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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), with hundreds of millions infected worldwide.
The life cycle stages: [43] The excretion of schistosome eggs in urine or feces depending on species; The hatching of the eggs leading to release of the free-swimming, ciliated larvae called miracidia; Miracidia find and penetrate the snails, which are the intermediate hosts (specific species of snails is dependent on the species of schistosoma)
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]
The life cycle of a typical trematode begins with an egg. Some trematode eggs hatch directly in the environment (water), while others are eaten and hatched within a host, typically a mollusc. The hatchling is called a miracidium, a free-swimming, ciliated larva. Miracidia will then grow and develop within the intermediate host into a sac-like ...
The stages in the snail include 2 generations of sporocysts (4) and the production of cercariae (5). 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).
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.
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.