What Is Schistosomiasis Disease?

Caused by parasitic worms found in fresh water

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Schistosomiasis is a disease caused by a parasitic worm. A parasite is an organism that invades a human body (called the host) and feeds off it to survive. The worm that causes schistosomiasis can damage several organs.

Without early treatment, schistosomiasis can also cause a range of concerns including miscarriage, anemia, liver disease, and brain inflammation.

In this article, you'll read about how different types of schistosomiasis affect the body and how the disease can be prevented and treated.

Schistosomes Parsitic Worms

NIBSC / Getty Images

Worldwide, schistosomiasis infects about 200 million people. It affects more people than any other parasitic disease with the exception of malaria

How Do You Get Schistosomiasis?

Schistosomiasis is caused by several different types of flatworms. These worms live in freshwater snails in tropical parts of the world, including:

  • South America
  • Africa
  • Asia
  • Some islands in the Caribbean Sea

In 2013, there was an outbreak of schistosomiasis in Corsica, an island in the Mediterranean Sea.

Schistosomiasis, which is also known as bilharziasis, isn’t found naturally in the United States. However, it is possible to come into contact with the parasite while traveling.

Parasites need hosts to survive. The worms that cause schistosomiasis have several hosts, including humans, other mammals, birds, and a specific type of water snail. These hosts are critical to the life cycle of the worm. They also play a part in helping schistosomiasis spread.

The eggs hatch in freshwater and the larvae infect water snails. The snails provide an environment for the larvae to mature. After maturation, the larvae leave the snail and go on to infect another host such as a person. They enter the body through the skin, often when a person is swimming or bathing.

Inside the next host, the worms reproduce and lay eggs. Some of these eggs are passed out of the body through urine and feces. Others travel to different parts of the body where they cause schistosomiasis. The disease can be either short-term (acute) or long-term (chronic). Where the eggs end up in the body depends on the type of schistosomiasis.

The worm's life cycle continues when the host urinates or defecates in a source of freshwater. This is why schistosomiasis is prevalent in regions that don’t have advanced sanitation systems. In these areas, as many as 60% to 80% of school-age children are actively infected.

Types of Schistosomiasis

There are six different species of flatworms, known as blood flukes, that cause schistosomiasis in humans.

  • Schistosoma mansoni: This is the most common species, infecting over 80 million people. S. mansoni is found in parts of South America, Africa, and the Middle East. It causes severe liver damage.
  • Schistosoma haematobium: These worms are also found in Africa and the Middle East. Eggs infect the bladder and urinary and genital tracts.
  • Schistosoma japonicum: This species is found in Asia, mostly in China and the Philippines. Its eggs usually lodge in the liver and intestines. In rare cases, it can infect the brain or spinal cord, resulting in seizures and paralysis.
  • Schistosoma intercalatum: This species is most often found in Gabon, the Democratic Republic of the Congo, and Cameroon. Like other types, it can cause stomach and intestinal problems.
  • Schistosoma guineensis: This species is found in west and central Africa. It becomes stuck in the blood vessels of the liver or intestine, which causes diarrhea, constipation, and bloody stool.
  • Schistosoma mekongi: This species is similar to S. japonicum, but it’s found along the Mekong River, especially in Cambodia and Laos. It infects the intestine and liver.


You may not have symptoms when you’re infected with the larvae that cause schistosomiasis. Many people, though, show signs of infection within weeks.

These symptoms can last for a short time, but in some instances, people have health problems for years.


Acute schistosomiasis can last two to eight weeks.

Symptoms may include:

  • Itchiness where the larvae entered
  • Rash
  • Fever
  • Headache
  • Muscle pain
  • Cough or other respiratory symptoms

This type of acute condition is known as Katayama syndrome. Symptoms may start when you’re first infected or sometime later.


Without treatment, schistosomiasis can become chronic. The symptoms can last for years and often become more serious. 

Long-term problems start if parasitic eggs get permanently trapped in organs like the liver. Your immune system recognizes they are harmful and fights the intruders. That leads to inflammation.

Symptoms of chronic schistosomiasis include:

  • Stomach pain
  • An enlarged liver
  • Blood in the urine and stool 
  • Problems passing urine
  • Sores or ulcers on the walls of your intestines or other internal body areas

People at high risk of repeated infections, like fishermen or people who regularly wash in infested lakes, are more likely to develop chronic schistosomiasis.

The parasitic flatworms live an average of three to 10 years. In some cases they can continue to lay eggs and infect a person for as long as 40 years.


Chronic schistosomiasis can cause serious and even permanent damage to your body. This can cause many health problems, including:

  • Urinary tract disorders: S. haematobium may damage the bladder and kidneys.
  • Sexual health concerns: S. haematobium eggs may infect the lining of the uterus, causing painful lesions that bleed. These lesions can also increase the risk of HIV infection. Infertility and miscarriage are other possible risks of schistosomiasis.
  • Liver health: Eggs from S. mansoni and S. mekongi can travel to and become lodged in the tissues of the liver. This can lead to the development of polyps (tissue growths). It can even cause dangerous scarring (cirrhosis) that can impact how this important organ works.
  • Children's health: In communities where schistosomiasis is common, children usually have their first infection by age 2. This can lead to anemia, stunted growth, malnutrition, and learning problems.
  • Cancer: When they travel to the liver, intestines, and bladder, these parasites can increase the risk of liver, colorectal, and bladder cancers.


Schistosomiasis is usually diagnosed with laboratory analysis of a urine or stool sample. Before taking a sample, your healthcare provider will ask about your travel history. This will help determine which type of infection you may have.

The laboratory will look for the parasite's eggs in the stool or urine sample. It may be necessary to examine multiple samples taken on different days. A blood test that looks for antibodies can also help identify the parasite.


Medication can cure schistosomiasis. Biltricide (praziquantel) is an anthelmintic drug, which means it kills worm-like parasites. It’s usually taken three times in one day to treat the infection and rid the body of the eggs. 

If the infection doesn’t completely clear up, another round of medication is given three to six weeks later. If you develop complications, you may need additional treatment.

Unfortunately, treatment to cure schistosomiasis may not work. Some cases of schistosomiasis are resistant to medication, which means the drug does not affect the worms. And if the disease is found late, damage that’s already been done can't be reversed. 


Schistosomiasis can cause severe medical problems before you even know you’re infected. That’s why avoiding infection is the best way to stay healthy. 

If you’re visiting an area where schistosomiasis is known to be present, take these cautionary steps:

  • Don’t go into freshwater. Even dipping your toes into a lake could lead to an infection.
  • Only drink safe water. You don’t get schistosomiasis by swallowing infected water, but the parasites can enter through your lips or other body parts that touch the water.
  • If you’re unsure where the water came from, boil it for at least one minute before drinking it or cooking with it.
  • Boil (and then cool) the water you use for bathing.
  • If you accidentally have contact with freshwater, rub a towel vigorously on your skin. This could help prevent the parasites from entering.

In some regions, the World Health Organization uses large-scale, periodic praziquantel treatment in affected populations.


Schistosomiasis is a dangerous disease. Not everyone who gets infected ends up with serious health problems, but the risks are high. 

If you travel to areas where the species are known to thrive, avoid freshwater. See a doctor if you think you’ve been exposed to parasite-infested water, even if you don’t have symptoms.

If you are diagnosed with an infection, medication usually works to get the eggs out of your system. It's important to start treatment early before any organ damage develops.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Megan Coffee, MD
Megan Coffee, MD, PhD, is a clinician specializing in infectious disease research and an attending clinical assistant professor of medicine.