Process & Systems Modelling

Climate-induced tipping points in macro-parasite infection risk

Macro-parasites present one of the most pervasive challenges to grazing livestock. Changing outbreak patterns in temperate regions have been attributed to climate change, as many stages of the macro-parasite life cycle are free-living (i.e. outside the host species) and are therefore sensitive to abiotic conditions. With potential for further climate driven increases in parasite prevalence and intensity, and consequent welfare and economic impacts, there is a need to foresee changes in risk and to develop control strategies. By developing a mechanistic model that incorporates the key elements of the transmission process, we have explored how changes in climate sensitive parameters will influence parasite outbreaks.

Our results show that changes in larval development and survival can result in non-linear responses in transmission dynamics, leading to distinct ‘tipping points’ in parasite burdens. Consequently, small changes in climatic conditions around the critical threshold could result in dramatic changes in outbreak patterns. The position of the tipping point is influenced by the initial level of larval contamination on pasture at the start of the grazing season, and once the tipping point has been surpassed, the magnitude of outbreaks will be determined by the host’s immune response. An understanding of this non-linear response to climate change will help inform management decisions and long term control strategies.

parasite burden plotted against larval development Plotting modelled parasite burden against larval development rate shows a non-linear threshold (or tipping point) above which disease burden increases rapidly.

Further details from: Glenn Marion

Article date 2013

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