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A genus of trematodes, Schistosoma spp., commonly known as blood-flukes and bilharzia, cause the most significant infection of humans by flatworms (schistosomiasis) and are considered by the World Health Organization as second in importance only to malaria, with hundreds of millions infected worldwide. Adult worms parasitize mesenteric blood vessels. Eggs are passed through urine or feces to fresh water, where larval stages can infect a new host by penetrating the skin.
Additional recommended knowledge
There are four species of schistosome which are infective to humans:
Adult schistosomes share all the fundamental features of the digenea. They have a basic bilateral symmetry, oral and ventral suckers, a body covering of a syncytial tegument, a blind-ending digestive system consisting of mouth, oesophagus and bifurcated caeca; the area between the tegument and alimentary canal filled with a loose network of mesoderm cells, and an excretory or osmoregulatory system based on flame cells. Adult worms tend to be 10-20 mm long and use globins from their hosts' hemoglobin for their own circulatory system.
Unlike other trematodes, the schistosomes are dioecious - i.e., the sexes are separate. The two sexes display a strong degree of sexual dimorphism, and the male is considerably larger than the female. The male surrounds the female and encloses her within his gynacophoric canal for the entire adult lives of the worms, where they reproduce sexually.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Schistosoma". A list of authors is available in Wikipedia.|