Scabby mouth is a viral disease due to orf virus that affects the skin of sheep and goats. Lesions are first seen as sticky exudates that quickly develop into small, hard brown scab. Coalescing of lesions can result in scabs covering a much larger area.
Mainly young animals are affected as older animals will have recovered from earlier infection. Australian goats appear to be considerably less susceptible than sheep.
Lesions are most commonly seen around the lips and nostrils, and less commonly on other areas of exposed skin such as ears, and feet. Weight loss can be rapid if lips are swollen or the mucosa of the mouth is affected.
The disease is seasonal in Australia's sheep producing areas, occurring especially in summer and autumn when feed consists of abrasive stubbles, dry grass, seeds and burrs, and when flies are abundant and active. This should be a consideration when assembling sheep and goats for export.
Viral challenge is expected to be high during the export process from mixing of young sheep in close confinement. Assembly facilities can become heavily contaminated as the virus is hardy and can survive in the environment for many years. Unvaccinated animals are susceptible as are some heavily challenged or immunosuppressed vaccinated animals (although with mild, rapid healing lesions).
Sticky exudates or hard brown scabs seen on the skin of sheep and goats especially around the lips and nostrils is probably scabby mouth. As the process ages the scab becomes a dry, cracked crust. Bacteria may infect the cracks and create purulent infections. If the crusts are dislodged, a granular surface is exposed and may show small amounts of pus and blood. Lesions will spontaneously regress over 3-4 weeks but may persist for longer if there is secondary bacterial infection.
Laboratory confirmation requires scabs with underlying tissue scrapings for virus isolation or identification with electron microscopy.
The disease must run its two to three week course as no effective treatment is available. Ready access to soft feed and clean water will encourage eating.
There is an effective vaccine that should be administered before expected disease onset or as dictated by importing country protocols.
People handling infected sheep can become infected and should take precautions.