Editing Haemonchus contortus

{{Short description|Species of roundworm}}
{{Italic title}}
{{Speciesbox
| name = ''Haemonchus contortus''
|image= CSIRO ScienceImage 10819 The tail ends of 11 Haemonchus contortus barbers pole worm adult females The worms are all taken from one sheep infected with a single strain of this worm species.jpg
| image_caption = These 11 ''Haemonchus contortus'' adult females were taken from one sheep infected with a single strain of this worm species.
| image2 = Haemonchus contortus.jpg
| image2_caption = ''Haemonchus contortus'' egg
| taxon = Haemonchus contortus
| authority = (Rudolphi, 1803) Cobb, 1898
| synonyms = ''Haemonchus placei'' <small>Place, 1893</small><ref name="IRMNG">{{cite web |title=IRMNG - Haemonchus placei Place, 1893 |url=https://www.irmng.org/aphia.php?p=taxdetails&id=11473085 |website=www.irmng.org |access-date=21 October 2021}}</ref> (closely related species)
}}

'''''Haemonchus contortus''''', also known as the [[barber's pole]] worm, is a very common parasite and one of the most pathogenic [[nematode]]s of [[ruminant]]s. Adult worms attach to [[abomasum|abomasal]] mucosa and feed on the blood. This parasite is responsible for [[anemia]], [[oedema]], and death of infected [[sheep]] and [[goats]], mainly during summer in warm, humid climates.<ref>[http://attra.ncat.org/downloads/goat_barber_pole.pdf Burke, Joan, Research Animal Scientist. ''Management of Barber pole Worm in Sheep and Goats in the Southern U.S.'' USDA, ARS, Dale Bumpers Small Farms Research Center, Booneville, AR.] {{Webarchive|url=https://web.archive.org/web/20090305042910/http://attra.ncat.org/downloads/goat_barber_pole.pdf |date=2009-03-05 }}></ref>

Females may lay over 10,000 eggs a day,<ref>{{Cite web|title=Barber's pole worm (''Haemonchus contortus'') at Australian Wool Innovation Limited.|url=http://www.wool.com/Grow_WormBoss_Know-your-worms_Barbers-pole-worm.htm|url-status=dead|archive-url=https://web.archive.org/web/20120430210231/http://www.wool.com/Grow_WormBoss_Know-your-worms_Barbers-pole-worm.htm|archive-date=2012-04-30|access-date=2010-11-04}}</ref> which pass from the host animal in the [[faeces]]. After hatching from their eggs, ''H. contortus'' [[larva]]e [[ecdysis|molt]] several times, resulting in an L3 form that is [[infection|infectious]] for the animals. The host ingests these larvae when grazing. The L4 larvae, formed after another molt, and adult worms suck blood in the abomasum of the animal, potentially giving rise to anaemia and oedema, which eventually can lead to death.<ref>{{cite web | title = ''Haemonchus'', ''Ostertagia'', and ''Trichostrongylus'' spp | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/22413.htm | access-date = 2007-07-01 }}</ref>

The infection, called haemonchosis, causes large economic losses for farmers around the world, especially for those living in warmer climates. [[Anthelminthics]] are used to prevent and treat these, and other, worm infections, but [[drug resistance|resistance]] of the [[parasitism|parasites]] against these [[chemical substance|chemicals]] is growing. Some breeds, such as the [[West African Dwarf goat]] and N'Dama cattle, are more resistant than other breeds to ''H. contortus'' (haemonchotolerance).<ref name="ChiejinaBehnke2015">{{cite journal |doi=10.1051/parasite/2015006 |pmid=25744655 |pmc=4321401 |title=Haemonchotolerance in West African Dwarf goats: Contribution to sustainable, anthelmintics-free helminth control in traditionally managed Nigerian dwarf goats |journal=Parasite |volume=22 |pages=7 |year=2015 |last1=Chiejina |first1=Samuel N |last2=Behnke |first2=Jerzy M |last3=Fakae |first3=Barineme B }}</ref>

==Morphology==
{{Unreferenced section|date=April 2020}}
The ova is yellowish in color. The egg is about 70–85&nbsp;μm long by 44&nbsp;μm wide, and the early stages of cleavage contain between 16 and 32 cells. The adult female is {{convert|18–30|mm|in|frac=8}} long and is easily recognized by its trademark "barber pole" coloration. The red and white appearance is because ''H. contortus'' is a blood feeder, and the white ovaries can be seen coiled around the blood-filled intestine. The male adult worm is much smaller at {{convert|10–20|mm|in|frac=16}} long, and displays the distinct feature of a well-developed copulatory bursa, containing an asymmetrical dorsal lobe and a Y-shaped dorsal ray.

==Life cycle==
The adult female worm can release between 5,000 and 10,000 eggs, which are passed out in the faeces.<ref>{{cite journal |last1=Emery |first1=David L. |last2=Hunt |first2=Peter W. |last3=Le Jambre |first3=Leo F. |title=Haemonchus contortus: the then and now, and where to from here? |journal=International Journal for Parasitology |date=November 2016 |volume=46 |issue=12 |pages=755–769 |doi=10.1016/j.ijpara.2016.07.001 |pmid=27620133 |doi-access=free }}</ref> Eggs then develop in moist conditions in the faeces and continue to develop into the L1 (rhabditiform), and L2 juvenile stages by feeding on bacteria in the dung. The L1 stage usually occurs within four to six days under the optimal conditions of {{convert|24–29|C|F|0}}. The L2 rhabditform sheds its cuticle and then develops into the L3 filiariform infective larvae. The L3 form has a protective cuticle, but under dry, hot conditions, survival is reduced.
Sheep, goats, and other ruminants become infected when they graze and ingest the L3 infective larvae. The infective larvae pass through the first three stomach chambers to reach the abomasum. There, the L3 shed their cuticles and burrow into the internal layer of the abomasum, where they develop into L4, usually within 48 hours, or preadult larvae. The L4 larvae then molt and develop into the L5 adult form. The male and female adults mate and live in the abomasum, where they feed on blood.

== Genetics ==
The ''H. contortus'' draft genome was published in 2013.<ref>{{cite journal |doi=10.1186/gb-2013-14-8-r88 |pmid=23985316 |pmc=4054779 |title=The genome and transcriptome of Haemonchus contortus, a key model parasite for drug and vaccine discovery |journal=Genome Biology |volume=14 |issue=8 |pages=R88 |year=2013 |last1=Laing |first1=Roz |last2=Kikuchi |first2=Taisei |last3=Martinelli |first3=Axel |last4=Tsai |first4=Isheng J |last5=Beech |first5=Robin N |last6=Redman |first6=Elizabeth |last7=Holroyd |first7=Nancy |last8=Bartley |first8=David J |last9=Beasley |first9=Helen |last10=Britton |first10=Collette |last11=Curran |first11=David |last12=Devaney |first12=Eileen |last13=Gilabert |first13=Aude |last14=Hunt |first14=Martin |last15=Jackson |first15=Frank |last16=Johnston |first16=Stephanie L |last17=Kryukov |first17=Ivan |last18=Li |first18=Keyu |last19=Morrison |first19=Alison A |last20=Reid |first20=Adam J |last21=Sargison |first21=Neil |last22=Saunders |first22=Gary I |last23=Wasmuth |first23=James D |last24=Wolstenholme |first24=Adrian |last25=Berriman |first25=Matthew |last26=Gilleard |first26=John S |last27=Cotton |first27=James A |doi-access=free }}</ref> Further work to complete the reference genome is underway at the [[Wellcome Trust Sanger Institute]] in collaboration with the University of Calgary, the University of Glasgow, and the [[Moredun Research Institute]]. Developing genetic and genomic resources for this parasite will facilitate the identification of the genetic changes conferring anthelmintic [[drug resistance|resistance]] and may help design new drugs or [[vaccine]]s to combat disease and improve animal health.<ref>{{Cite web|url=https://www.sanger.ac.uk/resources/downloads/helminths/haemonchus-contortus.html|title = Haemonchus contortus - Wellcome Sanger Institute}}</ref>

The ''H. contortus'' reference genome was published at chromosome-scale in 2020. 5 autosomes and one X chromosome were assembled. Quite remarkably, each chromosome had a very similar gene content compared to the corresponding chromosome in ''[[C. elegans]]'', yet there was little conservation of gene order. This genome is the fourth version from Wellcome Sanger.<ref>{{cite journal |last1=Doyle |first1=SR |last2=Tracey |first2=A |last3=Laing |first3=R |last4=Holroyd |first4=N |last5=Bartley |first5=D |last6=Bazant |first6=W |last7=Beasley |first7=H |last8=Beech |first8=R |last9=Britton |first9=C |last10=Brooks |first10=K |last11=Chaudhry |first11=U |last12=Maitland |first12=K |last13=Martinelli |first13=A |last14=Noonan |first14=JD |last15=Paulini |first15=M |last16=Quail |first16=MA |last17=Redman |first17=E |last18=Rodgers |first18=FH |last19=Sallé |first19=G |last20=Shabbir |first20=MZ |last21=Sankaranarayanan |first21=G |last22=Wit |first22=J |last23=Howe |first23=KL |last24=Sargison |first24=N |last25=Devaney |first25=E |last26=Berriman |first26=M |last27=Gilleard |first27=JS |last28=Cotton |first28=JA |title=Genomic and transcriptomic variation defines the chromosome-scale assembly of Haemonchus contortus, a model gastrointestinal worm. |journal=Communications Biology |date=9 November 2020 |volume=3 |issue=1 |pages=656 |doi=10.1038/s42003-020-01377-3 |pmid=33168940|pmc=7652881 }}</ref>

==Pathogenicity==
{{Unreferenced section|date=April 2020}}
Clinical signs are largely due to blood loss. Sudden death may be the only observation in acute infection, while other common clinical signs include pallor, anemia, oedema, ill thrift, lethargy, and depression. The accumulation of fluid in the submandibular tissue, a phenomenon commonly called "bottle jaw", may be seen. Growth and production are significantly reduced.

==Prevention and treatment==
Prophylactic anthelmintic treatment necessary to prevent infection in endemic regions, but wherever possible, a reduction on reliance on chemical treatment is warranted given the rapid rise of anthelmintic resistance.
A commercial vaccine known as Barbervax in Australia or Wirevax in South Africa has become available in recent years. This works mainly by reducing egg output and hence pasture contamination. The vaccine contains proteins from the lining of the intestines of the Barber's Pole worm. The animal produces antibodies against the protein which circulate in the blood. When the Barber's pole worm drinks the blood the antibodies attach to its stomach lining, preventing digestion and starving the animal. Following this, the worm produces fewer eggs and eventually dies off.<ref>{{cite web |title=Haemonchus contortus |url=https://www.moredun.org.uk/research/diseases/haemonchus-contortus |website=Moredun research institute |publisher=Moredun |access-date=16 February 2019}}</ref>

Targeted selective treatment methods such as the [[FAMACHA]] method may be valuable in reducing the number of dosing intervals, thus reducing the percentage of surviving parasites that are resistant to anthelmintics. Faecal egg counts are used to track parasite infestation levels, individual animals' susceptibility, and anthelmintic effectiveness.{{Citation needed|date=January 2021}}

Other management strategies include selective breeding for more parasite-resistant sheep or goats (e.g. by culling the most susceptible animals or by introducing parasite-resistant breeds such as [[Gulf Coast Native sheep]]); careful pasture management, such as [[managed intensive rotational grazing]], especially during peak parasite season; and "cleaning" infested pastures by haying, tilling, or grazing with a nonsusceptible species (e.g. swine or poultry).<ref>{{Cite web |last=Anderson |first=Samuel |title=Summary of Results: New England Small Ruminant Producer Survey |work=Northeast IPM Center |year=2013 |url=http://www.northeastipm.org/neipm/assets/File/New-England-Small-Ruminant-Survey-Results-2013.pdf}}</ref>

Recent research has also shown that the use of hair sheep breeds, such as Katahdins, Dorpers, and St. Croix, can be chosen for resistance to internal parasites for economical standards; additionally, the hair breeds provide resistance without showing any significant effect growth performance of their progeny.<ref>{{cite journal |doi=10.2527/asasann.2017.692 |title=692 Effects of high heat load conditions on rectal temperature, panting score, and respiration rate of hair sheep breeds from different regions of the United States |journal=Journal of Animal Science |volume=95 |pages=337–8 |year=2017 |last1=Tadesse |first1=D |last2=Puchala |first2=R |last3=Gipson |first3=T. A |last4=Portugal |first4=I |last5=Sahlu |first5=T |last6=Dawson |first6=L. J |last7=Goetsch |first7=A. L |doi-access=free }}</ref>

One of the riskiest methods that can be used for treatments is the use of copper oxide wire particles (COWP) to aid in the destruction of the parasites inside the gut without the use of organic chemicals. However, in sheep, the dosing would need to be monitored extremely closely because if they are administered too high of a dose, then they will slip into copper toxicity. For the COWP, the lowest recommended dose would need to be administered to remain safe for sheep. The study conducted found that treatment with the COWP reduced faecal egg counts by >85%. Treatment with the copper oxide wire particles could lead to less reliance on anthelmintics because the COWP allows for the reduction in establishment of parasitic infections, especially if the producer is trying to reduce the larval population on their pastures.<ref>{{cite journal |doi=10.1016/j.vetpar.2009.10.004 |pmid=19931291 |title=Efficacy of copper oxide wire particles against gastrointestinal nematodes in sheep and goats |journal=Veterinary Parasitology |volume=168 |issue=1–2 |pages=93–6 |year=2010 |last1=Soli |first1=F |last2=Terrill |first2=T.H |last3=Shaik |first3=S.A |last4=Getz |first4=W.R |last5=Miller |first5=J.E |last6=Vanguru |first6=M |last7=Burke |first7=J.M }}</ref>

Recent research shows fugal lectins are able to inhibit larval development. These fungal lectins are Corprinopsis cinerea lectins - CCL2, CGL2; Aleuria aurantia lectin - AAL; and Marasmius oreades agglutinin - MOA. These four toxic lectins bind to specific glycan structures found in ''H. controtus''. Some of these glycan structures might represent antigens which are not exposed to host immune system, and thus have potential for vaccine or drug development.<ref>{{cite journal |doi=10.1186/s13071-015-1032-x |pmid=26283415 |pmc=4539729 |title=Inhibition of Haemonchus contortus larval development by fungal lectins |journal=Parasites & Vectors |volume=8 |pages=425 |year=2015 |last1=Heim |first1=Christian |last2=Hertzberg |first2=Hubertus |last3=Butschi |first3=Alex |last4=Bleuler-Martinez |first4=Silvia |last5=Aebi |first5=Markus |last6=Deplazes |first6=Peter |last7=Künzler |first7=Markus |last8=Štefanić |first8=Saša |doi-access=free }}</ref>

== References ==

{{Reflist}}

===Further reading===
* {{cite journal | last1 = Newton | first1 = S | year = 1995 | title = Progress on vaccination of ''Haemonchus contortus'' | journal = [[International Journal for Parasitology]] | volume = 25 | issue = 11| pages = 1281–1289 | doi=10.1016/0020-7519(95)00065-a| pmid = 8635880 }}
* Roberts, L., J. Janovy. 2000. Foundations of Parasitology. US: The McGraw Hill Companies, Inc..
* {{cite journal | last1 = Fetterer | first1 = R. | last2 = Rhoads | first2 = M. | year = 1996 | title = The role of the sheath in resistance of ''Haemonchus contortus'' infective stage larvae to proteolytic digestion | url = https://zenodo.org/record/1258473| journal = [[Veterinary Parasitology (journal)|Veterinary Parasitology]] | volume = 64 | issue = 4| pages = 267–276 | doi=10.1016/0304-4017(95)00926-4| pmid = 8893481 }}
* {{cite journal | last1 = Dorny | first1 = P. | last2 = Batubara | first2 = A. | last3 = Iskander | first3 = M. | last4 = Pandey | first4 = V. | year = 1996 | title = Helminth infections of sheep in North Sumatra, Indonesia | journal = Veterinary Parasitology | volume = 61 | issue = 3–4| pages = 353–358 | doi=10.1016/0304-4017(95)00826-8| pmid = 8720574 }}

{{Taxonbar|from=Q1754336}}
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{{DEFAULTSORT:Haemonchus Contortus}}
[[Category:Parasitic diseases]]
[[Category:Parasitic nematodes of mammals]]
[[Category:Strongylida]]
[[Category:Sheep and goat diseases]]
[[Category:Veterinary helminthology]]