Potential transmission routes of Dichelobacter nodosus

Abstract

Footrot caused by Dichelobacter nodosus is a highly contagious bacterial disease affecting the claw of sheep and the main cause of lameness in these animals. It is not only an economic burden but also a serious animal welfare issue. More information about the transmission of D. nodosus is needed for effective footrot control programs. We therefore determined the prevalence of D. nodosus in sheep presented at shows and markets where commingling of animals occurs. Furthermore, possible transmission vectors during foot trimming were investigated and trimming knife decontamination protocols evaluated. Sheep at six markets and four shows were sampled and tested for the presence of D. nodosus by real-time PCR. Different vectors, such as trimming knives were tested by real-time PCR and for viable D. nodosus by culture. The prevalence of virulent D. nodosus in sheep presented at shows and markets ranged from 1.7% to 100%. Regions with an ongoing control program showed significantly lower prevalence. After trimming, positive real-time PCR and culture results were obtained from the knives, the hands of the claw trimmers as well as removed claw horn material whereas boots were only positive by real-time PCR. In conclusion, markets and shows pose a risk for transmission of D. nodosus. The risk of transmission is particularly high during claw trimming and recommended measures to limit this risk include wiping the knife with a disinfection towel, wearing and changing gloves after every sheep, as well as proper disposal of trimmed and infectious horn.