Schistosomiasis, also known as bilharzia, is a parasitic infection caught from contact with fresh water in many tropical and subtropical regions. There is no vaccine, so prevention relies on avoiding contact with potentially contaminated lakes, rivers and ponds.
How it spreads
Through skin contact with fresh water containing larvae (cercariae) released by infected freshwater snails — not from person to person.
Where it occurs
Mainly sub-Saharan Africa, with smaller risks in the Middle East, South America, the Caribbean, parts of Asia and a focus in Corsica.
Main symptoms
Often none at first; later an itchy rash, then fever and flu-like illness (Katayama syndrome), and over time blood in the urine or bowel symptoms.
Who is most at risk
Travellers who swim, paddle, wade, raft or wash in lakes, rivers, dams or slow streams in affected areas, including aid workers and adventure travellers.
Is a vaccine available
No. There is no vaccine and no preventive tablet — prevention relies on avoiding freshwater contact.
How to reduce your risk
Avoid all contact with fresh water in risk areas; the sea and properly chlorinated pools are safe. Arrange testing on return if you have been exposed.
Schistosomiasis (bilharzia) is a parasitic infection caught from contact with fresh water in tropical and subtropical regions, especially sub-Saharan Africa, where larvae released by freshwater snails burrow through the skin. There is no vaccine or preventive tablet, so the only reliable protection is avoiding swimming, paddling or washing in lakes, rivers and ponds in affected areas. Crewe Travel Clinic in Cheshire can advise on your destination and risk before you travel, and recommend testing on return if you have had freshwater contact.
Schistosomiasis, commonly called bilharzia, is a disease caused by parasitic flatworms (blood flukes) of the genus Schistosoma. Travellers become infected when they swim, wade, paddle or bathe in fresh water containing the tiny larval stage of the parasite, which can burrow through unbroken skin within minutes. It is one of the most widespread parasitic infections worldwide and is a notable risk for travellers to many parts of Africa in particular.
The parasite needs particular freshwater snails to complete part of its life cycle, so infection is linked to lakes, rivers, dams, irrigation channels and slow-moving streams rather than the open sea or properly treated swimming pools. Activities such as wild swimming, water-sports, rafting, fishing and even brief paddling or washing in fresh water can all carry a risk. Because the larvae are invisible, water that looks clean and inviting can still be a source of infection.
There is no vaccine and no preventive tablet against schistosomiasis, so avoiding contact with potentially contaminated fresh water is the only reliable way to prevent it. The infection is treatable with prescription medication once diagnosed, and travellers who may have been exposed are usually advised to be tested after they return home, even if they feel well. The team at Crewe Travel Clinic can discuss your itinerary and planned activities and advise on how to reduce your risk before you travel.
Schistosomiasis is not spread directly from person to person. People become infected through contact with fresh water containing the larval form of the Schistosoma parasite (called cercariae). These larvae are released into water by infected freshwater snails and can penetrate intact skin in a matter of minutes during swimming, wading, paddling, washing or other water contact. Once inside the body the worms mature and lay eggs; some eggs are passed out in urine or faeces, and if these reach fresh water containing the right snails the cycle continues. Drinking unsafe water is not the usual route of infection, and the disease cannot be caught from the sea or from chlorinated swimming pools.
Many people have no symptoms at first. Soon after exposure some travellers notice an itchy rash where the larvae entered the skin (sometimes called swimmer's itch). A few weeks later an acute reaction known as Katayama syndrome can develop, causing fever, chills, cough, muscle aches, tiredness and an enlarged liver or spleen. If left untreated, long-term (chronic) infection can cause ongoing problems including blood in the urine, tummy pain, diarrhoea, and damage to the bladder, bowel, liver or other organs over months or years. Because symptoms may be mild, delayed or absent, anyone who has had freshwater contact in a risk area should consider testing on return even if they feel well.
Schistosomiasis occurs across much of sub-Saharan Africa, which accounts for the great majority of cases, including popular destinations such as Lake Malawi, Lake Victoria, the Nile and rivers in East, West and Southern Africa. It is also found in parts of the Middle East, South America (including Brazil, Suriname and parts of the Caribbean), and pockets of South and Southeast Asia. Small, localised transmission has additionally been reported in parts of southern Europe, including the island of Corsica. Risk is highest where people have freshwater contact in rural and lakeside areas.
There is no vaccine and no preventive medication for schistosomiasis, so prevention is based entirely on avoiding contact with potentially contaminated fresh water. Travellers are advised to avoid swimming, paddling, wading or washing in lakes, rivers, dams, ponds and slow streams in risk areas, however clean the water appears. Swimming in the sea and in properly chlorinated pools is considered safe. If accidental freshwater contact occurs, drying the skin vigorously with a towel straight away may reduce (but not remove) the risk. Water for washing can be made safer by heating it to around 50C for five minutes, by allowing storage for at least 48 hours, or by filtering. Drinking water should be from a safe, treated source. Anyone who has been in fresh water in an affected region should seek testing after returning home, as early diagnosis and treatment are highly effective.
Schistosomiasis is not passed directly from one person to another. It is caught through contact with fresh water that contains the larval stage of the Schistosoma parasite. Infected freshwater snails release these larvae, called cercariae, into lakes, rivers, dams, ponds and slow-moving streams. The larvae can burrow through unbroken skin within minutes during swimming, wading, paddling, rafting, washing or other water contact. Once inside the body the worms mature and lay eggs, some of which pass out in urine or faeces and can continue the cycle if they reach water containing the right snails.
There is no vaccine and no preventive medication for schistosomiasis, so avoiding contact with potentially contaminated fresh water is the only reliable way to protect yourself. In risk areas, do not swim, paddle, wade or wash in lakes, rivers, dams, ponds or slow streams, however inviting the water appears. Swimming in the sea and in well-maintained chlorinated pools is considered safe. If freshwater contact is unavoidable or accidental, drying the skin vigorously with a towel straight away may reduce — but does not remove — the risk.
Many travellers have no symptoms when first infected. Some notice an itchy rash where the larvae entered the skin, and a few weeks later an acute reaction known as Katayama syndrome can develop, with fever, chills, cough, muscle aches and tiredness. If infection is not treated, long-term problems such as blood in the urine, tummy pain, diarrhoea and damage to the bladder, bowel or liver can develop over months or years. Because symptoms may be mild, delayed or absent, anyone who has had freshwater contact in a risk area is advised to arrange testing on return, even if they feel completely well. Schistosomiasis is treatable with prescription medication once diagnosed, and early diagnosis gives the best outcome.
No vaccine is available against schistosomiasis, and there is no tablet that can be taken in advance to prevent it. Protection therefore depends entirely on avoiding contact with potentially contaminated fresh water while travelling. Before your trip, the team at Crewe Travel Clinic can review your itinerary and planned activities, explain how to avoid freshwater exposure, and make sure any other recommended vaccinations and malaria precautions for your destination are in place. If you have already had freshwater contact in a risk area, we can advise on testing after you return.
The following vaccinations can help protect against Schistosomiasis (Bilharzia).
Book an appointment with our travel health team for tailored advice on protecting against Schistosomiasis (Bilharzia).