Bilharzia – rivers, dams and what to watch for
Swimming in fresh water in parts of South Africa carries a real risk of a parasite that causes long-term damage. It is easily treated once found.
How you get it
Bilharzia, or schistosomiasis, is caused by a parasitic worm whose larvae live in fresh water and burrow directly through intact skin — no swallowing required. The parasite depends on particular freshwater snails, so risk is tied to specific water bodies.
It is present in parts of South Africa, particularly in the warmer north and east — areas of KwaZulu-Natal, Mpumalanga and Limpopo — and across much of the region beyond our borders. Rivers, dams, streams and irrigation channels carry the risk; chlorinated pools and the sea do not.
Symptoms, and the long silence
- An itchy rash within hours of exposure, sometimes called swimmer's itch.
- Weeks later: fever, cough, muscle aches and fatigue in some people.
- Blood in the urine, or pain at the end of passing urine — the classic sign, and often the only one.
- Blood in the stool, abdominal pain or diarrhoea, depending on the species.
- Frequently nothing at all for months or years while damage accumulates.
Testing and treatment
Treatment is a short, effective course, and it is worth having even for a suspected exposure with no symptoms.
The standard treatment:
Praziquantel — Biltricide
Schistosomiasis (bilharzia); tapeworm infections
- Tell a clinician about freshwater exposure — where and roughly when. Without that, nobody will test for it.
- Testing is usually urine or stool, sometimes blood. It is often negative if done too early, so timing matters.
- Treatment works on adult worms, so it is generally given some weeks after exposure and may be repeated.
- Treatment does not prevent re-infection — going back into the same water means being infected again.
- Get anyone who swam with you tested too, especially children.
Avoiding it
- Do not swim, paddle or wade in fresh water in risk areas. Local advice that a spot is safe is often wrong.
- Risk is highest in shallow, slow-moving, reedy water near the edges — exactly where children play.
- Brief contact is enough; the larvae penetrate skin within minutes.
- Towel off vigorously immediately if you have been in the water. It helps somewhat and is far from reliable.
- Water for washing should be heated, filtered or left standing in a covered container for two days.
- Chlorinated swimming pools and the sea are safe.
Common questions
- Can I catch it from drinking the water?
- The main route is through skin contact, not swallowing. Water that is unsafe for bilharzia is usually unsafe to drink for other reasons too — treat it before drinking either way.
- I swam in a dam years ago and feel fine. Should I be tested?
- It is worth mentioning, because infection can persist quietly for years while causing damage. Testing and treatment are straightforward, and blood in the urine at any point after freshwater exposure should definitely be investigated.
- Does the parasite spread between people?
- Not directly. The life cycle requires specific freshwater snails, so transmission happens only through contaminated water.
Sources
- Communicable disease surveillance and clinical guidanceNational Institute for Communicable Diseases, South Africa
- Primary Healthcare Standard Treatment Guidelines and Essential Medicines ListNational Department of Health, South Africa
Last reviewed 4 August 2026.