Ascaris suum का स्रोत देखें

{{Short description|Species of roundworm}}
{{Use British English|date=February 2018}}{{Speciesbox
| image = Adult Ascaris in hand.jpg
| taxon = Ascaris suum
| authority = [[Johann August Ephraim Goeze|Goeze]], 1782
}}

'''''Ascaris suum''''', also known as the '''large roundworm of pig''', is a [[parasitism|parasitic]] [[nematode]] that causes [[ascariasis]] in [[pig]]s. While roundworms in pigs and humans are today considered as two species (''A. suum'' and ''[[Ascaris lumbricoides|A. lumbricoides]]'') with different hosts, cross-infection between humans and pigs is possible; some researchers have thus argued they are the same species.<ref>{{cite journal|last1=Leles|first1=Daniela|last2=Gardner|first2=Scott L.|last3=Reinhard|first3=Karl|last4=Iñiguez|first4=Alena|last5=Araujo|first5=Adauto|date=20 February 2012|title=Are ''Ascaris lumbricoides'' and ''Ascaris suum'' a single species?|journal=Parasites & Vectors|volume=5|page=42 |doi=10.1186/1756-3305-5-42 |doi-access=free|pmid=22348306|pmc=3293767}}</ref> Ascariasis is associated with contact to pigs and pig manure in [[Denmark]].<ref>{{Cite journal|last1=Nejsum|first1=Peter|last2=Parker|first2=E. Davis|last3=Frydenberg|first3=Jane|last4=Roepstorff|first4=Allan|last5=Boes|first5=Jaap|last6=Haque|first6=Rashidul|last7=Astrup|first7=Ingrid|last8=Prag|first8=Jørgen|last9=Sørensen|first9=Uffe B. Skov|date=2005-03-01|title=Ascariasis is a zoonosis in Denmark |url= |journal=Journal of Clinical Microbiology|language=en|volume=43|issue=3|pages=1142–1148|doi=10.1128/JCM.43.3.1142-1148.2005 |pmid=15750075|pmc=1081283}}</ref>

''A. suum'' is distributed worldwide and grows up to {{convert|40|cm|abbr=on}} in length. ''Ascaris'' infections are treated with [[ascaricide]]s. ''A. suum'' is in the family [[Ascarididae]], and is one of the oldest associations to mankind.

==Life cycle==
[[File:Camera 24b.jpg|thumb|Embryonated ''A. suum'' egg containing a visible, infective L3 stage larva.|148x148px|left]]
Pigs get infected with ''A. suum'' by ingesting infectious parasite [[egg]]s that are present in the environment. The [[larva]]e of Ascaris complete two [[Moulting|moults]] within the egg; therefore, the larvae emerging from the egg is not a second-stage larva (L2) as was previously presumed, but rather a third stage larva (L3) covered by a loosened L2 [[cuticle]].<ref>{{cite journal|last1=Fagerholm|first1=Hans-Peter|last2=Nansen|first2=Peter|last3=Roepstorff|first3=Allan|last4=Frandsen|first4=Flemming|last5=Eriksen|first5=Lis|date=1 June 2000|title=Differentiation of cuticular structures during the growth of the third-stage larva of ''Ascaris suum'' (Nematoda, Ascaridoidea) after emerging from the egg|journal=Journal of Parasitology|volume=86|issue=3|pages=421–427|doi=10.1645/0022-3395(2000)086[0421:DOCSDT]2.0.CO;2 }}</ref> The larvae hatch from the egg inside the pig's [[intestines]] and subsequently start their migration through the body. First, they penetrate the intestinal wall at [[Cecum|caecum]]/[[Large intestine|colon]]<ref>{{cite journal|last1=Murrell|first1=K. Darwin|last2=Eriksen|first2=Lis|last3=Nansen|first3=Peter|last4=Slotved|first4=H.-C. |last5=Rasmussen|first5=Tina|date=1997|title=''Ascaris suum'': a revision of its early migratory path and implications for human ascariasis |journal=Journal of Parasitology|volume=83|issue=2|pages=255–260|doi=10.2307/3284450 |jstor=3284450|pmid=9105307}}</ref> and use the [[Mesenteric arteries|mesenterial blood veins]] to migrate to the [[liver]]. After burrowing their way through the liver tissue, they again use the [[Efferent arteriole|efferent blood stream]] to carry them to the [[lungs]]. There, they get stuck in the [[capillaries]] surrounding the lungs and they penetrate the lung [[Pulmonary alveolus|alveoli]]. It takes approximately 7 days to reach the lungs. Once the larvae are inside the lung, they migrate up the respiratory tree and are eventually [[cough]]ed up and swallowed by the host to reach the [[small intestine]] again as soon as 10 days after infection. There, the larvae undergo their first molt inside the host to reach the L4 stage by day 14 post-infection. Around day 25 post infection, they develop into the L5 stage. Worms reach adulthood 6 weeks after infection, and when both female and male worms are present in the same host, [[fertilized egg]]s are produced and secreted by the female worm. These eggs are then excreted together with the [[faeces]]. After an incubation period, infective stage larvae develop in the eggs and are ready to cause infection in a new host.

[[Host (biology)#Paratenic hosts|Paratenic hosts]] ingest the eggs and the L3 larvae remain in the tissues of the paratenic host until a pig eats them. These may include [[beetles]] and [[earthworms]], as well as large to jumbo chicken eggs from at-risk [[fowl]].{{cn|date=November 2021}}

==Epidemiology==
''Ascaris'' eggs can remain infective for years in the soil, even in a [[temperate climate]].<ref>{{cite journal|last1=Roepstorff |first1= A. |last2= Murrell |first2=D. |date=1997 |title=Transmission dynamics of helminth parasites of pigs on continuous pasture: ''Ascaris suum'' and ''Trichuris suis'' |journal=International Journal for Parasitology |volume=27|issue=5 |pages=563–572 |doi=10.1016/S0020-7519(97)00022-2 | pmid=9193950}}</ref> The migration of ''A. suum'' larvae through the lungs may cause secondary bacterial infections and result in acute respiratory symptoms in pigs.<ref>{{cite journal|last1=Lassen |first1= B. |last2=Geldhof |first2=B. |last3=Hälli |first3=O. |last4=Vlaminck |first4= J. |last5=Oliviero |first5=C. |last6=Orro |first6=T. |last7=Heinonen|first7=M. |date=2019 |title=Anti-''Ascaris suum'' IgG antibodies in fattening pigs with different respiratory conditions |journal=Veterinary Parasitology |volume=265 |pages=85–90 |doi=10.1016/j.vetpar.2018.12.005 | pmid=30638525|hdl=10138/308653 |hdl-access=free }}</ref>

==Morphology==
[[File:Asuum male and female.jpg|thumb|359x359px|''A. suum'' adult male with typical curled posterior end together with a significantly larger female worm.|left]]
Males are about {{convert|15|-|31|cm|0|abbr=on}} long, and {{convert|2|-|4|mm|1|abbr=on}} wide. The [[Posterior (anatomy)|posterior]] end is curved toward the [[ventral]] side with a pointed tail. They have simple [[Spicule (nematode anatomy)|spicules]] that measure {{convert|2.0|-|3.5|mm|2|abbr=on}} long. Females are larger than males, measuring {{convert|20|-|49|cm|0|abbr=on}} long and {{convert|3|-|6|mm|2|abbr=on}} in diameter. From the [[anterior]] end, the [[vulva]] occupies about one-third of the body length. In addition to their large size, these species also have the three prominent [[lips]]. Each lip contains a dentigerous ridge, and no interlabia or [[Alae (nematode anatomy)|alae]]. Females can lay up to 200,000 eggs per day, and their [[uteri]] can contain up to 27 million eggs at a time. Fertilized eggs are ovoid, ranging from 45 to 75&nbsp;µm length and 35 to 50&nbsp;µm in diameter. The uterine wall contributes to the lumpy and thick outer layer of the egg. The mammillated layer is stained golden-brown by the host's [[bile]] when the eggs are passed in faeces. Females  can also deposit unfertilized eggs that are narrower and longer than normal fertilized eggs, ranging from 88 to 94&nbsp;µm in length, and 44&nbsp;µm diameter. Only the proteinaceous layer can be seen in unfertilized eggs, because after fertilization, the [[Vitelline layer|vitelline]], [[chitinous]], and lipid layers form.<ref name="Roberts">{{cite book |author1=Roberts, Larry S.  |author2=Janovy Jr., John  |name-list-style=amp |year=2008 |title=Foundations of Parasitology |edition=8th |publisher=[[McGraw-Hill]] |isbn=978-0-07-131103-8}}</ref>

==Incidents and outbreaks==
In Canada in 1970, a postgraduate student [[1970 ascariasis poisoning incident|tainted his roommates' food]] with ''A. suum''. Four of the victims became seriously ill; two of these suffered acute respiratory failure.<ref>{{cite journal |author1=James A. Phills |author2=A. John Harrold |author3=Gabriel V. Whiteman |author4=Lewis Perelmutter |year=1972 |title=Pulmonary infiltrates, asthma and eosinophilia due to ''Ascaris suum'' infestation in man |journal=[[New England Journal of Medicine]] |volume=286 |issue=18 |pages=965–970 |pmid=5062734 |url=http://www.k-state.edu/parasitology/articles/ascariasis.pdf |doi=10.1056/NEJM197205042861802}}</ref><ref>{{cite web |url=http://www.cfsan.fda.gov/~dms/rabtact.html |archive-url=https://web.archive.org/web/20090527230939/http://www.cfsan.fda.gov/~dms/rabtact.html |archive-date=May 27, 2009 |title=Risk Assessment for Food Terrorism and Other Food Safety Concerns |publisher=[[Food and Drug Administration]] [[Center for Food Safety and Applied Nutrition]] |date=October 13, 2003 |access-date=February 15, 2012}}</ref>

== Genetics ==
A 273-megabase draft genome for ''A. suum'' was published in 2011.<ref>{{Cite journal |author1=Aaron R. Jex |author2=Shiping Liu |author3=Bo Li |author4=Neil D. Young |author5=Ross S. Hall |year=2011 |title=''Ascaris suum'' draft genome |journal=[[Nature (journal)|Nature]] |volume=479 |issue=7374 |pages=529–533 |doi=10.1038/nature10553 |pmid=22031327 |url=http://www.ugent.be/di/nl/actueel/nieuws/nature.pdf |display-authors=etal|doi-access=free }}</ref>

== References ==
{{Reflist|32em}}
* {{Source-attribution|[https://web.archive.org/web/20090527230939/http://www.cfsan.fda.gov/~dms/rabtact.html Risk Assessment for Food Terrorism and Other Food Safety Concerns], published in 2003 by the U.S. Food and Drug Administration.}}

{{Taxonbar|from=Q2062253}}

[[Category:Ascaridida]]
[[Category:Parasitic nematodes of mammals]]
[[Category:Swine diseases]]
[[Category:Veterinary helminthology]]
[[Category:Nematodes described in 1782]]
[[Category:Taxa named by Johann August Ephraim Goeze]]