Schistosomiasis is an infection that is caused by parasites called schistosomes. These parasites can contaminate sources of fresh water, such as lakes and rivers. Schistosomiasis is also known as bilharzia.
Schistosomes are small, white-grey worms between 7mm and 20mm long. They are capable of burying into human skin. They can then move into other organs of the body, such as the liver or bladder, where they lay eggs.
Acute and chronic schistosomiasis
Schistosomiasis can cause both short-term (acute schistosomiasis) and long-term (chronic schistosomiasis) symptoms.
Symptoms of acute schistosomiasis include:
- skin rash,
- a high temperature (fever) above 38°C (100.4°F), and
- muscle aches.
Symptoms of chronic schistosomiasis include:
- weight loss,
- persistent diarrhoea, and
- breathing difficulties.
How common is schistosomiasis?
The parasites that cause schistosomiasis are only found in tropical and subtropical regions. All cases of schistosomiasis that have been reported in England developed in people who have travelled abroad.
Each year in England, Wales and Northern Ireland, an average of 100 cases of schistosomiasis are reported.
In global terms, schistosomiasis is the second most common disease caused by parasites after malaria. An estimated 200 million people are infected worldwide, and 85% of cases occur in sub-Saharan Africa.
Cases of schistosomiasis can also be found in:
- China,
- Brazil,
- Venezuela,
- the Middle East,
- the Caribbean, and
- Southeast Asia.
Schistosomiasis is a disease that is associated with poverty. Poor living conditions, overcrowding and lack of sanitation, access to clean water and medical services are major risk factors for this type of infection.
Schistosomiasis can be treated with a medication called praziquantel, which kills the parasites.
There is currently no vaccine available for schistosomiasis so it is important to take precautions when travelling in parts of the world where the infection is widespread. This includes not swimming or wading in fresh water. See Prevention for more advice.
Outlook
If schistosomiasis is diagnosed and treated promptly, the outlook is good. Most people will be cured after treatment with praziquantel or, at least, will experience a significant improvement in symptoms.
In parts of the world where schistosomiasis is widespread, access to medical treatment is limited and the risk of re-infection is high. Therefore, the symptoms of schistosomiasis can sometimes be fatal, particularly in people who are already vulnerable due to malnutrition or dehydration.
It is estimated that 14,000 people die worldwide each year from schistosomiasis, while a further 20 million experience serious complications.
