Orf (disease)
Template:Short description Template:Infobox medical condition (new) Orf is a farmyard pox, a type of zoonosis.<ref name=Kassa2021/> It causes small pustules in the skin of primarily sheep and goats, but can also occur on the hands of humans.<ref name=Kumar2020>Template:Cite book</ref> A pale halo forms around a red centre.<ref name=Goldman2020>Template:Cite book</ref> It may persist for several weeks before crusting and then either resolves or leaves a granuloma.<ref name=Goldman2020/> There is usually only one non-painful lesion, but there can be more.<ref name=Goldman2020/> Lymph nodes may also become swollen.<ref name=Goldman2020/>
It is caused by a parapoxvirus.<ref name=Andrew2020>Template:Cite book</ref> It can occur in humans who handle infected animals or contaminated objects.<ref name=Kassa2021>Template:Cite journal</ref> One third of cases may develop erythema multiforme.<ref name=Goldman2020/> Once resolved, a person can still be infected again.<ref name=Goldman2020/>
Generally, once infected, treatment options are limited.<ref name=Goldman2020/> Injecting the lesion with cidofovir or applying imiquimod has been studied.<ref name=Goldman2020/> However, it is sometimes required to excise the pustules.<ref name=Goldman2020/> The vaccine used in sheep to prevent orf is live and has been known to cause disease in humans.<ref name=Goldman2020/>
The disease is endemic in livestock herds worldwide.<ref name=Kassa2021/> A recent outbreak emerged in southwest Ethiopia between October 2019 and May 2020.<ref name=Kassa2021/>
Humans
Orf is a zoonotic disease, meaning humans can contract this disorder through direct contact with infected sheep and goats or with fomites carrying the orf virus.<ref name="Orf Virus (Sore Mouth Infection)">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It causes a purulent-appearing papule locally and generally no systemic symptoms. Infected locations can include the finger, hand, arm, face and even the penis (caused by infection either from contact with the hand during urination or from bestiality). Consequently, it is important to observe good personal hygiene and to wear gloves when treating infected animals.<ref name=Winter_Charnley/> It may appear similar to cowpox and pseudocowpox.<ref name=Kassa2021/> Template:Virusbox
While orf is usually a benign self-limiting illness which resolves in 3-6 weeks, in the immunocompromised it can be very progressive and even life-threatening. One percent topical cidofovir has been successfully used in a few patients with progressive disease. Serious damage may be inflicted on the eye if it is infected by orf, even among otherwise healthy patients. The virus can survive in the soil for at least six months.<ref name=Couch>Template:Cite thesis</ref>
Other animals
Orf is primarily a disease of sheep and goats although it has been reported as a natural disease in humans, steenbok and alpacas, chamois and tahrs, reindeer, musk oxen, dogs, cats, mountain goats, bighorn sheep, dall sheep, and red squirrels.<ref name=Couch/>
Sheep and goats
It has been recorded since the late 19th century and has been reported from most sheep-or goat-raising areas, including those in Europe, the Middle East, the United States, Africa, Asia, South America, Canada, New Zealand and Australia.<ref name=Couch/> Orf is spread by fomites and direct contact. In some environments, infection is injected by scratches from thistles<ref name=Winter_Charnley/> of both growing and felled plants. Symptoms include papules and pustules on the lips and muzzle, and less commonly in the mouth of young lambs and on the eyelids, feet, and teats of ewes. The lesions progress to thick crusts which may bleed. Orf in the mouths of lambs may prevent suckling and cause weight loss, and can infect the udder of the mother ewe, thus potentially leading to mastitis.<ref name=Winter_Charnley/> Sheep are prone to reinfection.<ref name=Fenner_1993>Template:Cite book</ref> Occasionally the infection can be extensive and persistent if the animal does not produce an immune response.<ref name=Winter_Charnley/>
A live virus vaccine (ATCvet code: Template:ATCvet) is made from scab material and usually given to ewes at the age of two months, but typically only given to lambs when there is a confirmed outbreak.<ref name=Carter>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The vaccine can cause minor cases of orf when used in humans. <ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In sheep and goats, the lesions mostly appear on or near the hairline and elsewhere on the lips and muzzle. In some cases the lesions appear on and in the nostrils, around the eyes, on the thigh, coronet, vulva, udder, and axilla. In rare cases, mostly involving young lambs, lesions are found on the tongue, gums, roof of the mouth and the esophagus. It has also been reported a number of times to cause lesions in the rumen. In one case it was shown that a severe form of orf virus caused an outbreak involving the gastrointestinal tract, lungs, heart, as well as the buccal cavity, cheeks, tongue and lips. Another severe case was reported pharyngitis, genital lesions and infection of the hooves which led to lameness and, in some cases, sloughing of the hoof.<ref name=Couch/>
More typically, sheep will become free of orf within a week or so as the disease runs its course. Sheep custodians can assist by ensuring infected lambs receive sufficient milk and separating out the infected stock to slow down cross-transmission to healthy animals. It is advisable for those handling infected animals to wear disposable gloves to prevent cross infection and self-infection. A veterinarian must be contacted if there is a risk of misdiagnosis with other, more serious conditions.<ref name=Winter_Charnley/>
See also
- Ecthyma
- List of cutaneous conditions
- List of immunofluorescence findings for autoimmune bullous conditions
- Imiquimod
- Cidofovir
References
External links
Template:Medical resources Template:Sister project Template:Viral cutaneous conditions Template:Taxonbar