Ixodes ricinus (Linnaeus, 1758)

Acarus ricinus Linnaeus, 1758: 616.

Ixodes reduvius (Linnaeus): Neumann 1911: 12.

Ixodes sanguisugus (Linnaeus): Morel and Pérez 1978: 201.

Ixodes vulgaris (Fabricius): Neumann 1911: 12.

Ixodes holsatus (Fabricius): Nuttall and Warburton 1911: 285.

Ixodes megathyreus Leach: Neumann 1911: 12.

Ixodes bipunctatus Risso: Neumann 1911: 12.

Ixodes trabeatus Audouin: Neumann 1911: 12.

Ixodes marginalis Hahn: Oudemans 1896: 191.

Ixodes sciuri Koch: Neumann 1911: 12.

Ixodes fuscus Koch: Neumann 1911: 12.

Ixodes sulcatus Koch: Neumann 1911: 12.

Ixodes rufus Koch: Neumann 1901: 249.

Ixodes lacertae Koch: Neumann 1911: 12.

Ixodes pustularum Mégnin: Neumann 1911: 12.

Ixodes vicinus Yerrill: Oudemans 1896: 191.

Ixodes fodiens Murray: Neumann 1904: 444.

Ixodes nigricans Neumann: Schulze 1939: 1.

Ixodes areolaris Olenev: Pomerantsev 1950: 37.

Recorded hosts.

The host spectrum of I. ricinus is extremely broad both systematically and ecologically, including literally almost all mammals and birds of its geographical range, rarely even reptiles inhabiting the same biotopes with the tick. The fact of mass parasitism of immature stages on lizards of the Lacertidae family, in particular species of the genus Darevskia in the Caucasus (Kidov et al. 2013; Orlova et al. 2022) in habitats where they outnumber small mammals probably brightly demonstrates that I. ricinus is a generalist tick capable to use almost any available terrestrial vertebrates as hosts. Overall, the list of hosts consists of more than 300 species of mammals, birds and reptiles which have been recorded (Gern et al. 2002). Humans and domestic animals can also be hosts for the tick (Filippova 1977).

Distribution

(Fig. 16). The distribution of I. ricinus in Russia includes almost the whole territory of its European part excluding subpolar tundra areas (see the map) (Filippova 1977; Kahl and Gray 2023) and due to climate changes, the distribution of this tick species becomes wider (Gray et al. 2009; Yasyukevich et al. 2009). Ixodes ricinus is part of the tick fauna of the following post-Soviet countries: Estonia, Latvia, Lithuania, Belarus, Russia, Ukraine, Moldova, Georgia, Azerbaijan, Armenia, Turkmenistan, and Kazakhstan (Guglielmone et al. 2023). In Kazakhstan a little number of specimens were found in the northern part of West Kazakhstan Oblast (Maikanov 2012). In Turkmenistan the tick was also recorded in few numbers in the western foothills of the Kopet-Dag (Kerbabaev 1960) which probably could be transported there by migratory birds.

Ecology and other information.

Ixodes ricinus is an exophilic tick species widely distributed in Europe, mostly inhabiting deciduous and mixed forest zones in both plain and mountainous areas, as well as forest-steppes bordering them. It also occurs in city parks and gardens (Gray 1998). In addition, it can be found in North Africa (Arthur 1965). In Ukraine I. ricinus colonized and reached a high abundance in artificial forest plantations of the Askania-Nova Nature Reserve surrounded from all sides by steppes for a period of less than 80 years (Emchuk 1972). In urban areas with conditions able to support tick populations, for example, Minsk or Kyiv, I. ricinus usually dominates among other tick species, especially among members of the genus Ixodes (Uspensky 2017). This tick species uses almost all forest vertebrate animals as hosts and, together with I. persulcatus, it is one of the most important vectors of a broad spectrum of tick-borne pathogens, first of all, tick-borne encephalitis virus (Filippova 1977).

Often it can be found in the same biotope with I. persulcatus, often exhibiting complete or partial coincidence of seasonal activity at each ontogenetic stage (Filippova 1999). In zones of sympatry their hybridization can occur, and although hybrid offspring are incapable of reproduction (Bugmyrin et al. 2015), they can still transmit tick-borne encephalitis virus and probably other pathogens (Kovalev et al. 2016; Belova et al. 2023). The absence of any morphological barrier for copulation was discovered in geographical points of probably the secondary sympatric zone (Filippova 2002) of I. persulcatus and I. ricinus in the north-west of the East European Plain (Balashov et al. 1998). However, in some areas of this sympatric zone, for example, in southern Karelia, its slight shrinking has recently been noted due to the withdrawal of I. ricinus from territories where it used to live (Bespyatova and Bugmyrin 2021).

Due to the high epidemiological significance and wide distribution of I. ricinus and its regular contacts with humans and domestic animals, its biology and life cycle were more extensively studied than in case of any other species of its genus inhabiting the same territories. As a species, I. ricinus probably appeared approximately 8–12 thousand years ago when deciduous and mixed forests formed in the southeast of Europe and the Mediterranean, as well as in the northern and northeastern slopes of the Greater Caucasus, when current environmental conditions of these territories have begun to shape. And the climate there was also milder than in Siberian taiga forests where I. persulcatus evolved (Filippova 2017).

It was revealed that in a certain region the duration of tick activity period and the number of adult ticks depend on spring and summer temperatures and air humidity (Korotkov et al. 2015; Korenberg et al. 2021). Females and larvae usually attach to hosts when the air near the soil warms up from + 2 to + 30 ° С, and in the case of nymphs from + 2 to + 22 ° С. The relative humidity of the surrounding air has to be higher than 60 % for an extended period of time (Sirotkin and Korenberg 2018). It is absolutely important for ticks to receive the necessary amount of warmth to complete their metamorphosis at each stage within a strictly defined period of time (Korenberg et al. 2013). As a consequence, the seasonal activity of all stages of I. ricinus is more extended than in the case of I. persulcatus, and engorged ticks begin oviposition or metamorphosis without strict dependance on the photoperiod. Therefore, in the southern range of distribution (the Mediterranean, Central Europe, the Caucasus) ticks initiate activity in the end of March – the beginning of April (Korenberg et al. 2021), whereas in Eastern European regions – in April (Medvedev et al. 2016; Korenberg et al. 2021). Ixodes ricinus also uses a diapause as a biological mechanism, although due to warmer conditions in the majority of its distribution range, no more than 10 – 20 % of ticks at each stage undergo such an interruption of development (Korenberg and Kovalevsky 1977; Korenberg et al. 2016).