Schistosomiasis is an infection caused by trematodes (flukes). These schistosomes (also called blood flukes) are parasitic flatworms that belong to the genus Schistosoma. Parasites are creatures who live in or on another organism (host) and get their food from the host. This has a negative effect on the host.

In the case of schistosomiasis, the flukes are found in snails and then are shed into the water. If your skin comes in contact with contaminated water, the parasites can move into you and live there for years. The form of the parasite that infects humans after developing in the snail has a kind of forked head that allows it to penetrate your skin.

The three main types of schistosomes are responsible for the two main forms of the condition: urogenital schistosomiasis and intestinal schistosomiasis. This condition is also known as bilharzia or snail fever.


The worms that cause schistosomiasis live in freshwater, such as:

  • ponds
  • lakes
  • rivers
  • reservoirs
  • canals

Showers that take unfiltered water directly from lakes or rivers may also spread the infection, but the worms aren't found in the sea, chlorinated swimming pools or properly treated water supplies. You can become infected if you come into contact with contaminated water for example, when paddling, swimming or washing – and the tiny worms burrow into your skin.

Once in your body, the worms move through your blood to areas such as the liver and bowel. After a few weeks, the worms start to lay eggs. Some eggs remain inside the body and are attacked by the immune system, while some are passed out in the person's pee or poo.

Without treatment, the worms can keep laying eggs for several years. If the eggs pass out of the body into water, they release tiny larvae that need to grow inside freshwater snails for a few weeks before they're able to infect another person.  This means it's not possible to catch the infection from someone else who has it.


Many people have no symptoms of schistosomiasis. Early signs and symptoms (those that happen within days of being infected) may include itchiness and a skin rash.

Later symptoms (those that develop within 30 to 60 days of being infected) may include:

  • Fever.
  • Chills.
  • Cough.
  • Muscle aches and pain.

If you aren’t treated, symptoms that develop after years of being infected may include:

  • Pain in your stomach.
  • Enlarged liver (hepatomegaly).
  • Blood in your urine (pee), also called hematuria.
  • Difficulty or pain while urinating (dysuria).
  • Blood in feces (poop), also called hematochezia.
  • Miscarriage.

Chronic (long-lasting) schistosomiasis may make it more likely that you’ll develop scars on your liver or bladder cancer.

In rare cases, you might have eggs in your brain or spinal cord. If this is true, you may have seizures, become paralyzed or have an inflamed spinal cord.


Schistosomiasis is diagnosed through the detection of parasite eggs in stool or urine specimens. Antibodies and/or antigens detected in blood or urine samples are also indications of infection.

For urogenital schistosomiasis, a filtration technique using nylon, paper or polycarbonate filters is the standard diagnostic technique. Children with S. haematobium almost always have microscopic blood in their urine which can be detected by chemical reagent strips.

The eggs of intestinal schistosomiasis can be detected in faecal specimens through a technique using methylene blue-stained cellophane soaked in glycerin or glass slides, known as the Kato-Katz technique. In S. mansoni transmission areas, CCA (Circulating Cathodic Antigen) test can also be used.

For people living in non-endemic or low-transmission areas, serological and immunological tests may be useful in showing exposure to infection and the need for thorough examination, treatment and follow-up.

Note: Rate under the appropriate body system any residual disability of infection, which includes, but is not limited to, conditions of the liver, intestinal system, female genital tract, genitourinary tract, or central nervous system.

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