Unveiling the seasonal dynamics of leishmaniosis: High-resolution monthly potential risk mapping and future expansion of Leishmania infantum in Europe.

BACKGROUND: Zoonotic leishmaniosis, caused by Leishmania infantum, is a major public health and veterinary concern in Europe. Traditionally restricted to the Mediterranean basin, the disease is currently undergoing a rapid geographical expansion towards Central and Northern Europe, driven by climate change and the plasticity of its vectors. Current epidemiological surveillance often relies on static annual prevalence maps, which fail to capture the critical intra-annual fluctuations in transmission risk. This study aims to bridge this gap by developing the first high-resolution spatiotemporal analysis of L. infantum potential infection risk across the entire European continent, providing a dynamic tool to optimize control strategies under a One Health framework. METHODS: We developed Ecological Niche Models (MaxEnt) for the two primary European vectors, Phlebotomus perniciosus and Phlebotomus perfiliewi. To estimate the transmission capability, we integrated these habitat suitability models with a biological model of parasite development (Rioux's algorithm), which calculates the infection rate based on daily mean temperatures (10-30 °C thermal window). This integration allowed for the generation of continuous annual and monthly potential risk maps. Furthermore, we projected the potential infection risk to the year 2100 under the SSP5-8.5 climate change scenario to quantify future range shifts and potential expansion into non-endemic territories. RESULTS: The models exhibited excellent predictive performance (AUC ≥ 0.900), with annual mean temperature being the dominant driver for both vectors. The results confirmed high endemic risk in the Mediterranean basin but revealed significant emerging risk zones in the Balkans, Romania and the Southern Plateau of Spain. The monthly analysis unveiled a dynamic seasonality: transmission is latent in winter, restricted to southern coastal refuges, but expands latitudinally during spring and summer, covering most of Central Europe before retracting in autumn. Future projections for 2100 indicate an alarming 347.9% net increase in infection risk areas. The models predict a massive colonization of northeastern Europe and high-altitude regions, with no current risk areas becoming unsuitable. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that L. infantum transmission in Europe is a highly dynamic phenomenon defined by seasonal thermal windows rather than static boundaries. The projected expansion towards northern latitudes challenges the historical notion of leishmaniosis as solely a southern European disease. These dynamic risk maps represent a strategic One Health tool, enabling health authorities and veterinarians to transition from rigid calendar-based prophylaxis to adaptive, evidence-based interventions. This is particularly crucial for identifying transmission periods in emerging transition zones, ensuring better protection for both animal and human populations in a changing climate.