Schistosomiasis

Key facts

• Schistosomiasis is a parasitic infection caused by blood flukes of the genus Schistosoma, caught by wading or swimming in contaminated freshwater.
• It is one of the most widespread parasitic diseases in tropical and subtropical freshwater environments.
• Early exposure can cause an itchy rash, followed within weeks by fever, chills, muscle aches and cough as the parasites migrate through the body.
• Chronic infection can cause organ damage over time as the immune system reacts to parasite eggs lodged in the liver, intestines or bladder.
• Praziquantel is the standard treatment, given as a single-day course that clears the adult worms reliably.

How the infection unfolds

Early exposure can trigger an itchy rash at the site of skin penetration. Within weeks, some people develop fever, chills, muscle aches and a cough as the parasites migrate through the body. Chronic infection, which can persist for years without obvious symptoms, is the more serious phase: the immune response to parasite eggs lodged in tissue drives inflammation in the liver, intestines or bladder, potentially causing organ damage over time if left untreated.

Treating schistosomiasis

Praziquantel is the standard treatment and works against all major Schistosoma species. It is given as a single-day course and clears the adult worms reliably. It sits within the broader antiparasitics drug class, and reinfection is possible with continued exposure to contaminated water, so avoiding further freshwater contact in affected areas matters alongside treatment.

When to see a doctor

Anyone with freshwater exposure in an area where the infection is known to occur, who then develops the symptoms above, should seek medical assessment. A stool, urine or blood test is needed to confirm the diagnosis before treatment starts, and follow-up testing can confirm the infection has cleared.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.