Development of an early warning predictive model for footrot in sheep

跛行是英国绵羊生产商面临的最重要问题之一，每年给该行业造成2400万至8400万英镑的损失。（Nieuwolf等人，2005; Wassink等人，2010年）。据估计，英格兰约90%的跛行是由结节叉尾轮虫引起的蹄疾（Kaler和绿色，2008）。D.节瘤状体，其中9种已在英格兰和威尔士被鉴定，其中几种菌株类型经常在个体脚、绵羊和羊群上发现（克拉克斯顿等人，1983; Ghimire等人，1998;摩尔等人，2005年）。腐蹄病是一种复杂的病害，宿主、病原和环境都对病害的发生起着关键作用。经验和实验室研究都表明，水分水平和温度会影响节瘤叉尾轮虫的生存能力（Cederlöf等人，2013）和疾病的发生（Graham和Egerton，1968; Smith等人，2014）。还有一些证据表明，英国跛行的患病率因地理位置而异，从英格兰东南部的最低水平到西北部的最高水平（Wassink等人，2004年）。最近，实验室证据表明，土壤类型影响D。nodosus（M. Mohd等人，2016）。许多羊群在春季爆发疾病，特别是在羔羊中（Wassink等人，2003年）。这通常归因于春季温暖潮湿的天气和羔羊免疫力下降。尽管有上述所有因素，农民无法预测每年会发生多少跛行，许多人报告说，春季跛行的爆发是“随机的”。因此，这个博士学位的目的是根据在农场收集的疾病数据和通过调查，以及每个农场的土壤类型和历史天气数据，为英格兰的蹄病的发生开发一个预测模型。

Lameness is one of the most important issues facing sheep producers in the UK, costing the industry between £24-84 million p.a. (Nieuwolf et al., 2005; Wassink et al., 2010). It is estimated that ~90% of lameness in England is footrot, caused by Dichelobacter nodosus (Kaler and Green, 2008). There are 10 serogroups of D. nodosus, of which 9 have been identified in England and Wales, with several strain types often found on individual feet, sheep and flocks (Claxton et al., 1983; Ghimire et al., 1998; Moore et al., 2005). Footrot is complex with host, pathogen and environment all playing a key role in expression of disease. Both empirical and laboratory research indicate that moisture level and temperature affect the viability of Dichelobacter nodosus (Cederlöf et al., 2013) and occurrence of disease (Graham and Egerton, 1968; Smith et al., 2014). There is also some evidence that the prevalence of lameness in England varies by geographical location from a lowest level in southeast England to the highest level in the northwest (Wassink et al., 2004). Most recently, laboratory evidence indicates that soil type influences survival of D. nodosus (M. Mohd et al, 2016). Many flocks experience an outbreak of disease in spring, particularly in lambs (Wassink et al, 2003). This is commonly attributed to the warm wet weather of spring and waning immunity in young lambs.Despite all the above, farmers cannot predict from year to year how much lameness will occur and many report that the outbreak of lameness in spring is 'random'. Therefore, the aim of this PhD is to develop a predictive model for the occurrence of footrot in England based on disease data collected on farms and via survey, together with soil type and historical weather data for each farm site.