Schistosomes belong to the phylum Plathelminthes, class Trematoda, family Schistosomatidae. Five species of schistosomes: Schistosoma mansoni, Schistosoma haematobium, Schistosoma japonicum, Schistosoma intercalation and Schistosoma mekongi - are the causative agents of helminthiasis in humans. Schistosomes differ from all other representatives of the class Trematoda in that they are dioecious and have sexual dimorphism.