In 2004, ovine footrot, which is caused by Dichelobacter nodosus, was diagnosed in Sweden for the first time. The disease has received considerable attention since then and especially after an outbreak in Norway in 20091. There is limited knowledge of how footrot manifests itself in Sweden and what strains that are present. Hence the aim of this study was to determine the frequency of D. nodosus, F. necrophorum and Treponema spp. in sheep with different clinical manifestations of footrot. A second aim was to characterize Swedish D. nodosus-isolates with respect to virulence (aprV2/B2) and serogroup (fimA).
A total of 1000 swab samples from 20 Swedish sheep flocks with different manifestations of footrot including healthy flocks were analyzed for the presence of D. nodosus, F. necrophorum and Treponema spp. by real-time PCR and culturing (only D. nodosus). Obtained D. nodosus-isolates (n=78) were characterized with respect to virulence (aprV2/B2) and serogroup (fimA). In addition, all D. nodosus-positive swabs (n=474) were analyzed by the aprV2/B2 real-time PCR assay.
The results showed that D. nodosus was more frequently found in sheep flocks affected with footrot (score ≥2) than in clinically healthy flocks (p<0.003). Moreover, there was a tendency (p<0.09) that F. necrophorum was more frequently found in footrot-affected flocks but for Treponema spp. no significant difference could be found. Virulent D. nodosus were only detected in one flock while benign D. nodosus were detected in twelve flocks. The virulent D. nodosus-isolates found belonged to serogroup G while the benign D. nodosus-isolates belonged to six different serogroups; A, B, C, E, G and H of which serogroup A was the most common.
In conclusion, the frequency of D. nodosus and F. necrophorum varied between sheep flocks with different clinical manifestations of footrot and both virulent and benign D. nodusus-isolates were identified which belonged to six different serogroups.