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Life cycle of S. haematobium. S. haematobium completes its life cycle in humans, as definitive hosts , and freshwater snails, as intermediate hosts, just like other schistosomes. But unlike other schistosomes that release eggs in the intestine, it releases its eggs in the urinary tract, which are excreted along with the urine. [ 15 ]
Schistosomiasis is known as bilharzia or bilharziosis in many countries, after German physician Theodor Bilharz, who first described the cause of urinary schistosomiasis in 1851. [ 82 ] [ 83 ] The first physician who described the entire disease cycle was the Brazilian parasitologist Pirajá da Silva in 1908.
Schistosoma is a genus of trematodes, commonly known as blood flukes.They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis, which is considered by the World Health Organization to be the second-most socioeconomically devastating parasitic disease (after malaria), infecting millions worldwide.
Schistosoma japonicum is an important parasite and one of the major infectious agents of schistosomiasis.This parasite has a very wide host range, infecting at least 31 species of wild mammals, including nine carnivores, 16 rodents, one primate (human), two insectivores and three artiodactyls and therefore it can be considered a true zoonosis.
An outline of the evolution of the schistosoma is now possible. The ancestral species infected freshwater turtles and the life cycle included gastropod hosts. Some of these species in their turn infected the marine turtles. [3] At some point members of species infecting marine turtles developed the ability to infect birds – most likely waterfowl.
Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host (6), and shed their forked tail, becoming schistosomulae (7). The schistosomulae migrate through several tissues and stages to their residence in the veins (8,9).
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). Clinical symptoms are caused by the eggs.
Cercariae use a tail-like appendage (often forked in genera causing swimmer's itch) to swim to the surface of the water; and use various physical and chemical cues in order to locate the next and final (definitive) host in the life cycle, a bird. These larvae can accidentally come into contact with the skin of a swimmer.