Orf

A 32-year-old man who had no significant medical history complained of “something growing on the knuckles of my right hand.” He reported that a “bump” was forming on the site of a cut he sustained while slaughtering sheep 3 weeks earlier. There was no blister, discharge, or pain. The patient denied any fever, cough, or malaise. He also did not recall seeing any lesions or “bumps” on the sheep.

The lesion was a solitary, well-defined, erythematous nodule that measured 1 cm in diameter and 0.6 cm in height, with a papillomatous surface. There was no lymphadenopathy or swelling of the involved metacarpal. Cultures were negative for acid-fast bacteria and anaerobic organisms; a culture for aerobes yielded Citrobacter koseri that was sensitive to ciprofloxacin.

Drs Amy E. Goldstein and Charles Gropper of New York report that the findings of a shave biopsy and the history were consistent with a diagnosis of orf, also called ecthyma contagiosum and contagious pustular dermatosis. The orf virus, a DNA Parapoxvirus, is endemic among sheep and goats and the products of these animals. Infected animals usually show a vesicular or papular eruption on the feet, lips, udders, and oral mucosa.

Humans acquire the disease by direct contact with infected animals or contaminated objects, such as fences and door frames. The virus has been known to remain infective for more than 15 years at room temperature and more than 20 years when refrigerated. It is a common occupational disease among meat industry employees who deal with sheep; reinfection occurs fairly frequently in these workers.

A solitary papule at the site of initial contact usually appears after an incubation period of fewer than 4 weeks. The typically benign lesion progresses through six distinct stages-maculopapular, target, acute, nodular, papillomatous (Figure), and regressive-and heals spontaneously within 4 to 24 weeks. The lesion may be misdiagnosed as a keratoacanthoma or a pyogenic granuloma; in the nodular stage, it can resemble a giant moluscum contagiosum.

Complications occur rarely; they include lymphangitis, lymphadenitis, chills and fever and, as seen in this patient, secondary bacterial infections. There is no specific antiviral therapy for orf. Antibiotics may be used when secondary bacterial infections have been proved. This patient completed a course of ciprofloxacin and the lesion resolved.