Environmental hazard of tick-borne diseases in urban and peri-urban sites in an endemic area of eastern France.

The occurrence of the Ixodes ricinus tick in forested and rural areas is well documented across Europe; however, its presence in urban environments remains less investigated. This study focused on the city of Strasbourg, located in eastern France, a region endemic for ticks and tick-borne diseases, to identify high-risk ecosystems along an urbanization gradient. Questing ticks were collected from eight sites: four urban parks, a botanical garden, and three peri-urban forests. A total of 880 ticks were collected, and 657 nymphs were analyzed for the presence of the pathogens Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Neoehrlichia mikurensis using molecular methods. Regularly maintained urban parks presented a low risk of tick bites or tick-borne bacterial infections, including Lyme borreliosis, anaplasmosis, and neoehrlichiosis. In contrast, peri-urban alluvial forests exhibited a high risk of tick bites and potentially infectious diseases, with a mean nymph density of 21.16 (range 18.25-24.75) per 100 m2 and a mean density of infected nymph of 7.00 (range 4.93-10.21) per 100 m2 for the three pathogens investigated. Owing to their high humidity and diverse fauna, alluvial forests provide particularly favorable microhabitats for Ixodes ticks and the circulation of their associated pathogens. In the context of climate change and increasing urban greening initiatives, greener cities may inadvertently increase the risk of tick-borne diseases in urban environments. Therefore, implementing appropriate park and forest management strategies, together with public awareness campaigns, is essential to reduce acarological risk.