Contents
Orf disease, also known as contagious pustular dermatitis or ecthyma contagiosum, is a zoonotic infection caused by the parapoxvirus, Orfviridae.
Orfvirida (poxvirus):
Zoonotic infection transmitted to humans via contact with infected goat and sheep
Clinical features
After a 3-5 day incubation period, well-described cutaneous lesions develop, progressing through 6 stages, about a week in duration.
- Maculopapular – erythematous
- Target lesion – target shaped with a necrotic center and surrounding red halo
- Acute nodular/weepy – draining papule
- Regenerative/dry – firm crusted papule
- Papilloma – papillomatous surface
- Regressive stage – resolution with little if any scarring
- Hand and digital involvement comprise > 90% of affected site
- Constitutional symptoms (uncommon): Fever, malaise and lymphadenopathy
- Immunocompromised state: Giant orf (large size)
Complications:
- Superinfection
- Lymphangitis
Differential diagnosis:
Disorders that share zoonotic-exposure history to farm animals and exhibit cutaneous lesions.
- Paravaccinia (Milker’s nodules): Very similar parapoxvirus infection arising from cows rather than goats/sheep as in orf disease. Clinically they are indistinguishable and resolve spontaneously within six weeks or so.
- Cutaneous anthrax
- Other differentials: Pyoderma, herpetic whitlow, cowpox, cat-scratch disease, tularemia, tuberculosis, other mycobacteria, syphilis, sportrichosis, keratoacanthoma, and pyogenic granuloma
Management
The lesions are self-limiting, and in immunocompetent patients – symptoms would spontaneously resolve in a 4- to 6-week window.
- Reassurance and expectant care
Immunocompromised hosts:
- Topical cidofovir (blocker of DNA dependent RNA polymerase enzyme) + mechanical eradication (cyotherapy, surgical excision, imiquimod)