Development of an early warning predictive model for footrot in sheep

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.