Exploring the relationship between habitat richness and tick-borne encephalitis (TBE) human cases in Europe: a multi-scale study

The natural transmission cycle of the TBE virus is enhanced by complex interactions between ticks and key hosts. The diversity of wildlife host species and their relative abundance is known to affect transmission of tick-borne diseases. In the current context of global biodiversity loss, we explored the relationship between habitat richness and the pattern of human TBE cases in Europe to assess biodiversity’s role in disease risk mitigation. Methods. We assessed human TBE case distribution across 879 European regions using data reported to the European Surveillance System (TESSy) between 2017 and 2021. We statistically explored the relationship between TBE presence and a novel variable - habitat richness index (HRI) - describing the diversity of European ecosystem types. We also validated our findings at local scale using data collected between 2017 and 2021 in 227 municipalities located in Trento and Belluno provinces, two known TBE foci in northern Italy. Results. Our results showed a significant effect of HRI on the probability of presence of human TBE cases in the regions included in our dataset, and a significant, negative effect of HRI on the local presence of TBE in northern Italy. At both spatial scales, TBE risk decreases in areas with high HRI. Interpretation. Here, we considered habitat richness as proxy of vertebrate host biodiversity to explore its role in driving TBE European occurrence at different spatial scales. The results suggest that biodiversity loss could considerably enhance disease risk for both humans and wildlife, which may influence biodiversity conservation policies