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. Although the disease is not immediately fatal, if untreated it can lead to extensive internal damage and ultimately, death.
According to the World Health Organization, over 220 million people required preventative treatment for bilharzia in 2017. Cases of bilharzia transmission have been reported from 78 different countries worldwide. It can be caught in parts of Asia and South America, but is most prevalent in Africa, especially in tropical central and sub-Saharan nations. In fact, 90% of people who require treatment for bilharzia live in Africa. The CDC calls the disease the second-most devastating parasitic disease after malaria in terms of impact.
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, then 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 You Avoid It?
There is no way of knowing whether or not a body of water is infected with bilharzia parasites; however, it must be considered 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. Others include cholera, hepatitis A and typhoid. In the long-term, solutions to bilharzia include better sanitation, improved access to safe water and snail control programs.
Symptoms and Effects
There are two main types of bilharzia: urogenital schistosomiasis and intestinal schistosomiasis. Symptoms for both are the 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 within a few hours of being infected and lasts for around seven days. This is usually the only early indication the disease, as other symptoms 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 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.
Diagnosis and Treatment
Bilharzia can be difficult to diagnose, especially if you are seeking medical attention in a country where the disease does not exist or is rarely seen. For this reason, if symptoms develop after returning home from your vacation, it's always important to tell your doctor that you have recently spent time in a bilharzia region. They will confirm or rule out infection via stool and urine tests, sometimes followed by a blood test if the results of the initial samples are inconclusive.
Although the long-term effects of bilharzia can be devastating, treatment is relatively easy. Praziquantel, a prescription drug, is used to treat all forms of the disease and is safe, affordable and effective in preventing long-term damage. Usually, you will only need to take the drug for one to two days. Currently, there is no vaccine for bilharzia; but other potentially life-threatening African illness can be vaccinated against, including yellow fever, rabies, polio and all three of the waterborne diseases mentioned above.