Observations on the indirect transmission of virulent ovine footrot in sheep yards and its spread in sheep on unimproved pasture.

Virulent ovine footrot was transmitted accidentally to a group of 23 adult Merino sheep (flock B) after holding for 1 hour in sheep yards, which earlier the same day had contained another flock (flock A) with < 1% prevalence of sheep with footrot lesions. Sheep in flock B were rendered susceptible to virulent footrot by grazing 600 mm high unimproved pasture dominated by paspalum (Paspalum dilatatum) and kangaroo grass (Themeda australis) during warm, humid and wet weather. In addition to moisture, interdigital abrasions caused by the pasture might have predisposed the interdigital skin to infection with Dichelobacter nodosus.