The changing abundance and distribution of parasitic helminths has been identified as one of the greatest threats to animal health in the UK under climate change. This is due to the strong influence of abiotic conditions on parasites’ free-living stages. Planning adaptation and mitigation strategies requires predictions of parasite risk, and understanding of subtle interactions between abiotic conditions and parasite transmission. This requires development and application of a range of different modelling approaches.
This thesis includes the first long-term forecast showing potential impacts of climate change on a parasitic helminth in the UK. By combining a correlative parasite risk model with UKCP09 climate projections, risk maps are generated identifying which areas of the UK are predicted to experience unprecedented levels of fasciolosis (liver fluke) risk in the future.
Correlative models provide warnings of future risk, indicating where resources for monitoring and control should be targeted. To address more complex issues, and foresee consequences of subtle interactions between various components of a system under climate influence, a drive towards process-based mechanistic models is required. Consequently, a spatially explicit mechanistic model is developed, for the transmission of gastro-intestinal nematodes in a controlled grazing system. This allows investigation into how climate impacts on different elements of transmission. A non-linear relationship between climate change and parasite risk is revealed, with a distinct ‘tipping point’ in outbreaks when temperature driven processes exceed critical rates. This indicates that climate change could lead to sudden and dramatic changes in parasite risk.
Through combining the models developed here with improved empirical data and a broader view of livestock systems, our understanding of future risks and opportunities can be increased. This will allow improved control of these physically and economically damaging parasites, reducing deleterious impacts on production efficiency and animal welfare.
