Schistosomiasis
- Slovak term: Slovenský termín
- A parasitic disease caused by five species of flatworms, or blood flukes, known as schistosomes throughout the tropics (WHO et al. 2003).
- A tropical parasite infection caused by blood flukes of the genus Schistosoma, whose lifecycle includes an obligatory passage through certain genera of freshwater snails, with certain mammals including humans as the final hosts (WHO 2009).
Explanation
Schistosiomiasis is a debilitating disease and some 200 M people are estimated to be infected worldwide (WHO 2009).
Water bodies get contaminated through the excreta of infected people; people get (re-)infected when wading in contaminated water where the snail intermediate hosts are present, when the infectious larvae, cercariae, penetrate the skin.
The eggs of the schistosomes in the excreta of an infected person hatch on contact with water and release larvae, the miracidia which penetrate a fresh water intermediate snail host and produce new parasites (cercariae). The cercariae are excreted by the snail into the water and penetrate human skin. Disease due to schistosomiasis is indicated either by the presence of blood in the urine (urinary schistosomiasis) leading eventually to bladder cancer or kidney problems or, in the case of intestinal schistosomiasis, by initial diarrhoea, which can lead to serious complications of the liver and spleen (WHO et al. 2003).
Example
References
- WHO, WNO and UNEP (2003) Climate change and human health: Risks and responses
- WHO(2009) Health impact assessment glossary: E-learning modules.
