Pathogens vectored by the tick, Dermacentor reticulatus, in endemic regions and zones of expansion in Poland

Background: Dermacentor reticulatus plays an important role in the maintenance of pathogens of medical and veterinary importance in the environment. Currently two isolated populations of D. reticulatus are present in Poland -Western and Eastern. The range of the Eastern population covers endemic areas in eastern Poland but this population is expanding westwards creating an expansion zone in the centre of the country. The expansion zone in western Poland is occupied by the recently discovered Western population, spreading eastwards. Methods: Questing adult ticks (n = 2585) were collected in 2012-2014 in endemic regions of north-eastern (Warminsko-Mazurskie Voivodeship) and central Poland (Masovian Voivodeship) and in the expansion zones in central and western Poland, in the region between the Vistula River and the western border of the country. Amplification of Babesia, Rickettsia spp. and Borrelia burgdorferi sensu lato DNAs was performed using specific starters. RNA of the TBE virus was detected using RT-PCR and representative PCR products were sequenced and compared with sequences deposited in GenBank. Results: Of the total 2585 examined ticks, 1197 (46.3 %) were infected with at least one pathogen. Overall prevalence of pathogens was 4.18 % (108/2585) for Babesia spp., 44.10 % (1140/2585) for Rickettsia spp., 0.09 % (1/1107) for Borrelia afzelii and 7.6 % (7/92) for TBEV. Sequence analysis of DNA showed 99.86 % similarity to R. raoulti and 99.81 % to B. canis. One male from north-eastern Poland was infected with B. microti. Prevalence of R. raoulti was highest in the Western population (52.03 %) and lowest in the Eastern population in north-eastern Poland (34.18 %). Babesia canis was not detected in 592 ticks collected in the Western population, while in the Eastern population overall prevalence was 5.42 %. There were significant differences in the prevalence of B. canis between tick samples from northern (0.68 %), central (1.18 %) and southern (14.8 %) areas of the expansion zone in central Poland. Conclusions: Our study found significant differences between the range and prevalence of vectored pathogens in D. reticulatus from the endemic areas and newly inhabited expansion zones. The differences were likely associated with the different time of settlement or 'source' of ticks populations, the Eastern and the Western one.