• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information

PubMed Health. A service of the National Library of Medicine, National Institutes of Health.

A.D.A.M. Medical Encyclopedia [Internet]. Atlanta (GA): A.D.A.M.; 2013.

A.D.A.M. Medical Encyclopedia.

Schistosomiasis

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

Last reviewed: October 6, 2012.

Schistosomiasis is infection with a type of Schistosoma parasite.

Causes, incidence, and risk factors

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

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

The doctor or nurse will examine you. Tests that may be done include:

Treatment

This infection is usually treated with the drug praziquantel. If the infection is severe or involves the brain, corticosteroids may be given.

Expectations (prognosis)

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

Complications

Calling your health care provider

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.

Prevention

  • 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.

References

  1. Carvalho EM, Lima AAM. Schistosomiasis (Bilharziasis). In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 363.
  2. Maguire JH. Trematodes (schistosomes and other flukes). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 289.

Review Date: 10/6/2012.

Reviewed by: 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, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

What works?

  • Drug treatments for worms in the bladder (urinary schistosomiasis)Drug treatments for worms in the bladder (urinary schistosomiasis)
    Worms residing in blood vessels of the bladder cause a chronic disease known as urinary schistosomiasis. The disease is commonly found in African and Eastern Mediterranean countries, especially in poor, rural areas. Humans become infected when they come into contact with contaminated water. The infection occurs when small larvae shed from snails in infected waters get into the individual through the skin and develop into adult worms that travel to the blood vessels of the bladder. There they can produce a large number of eggs, and the worm can live for three to five years. It is mainly the eggs that cause the disease. The main symptoms are blood in the urine and pain when passing urine. The eggs also cause tissue damage, and the severity of disease depends upon the intensity of the infection. Sometimes the infection can lead to bladder cancer or other kidney problems, including kidney failure. There are a number of measures that have been introduced to try to reduce the risk of infection. These include health education, improving clean water supplies and sanitation, environmental control measures to reduce numbers of intermediate host snails, and drug treatments. The review looked at the efficacy of drugs to reduce the ill‐health associated with these infections. The review identified 24 trials involving 6315 people. Praziquantel and metrifonate were both found to be efficacious with few adverse events, although adverse outcomes were poorly assessed. Evidence on the artemisinins was inconclusive, and further research is warranted on combination therapies.
See all (3) ...

Figures

  • Swimmer's itch.
    Antibodies.

PubMed Health Blog...

read all...

MedlinePlus.gov links to free, reliable, up-to-date health information from the National Institutes of Health (NIH) and other trusted health organizations.

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...