Schistosomiasis

John McCallen, 2009, mccallen@stanford.edu; Laura Davis, 2006 lmdavis@stanford.edu
Stanford University
Parasites & Pestilence: Infectious Public Health Challenges
Prof. D. Scott Smith, ssmith@stanford.edu

Schistosomiasis is an infection caused by one of the five species of the parasitic trematode helminths of the genus Schistosoma. The species of widespread importance are S. haematobium (Africa), S. japonicum (Japan, Southeast Asia, Western Pacific) and S. mansoni (Africa, Southwest Asia, Brazil, Caribbean). The two lesser species of Schistosomes that parasitize humans are S. intercalatum (Africa), and in the Mekong basin, S. mekongi 1 . Human infection takes place during contact with the free-swimming stage (cercariae) while swimming or bathing in slow-moving bodies of water which are inhabited by intermediate host snails of the genera Bulinus (S. haematobium), Biomphalaria (S. mansoni) or Oncomelania (S. japonicum) 1 .

Epidemiology

There are an estimated 200 million people worldwide afflicted with schistosomiasis, 120 million have symptomatic infections and 600 million individuals live at risk of contracting schistosomiasis 0 . The estimated mortality associated with S. mansoni and S. haematobium in sub-Saharan Africa is about 280,000 people per year 2 . The range of schistosomiasis endemicity can change either through movments of infected persons to areas inhabited by host snails, or the artificial creation of new habitat for infected snails (dams, canals, rice fields).

Regions of Endemicity

Schistosomiasis is endemic to over 70 countries 1 Including the following regions:

Africa: Southern, Sub-Saharan, Lake Malawi
Egypt: Nile River Valley
South America: Brazil, Suriname, Venezuela
Caribbean: Antigua, Dominican Republic, Guadeloupe, Martinique, Montserrat, Saint Lucia
Middle East: Iran, Iraq, Saudi Arabia, Syrian Arab Republic, Yemen
Asia: Philippines, Laos, Cambodia, Japan, Central Indonesia, Mekong Delta, Southern China

Part 1

Part 2

Part 3

Part 4

References

1 Mahmoud, Adel A. F., ed. Schistosomiasis. Tropical Medicine Science and Practice Vol. 3. Singapore: Imperial College Press, 2001.

2 Pearce, Edward J and Andrew S. MacDonald. 2002. "The Immunobiology of Schistosomiasis". Nature Reviews 2: 499-511.

0World Health Organization (1993). "The Control of Schistosomiasis:Second Report of the WHO Expert Committee." WHO Technical Report Series 803:1-86

img1 Centers for Disease Control and Prevention. Health Information for International Travel 2005-2006. Atlanta: US Department of Health and Human Services, Public Health Service, 2005.