Dispersal of Hyalomma rufipes by migratory birds in northeastern Spain: Implications for Crimean-Congo haemorrhagic fever surveillance.

Migratory birds play a crucial role in the long-distance dispersal of ticks and tick-borne pathogens, contributing to the introduction of tick species and pathogens into new areas. Among those ticks, Hyalomma rufipes is a key concern due to its role as a vector of Crimean-Congo haemorrhagic fever virus (CCHFV) and its potential to establish in southern Europe. We assessed tick infestation, CCHFV presence, and both the probability of H. rufipes infestation and its genetic diversity in migratory birds captured at four key stopovers in northeastern Spain Mediterranean (NESM) ecological region during spring migration from 2022 to 2024. A total of 14,472 birds representing 84 species were examined, of which 0.5% carried ticks, primarily H. rufipes (77% of ticks), while all ticks tested negative for CCHFV. Statistical analyses revealed that ground- and shrub-foraging species, as well as birds wintering in open habitats and wetlands, had significantly higher probabilities of H. rufipes infestation. Genetic analyses of 88H. rufipes sequences showed high haplotype diversity with no clear population structure, indicating that ticks were acquired from multiple geographic origins, predominantly Central-West Africa. Some birds carried genetically distinct ticks simultaneously, which could facilitate pathogen transmission between ticks from different origins through co-feeding. Notably, some pre-Saharan migratory birds carried H. rufipes, suggesting potential local acquisition in North Africa, where the species has been previously reported although its establishment remains debated. These findings highlight the ongoing risk of introduction and possible establishment of H. rufipes in the NESM, with important implications for future surveillance of vector populations and tick-borne pathogens, including CCHFV, in Europe.