Bilharzia: Symptoms, Causes, Treatment and Prevention

Bilharzia prevention and treatment
Medically reviewed by Dr. Mavra Farrukh

Bilharzia or ‘snail fever’ is also known as Schistosomiasis. It is an infection caused by a parasitic worm that lives in fresh water in tropical and subtropical regions (especially in poor communities without access to safe drinking water and sufficient sanitation). 

Here in this article, you will get information about everything thing you need to know about bilharzia.

What is Bilharzia?

Bilharzia is a severe condition that can lead to chronic illness. It is mainly found in Africa, South America, the Caribbean, the Middle East, and Asia. 

It affects the intestines and urinary system preferentially, but as it lives in the blood vessels, it can also harm other body systems. More than 140 million people are infected with bilharzia. 

Types of Bilharzia 

There are three types of bilharzia.

  • Schistosoma haematobium

It is a digenetic trematode species belonging to a group (genus) of blood flukes. It’s found in Africa, South America, and the Middle East. It is the primary agent of bilharzia. Besides causing urinary bilharzia, it is also the leading cause of bladder cancer.

  • Schistosoma japonicum

It is an important parasite and one of the major infectious agents of bilharzia. It has a very large host range, infecting at least 32 species of wild mammals, including nine carnivores, 17 rodents, one primate (human), two insectivores, and three artiodactyls. It is, therefore, an actual zoonotic disease.

  • Schistosoma mansoni 

It is a water-borne parasite of humans that belongs to the group of blood flukes. It causes intestinal bilharzia. The eggs cause clinical symptoms. As the leading cause of Schistosomiasis worldwide, it’s the most prevalent human parasite. 

  • Schistosoma intercalatum

It is a parasitic worm primarily found in parts of western and central Africa. It has two main strains: the Lower Guinea strain and the Zaire strain. Moreover, Schistosoma intercalatum is one of the major agents of the rectal form of bilharzia. Being a trematode, it belongs to the genus Schistosoma, and since its adult lives in the blood vessels, it is commonly called a blood fluke. Its life cycle is very similar to that of Schistosoma haematobium. It is usually diagnosed by using clinical and epidemiological information.

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What is Urinary Schistosomiasis(Bilharzia )?

It’s a human disease condition caused by infection of the trematode Schistosoma haematobium. It is found in the venous plexus draining the urinary bladder of humans. During this infection, the parasites deposit terminal spined eggs, which clog the venous plexus, impeding blood flow. This bursts the veins, allowing blood and eggs to enter the urinary bladder, resulting in the characteristic symptom of blood in urine or haematuria.

Symptoms of Bilharzia 

Many people with bilharzia do not experience any symptoms at all or for several months or even years.

You probably will not notice that you have been infected, although sometimes people may get small, itchy, red, or brown bumps on their skin for a few days or weeks where the worms burrow in.

Some common symptoms that may occur are the following:

  • High body temperature (fever)
  • Raised, red, and itchy rash
  • a cough
  • diarrhea 
  • muscle and joint pain
  • hepatomegaly (enlarged liver)
  • blood in feces or urine 
  • stomach pain
  • a general sense of feeling unwell

The symptoms known as acute Schistosomiasis often get better within a few days or weeks. Still, treating the parasite is important because it can remain in your body for a long time.

Symptoms of Schistosomiasis in the Brain

The clinical symptoms of neurological Schistosomiasis are mentioned below:

Seizures are also common in cerebral Schistosomiasis. While nausea, vomiting, brain hernia, and ataxia are more common in cerebellum and brainstem bilharzia.

Causes of Bilharzia:

A parasitic worm causes Schistosomiasis in certain snails that live in freshwater locations. Showers that use water directly from such lakes can spread this worm. Once this parasite comes in contact with the human body, it infects the body with its forked head. Schistosome larvae become adults inside the body. During their life cycle, female worms release eggs into blood vessels. Some eggs are excreted in feces or urine to continue the parasite’s life cycle. The rest are trapped in body tissues, resulting in immune reactions and progressive organ damage.

Also, when the Infected people release urine and feces infected with eggs into the water where the snails are, these eggs move into the snails, and the cycle goes on. Schistosoma mansoni, S. haematobium, or S. japonicum cause most infections. Infected children and adults get infected over and over again. However, people cannot infect each other. 

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Long-Term Complications Caused by Schistosomiasis

Schistosomiasis can cause a variety of long-term complications if left untreated. Some of these complications include:

Chronic Kidney Disease

Schistosomiasis can cause inflammation and scarring of the kidneys, leading to chronic kidney disease and eventual kidney failure.

Liver Damage

The eggs of the schistosome parasite can become trapped in the liver, causing inflammation and scarring that can lead to liver damage or cirrhosis.

Bladder Cancer

Chronic infections with Schistosoma haematobium, a parasite species that infect the urinary tract, can increase the risk of developing bladder cancer.


Schistosomiasis can cause chronic blood loss, leading to anemia and its associated symptoms, such as weakness, fatigue, and shortness of breath.


Chronic infections with schistosomiasis can lead to malnutrition, as the parasites can compete with the host for nutrients.

Cognitive Impairment

Schistosomiasis can cause neurological damage and cognitive impairment, especially in infected children.


Infection with Schistosoma haematobium can cause inflammation and scarring of the female reproductive organs, leading to infertility. In males, the infection can obstruct the vas deferens, leading to infertility.

Increased Susceptibility to Other Infections

Schistosomiasis can impair the immune system, making infected individuals more susceptible to other diseases.

Impaired Growth and Development 

Chronic infections with schistosomiasis can impair growth and development in children, leading to stunted growth and cognitive delays.

Medical Conditions Associated With Bilharzia

Regardless of their symptoms, some people with bilharzia eventually develop more severe problems in parts of the body the eggs have traveled to. This condition is known as chronic Schistosomiasis.

Chronic Schistosomiasis can include various symptoms and problems depending on the infected area.

For example, an infection in the:

  • The Digestive system can cause anemia, stomach pain, swelling, and diarrhea.
  • Hematochezia or rectal bleeding.
  • The Urinary system can irritate the bladder (cystitis), causing pain while peeing, a frequent need to pee, and blood in your pee.
  • Heart and lungs can cause a persistent cough, wheezing, and shortness of breath
  • Coughing up blood.
  • The nervous system or brain can cause seizures (fits) and headaches.
  • Weakness and numbness in your legs.
  • Dizziness 

Without treatment, it can damage the affected organs permanently.

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Prevention of Bilharzia

You should not do things in water from fresh pools, lakes, or rivers in areas known to have the snails and parasites that cause bilharzia.

  • Do not assume that the water is safe and clean because people tell you it is OK. It is better not to take the chance in places where the parasite is known to exist.
  • Do not drink from these bodies of water. It is not that you will get the parasites from drinking the water, but they can enter the skin around your mouth.
  • Do not bathe or swim in these water locations.
  • Do not wash clothes in these water locations.

You can use a towel to dry yourself off vigorously if you get wet. That may help, but you should not rely on it. Also, drink safe water. While bilharzia cannot be transmitted by drinking contaminated water, it can be transmitted by coming into contact with it. You should either boil or filter water before drinking it because water from canals, lakes, rivers, streams, or springs may be contaminated with germs and infectious organisms. Boiling the water for at least 2 minutes will kill harmful parasites, bacteria, or viruses. Iodine treatment alone cannot guarantee that water is safe and free of all parasites.

Diagnosis of Bilharzia 

Sometimes eggs can be found in stool or urine samples, but a blood test is often required for the diagnosis. All of these samples are examined under a microscope.

Moreover, diagnosing brain schistosomiasis is difficult, as clinical findings are not specific. Evidence of schistosome ova in stool or urine may or may not be present. In this case, neuroimaging examinations can give significant help. The leptomeninges and cerebral cortex are the most common sites involved, whereas the cerebellum, thalamus, hippocampus, midbrain, basal ganglia, choroid plexus, and white matter are less frequently involved. By examining these areas properly, a healthcare provider can successfully diagnose Schistosomiasis.

Investigations For Schistosomiasis

The diagnostic investigations for bilharzia, also known as schistosomiasis, include

Blood Tests for Schistosomiasis

These are done to detect antibodies against the schistosome parasite or to identify specific antigens produced by the parasite. These tests can help diagnose both active and past infections.

Microscopic Examination of Stool

Stool samples can be examined for the presence of schistosome eggs, which can indicate an active infection.

Microscopic Examination of Urine

Urine samples can be examined for the presence of schistosome eggs, which can indicate an active infection with Schistosoma haematobium, a species of parasite that infects the urinary tract.

Imaging Tests for Schistosomiasis

Imaging tests such as ultrasound or X-ray may be used to detect and assess the extent of organ damage caused by chronic infections.

Importance of Biopsy in Bilharzia

In some cases, a biopsy of affected tissue may be performed to confirm the presence of schistosome eggs and assess the extent of tissue damage.

Point-of-Care Tests

Point-of-care tests, also known as rapid diagnostic tests, are simple and easy-to-use tests that can detect antigens or antibodies to the schistosome parasite in blood or urine samples. These tests can be performed in the field or at the bedside and provide results within minutes. These are discussed in detail later in the blog.

Serology for Schistosomiasis

It is a blood test that detects antibodies against the schistosome parasite. Serology tests can be used to diagnose past or current infections and can also be used to monitor treatment efficacy.

Polymerase Chain Reaction (PCR) for Schistosomiasis

PCR is a molecular test that detects the DNA of the schistosome parasite in blood or tissue samples. PCR can detect the parasite early in infection, even before eggs are detectable in the stool or urine samples.

Treatment of Bilharzia

Bilharzia is treated with the prescription medication praziquantel (Biltricide). It is provided as a pill and belongs to a class of medications called anthelmintics. These types of drugs kill worms.

You can take praziquantel with water and food. It is usually taken for one day, either as a single larger dose or three smaller doses in one day.

Before taking any medication, you should tell your doctor what other medicines and supplements you take and what allergies you have.

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Who Is At Risk of Bilharzia?

Anyone can get infected by these parasites by swimming or bathing in contaminated water. This parasite is found in freshwater lakes, rivers, and ponds in the following areas:

  • Many parts of Africa, including sub-Saharan Africa and southern Africa. The worms are also found in the Maghreb, a region of North Africa, and the Nile River valley in Egypt and Sudan.
  • Brazil, Surinam, and Venezuela (South America).
  • Dominican Republic, Guadeloupe, Martinique (the Caribbean). The risk of bilharzia in the Caribbean is not very high.
  • Areas in Southeast Asia and the Philippines, Laos, and Cambodia.
  • Corsica 

Bilharzia mostly affects poor and rural communities, particularly agricultural and fishing populations. Women that perform domestic chores in infected water, such as washing clothes, are also at risk and can develop female genital Schistosomiasis. Inadequate hygiene and contact with infected water make children especially vulnerable to infection.

When to consult a doctor?

When symptoms are ignored, the disease may progress. In order to avoid the progression of illness, it’s recommended to consult a doctor timely.

If you have noticed any symptoms of bilharzia, you can consult our doctors by booking your appointment with your doctors online! 

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FAQs About Bilharzia Answered by Your Doctors Online Team

Who is mainly affected by bilharzia?

Bilharzia is more common in men, most likely because of their increased exposure to infected water via bathing, swimming, and agricultural activities. S haematobium causes genital lesions in 30% of infected women.

Can schistosomiases be cured?

Schistosomiases can usually be treated with a short course called praziquantel. It kills the worms most effectively once the worms have grown a bit. The treatment may need to be repeated a few days after the first dose.

What kills skin parasites?

Two medications can be used to kill skin parasites. Diethylcarbamazine (DEC) kills microfilariae and adult worms. Albendazole is sometimes used in patients not cured with multiple DEC treatments. 

Can bilharzia be transmitted from person to person?

No! People do not infect each other. It can be transmitted if your mouth or lips come in contact with water that contains the parasites.

How can I reduce my risk?

Avoid drinking unfiltered water. Only swim in chlorinated swimming pools. Vigorous towel drying after an accidental, short water exposure may help prevent parasites from penetrating the skin.

How long does it take for bilharzia to show?

You may develop a rash, bumps, or itchy skin within days after you get infected. Also, fever, dizziness, cough, and muscle aches can begin within 1 or 2 months of infection. Most people do not experience any symptoms in the early phase of the disease.

Where does bilharzia live in the body?

The adult worms are found in the veins draining the urinary tract and intestines, and most of the eggs they lay are trapped in the tissues.

Can schistosomiasis be transmitted through the skin?

Yes, schistosomiasis can be transmitted through the skin. The larvae of the Schistosoma flatworm can penetrate human skin when in contact with contaminated water. The larvae, known as cercariae, enter the bloodstream through the skin and migrate to the liver, where they develop into adult worms. Protective measures such as wearing protective clothing and avoiding water contact in areas where snails are known to be present can help reduce the risk of infection.

How long can schistosomiasis live in the body?

Schistosoma worms can live in the body for many years, sometimes even decades, if left untreated. Adult worms can live in the body’s blood vessels for several years, laying hundreds to thousands of eggs daily. These eggs can cause inflammation and damage various organs, leading to chronic health problems such as liver damage, bladder cancer, and infertility.

What areas can you get Schistosoma?

Primarily found in tropical and subtropical areas of Africa, South America, the Caribbean, the Middle East, and Asia, Schistosoma is a parasitic flatworm that causes schistosomiasis. People in endemic areas risk contracting the disease if they swim, bathe, or wade in freshwater sources such as rivers, lakes, and ponds.

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