Orf is a skin infection caused by parapox virus, a zoonotic contracted from goats and sheep. Because the condition causes crusts and scabs around the mouth, nose, teats, and other areas, it is also known as contagious pustular dermatitis. The disease lasts for roughly six weeks, and it is extremely contagious.

Cause and Mode of Transmission:

Direct inoculation of contaminated material, frequently through an already-existing wound or scratch, results in lesions in humans. Shearers, freezer workers, sheep producers, and anyone bottle-feeding a lamb run the danger of contracting orf. Youngsters may potentially get it from playing in a sheep shed or on contaminated pasture. There have been reports of human orf following unintentional contact with animal-targeted orf virus vaccination. It is not typically spread from person to person, however sporadic reports of this have occurred.

Clinical Features:

The incubation period lasts from 5-6 days. Patients usually present with a 2-3 cm solitary small, firm, red lump that enlarges to form a flat-topped, blood-tinged pustule or blister on the forearms, hands, and fingers. Large lesions could be observed in immunocompromised individuals.

Typically, making an incision through the skin will reveal firm, red tissue beneath, despite the appearance of pus from the skin. In the early stages, the orf lesion is frequently sensitive and irritating. Lymphangitis and lymphadenopathy of the inner side of the elbow and/or under the arm are not uncommon. These features could be associated with mild fever.

Diagnosis:

A clinical diagnosis of orf is typically made in a person who has experience working with sheep or goats. PCR can be used to confirm the infection in vesicular fluid, skin biopsies, or viral swabs. Electron microscopy can be used to identify it as well.

Management:

Most of the time, no special care is required because orf resolves on its own in roughly six weeks. While it is extremely rare, the lesion should be covered to avoid infecting the surrounding area or other persons. Shave excision is one method of removing large lesions. Antibiotics are the appropriate treatment for secondary bacterial infections. A few cases of orf have been found to respond well to imiquimod cream.

Complications:

The complications of orf include secondary bacterial infection, erythema multiforme, toxic eythemas, and rarely pemphigoid.

Prevention:

Farmers who raise sheep and goats should be mindful of the risk of orf and handle the animals especially lambs and young while using non-porous rubber gloves with washing hands. It is advised to vaccinate the herd using a live virus in the event of a severe orf outbreak.

Written by:

Mohammed Alahmadi, Medical Student.

Revised by:

Maee Barakeh, Medical Student.

References:

DermNet.

Fitzpatrick’s Color Atlas and Synopsis of Clinical Dermatology.

Andrews’ Diseases of the Skin: Clinical Dermatology.