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Modelling Footrot: The Interaction between Genetics and Epidemiology

Footrot is a bacterial disease of sheep causing lesions and lameness spread via contaminated pasture and where susceptibility is partly under genetic control. The resulting heterogeneity within a sheep flock could have an impact on the efficacy of treatment and control plans. Additionally, as there is a clear genetic component it also opens up the possibility for genetic selection, including footrot resistance as a criterion in estimated breeding values.

This project involves the creation of a stochastic simulation model to explore the interactions between genetics and epidemiology in footrot.

The model simulates a sheep flock with a base population of 200 ewes, each with their own unique genetic composition with regard to three traits:

  1. Susceptibility - affecting the probability an individual sheep becomes infected
  2. Recoverability - affecting the time taken for an individual sheep to recover from an infection
  3. Revertability - affecting the time taken for an individual sheep to revert to a susceptible state following infection i.e. how long a sheep remains immune

The footrot infection process is modelled within this heterogeneous flock, alongside population dynamics (including lambing and culling each year) and bacterial contamination of the environment.

The model will be used to explore the effects of different treatment and control strategies and investigate the potential for genetic selection to improve resistance within a flock over a number of years.

Publication

Russell, V. N. L., Green, L. E., Bishop, S. C. and Medley, G. F. (2012). A genetic and epidemiological model of footrot in a sheep flock. Proceedings of the Annual SVEPM Conference, Glasgow 2012.

Team members:

Vinca Russell (PhD Student)

Professor Laura Green

Professor Graham Medley

Professor Stephen Bishop (Roslin Institute, University of Edinburgh)

BBSRCPfizer

Bioscience KTN