A new focus of the tick Haemaphysalis concinna in Western Poland

The relict tick Haemaphysalis concinna has a fragmented and focal distribution in Central Europe and Asia. Although in the majority of neighboring countries the occurrence of this tick species is well-documented (i.e., in Germany, Czech Republic, Slovakia, Ukraine), to-date its occurrence in Poland has been registered only once, in 1953 in Troszyn in North-Western Pomerania, close to the German-Polish border. In the present study we report the first documented finding of H. concinna in Western Poland, confirmed both by collection of juvenile ticks from rodent hosts and questing ticks from vegetation. Trapping of rodents took place in the summer of 2018 in three locations in Western Poland (Słonin, Nowy Młyn 1, Nowy Młyn 2). Rodents were inspected for ectoparasites, which were detached and fixed in 70% ethanol. All the collected ticks were assigned to species and developmental stages using appropriate morphological keys, and representative individuals were genotyped by molecular methods. A total of 1482 feeding ticks were collected from 106 rodents from three sites. The common tick Ixodes ricinus was found in abundance on small rodents at all three sites; Dermacentor reticulatus ticks were identified at two sites in small numbers and, finally, numerous juvenile H. concinna (n = 427) were found at one of our study sites (Nowy Młyn 2). The highest prevalence and abundance of H. concinna were recorded on voles, Microtus agrestis and M. oeconomus, from this site in August. Additionally, questing nymphs and adult H. concinna were collected locally from vegetation (n = 20). Genotyping and phylogenetic analysis confirmed the species as H. concinna. A new focus of H. concinna has been described in Western Poland. Our long-term field work monitoring the expansion of the distribution of D. reticulatus in Poland, during which all collected ticks are identified, suggests that H. concinna is still very rare in the country.