Landscape heterogeneity, forest structure and mammalian host diversity shape Ixodes ricinus density and Borrelia prevalence in German forests

Abstract

Ticks, particularly Ixodes ricinus, and the associated Lyme borreliosis risk, represent key concerns within the One Health framework, prompting extensive research in this field. However, comprehensive studies that jointly consider landscape characteristics, local forest structure and management, climate, and host community composition - alongside direct measures of tick density and Borrelia spp. infection status - are scarce. In this study, we test the hypothesis that habitat diversity exerts a dilution effect, primarily by supporting greater diversity of mammal hosts. Therefore, we examined I. ricinus tick density and Borrelia spp. prevalence in relation to a comprehensive set of habitat and host-related variables. Ticks were collected using the flagging method and mammal hosts were monitored using an innovative camera-trapping approach across 25 forest plots along a land-use gradient within the Schwabische Alb exploratory in Germany. Our findings indicate that both tick density and Borrelia spp. prevalence are influenced by a complex interplay of habitat factors across different spatial scales, as well as the mammal host community composition. Overall, our results provide novel support to the dilution effect hypothesis, suggesting that greater habitat and host diversity contribute to a reduced Lyme borreliosis risk in this region.