Scabby Mouth is a contagious disease caused by Contagious Pustular Dermatitis Virus, also known as “Orf”.
As the name suggests it primarily causes scabs around the mouth of lambs, which interfere with feeding and therefore restrict growth. Scabs can get bad enough to make the mouth stick together so badly that the lamb can starve to death.
This disease is a zoonosis, which means it is transmissible to humans. Lesions seen in people are most often on the hands, and occur from handling infected sheep or from handling live vaccine. It can be transferred to other parts of the body such as the face by touching the face with contaminated hands, e.g. while smoking or eating. The vaccine is live, and is therefore just as dangerous to the operator as the virus.
Sheep of any age can be infected, but problems are most often seen in lambs in their first year of life. Grazing on plants that can cause damage to surfaces in the mouth can make the level of the problem worse e.g. thistles, hay, gorse or rushes.
Should I vaccinate?
Generally you should vaccinate your lambs only if your property has a history of the disease and it has been diagnosed by a vet, or a vaccine has been regularly used on the farm before. If the farm has no history of the virus the vaccine MUST NOT be used.
Vaccination is done with a scratch into the surface layers of the skin with the purpose-made applicator. If the scratch is too deep and bleeds, the blood can flush out the virus so the vaccination is ineffective. If the scratch is too shallow, the infection may not “take”. Vaccinated lambs should always be checked in 1 to 2 weeks (a sample of about 10 lambs) to see that the vaccination has been effective.
A vaccination which has “taken” will have inflammation and a broad whitish area on it. The idea is to give the lamb a dose of the disease on a safe part of its body where it will not interfere with feeding, so that when it is exposed to the virus at the mouth the animals’ immune system has already met the virus and can fight it off.
Usual areas to vaccinate are on the bare skin under the front or back legs. Contamination of either area with disinfectant or flystrike preventatives can kill the live virus in the vaccine and make it ineffective.
Vaccine should be refrigerated when not being used, and will not last from one season to the next once broached.
Treatment:
Antibiotics are ineffective unless there is a secondary bacterial infection present as well. The lesions are self limiting and resolve within a few weeks. Prevention is always far better than cure.
