Orf in humans: dramatic but benign
Case Reports
Staff Emergency Physician, St. Michael's Hospital, Toronto, Ont.; Assistant Professor, Department of Medicine, University of Toronto, Toronto, Ont.
CJEM 2005;7(6):417-419
Abstract
Orf is a parapoxvirus infection of sheep and goats that causes blistering lesions on the lips, nostrils, udders or toes of affected animals. Human contact can cause transmission by direct inoculation. Human orf has typically been confined to rural settings. A case is presented of an immigrant African inner-city housewife who contracted the disease after preparing a sheep's head for a meal. The lesions resolved completely after 1 month without treatment. Although relatively rare and benign, this infection is probably under-reported and over-treated in this country. This case highlights the fact that urban physicians can expect to encounter once rare or solely rural-based infections with increasing frequency.
Résumé
L'ecthyma contagieux est une infection par parapoxvirus du mouton et de la chèvre qui provoque l'apparition de cloques aux lèvres, aux narines, au pis ou aux doigts de patte des animaux touchés. Le contact humain peut causer la transmission par inoculation directe. L'ecthyma contagieux chez les êtres humains a toujours été confiné aux contextes ruraux. On présente le cas d'une immigrante africaine, ménagère installée au cœur du centre-ville, qui a contracté la maladie après avoir préparé une tête de mouton pour un repas. Les lésions se sont résorbées complètement après un mois sans traitement. Même si elle est relativement rare et bénigne, cette infection est probablement sous-déclarée et surtraitée au Canada. Ce cas démontre que les médecins urbains peuvent s'attendre à rencontrer de plus en plus souvent des infections auparavant rares ou présentes en milieu rural seulement.
Introduction
Orf is a localized viral exanthem that affects sheep and goats. It can be transmitted to humans by direct contact; the resulting skin lesions are dramatic but benign and resolve spontaneously. If unrecognized, the disease can be confused with more serious conditions, leading to overtreatment and unnecessary invasive procedures. Orf is classically a rural disease,1 but this report describes a case that presented to an inner-city Canadian emergency department.
Case report
A 43-year-old woman of East African origin presented to the emergency department with a complaint of "sheep bone fragments stuck in her finger." Her husband reported that 9 days before presentation she went to a butcher shop and bought a sheep's head to be used in preparing a traditional ethnic meal, including soup. Meal preparation required cutting and scraping the skull. She could not recall any injury, but several days later noted red bumps erupting on her left index finger. These became tender and swollen, and she concluded she must have had bony fragments lodged in it. Her primary care physician treated her with topical antibiotic ointment, but after several days the lesions worsened. Her physician referred her to a local inner-city emergency department for intravenous antibiotics and surgical exploration and drainage.
Her past history was unremarkable. She was not taking other medicines and had no allergies. On examination, her vital signs were normal and she was afebrile. Her left index finger showed moderate diffuse swelling; on the radial aspect was a 1-cm white nodule with a central plug of granulation tissue (Fig. 1); on the ulnar aspect were 3 identical but confluent lesions with surrounding hemorrhagic blisters (Fig. 2). The finger was moderately tender, and range of motion was limited due to swelling and pain. There was no associated lymphangitis, and no other lesions were present.
The tense blister was aspirated, and sanguinous fluid was sent for routine bacterial culture and sensitivity. X-rays of the finger revealed no bony fragments. Orf was diagnosed clinically based on the history of exposure to sheep and the typical cutaneous lesions seen (the author having been involved with previous similar rural cases). The patient was splinted and discharged on anti-inflammatory medication. Follow-up 3 days later showed no further progression and culture results were negative; one month later the lesions had completely resolved without residual scarring.
Discussion
Orf is a parapoxvirus that infects sheep and goats and is localized to their lips, nostrils and udders, but can also affect the toes. The term is a misnomer, being derived from the ancient Anglo-Saxon word meaning "cattle." Orf is also known as contagious ecthyma or contagious pustular dermatitis. Suckling lambs and kids may contract the disease while nursing from infected mothers, which may prove fatal because suckling becomes painful and starvation may ensue.
Fig. 1. Radial aspect of left index finger: 1-cm white nodule
with central plug of granulation tissue
Fig. 2. Ulnar aspect: 3 identical but confluent lesions with
surrounding hemorrhagic blisters.
The lesions are firm pustules that scab over, then slough over 3–6 weeks. Definitive diagnosis is rarely necessary, but can be made histologically by visualizing parapoxvirus on electron microscopy of scab samples. Scarifying (scratch) vaccines are effective prevention and are advised when entire flocks are threatened, but these remain expensive and they must be administered by veterinarians. Since orf is not a reportable disease, farmers are not restricted in their processing of these animals. The virus is hardy and persists on farm material and the ground for months to years.
Humans who handle infected animals, carcasses or contaminated equipment can contract orf by direct inoculation through cuts or abrasions in their skin; consequently, veterinarians, wool shearers, abattoir workers, farmers' children and housewives are at particular risk. Lesions appear as firm red papules on the hands, arms or face 3 to 7 days after contact. They are painful and expand to form a broad, thickened 1–3-cm lesion consisting of a central red area, surrounded by a raised whitish ring with an erythematous periphery. These lesions crust and resolve by 3–6 weeks with little or no residual scar.2 Transient lymphangitis and constitutional symptoms can occur, mimicking secondary bacterial infection. Erythema multiforme may appear as a late hypersensitivity reaction; rarely pemphigoid may result.3
Plain microcopy of biopsy specimens may suggest viral infection, but electron microscopy provides rapid confirmation of parapoxvirus infections by demonstrating typical oval viral particles. Sampling method is important, and inadequate specimens will generate false-negative test results; polymerase chain reaction is a more reliable way to identify viral-specific DNA in specimens regardless of disease stage.4
There is no established treatment for this typically self-limiting disease, so prevention is the first line of defence. Those at risk, particularly animal handlers, should wear gloves and wash their hands and arms with an iodine-based solution after contact. Unless lesions are huge and progressive, no intervention is recommended. Topical cidofovir shows promise in immune-compromised individuals,5,6 but both topical idoxuridine (40%) in dimethylsulphoxide (DMSO) and interferon with radiation have proven unsuccessful. No known human–human transmission has ever occurred, and immunity is transient.
Several zoonotic diseases, including anthrax, brucellosis, Chlamydia trachomatis, tularemia (Francisella tularensis), giardiasis, leptospirosis, Q fever, rabies and Yersinia enterocolitica, can be acquired from sheep,7 but the differential diagnosis for orf lesions in humans includes cutaneous anthrax, pyoderma gangrenosum, herpetic whitlow, felon, milker's nodule and malignant melanoma.8 Cutaneous anthrax begins as a red papule that progresses to a black painless ulcer; the surrounding tissue becomes edematous and painful regional lymphadenopathy is common. There may be a recent history of unprotected contact with an anthrax-infected animal or carcass, and lesions respond quickly to appropriate antibiotics. Pyoderma gangrenosum is most common in patients with underlying systemic disease, typically appearing as a papule or vesicle on the trunk or limbs, which then ulcerates and enlarges. Herpetic whitlow is manifested by an outbreak of small painful vesicles, typically on the fingers, and often after contact with human oral cavities. A felon is an exquisitely painful, tense abscess of the pulp space of the distal phalanx. Milker's nodule is a parapoxvirus infection identical to orf but related to cow exposure, and often with multiple lesions. Treatment is the same. Malignant melanoma can be confused with orf, especially if lesions are located on the face; however skin cancer is painless and develops slowly.
Summary
Orf is a disease that is prevalent in sheep and goats. It is well known to farmers and large-animal veterinarians, but growing numbers of at-risk immigrants may present to urban emergency departments with orf lesions after cultural traditions or dietary customs expose them to infected sheep or goat carcasses. Though the disease is benign and self-limited, early clinical diagnosis is important in order to avoid unnecessary testing and iatrogenic consequences of invasive, expensive and futile therapies.
References
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- Roingeard P, Machet L. Images in clinical medicine: Orf skin ulcer. N Engl J Med 1997;337:1131.
- Murphy JK, Ralfs IG. Bullous pemphigoid complicating human Orf. Br J Dermatol 1996;134:929-30.
- Scagliarini L, Gallina L, Dal Pozzo F, Battilani M, Ciulli S, et al. Diagnosis of Orf virus infection in humans by the polymerase chain reaction. New Microbiol 2004;27:403-5.
- Nettleton P, Gilray J, Reid H, Mercer A. Parapoxviruses are strongly inhibited in vitro by cidofovir. Antiviral Res 2000;48:205-8.
- Geerinck K, Lukito G, Snoeck R, De Vos R, De Clercq E, et al. A case of human Orf in an immunocompromised patient treated successfully with cidofovir cream. J Med Virol 2001;64:543-9.
- Pugh DG. Sheep and goat medicine. WB Saunders Co; 2002: 203-205.
- Inceoglu F. Orf (ecthyma contagiosum): an occasional diagnostic challenge. Plast Reconstr Surg 2000;106:733-4.
