Abstract Schistosomiasis is caused by parasitic flatworms (Schistosoma). The disease in humans can be caused by seven different species of Schistosoma: S. mansoni, S. japonicum, S. haematobium, S. malayensis, S. mekongi, S. guineensis and S. intercalatum, as well as by hybrids between species, including livestock schistosome species. People are infected when exposed to infested water and the parasite larvae penetrate the skin.