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The egg is found in the faeces, sputum, or urine of the definitive host. Depending on the species, it will either be non-embryonated (immature) or embryonated (ready to hatch). The eggs of all trematodes (except schistosomes) are operculated. Some eggs are eaten by the intermediate host (snail) or they are hatched in their habitat (water).
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.
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.
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]
Paragonimus westermani (Japanese lung fluke or oriental lung fluke) is the most common species of lung fluke that infects humans, causing paragonimiasis. [2] Human infections are most common in eastern Asia and in South America. Paragonimiasis may present as a sub-acute to chronic inflammatory disease of the lung. It was discovered by Dutch ...
Eggs are then sequestered within the portal system (or perivesicular plexus in some species) of homeotherms which restricts egg dispersal but limits the resulting pathology to less sensitive organs. A significant number of eggs may escape into the external environment before a heavily infected host is incapacitated by, or dies from, the infection.
The trematode Hirudinella ventricosa releases eggs in strings. Each egg contains a single miracidium, while the string contains living spermatozoa . Miracidia have cilia that are only present in the upper portion of the body near an apical gland with 12 hook-like spines in the opening.
There are two intermediate hosts involved, but there can also be paretic hosts, such as snakes, mice, birds, and humans. The eggs, which are oval, operculated, and light brown, are released from adult Alaria and excreted from the final host's faeces and hatched into miracidium that infect the snail host, in which the eggs then give rise to the ...