Ascaris Explained

Ascaris is a nematode genus of parasitic worms known as the "small intestinal roundworms", which is a type of parasitic worm.[1] One species, Ascaris lumbricoides, affects humans and causes the disease ascariasis. Another species, Ascaris suum, typically infects pigs. Other ascarid genera infect other animals, such as Parascaris equorum, the equine roundworm, and Toxocara and Toxascaris, which infect dogs and cats.

Their eggs are deposited in feces and soil. Plants with the eggs on them infect any organism that consumes them.[2] A. lumbricoides is the largest intestinal roundworm and is the most common helminth infection of humans worldwide. Infestation can cause morbidity by compromising nutritional status,[3] affecting cognitive processes,[4] inducing tissue reactions such as granuloma to larval stages, and by causing intestinal obstruction, which can be fatal.

Morphology

The body is long, cylindrical, and fusiform (pointed at both the ends). The body wall is composed of cuticle, epidermis and musculature. There is a pseudocoelom. Respiration is by simple diffusion. The nervous system consists of a nerve ring and many longitudinal nerve cords. Reproduction is exclusively sexual, and males are usually shorter than females.

Defense mechanism

As part of the parasite defense strategy, Ascaris roundworms secrete a series of inhibitors to target digestive and immune-related host proteases, which include pepsin, trypsin, chymotrypsin/elastase, cathepsins, and metallocarboxypeptidases (MCPs).Ascaris species inhibit MCPs by releasing an enzyme known as Ascaris carboxypeptidase inhibitor (ACI). This enzyme binds to the active site of MCP and blocks the cleavage of its own proteins by the host MCP.[5] Similarly, they inhibit trypsin by releasing the protein Ascaris Trypsin Inhibitor (pdb 1ATA).[6]

History

Ascaris has been present in humans for at least several thousand years, as evidenced by Ascaris eggs found in paleofeces and in the intestines of mummified humans.[7]

A. lumbricoides was originally called Lumbricus teres and was first described in detail by Edward Tyson in 1683.[8] The genus Ascaris was originally described as the genus for Ascaris lumbricoides by Carl Linnaeus in 1758.[9] The morphologically similar Ascaris suum was described from pigs by Johann August Ephraim Goeze in 1782.

See also

Notes and References

  1. Book: Carter. Burton J. Bogitsh, Clint E.. Human parasitology, Chapter 16: Intestinal nematodes. 2013. Academic Press. Amsterdam. 978-0-12-415915-0. 4th. 19 November 2015. 291.
  2. Web site: Parasites-Ascariasis. Centers for Disease Control and Prevention. 30 May 2013.
  3. Hall . Andrew . Hewitt . Gillian . Tuffrey . Veronica . de Silva . Nilanthi . A review and meta-analysis of the impact of intestinal worms on child growth and nutrition . Maternal & Child Nutrition . April 2008 . 4 . Suppl. 1 . 118–236 . 6860651. 10.1111/j.1740-8709.2007.00127.x . 18289159.
  4. Hookworm, Ascaris lumbricoides infection and polyparasitism associated with poor cognitive performance in Brazilian schoolchildren . Tropical Medicine and International Health. 18627581 . 10.1111/j.1365-3156.2008.02103.x. 13. 8. 994–1004 . Jardim-Botelho . A . Raff . S . Rodrigues Rde . A . Hoffman . HJ . Diemert . DJ . Corrêa-Oliveira . R . Bethony . JM . Gazzinelli . MF. 2008. 27755528.
  5. Sanglas . Laura . Aviles . Francesc X. . Huber . Robert . Gomis-Rüth . F. Xavier . Arolas . Joan L. . Mammalian metallopeptidase inhibition at the defense barrier of Ascaris parasite . Proceedings of the National Academy of Sciences . 2009 . 106 . 6 . 1743–1747 . 2644108 . 10.1073/pnas.0812623106 . 19179285 . 2009PNAS..106.1743S . free .
  6. Grasberger . Bruce L . Clore . G.Marius . Gronenborn . Angela M . High-resolution structure of Ascaris trypsin inhibitor in solution: direct evidence for a pH-induced conformational transition in the reactive site . Structure . 1994 . 2 . 7 . 669–678 . 10.1016/s0969-2126(00)00067-8 . 7922043. free .
  7. Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A. 2012. Are Ascaris lumbricoides and Ascaris suum a single species?. Parasites & Vectors. 5. 42. 42. 10.1186/1756-3305-5-42. 3293767. 22348306 . free .
  8. Book: Parasitic Diseases . 6 . Despommier DD, Griffin DO, Gwadz RW, Hotez PJ, Knirsch CA . 2017 . Parasites Without Borders . 978-0-9978400-1-8.
  9. Are Ascaris lumbricoides and Ascaris suum a single species? . Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A . Parasites & Vectors . 2012 . 5 . 42 . 42 . 10.1186/1756-3305-5-42. 22348306 . 3293767 . free .

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ascaris".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.