Detection of <i>Treponema</i> species associated with bovine digital dermatitis in cattle using novel real-time PCR assays

Three <i>Treponema</i> sp.-<i>T. medium</i>, <i>T. pedis</i>, and <i>T. phagedenis-</i>are associated with bovine digital dermatitis (BDD). This painful infectious disease has been reported worldwide, causing economic and animal welfare problems. Although detection by real-time PCR (rtPCR) is the method of choice, published assays differ in specificity and sensitivity. We multiplexed target regions of 2 published rtPCR assays and slightly optimized another one to compare their performance. We then used the 2 novel TaqMan rtPCR assays to determine the prevalence of the 3 <i>Treponema</i> sp. in a random sample of hind feet from 137 animals collected at slaughterhouses. An overall prevalence at the animal level of 31.4% was found for <i>T. phagedenis</i> and 10.2% for <i>T. medium</i>, with the latter always being detected together with <i>T. phagedenis</i>. We did not detect <i>T. pedis</i> in our sample set. Typical lesions of BDD were present in 16.2% of animals. Of the animals with BDD lesions, 52.6% were positive for any of the 3 <i>Treponema</i> sp. A significantly lower positive rate for <i>Treponema</i> sp. was found in animals without lesions, underscoring the role of these organisms in the development of BDD. Our study offers insight into the prevalence of BDD-associated <i>Treponema</i> sp. in cattle as well as a tool for routine diagnosis and future control of the disease.