In this study, D. reticulatus ticks were found for the first time in central-southern Poland in three localities (Radomsko, Żytno, and Kłobuck) situated at a distance of approx. 25-60 km from each other (Fig. 1). To date, this area has been regarded as a zone separating the eastern and western ornate dog tick populations in Poland 3.
In total, six D. reticulatus specimens were collected from six dogs and one specimen was removed from one cat (Fig. 2, Table 1). There were three fully engorged females, one partially engorged female, and three males. As declared by the keepers of the dogs and cat, their animals stayed in the same area throughout the study period.
The incidents of attachment of D. reticulatus adult ticks to companion animals in different study years indicate that this species has probably been present in central-eastern Poland since 2010. The collection of the D. reticulatus specimens in central-southern Poland confirms the findings of the rapid migration of this tick in Poland reported by other researchers 3,30,31.
Table 1. Dermacentor reticulatus ticks collected from companion animals in central-southern Poland (2010-2014).
Date of collection
|
Collection site
|
Host species
|
Anatomical location on host
|
Life stage of removed tick
|
22.10.2010
|
Radomsko *
|
Canis lupus familiaris
|
head
|
almost fully engorged female
|
11.05.2012
|
Radomsko
|
Canis lupus familiaris
|
abdomen
|
partially engorged
|
10.04.2012
|
Radomsko
|
Felis catus
|
head
|
male
|
03.05. 2013
|
Kłobuck **
|
Canis lupus familiaris
|
head
|
male
|
27.05.2014
|
Radomsko
|
Canis lupus familiaris
|
head
|
male
|
20.06.2014
|
Kłobuck
|
Canis lupus familiaris
|
neck
|
almost fully engorged female
|
10.05.2014
|
Żytno ***
|
Canis lupus familiaris
|
leg
|
almost fully engorged female
|
geographical coordinates of collection sites * 51°04′01″N, 19°26′41″E, 223 a.s.l.; ** 50°54′02″N, 18°56′12″E, 239 a.s.l.; *** 50°55'38"N 19°37'39"E, 202 a.s.l.
The incidents of attachment of D. reticulatus adult ticks to companion animals in different study years indicate that this species has probably been present in central-eastern Poland since 2010. The collection of the D. reticulatus specimens in central-southern Poland confirms the findings of the rapid migration of this tick in Poland reported by other researchers 3,30,31.
At the end of the 20th century and the beginning of the 21st century, the eastern and western D. reticulatus occurrence range in Europe was separated in Poland by an area between the Vistula River and the Oder River 32. The first localities of D. reticulatus west of the Vistula River were recorded in Pomeranian Lake District in the early 2000s 33,34 and in subsequent years, as reported by Dwużnik-Szarek et al. 3.
In western Poland, the tick species was first found near the border with Germany in Dolnośląskie and Lubuskie Provinces 35-38. In 2022, D. reticulatus specimens were collected near Poznań (west-central Poland) 39. Two specimens (one female and one male), probably from a local population, were removed from a dog in Racibórz in south-western Poland 40.
Dermacentor reticulatus ticks were probably brought to the area analyzed in this study by animals migrating from the western regions of Poland and/or eastern Germany, where stable populations of this species have been identified 4,6. The new D. reticulatus localities in central Poland are situated in or near urbanized areas. The shift in the range of these ticks towards urban areas has been observed for two decades in other parts of Poland 39,41-45 and Europe 10,46-48.
The environmental conditions in central Poland are highly favorable for this tick species. Within its distribution range, the species is most often found in riparian forests, river and lake banks, meadows, mid-forest clearings, and wastelands with a high groundwater level 1,7,8,23,24,30,31. The D. reticulatus colonization of the study area may have been facilitated by human activities changing the hydrographic network (conversion of smaller tributaries of the main rivers in the region into drainage ditches and construction of drainage ditches, regulation of rivers, construction of artificial water reservoirs) and landscape transformation (mid-field afforestation, fallow areas, urbanization, conversion of forests into agricultural land). The mosaic landscape creates not only open habitats preferred by D. reticulatus ticks but also various habitats suitable for their potential hosts in central Poland. The relationships between the reduction of forested areas and the presence of D. reticulatus were confirmed by Mierzejewska et al. 49.
In Poland, juvenile stages of D. reticulatus (larvae and/or nymphs) have been collected from various species of rodents from the families Murinae, Microtinae, and Soricidae 13,14,16,50-52, and nymphs have also been found to infest larger mammals, e.g. deer, roe deer, hares, and rabbits 32. Adult ticks parasitize large wild-living mammals, mainly representatives of the families Cervidae: Alces alces (moose), Dama dama (fallow deer), and Cervus elaphus (red deer) 34,38,53, Canidae: Canis lupus (wolf) and Vulpes vulpes (fox) 54, Bovidae: Bison bonasus (European bison) (55), and Suidae - Sus scofa (wild boar) 38,56. In the D. reticulatus occurrence range, adult specimens are collected from dogs and other domestic animals 43,45,57. In some habitats of central-eastern Poland, it is the dominant tick species infesting dogs 57.
The presence of D. reticulatus ticks in the study area poses a threat to the health of not only companion animals but also humans, who may be accidental hosts of adult stages 22,25,58. An interesting case of attachment of a female D. reticulatus tick to human skin was recorded in eastern Poland; the tick was transferred to the apartment by the pet dog (Buczek et al., unpublished data). As demonstrated by our research, after ingestion of dog’s blood, female D. reticulatus ticks can lay eggs that hatch into larvae in household conditions.
The high risk of D. reticulatus attacks on companion animals and humans is also associated with the fact that adult specimens are active throughout the day, mainly from 12:00 to ca. 16:00 in spring and from 10:00 to approx. 18:00 in autumn with a peak around 14:00 in both these seasons, i.e. at the time of possible presence of their hosts in tick habitats 59.
The expansion of D. reticulatus ticks into central-southern Poland may lead to the spread of pathogens transmitted by this species in the environment, which should be taken into account in the clinical diagnosis of tick-borne diseases in domestic animals and humans. In Poland and its western and southern neighbors, numerous pathogens with medical and veterinary importance have been detected in this tick species, e.g. R. raoultii and other SFG rickettsiae, Babesia spp., TBEV, Anaplasma phagocytophilum, and Francisella tularensis 43,60-63. Spotted fever group rickettsiae, mainly R. raoultii, exhibit the highest prevalence in D. reticulatus. In western Poland, they were detected in 38.3% of specimens collected from vegetation 43 and in 60% of ticks removed from dogs 63. In the endemic regions in eastern and northern Poland, the percentage of host seeking D. reticulatus infected with these bacteria ranged from 34.18% to 56.7% 60-62. A high prevalence of R. raoultii and host seeking D. reticulatus specimens was also recorded in Poland’s western and southern neighboring countries. The mean rates of infection with this bacterium were 64% -70.5% in Germany 10,64 and 47.9% in the Czech Republic and Slovakia 65. Depending on the habitat, TBE viruses causing tick-borne encephalitis in humans were detected in 0.33%-10.8% of D. reticulatus specimens from the tick population in eastern Poland 42,62,66 67. The presence of TBE viruses in this tick species was reported from the district of northern Saxony near the Polish border 68.
The greatest threat to the health of dogs attacked by ticks is associated with the transmission of Babesia protozoa. In Poland, the prevalence of B. canis in ornate dog ticks is usually in the range of 1–4%, depending on the region 61,62. However, it can reach even 21.3% in swampy habitats in eastern Poland 69. The incidence of clinical babesiosis in the Polish population of dogs is higher in eastern and central Poland (Eastern tick population) than in western Poland (new endemic region for the ornate dog tick) and in the tick-free area 3.