# The niche of Borrelia burgdorferi sensu lato in Europe is predictable and mappable

## TL;DR

This study maps the spread of the Lyme disease bacterium Borrelia burgdorferi in Europe by analyzing tick and animal habitats.

## Contribution

The study introduces a new method combining vertebrate communities and tick data to predict Borrelia burgdorferi distribution.

## Key findings

- Borrelia burgdorferi prevalence in ticks correlates strongly with specific vertebrate reservoirs, not overall biodiversity.
- Southern Europe lacks suitable ticks for B. burgdorferi despite having reservoirs, limiting its spread.
- A dataset linking climate, vegetation, and vertebrates helps predict human infection risk across Europe.

## Abstract

Classic environmental niche modelling to examine the distribution of the causative agent of Lyme borreliosis Borrelia burgdorferi sensu lato (Bb) in the Western Palearctic, is often inadequate because it depends on both its tick vector(s), like Ixodes ricinus, and vertebrate reservoirs. We aimed to better determine, identify, and map the geographic distribution of Bb genospecies compiling data from 15,032 I. ricinus samples and over 6.5 million vertebrate records across 103 genera. We leveraged Species Stacking Distribution Modelling and Principal Components Analysis to identify communities of co-occurring vertebrates and their associations between Bb prevalence in host-seeking Ixodes nymphs and. Four vertebrate communities were revealed, with one strongly linked as primary reservoirs to Bb geographic range. Distribution of Bb in southern Europe was limited by the absence of I. ricinus despite suitable reservoirs, while in northern regions, a lack of competent reservoirs restricts its spread. The Bb prevalence in questing ticks correlates significantly (R2 = 0.89) with the presence of key reservoirs rather than overall vertebrate diversity which suggests the Bb niche is predictable and tied to specific vertebrate-tick co-occurrences. We compiled a dataset with the climate, vegetation, and vertebrate-derived variables linked to the transmission pressure of Bb to humans for the complete European territory, aiming for the prevention of infection in humans. This research underscores the importance of integrating reservoir species and tick distribution data to better map and predict Bb spread. By capturing the effects of climate and community composition on the occurrence of Bb in Europe, this framework provides insights for tracking Lyme borreliosis at a continental-level.

•Borrelia burgdorferi s.l. occupies a niche in the Western Palearctic.•Climate drives the overlap between B. burgdorferi reservoirs and Ixodes tick vectors.•A bioregionalization approach captures occurrence and prevalence in questing ticks.

Borrelia burgdorferi s.l. occupies a niche in the Western Palearctic.

Climate drives the overlap between B. burgdorferi reservoirs and Ixodes tick vectors.

A bioregionalization approach captures occurrence and prevalence in questing ticks.