Serological classification and virulence determination of Dichelobacter nodosus isolated from Alberta and British Columbia sheep.

Ovine footrot is a contagious disease of sheep that occurs in temperature climates. It is caused by the strict anaerobe, Dichelobacter nodosus. Benign and virulent organisms are differentiated according to serotype and protease production. This study was conducted to identify the presence of virulent serotypes of D. nodosus in sheep flocks in Alberta and British Columbia. Dichelobacter nodosus was detected in lame sheep from 11 of 15 (73%) flocks in Alberta and in 4 of 5 (80%) British Columbia flocks. It was recovered from 57 of 107 (53%) lame sheep. In Alberta, 4 distinct serotypes were isolated from the 11 positive flocks while in British Columbia a total of 6 different serotypes were isolated. One British Columbia isolate could not be classified into existing serotypes. Of the 19 field strains tested, all but 3 were defined as virulent based upon the rapid rise in protease activity in vitro which was maintained between 3 and 5 d. The knowledge of the serotype and virulence of the D. nodosus isolated from affected animals can assist in the control and prevention of ovine footrot.