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Reviewed/Revised Jul 2023
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What is schistosomiasis?

Schistosomiasis is an infection caused by a tiny parasite called a fluke.

  • Flukes are common in rivers and lakes in tropical areas in South America, Africa, and Asia

  • You can get schistosomiasis by swimming or bathing in water that has flukes in it

  • The flukes burrow into your skin and travel through your blood

  • They eventually end up in small blood vessels inside your intestines or your bladder

  • Symptoms first include an itchy rash, followed by fever, chills, muscle aches, weakness, and belly pain

  • Doctors test samples of your stool (poop) and urine (pee) for fluke eggs

  • Doctors treat you with antiparasite medicine to kill the flukes

What causes schistosomiasis?

Schistosomiasis is caused by a parasite called a fluke, which is a type of roundworm. Adult flukes are about ¼ to ¾ of an inch long (1 to 2 centimeters).

You get schistosomiasis from swimming, wading, or bathing in fresh water that has these flukes.

  • While you're in the water, the flukes get on your skin

  • The flukes burrow into your skin, and then they travel through your blood to your bladder or intestine

The flukes in your bladder or intestine lay many eggs:

  • The eggs irritate your tissues and cause ulcers, scars, and bleeding

  • Some eggs flow from the intestine to the liver

  • The eggs leave your body in your stool or urine

  • If your urine or stool get into fresh water, the eggs hatch and grow up to be able to infect somebody else

When eggs flow from the intestine to the liver, your liver can become inflamed. That can lead to scarring and increased pressure in the portal vein. The portal vein carries blood between the intestinal tract and the liver. High blood pressure in the portal vein (called portal hypertension) can cause your spleen to enlarge. It can also cause bleeding from veins in your esophagus (the "food pipe" that connects your throat and your stomach).

What are the symptoms of schistosomiasis?

Most people have no symptoms. When the flukes first enter your skin, you may get:

  • An itchy rash

After a few weeks, you may start to feel sick and have symptoms such as:

  • Fever

  • Chills

  • Cough

  • Muscle aches

  • Belly pain

Depending on where the adult flukes are in your body you may have:

  • Pain when peeing and blood in your urine

  • Bloody diarrhea (loose, watery stool)

  • An enlarged liver and spleen

A bad infection can make you lose enough blood to develop:

Schistosomiasis can also affect other organs, such as your lungs, spinal cord, kidneys, and brain.

How can doctors tell if I have schistosomiasis?

Doctors suspect schistosomiasis from your symptoms, especially if you've recently been swimming or bathing in possibly infected water. Doctors check for schistosomiasis by looking for fluke eggs in your:

  • Stool

  • Urine

  • Intestine or bladder tissue

How do doctors treat schistosomiasis?

Doctors treat schistosomiasis using:

  • Antiparasite medicine

Doctors may also test your stool or urine 1 or 2 months later to make sure it no longer has any fluke eggs in it.

How can I prevent schistosomiasis?

You can help prevent schistosomiasis by:

  • Not swimming, bathing, or wading in areas known to contain flukes

  • In areas where flukes are a problem, boiling water or storing it for a day or two before washing with it

  • Drying off vigorously with a towel if you accidentally get into contaminated water—this helps remove parasites before they burrow through your skin

When the eggs hatch in water, the flukes infect snails. So sometimes people put chemicals that kill snails in bodies of fresh water known to contain flukes.

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