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Some internal fish parasites are spectacular, such as the philometrid nematode Philometra fasciati which is parasitic in the ovary of female Blacktip grouper; [14] the adult female parasite is a red worm which can reach up to 40 centimetres in length, for a diameter of only 1.6 millimetre; the males are tiny.
Several species of Trichinella can cause disease, with T. spiralis being the most common. [1] After the infected meat has been eaten, the larvae are released from their cysts in the stomach. [1] They then invade the wall of the small intestine, where they develop into adult worms. [1]
Routes of exposure and infection include ingestion of undercooked meat, drinking infected water, fecal–oral transmission and skin absorption. Some types of helminths and protozoa are classified as intestinal parasites that cause infection—those that reside in the intestines. These infections can damage or sicken the host (humans or other ...
In their Parasite Immunology article on worms and viral infections, Kamal et al. explain why some parasitic worms aggravate the immune response. [13] Because parasitic worms often induce Th2 cells and lead to suppressed Th1 cells, problems arise when Th1 cells are needed. [13] Such cases occur with viral diseases. [13]
The small adult worms mature in the small intestine of a definitive host, such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enters the blood (to feed on it) and lymphatic system, and are carried to striated muscle. Once in the muscle, they encyst, or become enclosed in a capsule.
Diphyllobothrium is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is D. latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is a pseudophyllid cestode that infects fish and mammals.
This wound on the fish then heals, leaving almost no scarring. Species of Philometra require two hosts to complete their life cycle. After the larval worms are released from the host fish, they are ingested by copepods which act as an intermediate host. Once inside the copepod, the larvae molt several times. Fish may then eat the infested copepod.
The life cycle of the parasite typically involves a fish-eating bird, a snail and a fish. [4] The black spot larvae grow to sexual maturity in the infected bird's intestine. The adult worms pass eggs with the bird's droppings. When the eggs reach water, they hatch into free-swimming organisms which then penetrate snails for further development.