14Bovine digital dermatitis (DD), is a highly prevalent disease among dairy cattle 15 characterized by ulcerative and painful lesions. While multiple risk factors are involved 16 in the disease, its precise etiology remains unclear and the effectiveness of the current 17 control strategies still highly variable. However, and even if the main role of Treponema 18 spp. in the development of the disease is consistently recognized, the importance of 19 other bacterial communities and the factors affecting the skin environment remains 20 uncertain. The objective of this study was to investigate the dynamics of microbiotas 21 from feet affected by DD, before and after the implementation of disinfectant footbaths 22 under field conditions. During this investigation, the diversity, structure, and 23 composition of microbiotas from DD lesions over time were explored according to 24 different clinical factors. The findings of this investigation confirmed a particular 25 lesions evidenced a different structure and diversity in comparison to non-proliferative 30 lesions. The composition of microbiotas changed over time revealing the potential main 31 role of Treponema spp., Fusobacterium spp., Mycoplasma spp. and Porphyromonas 32 spp. in the dynamics of DD lesion progression. Further studies are necessaries to 33 confirm if the clinical evolution of DD lesions is driven by a particular microbiota and 34 how this microbiota induces disease. 35
Highlights 39Multiple bacteria have been identified in DD lesions. However, a large part of these 40 microorganisms are inhabitants of the foot skin and the farm environment. For the first 41 time, the microbiotas of DD lesions were followed over 45 days under field conditions 42 to explore their evolution over time and how footbaths practices may affect their 43 dynamics. The results of this investigation confirmed a particular microbiota related to 44 DD lesions dominated by Treponema spp. and highly different from those microbiotas 45 of healthy skin. The microbiotas from DD lesions evolved over the study period and 46 the differential bacteria were identified. Further studies are guaranteed to determine 47 the role of the bacteria composing these microbiotas on the lesion occurrence and its 48 outcome. 49 50 polymicrobial disease spread across the world and characterized by ulcerative and 55 painful lesions which might persist as a chronic condition. DD lesions progress in 56 dynamic ways conditioned by multiple environmental factors that influence the spread 57 of associated-pathogens and the integrity of the foot skin. Currently, the control 58 strategies implemented in dairy farms such as footbaths or individual treatments, have 59 demonstrated variable effectiveness in the healing and prevention of DD lesions 2,3 . 60Although the precise etiology of DD remains unclear, the maceration of the foot skin 61 and the presence of Treponema spp. have been consistently identified as the major 62 etiological components of DD 4-7 . However, multiple other bacteria have also been 63 associa...