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Clonorchis sinensis under a light microscope: Notice the uterus; this species is monoecious. An adult C. sinensis is a flattened (dorsoventrally) and leaf-shaped fluke. The body is slightly elongated and slender, measuring 15–20 mm in length and 3–4 mm in width. [10]
The larvae are released into the environment from which the definitive hosts (humans and other mammals) acquire the infection. In some species another intermediate host is required, generally a cyprinid fish, and the definitive hosts are infected from eating infected fish. Hence, these species are food-borne parasites.
The second intermediate host include freshwater fish: Mugil cephalus, Tilapia nilotica, Aphanius fasciatus, and Acanthogobius sp. [6] The definitive host, such as humans or birds, eats the undercooked or raw meat of a fish and ingest the parasite. Natural definitive hosts are cats, dogs, foxes, wolves, pelicans, and humans. [6]
Clonorchis sinensis is a trematode (fluke) which is part of the phylum Platyhelminthes. The parasitic worm is as long as 10 to 25 mm and lives in the bile ducts of the liver. It is a hermaphroditic fluke that requires two intermediate hosts. The eggs of the worms are passed in fecal matter into a body of water and are then ingested by mollusks.
Although cholangiocarcinoma is known to have the histological and molecular features of an adenocarcinoma of epithelial cells lining the biliary tract, the actual cell of origin is unknown. Recent evidence has suggested that the initial transformed cell that generates the primary tumor may arise from a pluripotent hepatic stem cell.
In three-host life cycles, cercariae develop in the second intermediate host into a resting stage, the metacercaria, which is usually encysted in a cyst of host and parasite origin, or encapsulated in a layer of tissue derived from the host only. This stage is infective to the definitive host. Transmission occurs when the definitive host preys ...
Parasitic worms cannot reproduce entirely within their host's body; they have a life cycle that includes some stages that need to take place outside of the host. [3] Helminths are able to survive in their mammalian hosts for many years due to their ability to manipulate the host's immune response by secreting immunomodulatory products. [ 4 ]
Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.