Birds flyways and spread of Hyalomma ticks in Europe

This study modelled the probability of introduction of Hyalomma marginatum into Europe by predicting the potential migratory routes of 27 bird species and the probability to carry immatures of the tick. Flyways were modelled as a spatio-temporal feature, at weekly intervals, using satellite-derived data of temperature and vegetal phenology, together with cost surfaces derived from speed and direction of the wind (years 2002-2018). The probability of moulting of the engorged nymphs was modelled as a linear relationship of the daily sum of temperatures after tick introduction by birds. Positive probabilities of tick introduction extend the known northern range of permanent populations to central and west France, and large portions of central Europe. The flight of birds into an area and thence the risk of introduction of H. marginatum is very heterogeneous, sites receiving “waves” of different bird species at diverse moments of the year. Therefore, there is not a clear slice of time for introduction, as it depends on the modelled behaviour of the bird species. The probability of introduction into Baltic and Nordic countries is small. We hypothesize that conditions of warmer climate might support permanent populations of H. marginatum if a high number of immatures are introduced. Active surveys in risky territories, where the tick is not yet established, are advisable for a rapid intervention.