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What is schistosomiasis?

Schistosomiasis, known as bilharzia or ‘snail fever’, is a neglected tropical disease caused by parasites released by freshwater snails.

Infection occurs when the parasite’s larvae penetrate a person’s skin during contact with infested water, often through fishing, swimming, bathing and washing clothes.

Once inside the human body, the larvae develop into adult worms and the eggs they lay can become trapped in the body’s tissues.

At first, there are often no symptoms of schistosomiasis, but the parasite can remain in the body for many years and can cause more serious problems. This NTD can cause itchy rashes, abdominal pain and diarrhoea, and can lead to serious long-term problems affecting the digestive, urinary, respiratory and nervous systems.

Schistosomiasis is particularly common in sub-Saharan Africa, and mainly occurs in poorer communities that don’t have access to clean drinking water or adequate sanitation. Unfortunately, poverty is both a cause and consequence of the poor health caused by schistosomiasis. In children the disease can cause anaemia and stunted growth, and can affect their ability to learn. Many infected adults are unable to work, leading to economic hardship.

Watch our video to learn more about schistosomiasis.

A white and yellow icon of a small bottle of medicine, with one round tablet leaning on its side.

251 million people required preventive treatment for schistosomiasis in 2021

52 countries require large-scale preventative treatment

Source: World Health Organization

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How is schistosomiasis treated?

A crowd of children and adults watch as an eye health worker measures a child's height and gives medication to prevent NTDs.

Medication

To stop the spread of infection, praziquantel tablets, donated by Merck Serono, are distributed to people at risk.

Community drug distributors James and Elizabeth check medication for trachoma in Kenya.

Volunteers

The medication is administered via teachers and volunteers known as community-directed distributors (CDDs), who work locally.

A health worker takes notes during a mass drug administration campaign in Nigeria.

Combined treatment

Schistosomiasis is often treated alongside other neglected tropical diseases such as intestinal worms and river blindness.

What we’re doing

Sightsavers is taking steps to control schistosomiasis in the countries in which we work.

Our schistosomiasis treatment programmes specifically target school-age children and adults considered at risk, such as fishermen, living in endemic regions. In areas with very high rates of infection, entire communities may be treated through mass drug administration.

Sightsavers and partners also encourage non-drug-based practices such as water, sanitation and hygiene (WASH) initiatives.

In 2023, Sightsavers and partners helped to provide more than 12 million treatments for schistosomiasis. Since we began, we’ve also trained more than 519,000 local volunteers to distribute medication to treat a range of NTDs, including schistosomiasis.

How we’re making a difference

Sightsavers works with GiveWell to deliver cost-effective treatments for schistosomiasis and intestinal worms.

Our work with GiveWell

Find out about other diseases we treat

Neglected tropical diseases

More about schistosomiasis

A lab scientist in Nigeria examines samples under a microscope.
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A female researcher speaks to a woman about her experience of female genital schistosomiasis.
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Omosefe Osinoiki, April 2024
A school student in a classroom is handed a tablet by a health worker, as other health workers and his classmates look on.

Sightsavers’ deworming work gets $16.9 million funding boost

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May 2023