Scabby mouth
Scabby mouth, sometimes known as orf or contagious pustular dermatitis, is a highly contagious viral disease of sheep and goats. It commonly affects lambs and kids less than a year old.
What is scabby mouth?
Scabby mouth is a highly contagious viral disease that affects sheep and goats. The virus is zoonotic, meaning it can spread to humans.
The virus survives in the scabs from infected animals and can go on to contaminate the environment for a long time (potentially years). Severe disease outbreaks don’t necessarily occur every year, but they are more common in conditions where skin abrasion is occurring and providing a window of access for the virus.
While scabby mouth is rarely fatal, it can cause considerable production losses due to reduced feed intake. This causes delays in finishing and sale of affected mobs of lambs.
When scabby mouth occurs on the legs, it is known as ‘strawberry footrot’.
When to watch for it
Infection is more common during summer and autumn when abrasive feed, such as stubble, seeds, and thistle, is prevalent in the paddock. These feeds cause abrasions, resulting in a break in the skin’s defences necessary for viral entry and infection.
Wet conditions can also lead to skin damage around the feet, creating an entry point for the virus and resulting in foot lesions and lameness.
Clinical signs of scabby mouth
Scabby mouth causes pustules and scabs to develop, usually around the face (mouth and nostrils) of affected animals, but also on other non-woolled parts of the body like the legs and udder.
The classic presentation in outbreak form is young sheep, often weaners, with facial lesions after grazing rough feed (thistles, burr or stubbles).
How to manage
Moving the mob to a paddock where the feed is not abrasive can help stop new infections occurring.
Previously infected animals usually do not get severe disease again, although sometimes they may experience brief, mild reinfection.
Carrier sheep can remain a source of the virus. Once an outbreak has occurred on farm, the virus can remain in the environment and you may be more likely to consider vaccination in future.
How to treat
Scabby mouth is generally self-limiting, however for badly affected animals pain relief may be considered.
The lesions tend to ease after around 3 weeks, and normal feeding and movement resumes.
Infected animals usually recover on their own over 4 to 6 weeks.
Badly affected animals may be reluctant to eat and drink and suffer a setback, particularly unweaned lambs.
For ewes, lesions on their udders can make them reluctant to let their lambs drink, potentially leading to mastitis.
Antibiotics may increase the rate of healing where extensive sores are secondarily infected.
How to prevent
Scabby mouth vaccine is available. Seek advice before adopting it as an inclusion in your vaccination program. It may not be necessary for all operations, but it is worthwhile considering alongside risk of exposure, other procedures at lambing, and cost-benefit factors.
The scabby mouth vaccine is a live virus vaccine. It is administered to the lamb as a scratch on the inner thigh.
A mild infection then develops at the site of the scratch 5 to 10 days after vaccination, triggering immunity after around 2 weeks.
It is a good idea to check a few lambs about a week after vaccination to ensure that pustules are present at the scratch site, indicating that the vaccine is taking effect.
A single dose of vaccine is usually enough, as this provides good primary immunity. Natural environmental exposure over time usually maintains immunity.
Vaccination advice
Take care while vaccinating to protect yourself from the virus. The virus is easily inactivated by disinfectant, so frequent washing of hands and wearing gloves can help protect you.
It is also important that you don’t use disinfectant on the scratch applicator or near the scratch site on the animal as this can inactivate the vaccine and stop it working.
As with all vaccines, it is important to read the label to get the important information around dosage, handling and safety.