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Orf Disease (Contagious Ecthyma; Contagious Pustular Dermatitis)

Orf disease is a parapoxvirus infection that is endemic in many sheep flocks and goat herds throughout the United States. The disease affects all age groups, although young animals are most often and most severely affected. Orf produces proliferative, pustular encrustations on the lips, nostrils, mucous membranes of the oral cavity, and urogenital orifices of infected animals.

Orf, a double-stranded-DNA virus, is transmitted to humans by direct contact with virus-laden lesion exudates. External lesions are not always apparent, so recognition may be difficult. Transmission of the agent by fomites or contaminated animals is possible because of its environmental persistence. Rare cases of person-to-person transmission have been recorded.

The disease in humans is usually characterized by the development of a solitary lesion on the hand, arm, or face. The lesion is initially maculopapular or pustular (PDF) and progresses to a weeping proliferative nodule with central umbilication. Such lesions are sometimes mistaken for an abscess, but should not be lanced. Occasionally, several nodular lesions are present, each measuring up to 3 cm. in diameter, persisting for 3-6 weeks, and regressing spontaneously. Regional adenitis is uncommon.

The characteristic appearance of the lesion, and a history of recent contact with sheep or goats are diagnostic of this condition in humans. Vaccination of susceptible sheep and goats is effective in preventing the disease (PDF). Personnel who handle sheep and goats should be cautioned to wear protective clothing and gloves and to practice good personal hygiene.