Orf in Sheep: Symptoms, Treatment, and Prevention

Orf is a contagious viral skin disease of sheep, also called contagious ecthyma, contagious pustular dermatitis, or sore mouth. It is caused by the orf virus, a parapoxvirus, and it most often affects young lambs around the lips and mouth. In some sheep, lesions can also appear on the face, ears, feet, or on the teats and udder of nursing ewes.

The sores usually move through stages. They may begin as small papules, then form pustules, ulcerate, and develop thick crusts or scabs. Many sheep recover without scarring, but the disease can still have a meaningful impact because painful mouth lesions may reduce nursing and feed intake. Lambs can lose condition, and ewes with teat lesions may resist nursing.

Orf is also zoonotic, which means people can catch it through direct contact with infected sheep or contaminated items such as feeders, fencing, wool, or equipment. That makes early recognition and careful handling important for both flock health and human safety.

Orf is caused by orf virus (Parapoxvirus orf). The virus usually enters through small breaks in the skin, so abrasions from rough feed, grazing, tagging, nursing, fencing, or close contact can make infection more likely. It spreads by direct contact with infected sheep and by contact with contaminated surfaces, wool, feeders, waterers, bedding, and handling equipment.

One reason orf is so persistent in flocks is that the virus is very hardy in the environment. It can survive in dried scabs for years, which means old contamination can help restart problems in later lamb crops. Newly introduced animals may also bring infection into a flock, even when lesions are subtle or not yet obvious.

Outbreaks are often seen in young animals because they have less prior exposure and less immunity. Ewes can become infected on the teats while nursing affected lambs. In some flocks, recurring disease is linked to environmental contamination, skin trauma, and movement of infected animals between groups.

Your vet may suspect orf based on the sheep's age, the appearance and location of the lesions, and the way disease is spreading through the flock. The crusted, proliferative sores around the lips are often characteristic. A flock history of similar lesions in lambs or teat lesions in ewes can also support the diagnosis.

When confirmation is needed, your vet may collect scab material or a biopsy for PCR testing, which is the preferred laboratory method. Testing can be especially helpful when lesions are severe, unusual, or when there is concern for another disease that can look similar.

Diagnosis matters because not every mouth lesion is orf. Depending on the case, your vet may consider differentials such as ulcerative dermatosis, staphylococcal skin disease, bluetongue, or other reportable diseases that can cause oral lesions. That is one reason it is wise not to assume every scabby mouth lesion is harmless.

Prevention focuses on biosecurity, hygiene, and reducing skin trauma. Inspect new or returning sheep before they join the flock, and avoid mixing animals with active lesions into clean groups. If possible, handle affected sheep last, and clean or disinfect equipment, pens, feeders, and waterers after use. Because the virus can persist in crusts for years, removing contaminated bedding and managing scab-contaminated areas matters.

Protecting people is part of prevention too. Wear gloves when handling sheep with lesions, scabs, or live vaccine, and wash hands well after contact. Avoid touching your face during handling, and keep contaminated clothing and boots from spreading material between groups. If anyone develops a suspicious skin lesion after handling sheep, they should contact a human healthcare professional and mention the sheep exposure.

Vaccination can be part of flock control, but it should be planned with your vet. Orf vaccines are live vaccines and can contaminate premises, so they are generally not used casually on farms that have never had the disease. When vaccination is chosen, it is typically given by scarification, and your vet can help decide whether it fits your flock's risk, timing, and management goals.

Good nutrition, low-stress handling, and minimizing rough surfaces that injure lips or teats can also help reduce opportunities for infection. In flocks with recurring problems, a practical prevention plan usually combines isolation, environmental cleanup, careful lambing-group management, and a thoughtful vaccine discussion with your vet.