My PhD project is funded by the Natural Environment Research Council (NERC) and investigates the survival and persistence of the primary causative agent of ovine footrot, using molecular approaches in an epidemiological framework.
Footrot is an economically significant infectious disease with negative effects on animal health and productivity, affecting sheep producing countries worldwide. The main causative agent of fotrot is the gram-negative anaerobic bacterium Dichelobacter nodosus, a colonizer of the ovine hoof, which is transmitted through the environment via contaminated surfaces. Pathogen invasion of the interdigital space leads to a range of disease severities ranging from mild interdigital inflammation (ID) to separation of the hoof horn from underlying tissues (severe footrot) (FR), causing varying degrees of lameness.
Footrot may become re-established in a flock when climatic conditions become favourable for pathogen transmission, suggesting the existence of environmental reservoirs of infection. Recent evidence suggests that D. nodosus may survive for longer and at lower temperatures than previously expected. This might explain why disease eradication efforts in the UK, targeting the expected zero-transmission periods in winter, have been unsuccessful. D. nodosus was previously isolated from the farm environment and from feet in cross-sectional studies, indicating presence but not necessarily persistence of this organism.
My project aims to investigate persistence of D. nodosus, by identifying possible sites of survival that facilitate infection. Associations between D. nodosus presence/load and levels of disease over time will be investigated, focused on capturing the change between expected periods of transmission and non-transmission. Sheep and the farm environment will sampled in a longitudinal study design and D. nodosus will be detected, quantified and characterized by using a range of molecular detection and characterization methods. Information on bacterial load in combination with an effective molecular typing system will be used to monitor the occurrence of pathogenic trends and to identify possible reservoirs on infection.