Disease Information for Schistosomiasis (Mansoni): Definition

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  • Of the Trematodes, schistosomes are atypical, in that the adult stages have two sexes and are located in blood vessels in the definitive host. Most other trematodes are hermaphroditic, and are found in the intestinal tract, or organs such as the liver; The lifecycle of schistosomes includes two hosts, a definitive host (eg man) where the parasite undergoes sexual reproduction, and a single intermediate snail host where there are a number of asexual reproductive stages----------------

    Schistosomiasis is an infection of high prevalence and morbidity; Three species of schistosomes cause human disease; These differ in geographic distribution (S JAPONICUM, S MANSONI, S HAEMATOBIUM); Species also differ in location within the venous system but in all species, disease is produced primarily by acute and chronic inflammatory responses to schistosome eggs; Fibro-obstructive disease in the liver and portal hypertension are major responses to S mansoni infections although there may be little or no overt disease with chronic infection; Transmission cycle is complex with a snail intermediate host; Swimmer"s itch, which is caused by Schistosoma mansoni, can also be caused by other species of Schistosomes from birds or other animals----------------

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