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

蹄病是英国绵羊的一种地方性疾病，由于生产损失和疾病控制成本，对个体绵羊的健康和福利以及农场的经济不利。虽然对蹄病的控制似乎正在改善，但它仍然是一个地方性问题，2013年发现全球平均时期患病率为5%（Winter et al.，2015年）。然而，农民报告了这种疾病的流行方面-春季在羔羊中发生流行病。该项目旨在解决这种情况发生的原因。春季羔羊蹄病流行有四种可能的假说。首先，羔羊出生时对蹄病有被动免疫力，到春天时这种免疫力就会消失，导致这种流行病。第二个原因是，由于羔羊的出生，羊群内部的接触结构发生了变化。诺顿等人，（2012年）发现，由于羔羊的存在，羊群内的连通性总体增加，接触率增加可能导致疾病传播增加。第三，由于羔羊的出生而使羊群密度增加，这本身就足以造成一种流行病。最后，春季气候可能比一年中的其他时间更有利于足迹的传播。本项目将首先通过使用现有数据集来研究这些假设，然后设计一个纵向观测研究。将描述疾病严重程度和羔羊发生风险的模式，然后将研究羔羊对母羊和羔羊足蹄病发病率的影响。该分析的结果将影响纵向研究的设计，其中将记录跛行的发生率、气候数据和空间位置以及母羊和羔羊之间的接触模式。这将提高对疾病传播的理解，允许制定基于证据的方法来管理春季的蹄病。

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.