A STAMARIL Center
the short version
In areas with schisto, consider some kind of followup care if you wade or swim in untreated fresh water.
the long version
Schistosomiasis (called bilharzia outside the US), an infection estimated to occur worldwide among 200 million people, is caused by flukes (worms)whose complex life cycle involves a certain fresh water snail as the intermediate host. Infected snails release large numbers of tiny larvae which are capable of penetrating the unbroken skin of the human host. Even brief exposures to (even putting your hand into) contaminated water can result in infection. Exposure to schistosomiasis is a health hazard for U.S. citizens who travel to infested areas in Africa, less of a problem in some areas of the Caribbean, South America and Asia, particularly in Brazil, Puerto Rico, St. Lucia, Egypt, southern China, southeast Asia and the Philippines. Those at greatest risk are travelers who engage in fresh water swimming or wading in rural areas where poor sanitation and the snail host are present. Human schistosomiasis cannot be acquired by wading or swimming in salt water (oceans or seas), chlorinated swimming pools or tap water.
Although initial infection usually causes no symptoms, illness can occur within 2 to 3 weeks after exposure to infested water. The most common symptoms are not specific: fever, lack of appetite, weight loss, abdominal pain, weakness, headaches, joint and muscle pain, diarrhea, nausea and cough. Long term infections can cause disease of the lung, liver, intestines or bladder. Most people who develop long term infections can recall no symptoms immediately after exposure. Diagnosis of infection is usually confirmed by laboratory studies, such as blood tests or by finding eggs on microscopic examination of stool or urine as early as 6-8 weeks after exposure. Although there are no known effective preventive medicines, safe and effective one day treatment with pills is available for the treatment of schistosomiasis.
Since there is no practical
way for the traveler to distinguish infested from noninfested water, fresh water
swimming or wading in endemic countries should either be avoided or dealt with
after return to the US. Heating bathing water to 50 deg. C (122 deg. F) for 5
minutes or treating it with iodine or chlorine (in a manner similar to the
precautions recommended for preparing drinking water) will destroy larvae and
make the water safe. Filtering water with paper coffee filters may also be
effective in removing larvae from bathing water. If these measures are not
feasible, allowing bathing water to stand for 3 days is advisable since larvae
rarely survive longer than 48 hours. Upon return from foreign travel, if you
think you may have been exposed to schistosomiasis, you may see a physician to
undergo screening tests.
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© John D. Wilson, M.D. 1999-2018; Last Update 2/26/2018