What is schistosomiasis?

Schistosomiasis is a disease caused by parasitic worms called schistosomes. There are mainly three blood flukes: S mansoni, S haemotobium, S japonicum, causing respectively intestinal schistosomiasis, urinary schistosomiasis and Asiatic intestinal schistosomiasis. This infection occurs worldwide, affecting some 200 million people. It is most prevalent in sub-Saharan Africa, southern China, the Philippines, and Brazil.

Early infection is usually asymptomatic in persons who live in endemic areas. However, travellers without previous exposure may become seriously ill in the early stages of acute infection. A few hours after contact with schistosomes the person may experience tingling of the skin with a rash where the cercaria enters the body ("swimmers itch"). This usually resolves within 24 hours. Weeks later, once the adult worms begin to produce eggs, the person may develop flu-like symptoms, with high fever, malaise, cough, diarrhoea and hives. The liver and spleen can also be affected. Long-term consequences of infection include severe liver disease, kidney failure, and bladder cancer.

How does it spread?

Schistosomes live inside certain freshwater snails, which release large numbers of tiny free-swimming larvae (called cercariae) into the water. These cercariae can penetrate into intact skin of a person who comes in contact with infested water and migrate to veins around the liver or bladder where mature worms produce eggs. Adult worms can live up to 15 years and produce large numbers of eggs that exit the body through urine or faeces. An infected person can contaminate water by urination or defaecation.

Travellers usually contract the disease by bathing, swimming, wading, boating, or rafting in cercariae-infested waters. Even brief water exposure can lead to infection since the cercaria can penetrate into intact skin within 30 seconds to 10 minutes.

How can you prevent?

Travellers participating in recreational water activities in areas where schistosomiasis is endemic may be at increased risk and should consider the following preventive measures:

  • Avoid swimming or wading in fresh water when you are in areas with schistosomiasis. If water exposure cannot be avoided, try to prevent cercariae from reaching the skin by wearing protective footwear or clothing.

  • Drink safe and clean water. You should either boil water for 1 minute or filter water before drinking it. Boiling water for at least 1 minute will kill any harmful parasites, bacteria, or viruses present. Iodine treatment alone is not completely reliable.

  • Bath water should be heated for 5 minutes at 66oC. Water held in a storage tank for at least 48 hours should also be safe for bathing.

  • Vigorous towel drying after an accidental brief water exposure may help to prevent the parasite from penetrating the skin. You should not rely on vigorous towel drying to prevent schistosomiasis.

How is it treated?

Safe and effective oral drugs are available to treat the disease. You may consult your doctor for details.



Last revision date: 10 October 2012