Human schistosomiasis

• Published in: The Lancet (British edition) 2006-09, Vol.368 (9541), p.1106-1118
• Main Authors: Gryseels, Bruno, Polman, Katja, Clerinx, Jan, Kestens, Luc
• Format: Article
• Language: English
• Subjects: Animals; Anthelmintics - adverse effects; Anthelmintics - therapeutic use; Biological and medical sciences; Chemotherapy; Diseases caused by trematodes; Drugs; Eggs; Epidemiology; Female; Fever; General aspects; Helminthic diseases; Humans; Infections; Infectious diseases; Male; Medical sciences; Parasitic diseases; Pilot projects; Population distribution; Praziquantel - adverse effects; Praziquantel - therapeutic use; Rural areas; Schistosoma - growth & development; Schistosoma - pathogenicity; Schistosoma - physiology; Schistosomiases; Schistosomiasis; Schistosomiasis - drug therapy; Schistosomiasis - epidemiology; Schistosomiasis - physiopathology; Surface water; Tropical diseases; Water skiing
• ISSN: 0140-6736; 1474-547X
• DOI: 10.1016/S0140-6736(06)69440-3

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1·53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system ( S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis ( S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.