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Schistosomiasis or Bilharzia describes a vector borne parasitic disease caused by trematode flatworms of the genus Schistosomes.

  • it is second only to malaria in importance among the parasitic diseases
  • affects more than 230 million people worldwide with close 800 million people at risk of infection

Exposure to contaminated water results in Schistosomiasis.

  • infection is usually acquired through activities such as swimming, bathing, fishing, farming, and washing clothes.
  • once the parasites penetrates the skin, the adult male and female worms live and reproduce sexually within the veins of their human host (1,2)
    • in perivesicular venules - S haematobium
    • in mesenteric venules - S mansoni, S japonicum, and others

There are 3 main species of schistosomes that can infect humans: Schistosoma haematobium, Schistosoma mansoni, and Schistosoma japonicum (1)

  • S haematobium and S mansoni are seen in Africa and the Middle East
  • S mansoni is present in the Americas
  • S japonicum is localised to Asia, primarily the Philippines and China (1)

In addition to these main three species, several locally distributed species are also responsible for human disease:

  • Schistosoma mekongi - in the Mekong River basin in Cambodia and Lao People’s Democratic Republic (Laos).
  • Schistosoma guineensis and Schistosoma intercalatum - in west and central Africa (1)

There are two main forms of schitomiasis:

  • urinary schistosomiasis
    • caused by Schistosoma haematobium
    • mainly affects the bladder, ureters and kidneys
  • intestinal schistosomiasis 
    • caused by S. mansoni and S. japonicum
    • mainly affects the liver and spleen and causes intestinal damage and hypertension of the abdominal blood vessels (3).


Last reviewed 01/2018