Orf

Orf

Cause

Contagious pustular dermatitis is common in lambs. Its cause is a parapox virus that can be transmitted to those handling infected animals. The condition is therefore most commonly seen on the hands of shepherds, of their wives who bottle-feed lambs, and of butchers, vets and meat porters.

Presentation and course

The incubation period is 5– 6 days. Lesions, which may be single or multiple, start as small firm papules that change into flat-topped apparently pustular nodules with a violaceous and erythematous surround (Fig. 14.31). The condition clears up spontaneously in about a month.

Complications

•   Lymphadenitis and malaise are common.

•   Erythema multiforme.

‘Giant’ lesions can appear in the immunosuppressed.

Differential diagnosis

Diagnosis is usually simple if contact with sheep is recognized. Milker’s nodules, a pox virus infection acquired from cow’s udders, can look like orf, as can staphylococcal furuncles.

Investigations

None are usually needed. If there is any doubt, the diagnosis can be confirmed by the distinctive electron microscopic appearance of the virus obtained from crusts.

Treatment

A topical antibiotic helps to prevent secondary infec-tion; otherwise no active therapy is needed.