Checklist of the hard tick (Acari: Ixodidae) fauna of Hungary with emphasis on host-associations and the emergence of Rhipicephalus sanguineus

Hungary is situated in the southern part of Central Europe, next to the northern boundary of the Mediterranean region. This geographical position may allow the northward expansion of Mediterranean ixodid tick species into Hungary, particularly in the era of warming climate. During the past 14 years numerous surveys have been published on the species and activity of hard ticks occurring in the country. However, it was 60 years ago that the last comprehensive review of ixodid ticks of Hungary was published, and only in Hungarian language. The purpose of the present checklist is to provide a comprehensive and complete overview of the ixodid fauna of Hungary, based on tick reports published so far in Hungarian or English, also including hitherto unpublished data. Altogether 27 hard tick species were identified in Hungary, of which 21 can be regarded as indigenous. Most importantly, the autochthonous occurrence of Rhipicephalus sanguineus sensu lato was not known prior to 2005, but during the last 14 years increasing numbers of cases have been reported, attesting the emergence of this tick species in Hungary. Whereas R. sanguineus sensu lato was always associated with dogs and cats in Hungary, other tick species show differences in host associations according to habitat type, seasonal activity and questing height. Changes in the distribution, abundance and seasonality of a few tick species were also noted.


Introduction
Hungary has a continental climate and is situated in the southern part of Central Europe, next to the northern boundary of the Mediterranean region. This geographical position may allow the northward expansion of Mediterranean tick species into Hungary, since there are no continuous mountain ranges bordering the country from the south. Recently, this scenario has become more likely than ever, as a consequence of the warming climate. This may affect Hungary, among the other consequences, with the emergence of thermophilic tick species, because in Europe the increase of annual mean temperature will probably exceed the global warming rate in the 21st century (Bartholy et al. 2007).
This was one of the reasons why increasing importance was attributed to monitoring tick activity along the southern border of Hungary (Hornok and Farkas 2009) and in the context of bird and bat migration (e.g. Hornok et al. 2016a, b). Parallel with this, groundbound host species were also regularly sampled for ticks (e.g. Földvári and Farkas 2005a;Rigó et al. 2011;Földvári et al. 2011;Hornok et al. 2012a). These surveys resulted in an upsurge of publications between 2005 and 2019 on tick species occurring in the country. However, it was as long as 60 years ago that the last comprehensive review of ixodid ticks of Hungary was published, and only in Hungarian language (Janisch 1959). After that, as part of Fauna Hungariae, an identification guide was compiled (Babos 1965). Although it was also published in German language (Babos 1964), several species in that book were later synonymized with other species.
In light of the above, this concise review is built around three issues: (1) past data (from 1959-1973) on ticks hitherto published in Hungarian, (2) recent data (from 2005-2019) published in English and (3) new, not yet published data. This implies that a significant part of the data summarized here has not been available for the international community.
Considering the whole of Central Europe, comprehensive data are only available from a few countries (as exemplified by Germany: Petney et al. 2012), but are lacking from several countries neighboring Hungary. Therefore, data presented in this review may be highly relevant to a broader geographical region than only to Hungary and should be taken into account when assessing risks of tick-borne diseases or inadvertent transportation of ticks together with their host. This international relevance is further enhanced by focusing on host spectra of tick species.

Sources of unpublished data
Previously unpublished data were included here from the following studies.

Data presentation
To maintain the concise nature and user friendliness of this list, we do not mention broader, Palearctic distribution, general ecology and vector role of tick species found in Hungary. This information is available in recently published sources (e.g. Estrada-Peña et al. 2017). Earliest data (e.g. Kotlán 1921) were not used, because of missing or vague information on the exact localities. For the great majority of records (historical: Figs. 1-2, more recent:  1959-1973(Janisch 1959, 1973Molnár 1982). Ixodes ricinus was reported to be ubiquitous, without geographical data (Janisch 1959), therefore not shown  1959-1973(Janisch 1959, 1973Molnár 1982). Pictograms: = tick species usually associated with carnivores and hedgehogs; = tick species most frequently associated with rodents; = tick species associated with bats; = ornithophilic tick species  Hornok and Farkas 2009, but also including locations from references cited in the main text). Ixodes ricinus was found at all collection sites in Hornok and Farkas (2009), therefore not shown separately 1 3 Figs. 3-4) only geographical names of villages, cities, mountains are available, therefore coordinates are not used in the dataset (but can be retrieved from www.googl e.com/ maps according to the name of locality). On the maps of tick distribution based on collections from hosts (Figs. 2,4), locations are only shown according to region (i.e., without separation of places within 50 km distance from each other) for those tick species, which are associated with potentially migrating or at least mobile wild animal species. The latter include birds, bats and carnivores, which, unlike domestic animals, are not confined in their locality, therefore the exact place of the origin of their tick infestation is unknown.
Tick species names are used sensu Guglielmone et al. (2014), and valid names for synonyms (mentioned in Babos 1965) according to Camicas et al. (1998). Latin names of host species are listed in alphabetical order within taxonomic units. Host group or species name (whichever relevant) is followed by tick developmental stages (L: larva, N: nymph, A: adult, T: all three stages) if this information was available. Taking into account the multiplicity of identical genus name initials among listed host species, only consequent, identical genus names are abbreviated. Locations of historical data  are marked with asterisk (*) in the text.

Ixodid tick species indigenous (completing their life cycle) in Hungary
Ixodes ricinus (L.) Hosts  Distribution: Countrywide. Ecology: In forested habitats, up to altitudes of 900-1000 m a.s.l.; year-round, but biphasic (higher spring and lower autumn) activity, peaking in May; larvae and nymphs typically on lizards, ground feeding birds, rodents; adults on hedgehogs and larger mammals.

Ixodes vespertilionis Koch
Hosts Ecology: Pholeophilous (caves); active in all seasons, with peak numbers in the spring.

Ixodes simplex Neumann
Hosts Ecology: Typically on ground feeding birds, predominantly in (early) spring (data unavailable on seasonality of local, questing ticks).
Ecology: Pholeophilous, in tree holes or nesting boxes (regional seasonality unknown due to low availability).
Ecology: Nymphs arrive during spring (northward) bird migration; may molt to adult stage by autumn (adults on horse in November).
Ecology: Nymphs arrive during spring (northward) bird migration; may molt to adult stage by autumn (adults on cattle in September).
Ecology: Imported with a pet animal for sale. Reference: Hornok and Farkas (2005).

Discussion
Since more than half a century (Janisch 1959;Babos 1965), this is the first updated, complete list of ixodid tick species occurring in Hungary. Taken together, 27 hard tick species have been recorded in the country, of which 21 can be regarded as indigenous (i.e., completing their life cycle in Hungary) with either sporadic or regular occurrence. Considering tick species that have long been indigenous in Hungary, there seems to be no major difference in comparison with neighboring countries or other parts of Central Europe (Estrada-Peña et al. 2017). However, in the category of tick species imported into Hungary by migratory birds, to the best of our knowledge, I. festai, I. persulcatus and Hy. rufipes have not been reported in neighboring countries (Contini et al. 2011;Krčmar 2012;Mihalca et al. 2012;Estrada-Peña et al. 2017). Among tick species imported with the transportation of their host, this is the first identification of Ha. erinacei in Hungary, with the Libyan striped weasel (Ictonyx libycus) as a new host record. In addition, A. dissimile has only been reported on exotic reptiles in western Europe (cf. Mihalca 2015), therefore Hungary is the only Central European country, where this neotropical tick species was found.
Most importantly, several new foci of R. sanguineus are reported here for the first time in Hungary. In contrast to the non-indigenous status of this species (Janisch and Szabó 1961) and its previously anticipated (Babos 1965) and observed introductions (Hornok and Farkas 2005), these independent cases illustrate the growing importance and likely establishment of R. sanguineus in Hungary. This is especially true for places where multiple 1 3 infestations of dogs were noted (all in southern-central Hungary: Mohács, Szekszárd, Paks), implying at least temporary populations. Confirming this possibility, tick-borne pathogens transmitted by this species have already been detected in southern Hungary (e.g. Ehrlichia canis and Rickettsia massiliae: Hornok et al. 2013b).
Similarly, cases of autochthonous infestation (i.e., of non-avian hosts) suggest that Hy. marginatum and Hy. rufipes are able to molt to the adult stage under climatic conditions in Hungary. In addition, it is noteworthy that both cases of adult Hyalomma specimens (on horse and cattle) were observed in southwestern Hungary, which has the highest mean winter temperatures in the country. Therefore, the possibility of overwintering of Hyalomma species (as a prerequisite of population establishment) in Hungary cannot be excluded. In support of this, the geographical range of Hy. rufipes is limited to areas with up to 120 days of frost annually (Hoogstraal 1956).
Considering Hyalomma rufipes, it is hard to verify if Hy. impressum mentioned from imported livestock in Hungary (Babos 1965), is the same species or not, due to insufficient morphological characterization to distinguish it from Hy. impressum sensu stricto (especially because Babos mentioned the authority as Koch, who described in the same year, 1844, both Hy. rufipes and Hy. impressum as separate species). The same stands for Hy. aegyptium aegyptium, lacking detailed morphological description (Kotlán 1921). Therefore, identification of Hy. rufipes in 2012 is considered as the first (bona fide) finding of this species in the country (Hornok and Horváth 2012), and due to its uncertainty Hy. impressum was omitted from the list of species.
In comparison with neighboring countries, where comprehensive information is available on the tick fauna (i.e., Croatia : Krčmar 2012;and Romania: Mihalca et al. 2012), the most notable difference is that in these two countries (situated south or southeast from Hungary, respectively) several thermophilic Rhipicephalus and Hyalomma species have long been indigenous. The above new data on the autochthonous occurrence of Rh. sanguineus and Hyalomma species in Hungary indicate the emergence (growing significance) of these species and suggest a shift towards a more thermophilic tick fauna.
Over the past decades, shifts were also noted in the distribution and abundance of certain tick species. Most remarkably, D. marginatus had been widespread in western Hungary (Janisch 1959), but according to our data it has receded from this region (Hornok and Farkas 2009). By contrast, D. reticulatus gradually emerged in western Hungary (first in two foci: Janisch 1959, then in a few further foci: Rehácek et al. 1979, Molnár 1982, Janisch 1986, and eventually it became widespread in both western and eastern parts of the country (Hornok and Farkas 2009). Similarly, based on the past rarity of I. frontalis (Janisch 1959) and Ha. inermis (Babos 1965), more recent data attest their emerging character in the country (Hornok and Farkas 2009;Hornok et al. 2016a).
Regarding the host preference data of ixodid tick species in Hungary, this is interrelated with the ecological traits (habitat preference and seasonal activity) of tick species, as shown above. First of all, the nidiculous nature of rodent-associated tick species and of larvae/nymphs of Dermacentor species, as well as the pholeophilous character of I. canisuga, I. kaiseri, I. hexagonus and some ornithophilic tick species (I. arboricola, I. lividus) precludes their collection from the vegetation (with dragging-flagging), therefore these have been exclusively collected from host animals (Hornok et al. 2013b(Hornok et al. , 2016a(Hornok et al. , 2017a. On the other hand, for non-nidiculous tick species (all stages of Ixodes ricinus and Haemaphysalis species, adults of Dermacentor species), the local habitat type will define 1 3 their occurrence on the vegetation, and this will entail consequences on their host associations, as reflected by the above data. In particular, sheep as grazing animals are more likely accessed by open country ticks (e.g. Dermacentor species: Hornok et al. 2007), as contrasted to goats which browse leaves, thus tend to be more exposed to forest-associated ticks (e.g. Ixodes species) (Hornok et al. 2012a). Similarly, it has been observed in Hungary that adult Dermacentor ticks predominate over I. ricinus on cattle grazing pastures, whereas this is equilibrated on wild ruminants occurring in both open country and forested habitats (Hornok and Horváth 2012).
The questing height may also be significantly different between sympatric tick species. For instance, I. ricinus larvae and nymphs appear to have reptiles, ground feeding birds and rodents as primary hosts (Földvári et al. 2009;Rigó et al. 2011;Hornok et al. 2016a). This is in contrast to Ha. concinna larvae and nymphs, which are usually associated with birds feeding above the ground level and roe deer (Hornok et al. 2012a(Hornok et al. , 2016a. Unlike in case of I. ricinus (with only larvae and nymphs infesting birds) in case of ornithophilic tick species adults were also collected from avian hosts, as exemplified by I. frontalis, I. festai, I. lividus and I. arboricola (Janisch 1959;Hornok et al. 2016a). In Hungary, rodents typically do not harbor I. ricinus adults ) which quest higher on the vegetation compared to larvae and nymphs, whereas hedgehogs and larger mammals can become infested with all three stages Hornok et al. 2012a) because these vertebrates get into contact with both the lower and somewhat higher vegetation. Apart from questing height, other host derived factors may also influence the host preference of tick developmental stages, because apparently both D. marginatus and D. reticulatus nymphs may feed on non-pet dogs (Hornok et al. 2013b), but typically only adults of D. reticulatus (but not of D. marginatus) on pet dogs (Földvári and Farkas 2005a).
Concerning humans as hosts of ixodid ticks, four species were involved in such cases in Hungary, namely I. ricinus, D. marginatus, D. reticulatus and Ha. inermis (Janisch and Szabó 1961;Janisch 1973;Földvári et al. 2013). Taking into account the range of preferred hosts (Fig. 5), apart from the most generalist species, I. ricinus, tick species only rarely connect wild animals and humans. On the contrary, all ixodid species which typically infest domestic animals, may also frequently infest humans. Interestingly, while it is estimated that in a worldwide context 27% of prostriate and 45% of metastriate ticks may use humans as hosts (Guglielmone and Robbins 2018), in Hungary the overall ratio of hitherto reported Palearctic tick species potentially infecting humans is 80.8% (21 of 26).
Last, but not least seasonal activity will also influence the occurrence of ticks and thus infestation of their hosts. The peak activity depends on weather variables and, as observed in Hungary, extreme temperature fluctuations (i.e., sharply rising temperatures during late winter) may trigger 1-2 month earlier questing peaks of those tick species, which have early to middle spring activity (Hornok 2009). In addition, data of this review reflect that the migratory habit of bird species (implying early or late spring arrival in Hungary) is interrelated with their tick infestation. In particular, short and middle-distance migratory birds (e.g. the Robin, Erithacus rubecula) arrive early spring, thus they most likely carry I. ricinus and I. frontalis larvae and nymphs; whereas long-distance migrant avian hosts (e.g. warblers, Locustella luscinioides and Acrocephalus species) return to Hungary late spring or early summer, and consequently will become infested most likely with Ha. concinna larvae and nymphs from the local tick fauna (Hornok et al. 2016a).

Fig. 5
Ixodid tick species identified so far in Hungary, which are Palearctic or known to molt in the country. All species are shown next to their preferred hosts (outer circle), connected to humans (in the center) with bluish green or yellow arrow according to their frequent or rare blood-sucking on humans, respectively, as reported (Guglielmone and Robbins 2018). Palearctic tick species, which have been imported but are non-indigenous in Hungary, are marked with asterisk (*). Autochthonous, but sporadic occurrence is indicated with a small circle (°) next to the species name. The names of emerging tick species (i.e., which were shown to increase in abundance or have only been identified in the past 15 years) are written in red color