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

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Footrot is an endemic disease of sheep in Great Britain, which is detrimental to the health and welfare of individual sheep, and the economics of the farm due to losses in production and costs of disease control. While control of footrot appears to be improving, it remains an endemic problem, with a global mean period prevalence of 5% found in 2013 (Winter et al., 2015). However, farmers report an epidemic aspect to the disease- with an epidemic occurring in lambs in the spring time. This project aims to address the reasons behind why this occurs. There are four possible hypotheses for the epidemic of footrot in lambs in spring. The first is that lambs are born with passive immunity to footrot, which then wears off by spring time, resulting in the epidemic. The second is that the contact structure within the flock is altered as a result of the birth of the lambs. Norton et al., (2012) found an overall increase in connectivity within flocks as a result of the presence of lambs and increased contact rates can result in increased transmission of disease. The third is that the the increase in density of the flock due to the birth of lambs may sufficient in itself to create an epidemic. Finally, the spring climate may be more conducive to the spread of footrot than at other times of the year.This project will investigate these hypotheses, firstly by using an existing dataset, and then designing a longitudinal observational study. Patterns of disease severity and risks for occurrence in lambs will be described, and then the impact of lambs on the incidence rate of footfot in ewes and lambs will be investigated. The results of this analysis will influence the design of the longitudinal study, where occurrence of lameness, climate data and spatial location and contact patterns between ewes and lambs will be recorded. This will improve understanding of the spread of disease, allowing an evidence based approach to be formulated for management of footrot in in spring time.