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== Synonyms<br>  ==
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Also known as '''Contagious Pustular Dermatitis''', '''Contagious Ecthyma''' and '''Scabby Mouth''',
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'''Contagious Pustular Dermatitis''' <br>
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'''Contagious Ecthyma''' <br>
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'''Scabby Mouth'''
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<br>
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Orf is the most common viral '''zoonosis''' in the UK.
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== Introduction<br> ==
[[Image: Contagious ecthyma.jpg|200px|thumb|right|<small><center>Contagious ecthyma (Courtesy of Bristol BioMed Image Archive)</center></small>]]
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Orf is the most common viral '''zoonosis''' in the UK. It causes an acute debilitating but rarely fatal skin disease of sheep, goats and incidentally of ruminants and humans. It is a parapox virus and infects by entering a skin lesion in places such as the udder, mouth and throat. These lesions then coalesce to form scabbed masses. It is of particular concern in lambs as mouth lesions prevent them from suckling due to pain. If the sheep has lesions on her udder she is also unlikely to want to let her lambs suckle. <br>
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====Morphology====
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The virus is a large, enveloped, highly epitheliotropic, DNA virus which is ovoid in shape and measures 220‑300 x 140‑170 nm and there are over 100 polypeptides in the virion. The core proteins include a transcriptase and several other enzymes. The virus is immunologically related to those causing bovine papular stomatitis, pseudocowpox, sealpox, deer PPV, red squirrel PPV and camel PPV.&nbsp;There is extensive cross‑neutralization and cross‑protection between viruses belonging to the same genus, but not between those of different genera.<br>
*The virus is a large, enveloped, highly epitheliotropic, DNA virus which is ovoid in shape and measures 220‑300 x 140‑170 nm
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*There are over 100 polypeptides in the virion
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*The core proteins include a transcriptase and several other enzymes
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*The virus is immunologically related to those causing bovine papular stomatitis, pseudocowpox, sealpox, deer PPV, red squirrel PPV and camel PPV
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*There is extensive cross‑neutralization and cross‑protection between viruses belonging to the same genus, but not between those of different genera
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*The virus is resistant to desiccation
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*It is a parapox virus
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====Hosts====
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Morbidity in a flock may reach 90% but mortality is incredibly rare, reaching 1% maximum, unless secondary myiasis (blowfly strike) occurs. The course of the disease without complications is 2‑6 weeks, and it takes about 10 weeks to run a course through a naive flock, but often lingers indefinitely in the flock because it can reinfect the same animal many times and is resistant to desiccation.<br>
*Acute debilitating but rarely fatal skin disease of sheep, goats and incidentally of ruminants and humans
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====Pathogenesis====
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<br>
*Trauma, then lesions on skin without wool
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*Lesions on udder and throat and in mouth
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*Lesions coalesce to form scabbed masses
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*Particular concern for '''lambs''', who stop feeding due to mouth lesions
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*For more, see [[Viral skin infections - Pathology#Contagious ecthyma|here]]
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*In man, papules and pustules develop on hands within 10 days, enlarge and then regress after several weeks
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====Epidemiology====
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== Clinical Signs<br> ==
*Morbidity may reach 90%, but mortality rarely exceeds 1%, unless secondary infection or myiasis occurs
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*The course of the disease without complications is 2‑6 weeks, and it takes about 10 weeks to run a course through a naive flock, but often lingers indefinitely in the flock because it can reinfect the same animal many times and is resistant to desiccation
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====Differentials====
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Failure to gain weight in lambs, plus the presence of scabby lesions on the mouth. Similar lesions on the mouth and udder of ewes and a reluctance to eat in these animals. In man, papules and pustules develop on hands within 10 days, enlarge and then regress after several weeks.
*Sheep pox: A more severe disease
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**Characterized by elevated papules distributed diffusely over the skin surface
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**Inclusion bodies are often seen, but there is no down‑growth of epidermis
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**High mortality
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*Ulcerative dermatosis: 
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**Characterized by ulcers and crusts on the skin of the face, feet and genitalia
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**The lesions are not elevated because there is no epithelial hyperplasia
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*[[Bluetongue Virus]]: 
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**There is a lower morbidity but a high mortality
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**The disease is usually seen in adult animals
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**This is a severe systemic disease which is a differential only for the rare, systemic form of CE
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*Mycotic dermatitis:
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**The scabs are smaller and thinner and lighter and usually yellowish in color, with crusts not firmly attached
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*Foot and mouth disease:  When lesions occur in the mouth
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*[[Poxviridae]] infection
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<br>
*Quite a common '''zoonotic''' disease
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=====Clinical=====
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== Diagnosis<br> ==
*In sheep produces a proliferative nodule/papular mass on [[Lips|lips]]
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*In flocks in which it is endemic it is seen in lamb
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*If flock is non-immune seen in ewes too but much worse in lambs (may spread to inside of mouth)
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*Can spread to udder of ewe
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=====Pathology=====
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Differential diagnoses include Sheep pox, which is a more evere disease characterized by elevated papules distributed diffusely over the skin surface and high mortality rates are seen. Ulcerative dermatosis is another differential and is also characterized by ulcers and crusts on the skin of the face, feet and genitalia, however the lesions are not elevated because there is no epithelial hyperplasia. [[Bluetongue Virus]] is another differential. There is lower morbidity but a high mortality and the disease is usually seen in adult animals. Mycotic dermatitis is a differential although the scabs are smaller and thinner and lighter and usually yellowish in color, with crusts not firmly attached. Foot and mouth disease can be a differential when lesions occur in the mouth.
Papular proliferative pathology
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*Poxvirus infections produce local infection of [[prickle cells]] in epithelium with proliferation of cells and formation of papule followed by ulceration / necrosis and covered by necrotic epithelium
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*Eventually scabs form and crust drops off
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*Scabs - very infectious ( N.B.if touch -> catch it)
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====Control====
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<br>
*Attenuated virus can be applied by scarification to axillar, causing scabs to fall off in 30 days
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*Annual '''vaccination''' of ewes at least 8 weeks before lambing (all in contact should be done simultaneously)
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*In an outbreak, all lambs can be vaccinated
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==From pathology==
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== Control ==
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====Contagious ecthyma====
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Attenuated virus can be applied by scarification to axillar or tail base, causing scabs to fall off in 30 days. Annual '''vaccination''' of ewes at least 8 weeks before lambing (all in contact should be done simultaneously) is required. In an outbreak, all lambs can be vaccinated .<br>
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*Also called '''contagious pustular dermatitis, orf, sore mouth'''
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<br>
*Caused by a [[Poxviridae|parapox virus]]
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*Affects mainly young sheep, less commonly cattle, humans, dogs
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*Starts in abrasions around mouth commisures and spreads to [[Lips|lips]], oral mucosa, eyelids and feet
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*May also transfer to teats of the mother of an affected lamb
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*Lesions typical of poxvirus but very brief vesicle stage
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*Most obvious is the proliferative pustular stage
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== References<br> ==
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Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition) Elsevier Science<br>
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[[Category:Poxviridae]][[Category:Sheep Viruses]][[Category:Goat Viruses]][[Category:Zoonoses]]
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Bridger, J and Russell, P (2007) Virology Study Guide, Royal Veterinary College<br>
[[Category:Oral_Cavity_-_Proliferative_Pathology]]
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[[Category:To_Do_-_Clinical/Viruses]]
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Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences<br>
[[Category:Oral Diseases - Sheep]][[Category:Dermatological Diseases - Sheep]]
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[[Category:Oral Diseases - Goat]][[Category:Dermatological Diseases - Goat]]
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<br>
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[[Category:Poxviridae]] [[Category:Sheep_Viruses]] [[Category:Goat_Viruses]] [[Category:Zoonoses]] [[Category:Oral_Cavity_-_Proliferative_Pathology]] [[Category:To_Do_-_Review]] [[Category:Oral_Diseases_-_Sheep]] [[Category:Dermatological_Diseases_-_Sheep]] [[Category:Oral_Diseases_-_Goat]] [[Category:Dermatological_Diseases_-_Goat]]
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