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Schistosomiasis is a preventable but potentially serious disease. It affects the internal organs. It is the result of an infection of parasitic worms that live in certain varieties of freshwater snails. The parasites, also called cercariae, infect the water around the snails.
Skin exposure to infected water can lead to schistosomiasis. Schistosomiasis is also known as bilharzia or snail fever.
In 2012, the disease affected 240 million people worldwide, mainly in tropical and subtropical regions (WHO). The disease is found in many parts of Africa and South America. It is also found in parts of Asia and the Caribbean, though risk in these places may be lower. Areas without access to safe drinking water, as well as poor (and rural) areas, have the highest incidence of schistosomiasis. Many people contract the parasite from doing chores such as washing clothes in infected water or from bathing in infected water.
Skin exposure to fresh water infected with parasitic worms can cause schistosomiasis. Transmission of the infection doesn’t occur through drinking the water, but if the water touches skin or lips, an infection could develop.
Schistosomiasis can be introduced to clean fresh water when people with the disease urinate or defecate in the water. If certain species of snails are present in that water, the eggs of the parasite can find their way to the snails, where the parasite can multiply and spread further.
When the parasites leave the snails, they infect the water around them. Any contact skin contact with that water can lead to schistosomiasis.
After parasite eggs enter a human body, they develop into worms. This growth process can take several weeks. The worms take up residence in human blood vessels, where the females continue to lay eggs and reproduce. Schistosomiasis is spread when eggs make it to the bladder or intestines and are eliminated from the body.
People who live in or travel to countries with schistosomiasis and make contact with fresh water have the highest risk of developing the disease. Schistosomiasis occurs only in fresh water, such as lakes, canals, streams and ponds. Swimming in the ocean or swimming pools is not a risk.
Some signs and symptoms of schistosomiasis begin to develop within days. Others can take months. Some people don’t experience any symptoms in the early stage of the disease (first several months). The primary symptoms are the body’s reaction to the parasites.
Within days of infection, you may notice a rash or itchy skin.
Within one or two months, you may notice the following:
Over time (many years in some cases), schistosomiasis can cause serious damage to the liver, bladder, lungs, and intestines.
Other symptoms include inflammation and scarring in the liver, bladder, and intestines. Children with repeated exposure to schistosomiasis can develop anemia or malnutrition. Schistosomiasis can also lead to learning difficulties. If left untreated, schistosomiasis can cause seizures or inflammation in the spinal cord. If the parasite eggs make their way to the brain or spinal cord, paralysis can occur.
Children with schistosomiasis face developmental and intellectual challenges. Death can be a result of schistosomiasis. Treatment can help reverse some of these symptoms.
If you think you have been exposed to schistosomiasis, see your doctor right away. A healthcare provider will ask where you traveled to, whether you made contact with potentially infected fresh water, and the extent of contact..
To diagnose schistosomiasis, your doctor will examine a stool or urine sample to detect the parasite. A doctor may also take blood samples, but due to the nature of the disease and slow progression from egg to worm, you might be asked to wait up to eight weeks after exposure to do a blood test.
Treatment for schistosomiasis includes medications such as Praziquantel.
Serious complications can occur if schistosomiasis is left untreated, including liver damage and bladder cancer. Prognosis is good if treatment begins before there is internal damage.
Written by: Amber Erickson Gabbey
Medically reviewed on: May 29, 2014: George Krucik, MD, MBA
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