Mapping of Dermacentor reticulatusexpansion in Poland in 2012–2014

Rapid expansion of the tick Dermacentor reticulatus(Fabricius) has been reported in many European countries. In Poland its range was limited to the area on the eastern side of the Vistula River up until the 1990s. However, new foci were recently discovered, while the centre of the country and mountain regions are believed to be free of this tick and are known as “the gap”. A few unconfirmed factors, like unfavourable weather conditions, changes in land cover and absence of competent hosts have previously been reported as possible reasons for the absence of D. reticulatusin this area. Since D. reticulatusplays an important role for the maintenance and the circulation of tick-borne pathogens, we (1) determined its actual range in Poland, (2) monitored its expansion in 2012–2014 and (3) correlated abiotic conditions on its known range. Dragging was conducted in the area between the Vistula River and the western border of Poland in 2012–2014, along the three major Polish rivers and their tributaries. Temperature and humidity on the ground were recorded 4 times a day at a total of 32 sites.