Schistosomiasis Health Article

Definition

Schistosomiasis is an infection caused by one of the five species of the parasite Schistosoma.

Alternative Names

Bilharzia; Katayama fever; Swimmer's itch; Blood fluke

Causes, incidence, and risk factors

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 (the veins that serve the liver), spleen, and lungs.

Schistosomiasis is not usually found in the United States. However, it is common in many tropical or subtropical areas, and it is a common illness thought to affect more than 200 million people.

Symptoms

• Symptoms vary with the species of worm and the phase of infection.
• Initial invasion of the skin may cause itching and a rash (swimmer's itch).
• Heavy infestation (a large number of parasites) may cause fever, chills, lymph node enlargement, and liver and spleen enlargement.
• Urinary symptoms may include frequent urination, painful urination (dysuria), and blood in the urine (hematuria).
• Intestinal symptoms include abdominal pain and diarrhea (which may be bloody).

Signs and tests

• Test for schistosome eggs in urine
• Test for schistosome eggs in stool
• Biopsy of tissue suspected of being infected
• Anemia (low number of red blood cells)
• High eosinophil (a type of white blood cell) count in blood
• Low platelets
• Urinalysis
• Antibody test

Treatment

• Praziquantel
• With acute infection, corticosteroids may be given

Expectations (prognosis)

Treatment before significant damage or severe complications occur usually produces good results.

Complications

• Kidney and bladder obstruction
• Chronic renal failure
• Bladder cancer
• Chronic liver damage and an enlarged spleen
• Colon (large intestine) inflammation with bloody diarrhea
• Pulmonary hypertension
• Right-sided heart failure
• Seizures
• Repeated secondary blood infections can occur, because bacteria can enter the bloodstream via the colon if it has become irritated