Schistosomiasis is a chronic, parasitic disease transmitted by trematode worms or blood flukes of the genus Schistosoma. Over 207 million people are infected globally, while approximately 700 million are at risk in 74 countries where the infection is endemic. In sub-Saharan Africa the disease is responsible for over 200,000 deaths per year.
The infection develops after contact with the larval form of the parasitic worm occurs in infested water. The larvae penetrate the victim’s skin and develop into adults inside the body’s blood vessels where the females release their eggs. Some of the eggs pass out of the body during elimination, while others remain in bodily tissues causing an inflammatory immune system response that can cause progressive organ damage.
The disease is most prevalent in tropical and sub-tropical areas such as Asia, Africa, and South America. About 85% of the 207 million people infected with schistosomiasis live in Africa. It is especially prevalent in places where the water contains many freshwater snails that harbor the parasite. It tends to affect those in developing countries- often children who swim and play in infected water.
There are two main forms of schistosomiasis: internal schistosomiasis and urogenital schistosomiasis, depending on which species of worm is involved. The internal form usually causes abdominal pain, bloody stool, and diarrhoea. The classic symptom of the urogenital form is blood in the urine.
Schistosomiasis is effectively treated by administering a single dose of the drug praziquantel orally on an annual basis. There is also ongoing research to develop a vaccine.
The UNHCO focus is on reducing disease with regular, targeted treatment using praziquantel. The Bill & Melinda Gates Foundation is also helping by funding a research program with the goal of developing tools and strategies to be implemented in large scale drug administration campaigns.