Biopharmaceutical Solutions

Background information

• What is Schistosomiasis?
  Parasitic worms that infect blood vessels cause schistosomiasis. Symptoms of early infection include blood in urine or stool, and over time the infection leads to urinary tract or liver damage. Death can result from bladder cancer or from an internal hemorrhage.
• Global burden
  Schistosomiasis is endemic in 74 developing countries, infecting more than 200 million people in rural agricultural and peri-urban areas. Twenty million may suffer from severe disease, while approximately 120 million are thought to experience chronic debilitating symptoms such as anemia and impaired cognitive development. An estimated 779 million people worldwide are at risk for the disease.
• Geographic distribution
  More than 80 percent of people infected with schistosomiasis live in sub-Saharan Africa. The disease is also prevalent in the Middle East and can be found in parts of Southeast Asia and Latin America. 
• Causative agent/transmission
  Schistosomiasis is caused by trematode flatworms of the genus Schistosoma. Schistosoma eggs are expelled in the feces or urine of infected individuals. When humans come in contact with contaminated water, schistosome larvae, which initially develop in freshwater snails, penetrate the skin and enter the bloodstream. The parasites migrate through the lungs to the liver where they mature, mate, and migrate together to blood vessels near either the intestine (S. mansoni) or bladder (S. haematobium). Over the next five years, a female worm lays 200 to 2,000 eggs daily. About half the eggs produced are excreted in the feces or urine; the remainder become trapped in body tissues and organs, where they can cause severe damage, particularly to the liver. The parasite itself causes little damage to the human body.

Presentation

Schistosomiasis can take two forms—urinary and intestinal. In urinary schistosomiasis, urination becomes painful and urine turns blood red. There is progressive damage to the bladder, urine ducts, and then kidneys. In intestinal schistosomiasis, there is progressive enlargement of the liver and spleen and hypertension of the abdominal blood vessels. Eggs breaking through from blood vessels into the intestine leads to blood in stools. In advanced cases, the functioning of organs such as liver, spleen, and kidneys becomes impaired. Death can result from bladder cancer or renal failure (S. haematobium) or bleeding from varicose veins in the esophagus or gastrointestinal tract (S. mansoni).

Trends

Older estimates of the burden of schistosomiasis failed to adequately take into account the full range of symptoms, sequelae, and chronic nature of the disease. More recent analysis has revealed that it is among the most serious tropical diseases. Schistosomiasis often goes undiagnosed in children and is associated with stunting, vitamin deficiency, and developmental and cognitive problems. Children under 14 are especially vulnerable to severe infection leading to progressive disease and early death.

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