Impacts of deer management practices on the spatial dynamics of the tick Ixodes ricinus: A scenario analysis

Deer, for example roe deer, red deer and fallow deer, are the common reproduction host types for European Ixodes ricinus ticks. Understanding the consequences of deer management on the spatial dynamics of ticks may advise the risk management of tick-borne diseases, and thus be of public health importance. We present a scenario analysis to understand such consequences by integrating multi-disciplinary knowledge within a predictive modelling framework. A spatial tick population model was adopted to explore how changes in the host population may affect woodland patch- and landscape-level tick dynamics. Scenarios on current and foreseen European deer management strategies were built based on expert knowledge. These scenarios were then tested through the described model for their potential effectiveness as tick control strategies. Our models indicate that: (i) reducing local deer densities could not effectively reduce tick abundance if woodland patches are well-connected, allowing deer population exchanges, (ii) controlling deer grazing intensity in grassland may not be an effective tick control strategy, (iii) local extinction of deer could decrease tick abundance considerably but deer reintroduction could lead to fast tick upsurge, and (iv) controlling human disturbances may reduce the tick density at landscape-level, as well as tick “hotspots” (i.e., areas with unusually high tick density) at woodland patch-level. Our results can instruct policy-makers on the potential impact on public health of wildlife management strategies, and suggest empirical investigations of disease risks. For optimising such simulation studies on disease risks, however, a better understanding of how biodiversity may influence the ecology of tick and pathogen transmission is required.