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Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Orf (ecthyma contagiosum) is a zoonotic cutaneous infection caused by the orf virus of the genus Parapoxvirus . Transmission occurs due to direct exposure to infected animals and fomites. The most commonly associated animals are sheep, goats, and deer. As such, it is predominantly an occupational disease affecting hunters, livestock owners, butchers, farmers, veterinarians, and shepherds. Human-to-human transmission remains very rare. Affected animals usually have lesions around the mouth, muzzle, and eyes, and humans are affected most commonly on the hands. Orf usually presents as a single lesion but lesions can be recalcitrant, giant, or multiple in immunosuppressed individuals. Classically, there are five described stages: maculopapular, targetoid, nodular, regenerative, and regressive. Clinicians should maintain a broad differential diagnosis including a milker’s nodule, erysipeloid, pyogenic granuloma, sporotrichosis, atypical mycobacterial infection, anthrax, keratoacanthoma, and tularemia.
Management Strategy
Orf is a self-limiting infection, and treatment is usually not necessary . The immune response to the virus usually results in resolution of the disease within 2–7 weeks without any specific treatment. There is no available treatment that is specifically antiviral for the orf virus, and no human vaccine has been produced. Treatment is usually only indicated if there is secondary bacterial infection or immunosuppression. Erythema multiforme and id reactions have been reported as potential sequelae.
Preventive measures include vaccination of sheep before the lambing period to boost immune response and the wearing of non-porous gloves when handling animals with any sign of the disease.
Various treatments have been reported anecdotally. Idoxuridine , surgery , and cryotherapy have been suggested to reduce the time to healing. For persistent or more progressive cases, interventional treatment is warranted, and often treatments can be combined. Surgery may be performed to remove the bulk of the infected tissue. Idoxuridine, cryotherapy, cidofovir , interferon , and topical imiquimod cream have been reported to show benefit.
Specific Investigations
Diagnosis is usually clinical but can be confirmed by the noted investigations if required. Routine pathology with hematoxylin and eosin staining, electron microscopy, and PCR can all be used if needed.
The structure of the orf virus
Nagington J, Newton A, Horne RW. Virology 1964; 23: 4611–72.
The ultrastructural description of the orf virus.
Erythema multiforme after orf virus infection: a report of two cases and literature review
Joseph RH, Haddad, FA, Matthews AL, et al. Epidemiol Infect. 2015; 143: 385–90.
Polymerase chain reaction for laboratory diagnosis of orf virus infections
Torfason EG, Gunadottir S. J Clin Virol 2002; 24: 79–84.
Method for molecular diagnosis of orf initially used as a research tool but now used in the United States.
Ecthyma contagiosum (orf) – report of a human case from the United Arab Emirates and review of the literature
Al-Salam S, Nowotny N, Sohail MR, et al. J Cutan Pathol 2008; 35: 603–7.
More detailed method for molecular diagnosis of orf used in a clinical case.
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