Freshwater parasitic worms widespread

By Dr Cory Couillard

Be aware that contact with all freshwater from canals, rivers, streams, ponds or lakes can put you at risk of getting parasitic worms called schistosomiasis, or bilharzia. Schistosomiasis is especially prevalent in poor communities without access to safe drinking water and adequate sanitation.

Schistosomiasis often affects farming and fishing population as well as women doing domestic chores in infested water, such as washing clothes. Poor personal hygiene and play habits make children especially vulnerable to the parasites.

There are two major forms of schistosomiasis – intestinal and urogenital – caused by five species of parasites. Most people have no symptoms early in the infection but many develop itchy skin and a rash within days. Fever, chills, cough and muscle aches can follow and occur within 1 to 2 months after infection.

Fully matured worms often travel to the intestine, liver or bladder. The symptoms of intestinal schistosomiasis can include abdominal pain, diarrhoea and blood in the stool. Liver and spleen enlargement is also common in advanced cases.

The classic sign of urogenital schistosomiasis is blood in the urine. In women, urogenital schistosomiasis can present with genital lesions, vaginal bleeding, pain during sexual intercourse and nodules on the vulva. Due to bleeding, urogenital schistosomiasis is also a risk factor for HIV transmission, especially in women.

In men, urogenital schistosomiasis can affect the testicles, prostate and other organs. A serious, long-term irreversible consequence of schistosomiasis can include male infertility.

Rarely, eggs can be found in the brain or spinal cord and cause seizures, paralysis, or spinal cord inflammation. Children who are infected can develop anaemia, experience malnutrition and developmental setbacks as well as acquire learning disabilities.

How to prevent schistosomiasis

No vaccine is available. The control of schistosomiasis is based on improving access to safe water, sanitation, hygiene education and snail control. The best way to prevent schistosomiasis is to avoid swimming or wading in infested freshwater; there is no risk in seawater.

Vigorous towel drying is encouraged to help prevent the parasite from penetrating the skin should there be an accidental or very brief water exposure. One should not rely on vigorous towel drying to prevent schistosomiasis.

Stay away from the banks of streams and rivers. Parasites thrive in shallow water during peak daylight hours. Their presence is minimal in the centre of rivers, streams and where there is fast flowing water.

Water from a river or lake that is used for bathing and washing should be boiled or chlorinated. Bath water should be heated to a rolling boil for at least 1 minute. Water that is held in a storage tank for at least 1-2 days is generally classified as safe for bathing.

Drink safe water. Infection can occur if one’s mouth or lips come in contact with contaminated water. Boiling water for at least 1 minute will normally kill any harmful parasites, bacteria or viruses present.

Dr Cory Couillard is an international health columnist that works in collaboration with the World Health Organization's goals of disease prevention and global health care education. Views do not necessarily reflect endorsement.

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