Schistosomiasis is caused by three agents: Schistosoma japonicum, S. haematobium, and S. mansoni. It is transmitted through contact with contaminated freshwater where cercariae penetrate the skin. Treatment includes praziquantel and oxamniquine, while prevention focuses on sanitation and eliminating the host snail. The three agents vary in their natural hosts, snail hosts, locations within the human body, and geographic distributions.