The Spatial Distribution of Ticks (Ixodidae) in Germany-Evidence of a Continuing Spread of .

In Europe, two tick species of the genus occur, and . When the spatial distribution of both species in Germany was studied comprehensively for the first time in 1976, populations were recorded along the Rhine and Main river valleys in southwestern Germany, while was very rare. In the last 50 years, however, a considerable range expansion of has been noted in several European countries. To assess the current distribution of spp. in Germany, citizens were asked to send in ticks suspected to belong to the genus or that were of "unusual" appearance. From February 2019 until February 2020, 3,902 ticks were received in total. Of those, 15.48% (604/3,902) were identified as and 84.24% (3,287/3,902) as , while 11 specimens could not be identified to species level. The majority of specimens was collected from dogs (1,212/2,535; 47.12%), while was mostly collected from horses (184/526; 34.98%). Our results confirm that the adults of both species are active all year round. specimens were sent in from all federal states except the Free and Hanseatic City of Hamburg, while specimens were only received from locations in southwestern Germany. Overall, data obtained from this citizen-science study show that has significantly expanded its range, especially in northern Germany. Regarding , new locations northwest of the previous range were detected, although the distribution has remained rather stable as compared to . The spread of , the vector of , is of major importance for veterinarians and dog owners in terms of canine babesiosis outbreaks or endemization in hitherto -free areas. Thus, veterinarians and veterinary students need to be informed about the new situation to be able to give adequate advice to dog owners on the extended range and appropriate control measures.