Occurrence of juvenile Dermacentor reticulatus ticks in three regions in Poland: the final evidence of the conquest

Abstract

Background Two populations of Dermacentor reticulatus ticks (Western and Eastern) in Poland are among the most dynamic tick populations in Central Europe. Expansion and settlement of ticks in new localizations depend on the presence of suitable hosts, for both adult and juvenile ticks. Methods The current study was planned to complement our previous studies on questing adult ticks and was focused on a collection of juvenile D. reticulatus ticks from rodents from three regions in Poland, defined by the presence/absence of adult ticks (regions of the Western and Eastern tick population and the gap area between them) to confirm the existence of stable populations. Rodent trapping was conducted in open habitats (fallow lands, wasteland and submerged meadows) in 2016–2018 in June, July and/or August to encompass seasonal peaks of larvae and nymph activity. Results Altogether, three tick species were collected, 2866 D. reticulatus, 2141 Ixodes ricinus and 427 Haemaphysalis concinna. Dermacentor reticulatus was the most common (72.3%) and abundant (mean 17.94 ± 2.62 ticks/rodent) tick species on rodents from the Eastern region; in the Western region infestation of rodents was only 6.8%. Ixodes ricinus was found in all three regions and was the only tick species collected from rodents from the gap area. Haemaphysalis concinna was noted only in the Western region. The highest infestation of juvenile D. reticulatus was recorded on voles (Myodes and Microtus spp.), infestation of I. ricinus was the highest on Apodemus mice, and the majority of H. concinna ticks were collected from root voles Alexandromys oeconomus. Conclusions Our study confirmed a stable population of D. reticulatus in Eastern and Central Poland and a lower prevalence and mean abundance of this tick species among rodents from the Western region. A lack of juvenile D. reticulatus on rodents in Niewiadów confirmed the existence of the gap area, free of D. reticulatus ticks. Graphical abstract

Tick-borne pathogens in questing adults Dermacentor reticulatus from the Eastern European population (north-eastern Poland)

“…The prevalence of B. canis in ticks from the Eastern European population has been reported to vary from 0 to 6.8% 19 , 25 , 29 – 34 . It is worth underlining that in the current study, most of the D. reticulatus infected by B. canis were detected in an urban area of the city of Olsztyn in the central part of the Warmia and Mazury region, the oldest area known as endemic for D. reticulatus 3 , 5 . These results confirm the presence and relatively constant level of prevalence B. canis (2.5%) in this part of north-eastern Poland, previously established by other authors in the range of 2.3–6% 5 , 19 .…”

“…In several European countries (Slovakia, the Czech Republic, the United Kingdom, the Netherlands, and Germany), habitat expansion of D. reticulatus was noted 6 , and the northern distribution border in the Baltic countries (Lithuania, Latvia) moved further to the north 7 . On the Polish territory in “the gap” zone, new foci occurrences of this tick species have also been reported 5 , 8 – 10 which leads to closer borders between the western and the eastern D. reticulatus populations.…”

“…In between, there was a large area from the Baltic Sea coast through central Germany, western Poland to the southern border of Hungary where the meadow tick had never been observed 3 , 4 . Currently, those two populations of D. reticulatus (Western and Eastern) are among the most dynamic tick populations in Central Europe 5 . In several European countries (Slovakia, the Czech Republic, the United Kingdom, the Netherlands, and Germany), habitat expansion of D. reticulatus was noted 6 , and the northern distribution border in the Baltic countries (Lithuania, Latvia) moved further to the north 7 .…”

“…The eastern population of D. reticulatus ticks in Poland is considered a stable population and is the source of newly emerging foci of this species in the zone previously considered free (central and western Poland) 5 , 9 , and thus the spread of tick-borne microorganisms of significant veterinary and medical importance. The aim of the study was to assess the prevalence and diversity of tick-borne protozoa ( Babesia spp.)…”

Tick Activity, Host Range, and Tick-Borne Pathogen Prevalence in Mountain Habitats of the Western Carpathians, Poland

“…However, we believe that the limited numbers of these ticks collected in this region may indicate accidental introduction of D. reticulatus rather than their regular occurrence in this area. The hypothesis of accidental import may also be supported by the fact that juvenile D. reticulatus stages were collected both from Microtus rodents (meadow habitat), which are regarded as the main spectrum of hosts of this tick species [ 29 ], and from A. flavicollis (forest habitat), which may be potential hosts of D. reticulatus , but their infestations by this species are less frequent due to the different habitat preferences of the host ( A. flavicollis ) and the tick ( D. reticulatus ) [ 11 ]. Nevertheless, this phenomenon may contribute to future changes in the occurrence range of this tick species in the Western Carpathians.…”