Mouth Ulcers and Oral Lesions in Sheep

Mouth ulcers and oral lesions in sheep describe sores, scabs, erosions, blisters, or inflamed areas on the lips, gums, tongue, cheeks, or inside the mouth. These lesions can be painful and may make it hard for a sheep to graze, chew, or nurse. In some cases, the problem is mild and self-limited. In others, it can lead to dehydration, weight loss, or secondary infection.

One of the most common causes is contagious ecthyma, also called orf, sore mouth, or scabby mouth. Cornell notes that soremouth is the most common skin disease affecting sheep and goats, and lesions are often found around the mouth and other hairless areas. However, mouth lesions are not always orf. Trauma from rough hay, grass awns, chemical irritation, bacterial infection, and viral diseases such as bluetongue can also cause similar signs.

That is why a visible sore is only the starting point. Your vet will want to look at the pattern of lesions, whether the sheep has fever or lameness, how many animals are affected, and whether there is any risk to people handling the flock. Some causes are mainly supportive-care problems. Others need testing, isolation, or reporting.

The most common infectious cause is orf virus, also called contagious ecthyma or sore mouth. CDC states that infected animals typically develop lesions around the lips and muzzle and in the mouth. Cornell describes it as a highly contagious viral infection that causes scab formation, usually beginning as small red nodules at the lip margins. Lambs are often hit hardest because painful lesions can interfere with nursing.

Not every mouth sore is viral. Sheep can also develop oral ulcers from coarse or stemmy hay, grass awns, thorny browse, or other foreign material that irritates the mouth. Merck recommends checking ulcers for embedded material because trauma can be the primary cause. Secondary bacterial infection may then make the lesions deeper, smell worse, or heal more slowly.

Your vet may also consider more serious infectious diseases in the differential diagnosis. Merck lists bluetongue, vesicular diseases, actinobacillosis, and malignant catarrhal fever among conditions that can resemble other forms of stomatitis. Bluetongue in sheep can cause fever, facial swelling, oral hemorrhages, ulcers, and reduced feed intake. Because some of these diseases have flock-health and regulatory implications, do not assume every crusted mouth lesion is routine sore mouth.

Diagnosis starts with a careful history and physical exam. Your vet will ask when the lesions started, whether new sheep were introduced, what the flock is eating, and whether any people handling the sheep have developed skin sores. They will also look for fever, lameness, udder lesions in ewes, and signs of dehydration or weight loss.

A full oral exam is often needed. Merck notes that oral examination may be easier after sedation and should be done with a mouth speculum and light source. Ulcers should be checked visually and by touch for foreign material such as grass awns. This helps separate traumatic lesions from infectious disease and can guide immediate supportive care.

If the pattern is not typical, if the flock has systemic illness, or if a reportable disease is a concern, your vet may recommend laboratory testing. Depending on the case, this can include lesion swabs or scabs for PCR, bloodwork, or disease-specific testing for conditions such as bluetongue. Isolation while waiting for results is often a practical step, especially when several sheep are affected or when zoonotic risk is possible.

Prevention starts with flock management. Quarantine new arrivals, watch closely for lip and muzzle lesions, and avoid sharing equipment between affected and unaffected groups until it has been cleaned and disinfected. If orf is present, remember that the virus can spread by direct contact and contaminated equipment, and people can become infected through cuts or abrasions.

Feed quality matters too. Merck notes that foreign material such as grass awns can contribute to stomatitis, so reducing access to irritating forage and checking rough hay can lower trauma-related lesions. Make sure sheep have clean water, balanced nutrition, and enough feeder space so timid animals are not forced to eat poor-quality leftovers.

Use gloves when handling sheep with mouth lesions, especially if you have broken skin. CDC recommends gloves and good hand hygiene because orf can infect people, though it does not spread person to person. In flocks with recurring sore mouth, your vet can help you decide whether vaccination, stricter biosecurity, or changes in lambing and handling practices fit your operation best.