You get a schistosoma infection 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 stage (schistosomula), then migrates to the lungs and liver, where it matures into the adult form.
The adult worm then migrates to its preferred body part, depending on its species. These areas include the bladder, rectum, intestines, liver, portal venous system (the veins that carry blood from the intestines to liver), spleen, and lungs.
Schistosomiasis is not usually seen in the United States. It is common in many tropical and subtropical areas worldwide.
Symptoms vary with the species of worm and the phase of infection.
Heavy infestation (many parasites) may cause fever, chills, lymph node enlargement, and liver and spleen enlargement.
Initial invasion of the skin may cause itching and a rash (swimmer's itch). In this condition, the schistosome is destroyed within the skin.
Intestinal symptoms include abdominal pain and diarrhea (which may be bloody).
Urinary symptoms may include frequent urination, painful urination (dysuria), and blood in the urine (hematuria).
Signs and tests
Antibody test to checks for signs of schistosome infection
Biopsy of tissue suspected of being infected
Complete blood count (CBC) to check for signs of anemia
Eosinophil count to measure the number of certain white blood cells
Call your health care provider if you develop symptoms of schistosomiasis, especially if you have traveled to a tropical or sub-tropical area where the disease is known to exist or if you have been exposed to contaminated or suspect bodies of water.
Avoid swimming or bathing in contaminated or potentially contaminated water
Avoid bodies of water of unknown safety
Snails are an intermediate host for the parasite. Getting rid of snails in bodies of water used by humans would help prevent infection.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.