Environmental determinants and potential suitability for Phlebotomus mascittii sand flies in central-western Europe under future Shared Socioeconomic Pathways climate change projections

Background Climate warming is expected to drive the northwards expansion of sand flies in Europe, increasing the risk of infection by sand fly-borne pathogens such as Leishmania spp. This study assessed the probability of sand fly presence in central-western Europe under various climate change scenarios for the periods 2041–2060 and 2081–2100. Methods We used summer climatic data from 10 global climate models and CORINE Land Cover variables to develop a parsimonious mixed-effects logistic regression model for sand fly presence on the basis of findings from 2023 and 2024 surveys across France, Germany, Luxembourg, Belgium, and the Netherlands—covering the northernmost extent of the known sand fly distribution—where the dominant species was the Leishmania infantum vector, Phlebotomus mascittii . The logistic function derived from this model was applied to project future sand fly distributions under the Shared Socioeconomic Pathways (SSPs), SSP2-4.5, SSP3-7.0, and SSP5-8.5, depicting scenarios of socioeconomic development and their impact on greenhouse gas emissions as outlined in the Sixth Climate Change Assessment Report (AR6). Results The spatially distributed probability model, which incorporates average temperature and solar radiation, predicts a 20–30% increase in the likelihood of Ph. mascittii presence across Luxembourg, Belgium, western Germany, and the southern Netherlands from 2041–2060 under all three SSP scenarios. By 2081–2100, the projected expansion in these northern regions intensified, reaching 35% under SSP2-4.5, 60% under SSP3-7.0, and 80% under SSP5-8.5. There is considerable variability in the predicted probability both between and within countries, influenced by country topography and latitudinal range. Conclusions It is highly probable that Ph. mascittii , will expand its natural distribution in central-western Europe into areas that are presently too cold and have insufficient solar radiation, to an extent that will depend on how global society, demographics, and economics might evolve over the 21st century. These predictions emphasize the need for adaptive surveillance and proactive measures to mitigate the risks of sand fly vector expansion and leishmaniosis transmission, as outlined in the CLIMOS project's goal to develop an early warning system.