Schistosomiasis is a parasitic infection caught from contact with contaminated fresh water on the skin. The parasite is a helminth and has a lifecycle where the eggs hatch inside certain types of freshwater snails and then are released as Cercariae (a sort of larval stage) – these contaminate the water and enter through the skin. The Cercariae migrate through the lymphatics to the liver and become adults. The adults release eggs, which travel through the circulation causing the illness. The different species create slightly different diseases, either affecting the bladder or the gut.
It is found in Africa, the Middle East, parts of Asia and Central and South America. Africa has the greatest risk of Schistosomiasis. Local information is not always correct about the safety of water. This is especially true of Lake Malawi where many travellers have caught Schistosomiasis.
The Cercariae stage burrows through the skin when bathing, swimming or wading through infected fresh water. Salt water and chlorinated swimming pool water is safe.
There may be a rash at the site where the Cercariae entered the skin, starting up after a few hours or up to a week later. There is usually no other illness for between 2 and 12 weeks. When the adult helminths start to release their eggs people may get an illness with fever, headache, muscle pains, diarrhoea and cough or breathing problems. The different types of Schistosomiasis may cause abdominal pain, diarrhoea/constipation and blood in the stool or urinary symptoms with pain on passing urine and blood in the urine. Chronic infection can occur without any significant symptoms and can lead to significant complications in the longer term.
Schistosomiasis can be difficult to diagnose. When suspected tests of urine and stool culture may show the eggs. Blood tests can be done to show the body’s reaction to the infection. Where it is found the infection can be treated with a type of anti-parasite medication called Praziquantel. This is only effective against the adult forms of Schistosomiasis so is not helpful if taken too soon after exposure. In many parts of the world where Schistosomiasis is found, access to medications may be limited and those that are available may be fake or ineffective.
Check the risk of Schistosomiasis in the countries you are traveling to before you go. Discuss this with your Travel Doctor and consult reliable resources such as the CDC website: https://wwwnc.cdc.gov/travel/destinations/traveler/none/new-zealand
When traveling in areas with Schistosomiasis risk, avoid contact with untreated fresh water.
Because many features of the illness may look like other tropical diseases it is important to report any contact with fresh water in risk areas if you do become ill.
If you think you have caught Schistosomiasis while travelling or on return home consult with a doctor.
