Human schistosomiasis

Abstract

Human schistosomiasis—or bilharzia—is a parasitic disease caused by trematode flukes of the genus Schistosoma. By conservative estimates, at least 230 million people worldwide are infected with Schistosoma spp. Adult schistosome worms colonise human blood vessels for years, successfully evading the immune system while excreting hundreds to thousands of eggs daily, which must either leave the body in excreta or become trapped in nearby tissues. Trapped eggs induce a distinct immune-mediated granulomatous response that causes local and systemic pathological effects ranging from anaemia, growth stunting, impaired cognition, and decreased physical fitness, to organ-specific effects such as severe hepatosplenism, periportal fibrosis with portal hypertension, and urogenital inflammation and scarring. At present, preventive public health measures in endemic regions consist of treatment once every 1 or 2 years with the isoquinolinone drug, praziquantel, to suppress morbidity. In some locations, elimination of transmission is now the goal; however, more sensitive diagnostics are needed in both the field and clinics, and integrated environmental and health-care management will be needed to ensure elimination.

Pulmonary nodules in African migrants caused by chronic schistosomiasis

“…1 Three main species of schistosome infect human beings: Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum. S mansoni is present in Africa, Latin America, and in the Middle East, whereas S haematobium exists in Africa and the Middle East and S japonicum in Asia.…”

“…Three other locally distributed species also cause human disease: Schistosoma mekongi, which exists in the Mekong river basin, and Schistosoma guineensis and Schistosoma intercalutum, which are found in west and central Africa. 1 Infected people shed schistosoma eggs into the environment through faeces or urine. Upon contact with freshwater, free-living, ciliated miracidia emerge from the eggs and seek out a compatible snail host (Biomphalaria spp, Bulinus spp, or Oncomelania spp, depending on the Schistosoma species).…”

Prognostic Analysis of Schistosomal Rectal Cancer

“…Praziquantel was one of choices for schistosomiasis (Colley et al, 2014). But it was uncertain that patients could benefit from the use of drugs against Schistosoma before or after the operation.…”

Deworming Delusions? Mass Drug Administration in East African Schools

“…In addition to Gryseels (Gryseels et al, 2001;Gryseels 2006), many biomedical researchers have highlighted drug resistance as a possibility (for example, Mahmoud & Zerhouni, 2009;Gray et al, 2010;Utzinger et al, 2011;Humphries et al, 2012). Moreover, resistance can be experimentally induced, and praziquantel-tolerant schistosomes have been reported (Colley et al, 2014). There are reports, too, of treatment failing in field settings, although those failures are likely to be explained by praziquantel's inactivity on immature worms.…”