Schistosomiasis << `shihs` tuh soh MY uh sihs >> is the name for a sometimes fatal disease caused by three species of parasitic worms called schistosomes. Schistosomiasis is widespread throughout the world and afflicts more than 200 million people in Africa, Asia, South America, and some Caribbean islands. It is also called bilharziasis in honor of the German physician Theodor Bilharz, who identified the disease in 1851.
The schistosomes that cause schistosomiasis have the scientific names S. mansoni, S. japonicum, and S. haematobium. (The S. stands for Schistosoma. ) During part of their life cycle, they live as parasites in certain freshwater snails. Later, schistosomes swim about and may enter the skin of people who wade or swim in the waters. Eventually, the worms invade the bloodstream and settle in small veins near the bladder or intestines.
The adult male and female schistosomes live in close physical association. Eggs are passed daily into the blood vessels. Most eggs are discharged into the intestine and the bladder and are eliminated with the feces (solid body wastes) and urine. However, some of the eggs may find their way into other organs, such as the liver and the spleen. The infected person’s reaction to these eggs may cause disease.
The first sign of schistosomiasis infection is a temporary, itchy rash where the schistosomes have entered the skin. The main symptoms of the disease develop a few weeks later and include abdominal pain, coughing, discomfort, fever, nausea, and rash. Many patients experience diarrhea and weight loss. Severe cases damage the liver, spleen, and intestines. Doctors treat schistosomiasis with the drug praziquantel. Governments and health authorities try to prevent the disease by improving sanitation methods and by removing the snails from bodies of waters.
