Virulent strains of D. nodosus were detected in 4 of 9 flocks without clinical signs.
Change from benign to virulent sheep status was not found.
New infections with virulent strains of D. nodosus were explainable by sheep contact.
The RT PCR allowed detection of D. nodosus before clinical signs of footrot occurred.
The RT PCR for AprV2/B2 is a useful tool in a footrot control program.