What is Bilharzia and How Can it be Avoided?

The Limpopo River near Xai-Xai
Ulrich Münstermann / Getty Images

Also known as schistosomiasis or snail fever, bilharzia is a disease caused by parasitic flatworms called schistosomes. The parasites are carried by freshwater snails, and humans can become infected after direct contact with contaminated bodies of water including ponds, lakes and irrigation canals. There are several different types of Schistosoma parasite, each of which affects different internal organs.

According to the World Health Organization, approximately 258 million people were infected with bilharzia in 2014. Although the disease is not immediately fatal, if untreated it can lead to extensive internal damage and ultimately, death. It occurs in parts of Asia and South America, but is most prevalent in Africa, especially in tropical central and sub-Saharan nations. 

How is Bilharzia Contracted?

Lakes and canals initially become contaminated after humans with bilharzia urinate or defecate in them. Schistosoma eggs pass from the infected human into the water, where they hatch and subsequently use freshwater snails as a host for reproduction. The resulting larvae are then released into the water, after which they can be absorbed through the skin of humans that come to the water to bathe, swim, wash clothes or fish. 

The larvae then develop into adults that live in the bloodstream, enabling them to travel around the body and infect organs including the lungs, liver, and intestines. After several weeks, the adult parasites mate and produce more eggs. It is possible to contract bilharzia through drinking untreated water; however, the disease is not contagious and can't be passed from one human to another. 

How Can Bilharzia be Avoided?

There is no way of knowing whether or not a body of water is infected with bilharzia parasites; however, it must be considered as a possibility throughout sub-Saharan Africa, in the Nile River valley of Sudan and Egypt, and in the Maghreb Region of northwest Africa. Although in reality, freshwater swimming is often perfectly safe, the only way to avoid the risk of bilharzia completely is not to indulge at all.  ​

In particular, avoid swimming in areas known to be infected, including many of the Rift Valley lakes and beautiful Lake Malawi. Obviously, drinking untreated water is also a bad idea, especially as bilharzia is just one of many African diseases transferred by contaminated water. In the long-term, solutions to bilharzia include improved sanitation, snail control and increased access to safe water. 

Symptoms & Effects of Bilharzia

There are two main types of bilharzia: urogenital schistosomiasis and intestinal schistosomiasis. Symptoms for both manifest as a result of the victim's reaction to the parasites' eggs, rather than to the parasites themselves. The first sign of infection is a rash and/ or itchy skin, often referred to as Swimmer's Itch. This can occur with a few hours of being affected and lasts for around seven days. 

This is usually the only early indication of infection, as other symptoms can take three to eight weeks to appear. For urogenital schistosomiasis, the key symptom is blood in the urine. For women, it may make intercourse painful as well as causing vaginal bleeding and genital lesions (the latter of which may make victims more susceptible to HIV infection). For both sexes, bladder cancer and infertility may result from long-term exposure to Schistosoma parasites. 

Intestinal schistosomiasis often manifests itself through a variety of symptoms, including fatigue, severe abdominal pain, diarrhea and the passing of bloody stools. In extreme cases, this kind of infection also causes the enlargement of the liver and spleen; as well as liver and/ or kidney failure. Children are especially affected by bilharzia and may suffer from anemia, stunted growth and cognitive problems that make it difficult for them to concentrate and learn in school. 

Treatment for Bilharzia

Although the long-term effects of bilharzia can be devastating, there are anti-schistosomiasis drugs available. Praziquantel is used to treat all forms of the disease and is safe, affordable and effective in preventing long-term damage. Diagnosis can be difficult, however, especially if you are seeking medical attention in a country where bilharzia is rarely seen. For this reason, it's always important to mention that you have recently returned from Africa. 

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