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Disease

Schistosomiasis (Bilharzia)

Learn about schistosomiasis, including its symptoms, diagnosis, laboratory tests, treatment and prevention.

Last Reviewed 26 Jul 2026
Reading Time 9 min read

Overview

Wading into a river to fish, washing clothes at the water’s edge, children swimming and playing in a lake, these are some of the most ordinary activities in many communities, and also exactly how schistosomiasis spreads. The parasite does not need dramatic circumstances to find its way in, just everyday contact with the wrong water.

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Key Fact

The larvae that cause schistosomiasis do not need to be swallowed or bitten into the body. They can penetrate directly through intact skin during ordinary contact with contaminated freshwater, often without the person even noticing at the time.

Warning

Blood in the urine or stool, or worsening abdominal pain and swelling, are signs of significant schistosomiasis and need medical assessment. If you live in or have visited an area where schistosomiasis is common and have had contact with freshwater, ask your doctor about testing even without symptoms.

AT A GLANCE

Disease Summary

Category Infectious Disease
Cause Parasitic flatworms (blood flukes) of the genus Schistosoma
Transmission Skin contact with freshwater containing larvae released by infected freshwater snails
Body System Urinary Tract and Intestines
Preventable Yes
Curable Yes

Symptoms

Common Symptoms

Symptoms depend on which form of schistosomiasis is present, and many people, especially with mild infection, have few or no symptoms at first. In some people, particularly those newly exposed, a feverish illness with cough and abdominal pain can develop several weeks after infection.

Blood in the Urine

The classic sign of urogenital schistosomiasis, sometimes visible, sometimes only detectable through a urine test.

Abdominal Pain

Common in intestinal schistosomiasis, often alongside general discomfort.

Diarrhoea or Blood in the Stool

Can occur with intestinal schistosomiasis, particularly with heavier infection.

Skin Rash or Itching

Can appear at the site where larvae entered the skin, sometimes called swimmer’s itch.

Fatigue

General tiredness can accompany the infection, particularly if it has caused anaemia.

Signs of Advanced Disease

These can indicate significant organ involvement and need prompt medical assessment.

Severe Abdominal Swelling

Can indicate fluid buildup from advanced liver involvement and needs prompt assessment.

Persistent Blood in Urine or Stool

Ongoing bleeding should be evaluated, particularly to rule out complications like bladder or organ damage.

Difficulty or Pain When Urinating

Can indicate bladder or urinary tract involvement that needs assessment.

Unusual Vaginal Bleeding or Pelvic Pain

In women, these can be signs of female genital schistosomiasis and deserve prompt evaluation, especially in areas where the disease is common.

Diagnosis

Stool Examination

Detects parasite eggs in the stool, the standard method for diagnosing intestinal schistosomiasis.

Urine Examination

Detects parasite eggs or microscopic blood in the urine, the standard method for diagnosing urogenital schistosomiasis.

Blood Test for Antibodies or Antigens

Useful for people who have travelled to or from endemic areas, or in settings where egg detection is less reliable.
Important
Because eggs are not always present in every sample, especially with lighter infections, more than one stool or urine sample may be needed to confirm the diagnosis.

Laboratory Tests

Kato-Katz Stool Examination

A standard microscopy technique that detects and counts Schistosoma eggs in the stool, used mainly for intestinal schistosomiasis.

Sample Stool
Time Same day

Urine Filtration and Microscopy

Detects Schistosoma eggs in urine, the standard method for urogenital schistosomiasis.

Sample Urine
Time Same day

Urine Reagent Strip Test

Checks for microscopic blood in the urine, a simple field test often used for community screening.

Sample Urine
Time Immediate

Circulating Cathodic Antigen (CCA) Test

Detects a parasite antigen and is particularly useful for Schistosoma mansoni infection.

Sample Urine
Time Same day

Laboratory Note

Community screening programmes often rely on simple field tests, such as urine reagent strips, to identify people and areas that need treatment, rather than requiring laboratory microscopy for every person.

Treatment

Praziquantel

An effective, safe, and low-cost medication that treats all forms of schistosomiasis and is used both for individual treatment and large-scale community programmes.

Route Oral
Duration Single dose

Management of Complications

For advanced disease, additional care may be needed for complications such as bladder or liver damage, separate from treating the underlying infection.

Route Varies
Duration Ongoing, as needed

Treatment Note

Praziquantel clears the infection effectively, but reinfection is common in areas where contact with contaminated water continues. Repeated treatment over time is often part of long-term control in endemic communities.

Prevention

Avoid contact with untreated freshwater in endemic areas

Swimming, wading, or washing in lakes, rivers, or irrigation canals in endemic areas carries a risk of infection.

Support mass treatment programmes

Periodic praziquantel treatment of at-risk communities, especially school-aged children, reduces both illness and transmission.

Improve access to safe water and sanitation

Reduces both the need for contact with natural water sources and the contamination of water with parasite eggs.

Support snail control efforts

Reducing the population of the freshwater snails that carry the parasite’s larval stage helps interrupt transmission.

Prevention Note

Because the parasite depends on both contaminated water and a specific freshwater snail to complete its lifecycle, prevention works best when it combines treatment, safe water access, and environmental measures together.

Risk Factors

Higher Risk of Infection

These groups have the most frequent contact with contaminated freshwater.

  • School-aged children, who often swim or play in infested water
  • Fishermen, farmers, and irrigation workers
  • Women doing domestic tasks such as washing clothes in infested water

Increased Risk of Severe Disease

These factors increase the chance of developing more significant illness.

  • Heavy or repeated infection over time
  • Limited access to treatment or healthcare

Geographic Risk

Where someone lives significantly affects their risk of exposure.

  • Living in or travelling to one of the more than 75 countries where schistosomiasis is transmitted, with the highest burden in sub-Saharan Africa

Risk Note

Nearly 94 percent of people needing treatment for schistosomiasis live in Africa, making it one of the most significant neglected tropical diseases on the continent.

Complications

Bladder and Kidney Damage

Long-term urogenital schistosomiasis can scar the bladder and ureters and, in advanced cases, damage the kidneys.

Liver and Spleen Damage

Chronic intestinal schistosomiasis can enlarge the liver and spleen and lead to fluid buildup in the abdomen.

Infertility

Genital schistosomiasis in both women and men can cause lasting reproductive harm if untreated.

Complication Note

Most of these complications develop after years of untreated or repeated infection, which is why periodic treatment in endemic communities focuses on preventing this kind of long-term damage, not just treating symptoms.

When to Seek Medical Care

Blood in the Urine or Stool

Should be evaluated, particularly in or after time spent in an area where schistosomiasis is common.

Persistent Abdominal Pain or Swelling

Can indicate liver involvement and needs assessment.

Unusual Vaginal Bleeding, Pelvic Pain, or Genital Lesions

May indicate female genital schistosomiasis and deserve prompt evaluation.

Known Freshwater Contact in an Endemic Area

Even without symptoms, anyone with this kind of exposure should ask a healthcare provider about testing.

Emergency Advice

Because early and mild schistosomiasis often causes few or no symptoms, testing after known exposure matters as much as responding to visible signs.

Prognosis

Excellent With Treatment

A single dose of praziquantel effectively treats the infection and prevents progression to severe disease.

Reinfection Is Common in Endemic Areas

Ongoing contact with contaminated water means periodic retreatment is often needed.

Complications Are Preventable With Early and Repeated Treatment

Even where reinfection occurs, regular treatment substantially reduces the risk of severe, long-term organ damage.

Prognosis Note

Schistosomiasis disables far more than it kills, but its long-term effects on the liver, kidneys, bladder, and reproductive health are almost entirely preventable with access to regular treatment.

Differential Diagnosis

Urinary Tract Infection

Can also cause blood in the urine and discomfort, though it is caused by bacteria rather than a parasite and responds to antibiotics rather than praziquantel.

Typhoid Fever

Can cause abdominal pain and general illness in the same regions, though it typically also causes a prolonged fever.

Liver Disease from Hepatitis B

Can also cause liver enlargement and abdominal swelling in the same regions, and the two can occur together.

Clinical Note

Blood in the urine or stool without an obvious infection, especially in someone with a history of freshwater contact in an endemic area, should prompt specific testing for schistosomiasis.

References

World Health Organization (WHO)

World Health Organization fact sheet on schistosomiasis transmission, epidemiology, symptoms, diagnosis, and control strategy.

Centers for Disease Control and Prevention (CDC)

Public information on schistosomiasis causes, symptoms, diagnosis, and treatment.

CDC Clinical Overview of Schistosomiasis

Clinical guidance for healthcare providers on acute and chronic schistosomiasis, testing, and treatment.

Frequently Asked Questions

Is schistosomiasis contagious between people?
No, not directly. It spreads through contact with freshwater containing larvae released by infected snails, not through contact with an infected person.
Can schistosomiasis be cured?
Yes. A single dose of praziquantel effectively treats the infection. Reinfection is common in areas with ongoing water contact, so periodic retreatment is often part of long-term care.
How do I know if water is safe?
In areas where schistosomiasis is common, any untreated freshwater, lakes, rivers, ponds, or irrigation canals, should be considered a possible risk. Water that has been properly treated or comes from a safe piped source does not carry this risk.
Can children get schistosomiasis?
Yes, and school-aged children are among those most affected, since swimming and playing in infested water is common. This is why many treatment programmes specifically target children in endemic areas.