Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Although the worms that cause schistosomiasis are not found in the United States, more than 200 million people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease. Schistosomiasis is considered one of the Neglected Tropical Diseases (NTDs).
The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, hence contaminating water. You can become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by Schistosoma mansoni, S. haematobium, or S. japonicum.
Image: Left: Biomphalaria sp., the intermediate host for S. mansoni. Right: Bulinus sp., the intermediate host for S. haematobium and S. intercalatum. Center: Adults of S. mansoni. The thin female resides in the gynecophoral canal of the thicker male. Credit: DPDx