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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]
The migration of adult worms in the intestinal epithelium can cause traumatic damage to the host tissue, and the waste products they excrete can provoke an immunological reaction. [2] The resulting inflammation can cause symptoms such as nausea, vomiting, sweating, and diarrhea.
Over the next two to three months the larvae develop into adult male and female worms. The male remains small at 4 cm (1.6 in) long and 0.4 mm (0.016 in) wide; the female is comparatively large, often over 100 cm (39 in) long and 1.5 mm (0.059 in) wide. [5] Once the worms reach their adult size they mate, and the male dies. [6]
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]
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.
In the small intestine, the larvae moult into stage four (L4) the adult worm. It takes from five to nine weeks from penetration to maturity in the intestine. [8] [9] Necator americanus can cause a prolonged infection lasting from one to five years with many worms dying in the first year or two. Some worms though have been recorded as living for ...