Schistosoma infections are contracted through contact with contaminated water. The parasite in its infective stages is called a cercaria. It swims freely in open bodies of water. On contact with humans, the parasite burrows into the skin, matures into another larval stage (schistosomula), then migrates to the lungs and liver (where it matures into the adult form). The adult worm then migrates to the anatomic area of its preference, depending on which species is involved. Likely areas include the bladder, rectum, intestines, liver, portal venous system, spleen, and lungs.
Schistosomiasis is not usually found in the United States. However, it is prevalent in many tropical or subtropical areas, and it is a common illness thought to affect more than 200 million people.
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