Changes in the ranges of pasture ixodid ticks of the genus Ixodes Latr., 1795 (Parasitiformes, Ixodidae) in West Siberia

The distribution pattern of two tick species, Ixodes persulcatus and Ixodes pavlovskyi, in the plain part of West Siberia is analyzed. The exact northern range boundary of I. persulcatus in the Khanty-Mansi Autonomous Area is determined based on long-term data on the population density of adult and immature ticks (1960–2011). The shift of the southern boundary of the species range in West Siberia as related to anthropogenic transformation (reforestation measures, reduced or stopped sanitary forest cutting, road construction, etc.) is demonstrated. The specific traits of distribution of the taiga tick I. persulcatus in some localities of Southwest Siberia are analyzed. The modern state of the tick population in the areas co-inhabited by the two species is characterized. The possible reasons of changes in the structure of tick communities toward complete prevalence of I. pavlovskyi in recreational zones of Novosibirsk and Tomsk are discussed. The most significant changes in the distribution pattern of these two tick species in West Siberia seem to have occurred after 1990. During this period, the local stable populations of the taiga tick to the south of its main range in West Siberia (within Omsk and Novosibirsk provinces) were formed, the pattern of its distribution on the right bank of the Ob River (Novosibirsk Province) and in the Tom River valley (Tomsk Province) changed, whereas I. pavlovskyi became the dominant species.     

Significance of ixodid tick (Parasitiformes,Ixodidae) population structure for maintenance of natural foci of infection

Basic postulates of the theory of natural focality of infections are considered in terms of modern ecological parasitology using the example of Ixodes ricinus and I. persulcatus ticks, the main vectors of tickborne encephalitis and borrelioses in Eurasia. Consideration is given to data on the population structure of ticks, their distribution in ecosystems, abundance, mortality at different stages of the life cycle, seasonal dynamics of activity, occurrence on different vertebrate species, relationships with potential hosts, and connections agents of infections. Due to long individual life span and development of one generation over 3–6 years, tick vector provide not only for transmission of pathogens, but also for their long-term storage and amplification. Several alternative routes of tick infection of ticks provide for pathogen exchange between individuals at different phases of development within one generation and between feeding ticks of different generations.     

Experience in the absolute calculation of pasture ixodid ticks (Parasitiformes, Ixodidae) on the eastern macroslopes of Sikhoté-Alin]

A new technique is suggested for absolute registration of adult ixodid ticks with an improved furrow plough. Due to this the number of ticks can be estimated per square unit to various biotopes. As a result of registrations conducted in 1973 the density of ticks populations from the main landscape zones of eastern Sikhote-Alin (from watershed spruce-abietic forests to coastal oak woods) was estimated for the first time.     

Long-term dynamics of density and diversity of ticks (Ixodidae) on the natural and disturbed territories

As result of long-years monitoring of density and diversity of Ixodidae living on Tomsk territory and in suburbs it has been shown that at least two species of ticks (I. persulcatus and I. pavlovskyi) inhabit there simultaneously. It has been studied that percent of I. pavlovskyi increased nearby town buildings. In the natural biotopes I. persulcatus is dominated, while I. pavlovskyi is founded rare. It has been shown, that during last 15 years (since 1996 till 2010) density of ticks increase on the town suburbs. The combination of ecological and chemical methods of tick suppression on the limited territory may leads to significant decreasing of ticks density. There is one biotope only, where non-typical for this region species (Dermacentor reticulatus and Haemaphysalis concinna).     

New species of ixodid ticks (Ixodidae) for the fauna of Armenia

Two species of ixodids , Ixodes arboricola Schulze et Schlottke and I. frontalis ( Panzer ), new for the fauna of Armenia are given. Larvae and nymphs of these ticks were found on birds in the forest zone and gardens.     

Birds as hosts of ixodid ticks (Acarina,Ixodidae)

rophic relations between ixodid ticks of the world fauna parasitizing as adults on birds are analyzed. These ticks include 60 out of 650 species of the family Ixodidae and belong to the genera Ixodes, Haemaphysalis, and Amblyomma. Relations between birds and ticks of the genus Ixodes are most ancient. Colonial marine birds seem to be the first hosts of ixodid ticks in the class of birds. Trophic specialization of ticks is not associated with bird taxa, because in most cases no tick specificity is caused by either phylogenetic features of hosts, or specific environmental conditions.     

The intraspecific taxonomic structure and identification of closely related species of ixodid ticks (Ixodidae)

Two variants of intraspecific morphological differentiation of 7 palearctic species of Ixodidae and respectively two variants of their intraspecific taxonomic pattern have been revealed on the basis of the study of geographic variation of each species. Three species--Ixodes pavlovskyi Pom., 1946, Haemaphysalis erinacei Pavesi, 1884, Hyalomma asiaticum Sch. et Schl., 1929, are subdivided into subspecies, and four ones--I. ricinus (L., 1758), I. persulcatus Sch., 1930, I. crenulatus Koch, 1844, Dermacentor marginatus (Sulzer, 1776),--into morphotypes by the degree of distinction of the whole complex of active stages in ontogenesis. Acknowledging the conventional character of the categories of subspecies and morphotype their criteria have been formulated for ixodid ticks. Paleogeographic and ecological grounds are given. Some data of geographic variation of immature stages favour the identification of closely related species in concrete localities.     

Detection of the West Nile Virus and its genetic typing in ixodid ticks (Parasitiformes: Ixodidae) in Tomsk City and its suburbs

Four tick species, Ixodes persulcatus, I. pavlovskyi, I. trianguliceps, and Dermacentor reticulatus, were found in Tomsk and its suburbs in 2006. The species I. pavlovskyi was found to be dominant in the localities situated in Tomsk City, and I. persulcatus was dominant in its suburbs. Viral RNA and viral antigen of the West Nile virus (WNV) were detected in the ticks I. pavlovskyi and I. persulcatus collected in the city and its suburbs by the RT PCR method and enzyme immunoassay with monoclonal antibodies against protein E of the WNV. Average rate of the WNV infected ticks varied from 5.2 up to 11.7% in different localities. Identification of the nucleotide sequence of the protein E gene fragment allowed classifying the cDNA obtained as genotype Ia of the WNV. The sequences are proved similar to the strain LEIV-Vlg99-27889-human of the WNV isolated in Volgograd. The obtained data showed that natural foci of the WNV virus can appear in the city and its suburbs probably involving two dominant tick species. The WNV infected imagoes, larvae, and nymphs of I. persulcatus and I. pavlovskyi were collected from small mammals, lizards, and birds. Therefore we presume that these hosts can be involved in the circulation and distribution of WNV on the territory of Tomsk Region.     

Sites of attachment and density assessment of ixodid ticks (Acari: Ixodidae) on impala (Aepyceros melampus)

During 1994 and 1995, 45 impala ewes, Aepyceros melampus were examined at Letaba Ranch in the Northern Province. Tick counts were made from 15 animals on three occasions, in July, October and February. The objective was to determine whether the total body tick counts can be estimated from counts done on specific, selected sampling sites on the skin. Twelve sites were shaved within ten predilection sites and the parasite numbers counted from these samples. These counts were compared to the total body parasite count as determined by the scrub and digestion techniques. More than 80% of all the ticks were present on the muzzle, the head, the pinna and the legs. Larger numbers of ticks were collected in October than in July or February. Two mathematical models were tested for the tick counts. The first model was made up of tick counts from a single shaved sampling site, the pinna. The correlation between the tick counts on the pinna and the total tick counts was highly significant (p values ranging between 0.0208 and 0.0001). The second model was developed based on tick counts from four regions, namely the head, the pinna and the front and hind feet. A less significant correlation was obtained between the number of ticks counted on the four sites and the total tick count.     

Characteristic features of biodiversity in European ixodid ticks (Acari, Ixodidae) as vectors of diseses with natural foci

The diapason of some biodiversity characteristics of ixodid ticks of the fauna of Europe and adjacent territories is analyzed. These characteristics include taxonomic and morphological diversity, the diversity of life cycles, host-parasite relations, species ranges, and biotopic associations. The significance of different aspects of biodiversity of ixodid ticks as a prerequisite of interrelations with pathogens with natural foci is estimated.     

Sexual transmission of the tick-borne encephalitis virus in ixodid ticks (Ixodidae)

Sexual transmission of tick-borne encephalitis virus from infected ixodid males to noninfected females is shown: in Ixodes persulcatus in 50% (6 of 12) and in Hyalomma anatolicum in 6.2% (1 of 16). The sexual transmission of tick-borne encephalitis virus is shown to provide a transmissible transfer of the virus into eggs in ixodid ticks. Electron microscope studies of the sexual system of ixodid males infected with the virus have revealed numerous morphologically mature virus particles in lumens of endoplasmic reticulum, in vacuoles of Golgi complex of spermatocytes and in association with tubular elements of spermatids.     

Evolution of the basic types of life cycle in ixodid ticks (Ixodidae)

The burrow-nest life scheme of ixodid ticks, which was formed at the beginning of the Chalk, gave rise to the subsequent types of parasitism: pasture (end of the Chalk), pasture-burrow (end of Paleogene) and pasture-stall one (late Neogene). Changes in the climate in different geological epochs and regions together with the hosts' evolution, natural selection in the aggregate of variability and heredity of ixodids in their populations were the cause of the evolution.     

Ability of successful attack in two species of ixodid ticks (Acari: Ixodidae) as a manifestation of their aggressiveness

Patterns of attacking hosts by two closely related species of ixodid ticks (Ixodes persulcatus and I. ricinus) were compared in parallel field tests. The ability of active unfed adults of both sexes to adhere to a flannel flag dragged over grass vegetation and to remain on the flag during this process were estimated. The tests were conducted under two temperature conditions, 6–10°C and 17–22°C. In all test versions, adults of I. persulcatus were more successful both in adhering to the flag and in remaining on it. There were no consistent differences between males and females of the same species. The results demonstrated a differing ability of successful attack in both tick species. This ability is a complex derivative of the tick activity and aggressiveness. An attempt is made to analyse the latter phenomenon, which is considered as a general one for all bloodsucking arthropods. The aggressiveness of arthropods should be taken into account as one of the leading factors influencing the sampling results.     

History of the species range of ixodid ticks,vectors of pathogens with natural nidality (Acari,Ixodidae), as a prerequisite of their intraspecific biodiversity

Morphological, taxonomic, and some ecological aspects of intraspecific biodiversity of five ixodid species transmitting pathogens with natural nidality, with extensive ranges of different types are examined. Causal relations of ixodid intraspecific biodiversity with the origin of the species ranges are considered.     

Characteristic features of the ranks genus and subgenus, and an intercalary rank "species complex" in ixodid ticks (Acari: Ixodidae)

The work was carries our from the standpoint of the morphological conception of species. Vast collections of the Zoological Institute of the Russian Academy of Science testify to the existence of hiatuses in both genera and subgenera of Palearctic ixodids at all active phases of their ontogenesis. The fact that the subgenera of Palearctic genera have been well studies is notes, and composition of the subgenera is presented. The question of a taxonomic intercalary rank "species complex" is considered in detail in the context of the coevolution between some complexes of closely related species of ixodid ticks and some closely related species (genospecies, strains) of pathogens. The question of the taxonomic rank "species complex" in ixodid ticks as a phyletic species association is postulated on the basis of comparative ontogenetic data. Nomenclature status of the intercalary association "species complex" is specified in conformity with the fourth edition of the International Code of Zoological Nomenclature. Species composition of most studied complexes is presented. Some variants of morphological differentiation between species complexes within subgenus are considered. Significance of the taxonomic concept "species complex" for zoological. parasitological, and medical aspects of the ixodid ticks study was evaluated. Prognostic significance of the rank "species complex" for the study of the relationships between ixodid ticks and pathogens is discussed.     

Exoskeletal Anomalies in Ixodes pavlovskyi pavlovskyi (Parasitiformes,Ixodidae)

Entomological Review - Types of exoskeleton anomalies and frequency of their occurrence were described in 437 females and 366 males of Ixodes pavlovskyi pavlovskyi Pomerantsev 1946, collected by...     

Morpho-functional changes in the midgut of ixodid ticks (Acari: Ixodidae) during the life cycle

Morpho-functional studies performed in five species of the genus Ixodes, including I. pacificus, I. pavlovskyi, I. persulcatus, I. ricinus, and I. scapularis demonstrated that the replacement of the midgut epithelium lags in each consecutive life stage and is not synchronized with basic processes of morphogenesis and organogenesis during molts. The midgut epithelium of each preceding stage is retained and functions during feeding of the subsequent life stage.     

Ixodid ticks (Parasitiformes: Ixodidae) from small mammals in reforesting boreal habitats of the northern European Russia

Abundance of 2 ixodid tick species, Ixodes (Exopalpiger) trianguliceps Birula, 1895 and Ixodes (Ixodes) persulcatus Schulze, 1930 was studied during 6 years, in 1998–2001 and 2003–2004, at a research station in Gomselga Village (central Karelia, Kondopoga District, 62°04′N, 33°55′E). New data on host species composition and ixodid tick abundance were obtained from 4 forest plots at different stages of reforestation (secondary succession) following felling that occurred 7–14, 12–19, 25–32, and 80–87 years ago. Individuals of I. persulcatus predominated and constituted 73% of the total ticks collected. The occurrence rates of different developmental stages were shown to fluctuate in the course of reforestation both in I. trianguliceps (larvae, 2.8–5.3; nymphs, 1.5–2.2; adults, 0–0.09) and in I. persulcatus (larvae, 4.3–10.6; nymphs, 0.6–4.2).