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Orf Virus

Orf, also known as contagious ecthyma, is a zoonotic infection caused by a dermatotropic parapoxvirus that commonly infects sheep and goats. It can be transmitted to humans through contact with an infected animal or fomites. Human infection typically is associated with occupational animal contact and has been reported in children after visiting petting zoos and livestock fairs. Human-to-human transmission has not been reported.

Orf infection is rare in the general community. Persons who contract the virus occupationally likely know of its benign nature and might not seek treatment. Most physicians, therefore, have not encountered patients with orf virus infections and might mistake orf lesions for life-threatening conditions such as cutaneous anthrax or neoplasm. Orf should be included in the differential diagnosis of patients with clinically compatible skin lesions and a history of household meat processing or animal slaughter.

In humans, orf manifests as an ulcerative skin lesion sometimes resembling bacterial infection or neoplasm. Human orf lesions generally appear on fingers, hands, or forearms after a 3–7 day incubation period. A typical lesion slowly progresses from a small, erythematous macule or papule to a large nodule with a red center, white halo, and peripheral erythema. The nodule weeps, ulcerates, and crusts over. Most infections are self-limited, resolving in 4 to 8 weeks without scarring. No specific treatment is usually required. Potential complications include erythema multiforme, deforming scars, and secondary bacterial infections. Severe disease has occurred in immunocompromised hosts. Topical imiquimod might facilitate healing, especially in immunocompromised patients Protective immunity to orf is incomplete, indicating that persons can be infected with orf virus multiple times.

PCR can definitively identify orf virus and is available at the Centers for Disease Control (CDC). Histopathology and microscopy can support a diagnosis of a parapoxvirus infection.

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