The role of lambs, time and space in persistence of Dichelobacter nodosus, the causative agent of footrot

Lameness in sheep is a significant health and welfare problem in UK sheep flocks, with economic impacts that cost sheep farmers in both lost productivity and costs of treatment. Most lameness is caused by footrot, an infectious bacterial disease. The causative agent of footrot is Dichelobacter nodosus, which persists on the feet of infected sheep and is found transiently in soil, suggesting the most likely route of transmission between sheep is via the environment. Both ewes and lambs are affected by footrot, although the disease can present differently. While there is a large evidence base for management of lameness in ewes, less is known about how management practices are associated with prevalence of lameness in lambs. Two cross-sectional, questionnaire-based studies were used to identify relationships between management of lambs and prevalence of lameness in ewes and lambs and found managements linked with high prevalence of lameness in ewes are also associated with prevalence of lameness in lambs. Network-based diffusion analysis was used to investigate possible transmission pathways of D. nodosus using data from a longitudinal observational study of a flock of ewes and their lambs. Over the two-week study period, ewes were more likely to become lame without social contact with other sheep – presumably as some were already infected prior to lambing. These infectious ewes most likely acted as a reservoir of infection that led to infection in their lambs. Twin lambs were less likely to become lame over the study period, which may be because they spend less time with their mother than single lambs. These insights into the spread of D. nodosus may suggest that it would be beneficial for farmers to avoid turning out lame ewes and their lambs with the rest of the flock after lambing