View source for Sheeppox

{{short description|Infectious disease of sheep caused by the sheeppox virus}}
{{Virusbox
| image = Bacilli of milignant odema and in cornea of pox in sheep Wellcome M0013310.jpg
| image_alt = Bacilli of malignant edema and in cornea of pox in sheep
| image_caption = [[Bacillus (shape)|Bacilli]] of [[malignant edema]] and in [[cornea]] of pox in sheep
| parent = Capripoxvirus
| species = Sheeppox virus
| synonyms = ''Sheep pox virus''
| synonyms_ref = <ref>1ICTV 5thReportFrancki, R. I. B., Fauquet, C. M., Knudson, D. L. & Brown, F. (eds)(1991). Classification and nomenclature of viruses. Fifthreport of the International Committee on Taxonomy of Viruses. Archives of Virology Supplementum 2, 452 pp. https://ictv.global/ictv/proposals/ICTV%205th%20Report.pdf</ref>
| subdivision_ranks =
| subdivision =
}}
'''Sheeppox''' (or '''sheep pox''', known as {{lang|la|variola ovina}} in [[Latin]], {{lang|fr|clavelée}} in [[French language|French]], {{Lang|de|Pockenseuche}} in [[German language|German]]) is a highly [[contagious disease]] of [[sheep]] caused by a [[poxvirus]] different from the benign [[Orf (animal disease)|orf]] (or [[contagious ecthyma]]). This virus is in the family ''[[Poxviridae]]'' and genus ''[[Capripoxvirus]]''. '''''Sheeppox virus''''' (SPV) is the most severe of all the animal pox diseases and can result in some of the most significant economic consequences due to poor wool and leather quality.<ref name=":2">{{cite book |author1=D.C. Blood |author2=J.A. Henderson |author3=O.M. Radostits | title = Veterinary Medicine | publisher = Baillière Tindall | location = London | edition = 5th | year = 1979 | isbn = 978-0-7020-0718-7 | pages = 708–709 (Sheeppox and goatpox)}}</ref><ref name=":0">{{Cite journal|last=Tulman|first=E. R.|last2=Afonso|first2=C. L.|last3=Lu|first3=Z.|last4=Zsak|first4=L.|last5=Sur|first5=J.-H.|last6=Sandybaev|first6=N. T.|last7=Kerembekova|first7=U. Z.|last8=Zaitsev|first8=V. L.|last9=Kutish|first9=G. F.|date=June 2002|title=The Genomes of Sheeppox and Goatpox Viruses|pmc=136203|journal=Journal of Virology|volume=76|issue=12|pages=6054–6061|doi=10.1128/JVI.76.12.6054-6061.2002|issn=0022-538X|pmid=12021338}}</ref>
'''Goatpox''' is a similar disease of [[goat]]s, caused by a virus antigenically distinct from ''sheeppox virus''.
== Virology ==
=== Structure ===
Sheeppox virus is approximately 150 kbp and shares 96% and 97% nucleotide identity with goatpox virus and [[Lumpy skin disease|lumpy skin disease virus]], respectively.<ref name=":0" /> This virus has a linear, '''dsDNA genome''' and is thus a part of group I according to the [[Baltimore classification|Baltimore Classification System]]. The virus has a complex coat and capsid symmetry.{{cn|date=November 2022}}
=== Host ===
The hosts for sheeppox virus are all breeds of wild and domesticated sheep. However, those animals native to the region where SPV is endemic, are far less susceptible. Young, lactating, and older animals are more susceptible to this viral infection though no viral preference has been found. This virus is endemic to Africa, Asia, India, and the Middle East.<ref name=":5">{{Cite web|url=http://lrd.spc.int/ext/Disease_Manual_Final/a100__sheep_pox_and_goat_pox.html|title=A100 - SHEEP POX AND GOAT POX|website=lrd.spc.int|access-date=2017-11-03}}</ref>
=== Replication ===
The virus enters the host cell via '''[[endocytosis]]''' which is initiated by the attachment of viral proteins to [[Glycosaminoglycan|host glycosaminoglycans]]. Then, SPV fuses with the plasma membrane which releases the [[viral core]] into the cytoplasm. Viral proteins help contribute to early gene transcription in the host cytoplasm and expression begins 30 minutes post infection. After early expression, the viral genome becomes free in the cytoplasm due to the core no longer being coated with the [[capsid]].{{cn|date=November 2022}}
The intermediate phase, approximately 100 minutes post infection, stimulates [[DNA replication|genomic replication]] as the intermediate genes are expressed. 140 minutes to 48 hours post infection is considered the late phase which is when all structural proteins are produced. [[Virus|Virion]] assembly begins in the cytoplasm with the formation of an immature spherical particle. Once maturation occurs, it is considered an intracellular mature virion. These are brick-shaped particles that can then be released from the cell either by [[budding]] or [[Lysis|cell lysis]].<ref>{{Cite web|url=http://viralzone.expasy.org/152?outline=all_by_protein|title=Capripoxvirus|website=viralzone.expasy.org|access-date=2017-11-03}}</ref>
=== Transmission ===
Sheeppox virus is an aerosol and can also be transmitted via contact with an infected animal. The [[saliva]], secretions, feces, milk or scabs of those with SPV also cary the virus.  Contaminated equipment is another major transmission factor and [[Vector (epidemiology)|insect vectors]] play a minor role. SPV is mainly spread to new areas due to the movement of infected individuals. [[Immunity (medical)|Immunity]] results after infection and there are [[vaccine]]s available. The [[Attenuated vaccine|live, attenuated]] vaccines produce longer lasting and stronger immunity than the [[inactivated vaccine]]. It has been suggested that the [[Lumpy skin disease|lumpy skin disease virus]] vaccine is can also be used to prevent sheeppox.<ref name=":1">{{Cite news|url=http://www.merckvetmanual.com/integumentary-system/pox-diseases/sheeppox-and-goatpox|title=Sheeppox and Goatpox - Integumentary System - Merck Veterinary Manual|work=Merck Veterinary Manual|access-date=2017-11-03|language=en-US}}</ref><ref name=":4">{{Cite web|url=http://www.oie.int/search/|title=Search: OIE - World Organisation for Animal Health|website=www.oie.int|language=en|access-date=2017-11-03}}</ref>
== Symptoms and diagnosis ==
=== Symptoms ===
Symptoms can range from mild to severe depending on things such as age, breed, and immunity of the host. The [[virulence]] of the virus is also a contributing factor. The [[incubation period]] of the virus is 4–12 days. <gallery>
File:CSIRO ScienceImage 1377 Capripox virus disease.jpg|Lesions around lips (orf is '''on''' lips)
File:Noerès plokes berbis axhele3.jpg|Starting lesions (reddening) in axilla
File:Noerès plokes berbis axhele1.jpg|Crusty lesions in axilla
File:Noerès plokes berbis cawe.jpg|Crusty lesions on tail
File:Noerès pokes agnea cawe.jpg|Crusty lesions on tail (lamb)
</gallery>Early symptoms include increased temperature and [[Cutaneous condition|macules]]. The [[Cutaneous condition|skin lesions]] are most common on the muzzle, ears, and areas that are free of wool. Lesions on the skin quickly become raised due to local inflammation and [[edema]]. At this stage, the virus is extremely prevalent in the lesions.{{cn|date=November 2022}}
The acute phase is characterized as 24 hours after papule appearance. In this phase the sheep may develop [[rhinitis]], [[conjunctivitis]], and swollen [[lymph node]]s, up to eight times the normal size. [[Blepharitis]] can result from papules on the eyelids, mucosa becomes [[Necrosis|necrotic]], and ulcers on the [[mucous membrane]]s may create discharge. Due to lymph node swelling and developing lung lesions, breathing can become loud and labored.{{cn|date=November 2022}}
The acute phase has passed when the papules become [[Necrosis|necrotic]] and scabs start to form. These scabs can last up to 6 weeks and typically leave a star-shaped scar. The presence of the skin lesions can lead to movement restriction of the animal, [[Pharynx|oropharynx]] lesions impact feeding and drinking ability,  and lesions on the udder interfere with [[suckling]]. [[Pneumonia|Secondary pneumonia]] is another common symptom, which is often fatal. In [[Endemic (epidemiology)|endemic areas]] morbidity is around 70-90% while SPV mortality is 5-10%, with its peak two weeks after the appearance of lesions.<ref name=":1" /><ref name=":4" /><ref name=":5"/><ref name=":6">{{Cite web|url=https://www.cabi.org/isc/datasheet/81537|title=sheep and goat pox|website=www.cabi.org|access-date=2017-11-03}}</ref> It is the cell mediated immune response which eliminates the infection.<ref name=":6" />
There have only been two reported cases of [[Zoonosis|zoonotic transmission]] which result in a mild localized reaction limited to the skin.<ref name=":6" />
=== Diagnosis ===
==== Differential ====
Can include<ref name=":5"/>
* [[Contagious pustular dermatitis]] (scabby mouth)
* [[Bluetongue disease|Blue tongue]]
* [[Mycosis|Mycotic dermatitis]]
* Sheep scab
* [[Mange]]
* Photosensitisation
==== Laboratory ====
Samples can include<ref name=":4" />
* [[Biopsy|Full skin thickness biopsies]]
* Vesicular fluid if available
* Scabs
* [[Lymph node]] aspirates
* Lung and skin lesions
Techniques that can be used include
* [[Polymerase chain reaction|Polymerase Chain Reaction (PCR)]]
* Agar gel immunodiffusion test (AGID)
* [[ELISA|Enzyme-linked immunosorbent assay]] (ELISA)
* [[Transmission electron microscopy]]
* Virus isolation in cell culture
== History ==
In the 20th century, sheeppox virus was eradicated from continental Europe, but since then, there have been sporadic outbreaks, which are most likely due to imported animals. The countries with the highest number of cases are Ethiopia (223), Somalia (170), and Algeria (44). This resulted in a 16.3% case fatality rate out of the 9932 cases involved. From 2010 to 2011 there was a 46% decrease in the number of outbreaks with no specific explanation for this decrease. There has been no seasonal variability identified.<ref name=":6" />
== Outbreaks ==
A relatively recent [[outbreak]] occurred in Russia in October 2016. This showed 25 cases, there were 5 deaths, and thus, puts the [[case fatality rate]] at 20. Responses included vaccinations, movement control within the country, and disinfection. The laboratory test to confirm this viral outbreak, was again [[Polymerase chain reaction|PCR]], with the results being positive.<ref name=":7">{{Cite web|url=https://www.promedmail.org|title=ProMED-mail|website=www.promedmail.org|language=en|access-date=2017-11-03}}</ref>
Most recently, in early September 2017, there have been 2 outbreaks of sheeppox virus in Greece. This current location had 3 previous outbreaks in January 2017 with the origin of infection unknown. Real time [[Polymerase chain reaction|PCR]] results tested positive for SPV and the infected were removed from the population either through death, destruction, or slaughter. Measures that were taken in response to these outbreaks were proper disposal of the carcasses, movement control within the country, and quarantine.<ref name=":7" />
== Prevention ==
There is no treatment for sheeppox virus, thus efforts are directed towards prevention. [[File:Volantès pokes après eploctaedje tiesse fritches.jpg|thumb|Vaccinal disease due to poorly inactivated vaccine]]
=== Vaccines ===
The most effective control over the disease has been the [[Vaccine|live, attenuated virus vaccine]] which have been shown to produce good immunity. There are [[inactivated vaccine]]s, but they have shown to only provide around 5 months of immunity. In the case of an [[outbreak]], it is suggested that the animals be [[Animal euthanasia|euthanized]] and their carcasses burnt or buried.<ref name=":5"/> In most countries, large scale state [[vaccination]] programs are implemented against the disease. But, so far, few have succeeded in eradicating it.<ref name=":2" />
=== Sanitation ===
Cleaning of farms and equipment is important in helping to prevent the spread of SPV. Infected animals may be quarantined and new animals should be isolated from the infected herds while transmission is still possible. If necessary, slaughtering or euthanasia of the herd can help prevent further disease transmission. Crucial is the proper disposal of the animals, either by burning or burying them.<ref name=":5" /><ref name=":4" />
== References ==
<references />
{{Taxonbar|from=Q7480670}}
[[Category:Virus-related cutaneous conditions]]
[[Category:Sheep and goat diseases]]
[[Category:Chordopoxvirinae]]