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Electron micrograph of an adult male Schistosoma parasite worm. The bar (bottom left) represents a length of 500 μm. The origins of this genus remain unclear. For many years it was believed that this genus had an African origin, but DNA sequencing suggests that the species (S. edwardiense and S. hippopotami) that infect the hippo (Hippopotamus amphibius) could be basal.
Schistosoma mansoni is a water-borne parasite of humans, and belongs to the group of blood flukes (Schistosoma). The adult lives in the blood vessels ( mesenteric veins ) near the human intestine. It causes intestinal schistosomiasis (similar to S. japonicum , S. mekongi , S. guineensis , and S. intercalatum ).
Immunoblots with adult worm microsomal antigens are species-specific, so a positive reaction indicates the infecting species. The antibody's presence only indicates that schistosome infection occurred at some time and cannot be correlated with clinical status, worm burden, egg production, or prognosis.
It primarily infects African hippopotamuses (Hippopotamus anphibius) and has a more limited host range compared to other Schistosoma species. Adult parasites have only been found in the heart, aorta, and multiple veins and arteries of the hippopotamuses. [2] It has been suggested that the hippopotamus is the definitive host of S. hippopotami. [3]
The four species in this genus have recently (2012) been moved to the genus Schistosoma on the basis of morphology and molecular studies. [5] The genus name should now be regarded as a junior synonym of Schistosoma. The genera Bivitellobilharzia and Schistosoma form a clade in this family.
Schistosoma haematobium (urinary blood fluke) is a species of digenetic trematode, belonging to a group (genus) of blood flukes (Schistosoma). It is found in Africa and the Middle East. It is the major agent of schistosomiasis, the most prevalent parasitic infection in humans. [1]
It is a trematode, and being part of the genus Schistosoma, it is commonly referred to as a blood-fluke since the adult resides in blood vessels. Humans are the definitive host and two species of freshwater snail make up the intermediate host, Bulinus forskalii for the Lower Guinea strain and Bulinus africanus for the Zaire strain. [1]
The frequency of egg deposition from an adult helminth is generally daily, and can occur up to six times per day for some Taenia species. Adult trematodes lay smaller numbers of eggs compared to cestodes or nematodes. However, the egg develops into a miracidia from which thousands of cercariae, or swimming larvae, develop.