Pathogenicity testing of field isolates of the footrot bacteria Dichelobacter nodosus in a pen trial experiment

Rosser, Michael
Sydney University


The aprV2 allele is thought to be essential for virulence in the footrot bacteria D. nodosus, however recent studies have suggested that aprV2 may not be an accurate indicator of virulence. The conducted study experimentally evaluated the pathogenicity of low virulent D. nodosus isolates, which contain the aprV2 allele, under optimal environmental conditions. This was conducted using an experimental model with five small groups of five penned sheep, with the pathogenicity of the isolates evaluated using weighted foot scores and elastase testing. The results showed that all tested field isolates were unable to induce severe disease (score > 3) and weighted foot scores were shown to be significantly lower than the known virulent positive control. This suggests that there are other factors which effect the activity or excretion of AprV2 protease, with further research needing to be conducted to assess molecular basis of virulence in D. nodosus.


AprV2, footrot, ovine, pathogenicity, protease, virulence