Spatial modeling of Borrelia genospecies in human-biting ticks from the French citizen science programme CiTIQUE

In Europe, Lyme borreliosis is the most common vector-borne human disease, mainly caused by Borrelia afzelii and Borrelia garinii, two species of the Borrelia burgdorferi sensu lato (Bbsl) complex transmitted by Ixodes ricinus. Assessing the spatial risk of human exposure to these pathogens is essential for efficient public health surveillance, yet conventional monitoring often fails to produce geographically explicit, large-scale data capturing exposure heterogeneity and its drivers. Focusing on continental France, we used data from the CiTIQUE citizen science programme to analyse spatial variation of Bbsl infection in georeferenced human-biting ticks and to model its associations with environmental, ecological, and anthropogenic factors. From 2017 to 2019, 1,891 ticks were analysed, with 15% testing positive for Bbsl. The most prevalent genospecies were B. afzelii (7.2%) and B. garinii (4.2%), showing distinct spatial patterns. I. ricinus habitat suitability was the most consistent predictor of Bbsl infection probability. Genospecies-specific models highlighted host influences: B. afzelii occurrence increased with rodent species richness, whereas B. garinii was associated with Turdidae species and showed possible dilution effect by rodents. Our findings demonstrate the value of citizen science in complementing surveillance and provide large-scale, spatially explicit insights into Bbsl eco-epidemiology in France, offering an adaptable framework for vector-borne disease monitoring.