The effect of historic climate change on the population dynamics of Ixodes ricinus

The distribution and intensity of tick-borne disease (TBD) transmission events across Europe are increasing in response to changes in climate, land use and host populations. Understanding how changing environmental factors drive seasonal tick population dynamics is critical for predicting the public health impacts of TBDs. Here, we develop an environmentally driven system of stage-structured delay-differential equations to predict the population dynamics of Ixodes ricinus, the primary vector of human TBDs in Europe. We validate the model against data from 77 tick populations in 20 European countries, finding that 55% of the variation observed in the population dynamics of nymphs can be attributed to the effects of climatic variation. Over the last 40 years, we predict a climate change-induced increase in tick abundance and seasonal activity in northern Europe, and commensurate decreases across southern Europe, which should be accounted for in national health policy and climate change adaptation plans.