View source for Ascaris

{{Short description|Genus of roundworms}}
{{About|the worm|the infection caused by this worm|Ascariasis|the singular of Ascaris|Ascari (disambiguation)}}
{{Automatic taxobox
| image = Ascaris lumbricoides.jpeg
| image_caption = Adult female
| taxon = Ascaris
| authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| subdivision_ranks = Species
| subdivision  = *''[[Ascaris lumbricoides]]'' <small>[[Carl Linnaeus|Linn.]], [[10th edition of Systema Naturae|1758]]</small>
*''[[Ascaris suum]]'' <small>([[Johann August Ephraim Goeze|Goeze]], 1782)</small>
|image2= Ascaris lumbricoides life cycle.tif
|image2_caption=Life cycle inside and outside of the human body of one fairly well described helminth: ''Ascaris lumbricoides''
}}
'''''Ascaris''''' is a [[nematode]] genus of [[parasitic worms]] known as the "small intestinal roundworms".<ref>{{cite book|last1 = Carter|first1 = Burton J. Bogitsh, Clint E.|title = Human parasitology, Chapter 16: Intestinal nematodes|date = 2013|publisher = Academic Press|location = Amsterdam|isbn = 978-0-12-415915-0|edition = 4th|url = https://books.google.com/books?id=wsvKs8v9dvYC|access-date = 19 November 2015|page = 291}}</ref> 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.<ref>{{cite web|title=Parasites-Ascariasis|url=https://www.cdc.gov/parasites/ascariasis/|publisher=Centers for Disease Control and Prevention|access-date=30 May 2013}}</ref> ''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,<ref name=Hall1>{{cite journal |last1=Hall |first1=Andrew |last2=Hewitt |first2=Gillian |last3=Tuffrey |first3=Veronica |last4=de Silva |first4=Nilanthi |title=A review and meta-analysis of the impact of intestinal worms on child growth and nutrition |journal=Maternal & Child Nutrition |date=April 2008 |volume=4 |issue=Suppl. 1 |pages=118–236 | pmc=6860651|doi=10.1111/j.1740-8709.2007.00127.x |pmid=18289159}}</ref> affecting cognitive processes,<ref>{{cite journal|title=Hookworm, ''Ascaris lumbricoides'' infection and polyparasitism associated with poor cognitive performance in Brazilian schoolchildren |journal=Tropical Medicine and International Health|pmid=18627581 | doi=10.1111/j.1365-3156.2008.02103.x|volume=13|issue=8|pages=994–1004 | last1 = Jardim-Botelho | first1 = A | last2 = Raff | first2 = S | last3 = Rodrigues Rde | first3 = A | last4 = Hoffman | first4 = HJ | last5 = Diemert | first5 = DJ | last6 = Corrêa-Oliveira | first6 = R | last7 = Bethony | first7 = JM | last8 = Gazzinelli | first8 = MF|year=2008|s2cid=27755528| doi-access =  }}</ref> inducing tissue reactions such as granuloma to larval stages, and by causing [[intestinal obstruction]], which can be fatal.
==Morphology==
[[File:Ascaris female 200x section.jpg|thumb|left|''Ascaris'' cross section]]
[[File:Ascaris esophagus (cropped).jpg|thumb|upright|left|Esophagus of an ''Ascaris'' worm]]
* Adult: cylindrical shape, creamy white or pinkish in color
* Male: average {{Convert|15–30|cm}}; more slender than the female
* Female: average {{Convert|20–35|cm}}
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 (physiology)|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]], [[cathepsin]]s, and [[metallocarboxypeptidase]]s (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.<ref>{{cite journal |last1=Sanglas |first1=Laura |last2=Aviles |first2=Francesc X. |last3=Huber |first3=Robert |last4=Gomis-Rüth |first4=F. Xavier |last5=Arolas |first5=Joan L. |title=Mammalian metallopeptidase inhibition at the defense barrier of ''Ascaris'' parasite |journal=Proceedings of the National Academy of Sciences |date=2009 |volume=106 |issue=6 |pages=1743–1747 | pmc=2644108 | doi=10.1073/pnas.0812623106 |pmid=19179285 |bibcode=2009PNAS..106.1743S |doi-access=free }}</ref> Similarly, they inhibit trypsin by releasing the protein Ascaris Trypsin Inhibitor ([https://www.rcsb.org/structure/1ATA pdb 1ATA]).<ref>{{cite journal |last1=Grasberger |first1=Bruce L |last2=Clore |first2=G.Marius |last3=Gronenborn |first3=Angela M |title=High-resolution structure of ''Ascaris'' trypsin inhibitor in solution: direct evidence for a pH-induced conformational transition in the reactive site |journal=Structure |date=1994 |volume=2 |issue=7 |pages=669–678 |doi=10.1016/s0969-2126(00)00067-8 |pmid=7922043|doi-access=free }}</ref>
==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 [[Mummy|mummified humans]].<ref name="Leles20122">{{cite journal|vauthors=Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A|date=2012|title=Are ''Ascaris lumbricoides'' and ''Ascaris suum'' a single species?|journal=Parasites & Vectors|volume=5|issue=42|pages=42|doi=10.1186/1756-3305-5-42|pmc=3293767|pmid=22348306 |doi-access=free }}</ref>
''A. lumbricoides'' was originally called ''Lumbricus teres'' and was first described in detail by [[Edward Tyson]] in 1683.<ref name="PD6">{{cite book|title=Parasitic Diseases |edition=6 |vauthors=Despommier DD, Griffin DO, Gwadz RW, Hotez PJ, Knirsch CA |date=2017 |publisher=Parasites Without Borders |isbn=978-0-9978400-1-8}}</ref> The genus ''Ascaris'' was originally described as the genus for ''Ascaris lumbricoides'' by [[Carl Linnaeus]] in 1758.<ref name="Leles2012">{{cite journal|title=Are ''Ascaris lumbricoides'' and ''Ascaris suum'' a single species? |vauthors=Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A |journal=Parasites & Vectors |date=2012 |volume=5 |issue=42 |pages=42 |doi=10.1186/1756-3305-5-42|pmid=22348306 |pmc=3293767 |doi-access=free }}</ref> The morphologically similar ''Ascaris suum'' was described from pigs by [[Johann August Ephraim Goeze]] in 1782.<ref name="Leles2012" />
== See also ==
* [[List of parasites (human)]]
== References ==
{{Reflist|30em}}
{{Taxonbar|from=Q310838}}
{{Authority control}}
[[Category:Ascaridomorpha]]
[[Category:Chromadorea genera]]
[[Category:Taxa named by Carl Linnaeus]]