Schistosoma spp.


Published on:
-

Authors: 
Jerome Boissier (University of Perpignan)Gabriel Mouahid (University of Perpignan Via Domitia)Hélène Moné (University of Perpignan Via Domitia)

Summary

Schistosomiasis (or bilharzia) is one of the most prevalent waterborne parasitic diseases. The epidemiological statistics associated with schistosomiasis are impressive: 800 million people are at risk in 78 countries, mostly concentrated in sub-Saharan Africa; 230 million are infected and the disease is responsible for between 1.7 and 4.5 million disability adjusted life years (DALYs). The most exposed people are children or young adults.
The etiological agent of schistosomiasis is a helminth from Schistosoma genus living in the blood vessels of the body. Six species are known to be pathogenic for humans. Five species live in the mesenteric vein system and cause intestinal schistosomiasis (Schistosoma mansoni, S. intercalatum, S. guineensis, S. mekongi, S. japonicum) while S. haematobium lives in the venous plexus around the bladder and causes urinary schistosomiasis. Humans excrete the pathogen in faeces or urine, depending on species and location. Female worms produce numerous eggs (200-3,000 per day), thus resulting in the potential for considerable environmental contamination. In contaminated water, the parasite species uses a specific freshwater snail as an intermediate host for completion of the lifecycle.   Transmission to humans occurs when the parasite penetrates the skin on the definitive host, including humans.
The pathology is mainly of schistosomiasis is largely caused by the accumulation of the parasite eggs that are not excreted. Many eggs become trapped in different organs, mainly in the intestines and the liver for intestinal schistosomiasis or in the urogenital system for urinary schistosomiasis. Few patients develop acute schistosomiasis and most symptoms appear several months after parasite penetration (chronic schistosomiasis). Intestinal schistosomiasis causes hepatosplenomegaly, fever, abdominal pain, and bloody diarrhea. Urinary schistosomiasis causes blood in the urine and painful urinations. Schistosomiasis also impacts child development and school performance.
The diagnostic standard for schistosomiasis requires urine (Schistosoma haematobium) or faeces (Schistosoma mansoni, S. intercalatum, S. guineensis, S. mekongi, S. japonicum) examination. The egg shape gives indication on the species concerned. Serological tests like Elisa or Western Blot, and DNA detection in the faeces, urine or serum are also available. Treatment mainly relies on the use of a single antihelminthic drug: praziquantel (no vaccine is available). Control programmes also include molluscicide treatment (to remove the intermediate host), improved environmental sanitation, and health education. 

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"><meta http-equiv="content-type" content="text/html; charset=utf-8"></head></html>

Toggle