Experimental infection of sheep with ovine and bovine Dichelobacter nodosus isolates

- We investigated infection of sheep with ovine and bovine isolates of Dichelobacter nodosus of varying virulence.
- The efficacy of gamithromycin as a treatment for the experimentally induced infections was examined.
- 5/24 sheep were infected and all sheep tested negative for D. nodosus within six weeks after treatment with gamithromycin.
- Strong indications that D. nodosus isolated from sheep and cattle can be transferred to sheep under experimental conditions.
- The study suggests that gamithromycin may be effective against D. nodosus.

The aim of this study was, under experimental conditions, to investigate infection of Norwegian White sheep with ovine and bovine isolates of Dichelobacter nodosus of varying virulence. In addition, the efficacy of gamithromycin as a treatment for the experimentally induced infections was examined. The study was performed as a single foot inoculation using a boot. Four groups, each with six lambs, were inoculated with four different challenge strains (Group 1: benign bovine strain; Group 2: virulent bovine strain; Group 3: benign ovine strain; Group 4: virulent ovine strain). The main criterion to determine that infection was transferred was that D. nodosus isolate was obtained by culture. After the trial all lambs were treated with gamithromycin. Clinical symptoms of footrot developed in all groups, and when removing the boots two weeks after challenge, D. nodosus was isolated from 5 of 24 experimental lambs. All lambs tested negative for D. nodosus by PCR within six weeks after treatment with gamithromycin. This study strongly indicates that D. nodosus isolates from both sheep and cattle can be transferred to sheep under experimental conditions. The study also indicates that gamithromycin may be effective against D. nodosus.