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What is schistosomiasis?

Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Infection with Schistosoma mansoni, S. haematobium, and S. japonicum most commonly cause illness in humans.

In what parts of the world does it occur?

Schistosomiasis is endemic in the tropics and worldwide.


How do you get schistosomiasis?

Infection can occur when your skin comes into contact with contaminated freshwater in which certain types of snails live. These snails can carry the parasitic worms which cause schistosomiasis infection. Within several weeks, the parasites mature into adult worms and live in the blood vessels of the body where the females produce eggs. Some of the eggs travel to the bladder or intestine and are passed into the urine or stool.

What are the symptoms?

You may develop a rash or itchy skin (sometimes called ‘swimmers itch’). Fever, chills, cough, and muscle aches can begin within 1-2 months of infection. Most people have no symptoms at this early phase of infection. When adult worms are present, the eggs that are produced usually travel to the intestine, liver or bladder, causing inflammation or scarring. The parasite can also damage the liver, intestine, lungs, and bladder if left untreated. Rarely, eggs are found in the brain or spinal cord and can cause seizures, paralysis, or spinal cord inflammation.

How can I reduce my risk?

Avoid swimming, wading or washing in freshwater when you are in schistosomiasis endemic countries. This includes destinations like Lake Malawi and the River Nile. Wear shoes, avoid walking bare footed.

What is the treatment for schistosomiasis?

No vaccine or drug currently exists to prevent schistosomiasis. Schistosomiasis can be treated, with a medication called Praziquantel. Praziquantel is only effective in killing adult worms. Therefore, taking it just after you have swum in freshwater is not useful.

How do you test for schistosomiasis?

Testing is done by looking for eggs in stool and urine; a blood sample can also be tested for evidence of infection. Schistosomiasis infection is rarely an emergency, so try not to be concerned if any of your results are positive. It is possible to have this infection and not have any symptoms. If you are concerned you may have been infected, contact our team for information about our post tropical screening clinic.

We recommend waiting to be tested for at least 3 months after exposure. The blood test can remain positive for a long time, as the reaction to the worm’s eggs can still be present for some years after successful treatment. Therefore, re-testing after treatment is rarely useful.

Further reading and references

Further information

Have you travelled to a tropical country in the last 6-12 months and are you acutely unwell? You can be seen in our emergency walk-in clinic Monday to Friday 9am-4pm

Our travel medicine service offers specialist travel advice including for individuals with complex health conditions. We offer this on a privately and via NHS referral basis.
Please contact: or 020 3447 7999 for more information about our services.