworm called Schistosoma. In Madagascar we find three species of Schistosoma, namely Schistosoma mansoni, responsible for intestinal Bilharzia; Schistosoma haematobium, responsible for Bilharzia bladder and Schistosoma intercalatum, responsible for rectal Bilharzia. They are found in fresh standing water or in streams with little flow. They first pass through intermediate hosts, which are snails, before being transmitted to humans.