Schistosomiasis, also known as bilharzia or snail fever, is a parasitic infection caused by trematode worms of the Schistosoma genus. The infection occurs when an individual comes into contact with freshwater contaminated with the larvae of the parasite. The larvae penetrate the skin and migrate through the body, maturing into adult worms that reside in blood vessels, where they lay eggs. Some eggs are passed out of the body in urine or feces, while others become trapped in tissues, causing an immune response and various symptoms.