Modelling livestock parasite risk under climate change

Parasitic worms present one of the most pervasive threats to grazing livestock, and climate change has been implicated as a driving force for recent increases in their intensity and range (van Dijk et al., 2008; Kenyon et al., 2009; Fox et al., 2011). Owing to the potential for climate driven disease outbreaks to have food security, animal welfare and economic implications (Moran et al., 2013), there is a need to predict future parasite risk. At the coarse scale parasite distribution will be dependent on the species’ climate envelope, and the survival and development of free-living parasite stages are dependent on temperature and moisture levels (Armour, 1980). Consequently, our first model focuses on how changes in parasite development and survival affect nematode outbreaks in livestock. However, such predictions do not account for variations in transmission at the farm level, and impacts of climate change on host physiology and management should also be considered in development and parameterisation of parasite models. By applying a second mechanistic model which incorporates a number of additional elements of the system dynamics, we determine the robustness of our findings to the inclusion of a number of realistic farm-level processes.