{{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 = Linnaeus, 1758 | subdivision_ranks = Species | subdivision = *''Ascaris lumbricoides'' <small>Linn., 1758</small> *''Ascaris suum'' <small>(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 and anatomy== thumb|left|''Ascaris'' cross section 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. The digestive tract is complete with prominent muscular pharynx. Respiration is by simple diffusion across body wall. The nervous system consists of a nerve ring and many longitudinal nerve cord. They are dioecious and have separate reproductive systems consisting of thread like gonads and genital ducts that open outside by apertures. Fertilization is internal and development is mostly indirect. Sexual dimorphism is well marked. Externally, males are much shorter than females and males also have a curved posterior end, unlike females. Internally, in males, all the digestive, reproductive systems open in a common chamber- cloaca whereas in females, there is a separate anus for digestive tract and female genital pore for female reproductive system.
==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.<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 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 of humans
== References == {{Reflist|30em}}
{{Taxonbar|from=Q310838}} {{Authority control}}
Category:Ascaridomorpha Category:Chromadorea genera Category:Animal taxa named by Carl Linnaeus