Schistosomiasis is a type of infection caused by parasites that live in fresh water, such as rivers or lakes, in subtropical and tropical regions worldwide.
Schistosomiasis is also known as bilharzia.
Symptoms can develop a few weeks after someone is infected by the parasite and include:
- flu-like symptoms, such as a high temperature (fever) above 38ºC (100.4ºF) and muscle aches
- a skin rash
- a cough
Alternatively, more serious symptoms can develop months – and possibly years – after infection, and include:
Doctors refer to this as chronic schistosomiasis.
Read more information about the symptoms of schistosomiasis.
Seeing your GP
Contact your GP if you develop any of the above symptoms after travelling to parts of the world where schistosomiasis is widespread.
They will ask you about your recent travel history and whether you may have been exposed to contaminated water.
If your GP suspects you have schistosomiasis, you will probably be referred to an expert in tropical diseases. The diagnosis is usually made by testing a sample of your blood. In some cases, eggs may be seen in a urine or stool (faeces) sample.
In cases of chronic schistosomiasis, ultrasound scans are often used to check whether there is any damage to the urinary system.
How do you get schistosomiasis?
The parasites that cause schistosomiasis are called schistosomes. At the stage of infection, they are just barely visible to the naked eye and known as a cercaria.
They are capable of burrowing into human skin, where they develop into later stages and move closer to the abdomen to lay eggs. The disease is caused by the immune system reacting to these eggs.
Schistosomes live in lakes, rivers, reservoirs and canals, and can infect anyone who comes into contact with contaminated water.
An infected person will pass out parasite eggs in their urine or faeces (stools), which can survive in water for up to seven days.
Schistosomiasis is a disease associated with poverty. Poor living conditions, overcrowding, poor sanitation, and a lack of clean water and medical services all increase the risk of getting schistosomiasis.
Read more about the causes of schistosomiasis.
If schistosomiasis is diagnosed and treated promptly, it can usually be successfully treated with a medication called praziquantel. This kills the adult worms, which will be broken down by the body.
Schistosomiasis is usually only a serious health problem for people who do not have access to effective medical treatment, particularly people who are already vulnerable because of malnutrition or dehydration.
Read more about treating schistosomiasis.
Who is affected?
All cases of schistosomiasis that have been reported in England developed in people who travelled abroad. There were 77 reported cases in England in 2011-12.
Popular tourist destinations that are known to have high levels of parasites include:
- Lake Malawi, Lake Victoria and the White Nile in Africa
- the Mekong River in Cambodia and Laos
Schistosomiasis is also present in Egypt, many sub-Saharan African countries, the Philippines and China.
Globally, schistosomiasis is the second most common disease caused by parasites after malaria. An estimated 243 million people are infected worldwide, and around 90% of cases occur in sub-Saharan Africa.
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.
There is some evidence that applying the insect repellent DEET (diethyltoluamide) at 50% concentration immediately after exposure kills the parasite in the skin.
Read more about preventing schistosomiasis.