Skin microbiota dynamics of dairy cows affected by digital dermatitis

Bovine digital dermatitis (DD), is a highly prevalent disease among dairy cattle characterized by ulcerative and painful lesions. While multiple management factors are involved in the disease, its precise etiology remains uncertain and the effectiveness of current control strategies remains highly variable. The major role of Treponema spp. in the development of the disease is consistently recognized. Nevertheless, it remains unclear how other bacterial communities are relevant to the onset and progression of the disease, and how the skin microbiota is affected by the environment during the course of the disease. The objective of this study was to describe the dynamics of microbiota recovered from DD affected feet under field conditions. This study described the diversity, structure, and composition of DD lesion microbiota over 45 days according to different clinical and management factors. The results of this investigation confirmed the existence of a specific skin microbiota associated with DD lesions, dominated by Treponema spp. and very different from the microbiota of healthy skin. Interestingly, the diversity and structure of the microbiota in DD lesions did not vary with the footbath disinfectant or the individual topical antibiotic treatments used. In addition, microbiotas from proliferative lesions evidenced a different structure and diversity in comparison to non-proliferative lesions. Our results confirm the major role of Treponema spp. And highlight the potential role of Mycoplasmopsis spp. in the DD lesion onset. Further studies are needed to confirm whether the clinical course of DD lesions is driven by a particular microbiota and how that microbiota may induce disease. Highlights Multiple bacteria have been identified in DD lesions. However, many of these microorganisms are inhabitants of the foot skin and the farm environment. For the first time, the microbiota of DD lesions was monitored for 45 days under field conditions to describe its evolution over time. The results of this investigation highlighted a particular microbiota dominated by Treponema spp. present on the skin of DD affected animals and highly different from those microbiotas of healthy skin. The microbiota of DD lesions evolved over the study period and differential bacteria were identified. Further studies are warranted to determine the role of the bacteria composing these microbiotas on lesion onset and outcome.