What are the Schistosoma species?
Schistosoma species are parasitic worms that cause schistosomiasis, an infection acquired when skin is exposed to freshwater contaminated with the parasite’s larval stage. Infection occurs during activities such as swimming, wading, or bathing in lakes, rivers, or ponds in affected regions. The larvae are able to penetrate intact skin, meaning even brief exposure can be enough for infection.
Different species affect different organs. Schistosoma haematobium mainly involves the urinary system and may cause blood in the urine. Schistosoma mansoni and Schistosoma japonicum more commonly affect the intestines and liver, and can lead to abdominal symptoms. These infections can lead to longer-term complications if untreated.
According to the World Health Organization (WHO), schistosomiasis affects over 200 million people worldwide and remains one of the most important parasitic diseases linked to freshwater exposure in tropical and subtropical regions.
FAQs
What travel locations are more likely for schistosomiasis exposure to occur?
+
Exposure occurs in freshwater environments in endemic regions, particularly lakes, rivers, ponds, and slow-moving streams where the parasite’s life cycle is present. Risk is highest in parts of Africa, the Middle East, South America, and some areas of Asia. Activities such as swimming, wading, bathing, or washing in untreated freshwater are the main ways infection occurs. Even shallow or commonly used water sources can carry risk if contaminated.
How can I tell if freshwater is safe to swim in while overseas?
+
It is usually not possible to determine safety just by looking at the water. Clear, flowing, or popular swimming locations may still be unsafe in endemic areas. Local use by residents does not guarantee safety either, as exposure risk is linked to the presence of infected snails rather than water quality alone. The most reliable precaution is to avoid freshwater exposure in known risk regions unless health authorities confirm it is safe.
What should I do if I accidentally went in freshwater while travelling in a risk area?
+
If accidental exposure occurs, there is no immediate way to fully prevent infection after contact. Drying the skin promptly may slightly reduce risk by reducing the chance of larvae penetration, but does not eliminate risk. Avoid further freshwater exposure during your trip and make a note of when and where it happened. Medical review after travel is recommended so appropriate testing can be arranged if needed, even if there are no symptoms.
Can schistosomiasis cause problems even if I feel completely well?
+
Yes. Early infection may cause no symptoms at all, and some people remain unaware they are infected for weeks or months.
Over time, untreated infection can lead to inflammation affecting the bladder, intestines, or liver depending on the species involved. Because of this, a history of freshwater exposure in an endemic region is often enough to justify medical assessment by your usual GP, even in the absence of symptoms.
What to Know
Schistosomiasis symptoms
Schistosomiasis symptoms can vary depending on the stage of infection and the species involved. Some people notice early skin changes within days of exposure, including itching, a rash, or a tingling sensation where the parasite entered the skin. This early phase may be mild and is sometimes missed entirely.
As the infection develops over weeks to months, symptoms may become more general and affect the whole body. These can include tiredness, fever, abdominal discomfort, diarrhoea, or a general sense of being unwell. Depending on the species, there may also be blood in the urine or faeces.
In longer-term or untreated infection, inflammation caused by the parasite’s eggs can affect internal organs. This may involve the bladder, intestines, liver, and, less commonly, the lungs or nervous system. Some people may remain without obvious symptoms for an extended period despite ongoing infection.
Schistosomiasis diagnosis and treatment
Diagnosis is based on a combination of travel history, symptoms, and specific laboratory testing. A key part of assessment is identifying whether there has been freshwater exposure in an area where schistosomiasis is known to occur, even if this exposure was brief or occurred some time ago.
Blood tests may be used to detect the body’s immune response to infection, while stool or urine samples can sometimes identify parasite eggs, depending on the type of schistosomiasis suspected. Because early infection may not show clear results, repeat or follow-up testing is sometimes needed to confirm the diagnosis.
Treatment is generally straightforward and highly effective after clinical assessment and diagnostic confirmation by a doctor. The main medication used targets the adult worms in the body. It is usually given as a short course and is well tolerated in most cases. Treatment may be recommended even when symptoms are mild or absent, particularly if there is a clear exposure history. Follow-up may be arranged in some cases to ensure the infection has fully cleared.
Schistosomiasis prevention
Prevention relies almost entirely on avoiding contact with contaminated freshwater in areas where schistosomiasis is present. This includes not swimming, wading, bathing, or washing in lakes, rivers, ponds, or streams in known risk regions, even if the water appears clean or is commonly used by local communities.
Chlorinated swimming pools, treated water supplies, and seawater are considered safe and do not carry risk. Washing clothes or bathing in untreated freshwater sources should also be avoided in endemic areas, as even brief skin exposure can lead to infection.
Because there is no vaccine available, prevention depends on awareness and behaviour. Checking travel advice before engaging in freshwater activities is important, particularly when travelling outside major tourist centres or when local water safety cannot be confirmed.