- Parasitic worm
Parasitic worm (disambiguation)"Parasitic worms or helminths are a division of eukaroytic parasitesthat, unlike external parasites such as liceand fleas, live inside their host.cite journal |author=Maizels RM, Yazdanbakhsh M |title=Immune regulation by helminth parasites: cellular and molecular mechanisms |journal=Nat. Rev. Immunol. |volume=3 |issue=9 |pages=733–44 |year=2003 |pmid=12949497 |url=http://www.era.lib.ed.ac.uk/bitstream/1842/465/1/Maizels_%26_Yazdanbakhsh.pdf |doi=10.1038/nri1183] They are worm-like organisms that live and feed off living hosts, receiving nourishmentand protection while disrupting their hosts' nutrientabsorption, causing weakness and disease. Those that live inside the digestive tractare called intestinal parasites. They can live inside humans as well as other animals. Helminthologyis the study of parasitic worms and their effect on their hosts.
Parasitic worms are categorized into three groups:
cestodes, nematodes, and trematodes.
These are the principal morphologic differences of the different families of helminths:
Diseases caused in humans by helminth infection include
ascariasis, dracunculiasis, elephantiasis, hookworm, lymphatic filariasis, onchocerciasis, schistosomiasis, and trichuriasis.
Parasitic worms are sequential hermaphrodites and reproduce depending on the species of worm, either with the presence of a male and female worm, joining
spermand eggs, producing fertile eggs, such as hookworms, or by breaking off segments that contain both male and female sex organs that are able to produce fertile eggs without the presence of a male or female. (e.g., tapeworms)
All worm offspring are passed on through poorly-cooked
meat, especially pork, wild fish, and beef, contaminated water, fecesand mosquitoes. However, it is estimated that 40 million Americans are infected with the most common roundworm, the pinworm. Medical expertswho? theorize that widespread intestinal parasite infestation is leading to the rise of colon cancerin the United States.
Worm eggs or
larvae or even adults enter the human body through the mouth, anus, nose, or skin, with most speciesattaching themselves to the intestinal tract. With the presence of digestive enzymes, worm egg shells are dissolved, releasing a brand-new worm; unlike its egg shell, the parasitic worm is protected from the body's powerful digestive enzymes by producing a protective keratinlayer.
The immune response to worm infection in humans is a Th2 response in the majority of cases. This results in
inflammationof the gut, and results in cyst-like structures forming around the egg deposits throughout the body. The host's lymphatic system is also heavily taxed the longer helminths propagate, which excrete toxins after feeding. These toxins are released into the intestines to be absorbed by the host's bloodstream. This phenomena makes the host susceptible to more common diseases such as seasonal viruses and bacterial infection.
* [http://www.niaid.nih.gov/factsheets/roundwor.htm Parasitic Roundworm Diseases]
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parasitic worm — noun worm that is parasitic on the intestines of vertebrates especially roundworms and tapeworms and flukes • Syn: ↑helminth • Hypernyms: ↑worm • Member Holonyms: ↑Nematoda, ↑phylum Nematoda, ↑Aschelminthes, ↑ … Useful english dictionary
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