Distribution of the ticks <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> and <Emphasis Type="Italic">Ixodes pavlovskyi</Emphasis> on the boundary of the forest and forest-steppe zones in the Ob region

Surveys of ixodoid ticks were performed in Novosibirsk Province (Novosibirsk and Toguchin Districts) and in the vicinity of Akademgorodok (Novosibirsk) in 2009–2010. The abundance and distribution of ticks were assessed in 8 types of habitats. Ixodes persulcatus (Schulze, 1930) was collected by flagging in Novosibirsk and Toguchin Districts, with the highest densities of 19 ind./km being observed in habitats with small-leaved trees. Three species of ticks: Ixodes persulcatus, I. pavlovskyi (subspecies I. pavlovskyi occidentalis Filip. et Pan., 1998), and Dermacentor reticulatus (Fabricius, 1794) were recorded in a recreational forest of Akademgorodok. A high abundance (22 ind./km) of I. pavlovskyi was observed in pine forests subjected to considerable recreational load. The abundance of I. persulcatus was the highest in aspen-birch and birch-aspen forests. D. reticulatus was captured in pine forests and fallow lands, its abundance varying from 0.2 to 2 ind./km.     

Multistage mechanism of reproductive sympatric isolation of the closely-related species, Ixodes persulcatus and I. Pavloskyi (Ixodidae)

The closely related species Ixodes persulcatus and I. pavlovskyi are vectors of agents tick-born encephalitis and Lyme disease. These species have two great disjunctive sympatric distribution areas (fig. 1), where both species inhabit the same biotopes, and during the same season. In these conditions there are prerequisites of contacts of opposite sexes of the different species during ambushing the hosts on vegetation. Sequence of "switching on" of the morphological, physiological, and hostparasite factors of reproductive isolation has been established. The features and the range of manifestation of these factors at different combinations of sexes and species of the partners have been revealed. The studied factors, such as precopulative and postcopulative components of the mechanism of reproductive isolation of I. persulcatus and I. pavlovskyi were considered. A hypothesis for sympatric origin of the species as a result of specialization the adults of I. persulcatus to mammals, and I. pavlovskyi to birds is proposed.     

Morphological barrier in mechanisms of reproductive isolation acting in areas of sympatry of closely related species Ixodes persulcatus-I.pavlovskyi and I. persulcatus-I. ricinus (Ixodidae)

A morphometric analysis of different male and female organs used in the process of copulation, including an attachment of the spermatophore to the genital opening of female and placing the spermatophore into the vestibular part of vagina, was carried out for the pairs of ixodid tick species Ixodes persulcatus--I. pavlovskyi and I. persulcatus--I. ricinus in areas of their sympatry. In two disjunctive areas of sympatry of I. persulcatus--I. pavlovskyi (South-East Altai and Southern Primorye), the morphological barrier is displayed in the precopulation mechanism of reproductive isolation and does act only in the pair I. pavlovskyi female--I. persulcatus male. It is proved by the reliable prevalence of the hypostome diameter (in widest part) of I. persulcatus male over the genital opening length of I. pavlovkyi female. Because of this reason, the copulation between these partners cannot take place. On the other hand, there are no any morphological obstacles for a copulation within each species examined and in the combination I. persulcatus female--I. pavlovskyi male, and in any combination of the partners I. persulcatus--I. ricinus in sympatry areas (samples from two locations in the north-west of the Eastern-European Plane have been examined). Morphological peculiarities causing differences in host preference of tick species, that in turn realizes the isolation mechanisms between species, are discussed. Postcopulation non-genetic components of the reproductive isolation mechanism have been found in examined species.     

The infection of ixodid ticks collected from humans with the tick-borne encephalitis virus in Tomsk city and its suburbs

The ticks Ixodes persulcatus and I. pavlovskyi collected from people visited gardens and suburban forests have been examined by the IFA methods on the presence of tick-borne encephalitis virus (TEV). It was established, that the most part of ticks collected from humans belongs to I. persulcatus, despite the fact that I. pavlovskyi dominates on the territory of the city and its suburbs. TEV infection was registered more often in fed ticks, in comparison with those without signs of preceding feeding. Infected specimens constituted 9.4% of 53 I. persulcatus individuals examined. In I. pavlovskyi 3.7% of 27 examined specimens were infected. In fed ticks (41 specimens of I. persulcatus and 20 I. pavlovskvi) the rates of infected specimens were higher and constituted 48.8 and 35%, respectively. In suburban forests, as well as in the city, I. persulcatus was found to attack humans more often than I. pavlovskyi. TEV infection was recorded in 12.7% of 220 unfed I. persulcatus specimens examined and in 41.6% of 142 fed individuals. In I. pavlovskyi, 6.6% of unfed and 25% of fed specimens was infected (33 unfed and 24 fed specimens were examined). Thus, in all territories examined, percent of infected specimens was significantly lower in I. pavlovskyi, and in fed ticks of both species, TEV was recorded more often.     

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.     

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).     

The peculiarities of the biology of ticks inhabiting the environs of Tomsk City

The presence of ticks Ixodes persulcatus and I. pavlovskyi occidentalis is revealed in urban parks and the forests directly adjoined to buildings. I. pavlovskyi occidentalis is found to be the dominant species nearby the city. The both species are occurred almost simultaneously, and the peak of their abundance usually falls on 2nd or 3rd ten-day period of May. In the city the ticks species ceased occurring in registers in the end of May, and in the adjacent forests they disappeared in the end of June. I. pavlovskyi occidentalis has not been found in the forests remote from the city at the distance more than 15 kilometers. Besides the above species the ticks Dermacentor reticulatus and Haemaphysalis concinna are occurred rarely in the territory examined.     

Peritrophic matrix in the midgut of tick females of the genus Ixodes (Acari: Ixodidae)

The formation of the peritrophic matrix in the midgut of females of 5 ixodid tick species (Ixodes pacificus, I. pavlovskyi, I. persulcatus, I. ricinus and I. scapularis) was studied by means of light and electron microscopy in different periods of the feeding and after detachment. The formation of the peritrophic matrix started when the first food portions came into the gut lumen, 9-12 hours after the attachment. Renovation of the peritrophic matrix took place during the whole feeding period; every new generation of midgut cells synthesized their own matrix. It was deposited on the apical surface of every midgut cell in the beginning of differentiation, and was functioning during the life of the cell. The peritrophic matrix separates spaces of the cavitary and cytozoic digestions.     

Detection of Babesia spp. DNA in small mammals and ixodic ticks on the territory of north Ural, west Siberia and far east of Russia

Totally, 932 small mammals and 458 questing adult Ixodes persulcatus from Sverdlovsk and Novosibirsk regions and Khabarovsk Territory, as well as 128 Haemaphysalis japonica, 34 H. concinna and 29 Dermacentor silvarum from Khabarovsk Territory were examined for the presence of Babesia by nested PCR based on the 18S rRNA gene. Babesia microti DNA was found in samples of small mammals from all the studied regions--in 36.2% of samples from Sverdlovsk region, 5.3% of samples from Novosibirsk region, and 6.7% of samples from Khabarovsk Territory. The determined B. microti 18S rRNA gene sequences from Novosibirsk region (6 sequences) and from Khabarovsk Territory (10 sequences) were identical to each other and to the sequences of pathogenic for human B. microti US-type, while the determined B. microti 18S rRNA gene sequences from Sverdlovsk region (12 sequences) were identical to those of B. microti strain Munich. B. microti were found most frequently in samples of Myodes spp., they were found also in Microtus spp., Apodemus spp., Sorer spp., and Sicista betulinav. It was shown that one of 347 analyzed I. persulcatus from Novosibirsk region and one of 77 I. persulcatus from Khabarovsk Territory contained B. microti US-type DNA. One I. persulcatus from Novosibirsk region contained B. divergens DNA. In this work B. divergens was for the first time determined in I. persulcatus and B. microti in I. persulcatus in Asian part of Russia. Three different genetic variants of Babesia sensu stricto were found in three H. japonica from Khabarovsk Territory. The first genetic variant was closely related to Babesia sp. revealed in a feral raccoon in Japan (99.9% similarity on the basis of 18S rRNA gene sequences). Two others Babesia genetic variants were most similar to the ovine pathogen Babesia crassa (97.1-97.6% similarity on the basis of 18S rRNA gene sequences).     

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.     

The abundance and distribution of the Ixodes persulcatus (Acari: Ixodidae) near its northern spreading limit in the Ural Mountains

A count of the tick species Ixodes persulcatus Schulze, 1930 was carried out in the "Denezhkin Kamen" Nature Reserve and adjacent territories (the Severoural'sk and Ivdel' Districts of the Sverdlovsk Region, the Northern Urals geographical province) in the 2005. The abundance and distribution of unengorged adults has been evaluated on an area of 22.5 square kilometers (N 60 degrees 27'-60 degrees 30' E 059 degrees 38'-059 degrees 42'). The area includes proportionally main landscape and vegetation elements of the region studied, from mountain analogues of the middle and northern taiga up to tundra. One tick species, I. persulcatus, has been collected by flagging with the abundance from 0.4 up to 6.8 (average 1.6 +/- 0.9) specimens per flag-hour. The observed values of abundance are classified into three classes (I - ticks are absent, II - 1-2 specimens, and III - 3-7 specimens per flag-hour). The class I amounts 20, II - 75, and III - 5% of the area examined. It has been revealed by the expert evaluation of the 2003-2004 and counts of the 2005 that ticks occur stably in the Northern Ural, reaching N 61 degrees and 400 m above sea level. The level of the species abundance remained constant till the middle of summer. In this period the activity of ticks dependent on the weather optimum only.     

The taxonomic aspects of the transmission of the causative agent of Lyme disease

According to world literature data 17 species of ixodid ticks have been studied for natural infection with the Lyme disease agent. Analysis of the data on the level of the infection, transovarial and transphase transmission has shown that main biological vectors of Borrelia burgdorferi are the species of the subgenus Ixodes s. str. - I. ricinus, I. persulcatus (Eurasia), I. dammini, I. pacificus (North America). Potential vectors are I. scapularis, I. dentatus, Amblyomma americanum, Dermacentor variabilis. Single isolations were registered for I. neotomae, Haemaphysalis leporispalustris, D. occidentalis. Nonidentified spirocheta was isolated from A. americanum, D. variabilis, D. parumapertum, Rhipicephalus sanguineus. No agent was isolated from I. cookey, D. albipictus, R. reticulatus, H. concinna. On the basis of comparative and ontogenetic data the species from a group of main vectors: I. ricinus, I. persulcatus, I. pacificus had been attributed by me to the phyletic group persulcatus before Lyme disease was discovered and its causative agent isolated. The question whether I. scapularis belongs to the group persulcatus was also discussed at that time but left open due to somewhat aberrant structure of gnathosoma at preimaginal phases (Filippova, 1969, 1971, 1973). 6 Palaearctic, 2 Indomalayan and 3 Nearctic species were referred to the group persulcatus at the time. I. dammini was described later, in 1979. Gnathosoma of its preimaginal phases has an intermediate structure between I. scapularis and other species of the group persulcatus. Sexually mature phase and nymph of I. dentatus have much in common with Palaearctic members of the group, I. pavlovskyi, I. kazakstani, I. kashmicus. Preimaginal phases of I. scapularis and nymph of I. dentatus were studied by me on the collection material. Thus, it is possible to speak of the belonging of main vectors of B. burgdorferi to a common phyletic group within the subgenus Ixodes s. str. and, therefore, of common origin of ecological medium for the agent. At the same time each species of the vector is an evolutionally developed difference of ecological medium for B. burgdorferi. Roots of the group persulcatus could originate as far as in Paleocene before the land connection between North America and Europe disappeared. Conditions for the existence of recent species, however, appeared considerably later and their flourishing is dated by Pliocene. The main epidemiological role belongs now to I. ricinus, I. persulcatus, I. dammini, I. pacificus.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characteristics of the distribution of Ixodes persulcatus in the forest-park area of Novosibirsk

Only one species of ixodid ticks Ixodes persulcatus occurs in the forest-park zone. Conditions of foliage forests with high grass, where occur hosts of all developmental phases of ticks (elks, hares, rodents, insectivores), are most favourable for I. persulcatus. Preimaginal phases of I. persulcatus feed, in general, on dominant species (common shrew, redbacked and narrow-skulled voles, field mouse and northern birch mouse).     

Ecological and molecular genetic features of <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> and <Emphasis Type="Italic">I. pavlovskyi</Emphasis> ticks in Southern West Siberia

Ixodiae ticks have been counted and sampled in six distant locations within the Altai-Sayan Mountain Area and northern forest steppe in 2012. In total, 1829 individuals of I. persulcatus and 719 of I. pavlovskyi ticks were collected by flagging. I. persulcatus is found in all six examined locations and I. pavlovskyi is found in Western Altai, Northeastern Altai, and Northern Altai, as well as in forest parks near Akademgorodok of Novosibirsk. In total, 16S rRNA and COI sequences have been determined in 144 and 164 I. persulcatus individuals, as well as in 60 and 55 I. pavlovskyi. Selectively equivalent mutant forms are present in I. pavlovskyi populations of Northeastern Altai and Northern Altai. The hydrothermal regime in the forest parks near Novosibirsk is optimal for the I. pavlovskyi ticks. These ticks have recently colonized the forest parks near Novosibirsk and therefore are genetically close to I. pavloskyi from the Altai–Sayan Mountain Area populations.     

Effect of forest fires on the population count and spatial structure of the taiga tick (Ixodidae)

Results of two large-scale surveys of Ixodes persulcatus distribution were compared. Surveys were conducted in a south taiga forest area in the Khabarovsk region two and ten years after a great fire. The direct inhibiting effect of the fire on the population of I. persulcatus was not continuous though apparent. By the moment of pyrogenic small forests formation on slash fires, i.e. during the period not exceeding 2-3 complete developmental cycles of I. persulcatus, the abundance and spatial structure of its population are restored completely.     

Ability of Ixodes persulcatus, Haemaphysalis concinna and Dermacentor silvarum ticks to acquire and transstadially transmit Borrelia garinii

In China, the ability of Ixodes persulcatus, Haemaphysalis concinna and Dermacentor silvarum to transmit Borrelia spirochetes was determined under laboratory conditions. Results showed that all three tick species can acquire spirochetes by feeding on infected mice. However, the capability of the three species to maintain spirochetes was different. Only I. persulcatus is able to maintain spirochetes alive during molting, and subsequent tick stages transmitted the infection to naive mice. In H. concinna and D. silvarum ticks, spirochetes could not survive after the digestion period of blood and after the molting process was finished, spirochetes were no longer detected. Contrary to H. concinna and D. silvarum, I. persulcatus should be considered the principal vector of Lyme disease in north China.     

Detection of two zoonotic Babesia microti lineages, the Hobetsu and U.S. lineages, in two sympatric tick species, ixodes ovatus and Ixodes persulcatus, respectively, in Japan

The species Babesia microti, commonly found in rodents, demonstrates a high degree of genetic diversity. Three lineages, U.S., Kobe, and Hobetsu, are known to have zoonotic potential, but their tick vector(s) in Japan remains to be elucidated. We conducted a field investigation at Nemuro on Hokkaido Island and at Sumoto on Awaji Island, where up to two of the three lineages occur with similar frequencies in reservoirs. By flagging vegetation at these spots and surrounding areas, 4,010 ticks, comprising six species, were collected. A nested PCR that detects the 18S rRNA gene of Babesia species revealed that Ixodes ovatus and I. persulcatus alone were positive. Lineage-specific PCR for rRNA-positive samples demonstrated that I. ovatus and I. persulcatus carried, respectively, the Hobetsu and U.S. parasites. No Kobe-specific DNA was detected. Infected I. ovatus ticks were found at multiple sites, including Nemuro and Sumoto, with minimum infection rates (MIR) of ～12.3%. However, all I. persulcatus ticks collected within the same regions, a total of 535, were negative for the Hobetsu lineage, indicating that I. ovatus, but not I. persulcatus, was the vector for the lineage. At Nemuro, U.S. lineage was detected in 2 of 139 adult I. persulcatus ticks (MIR, 1.4%), for the first time, while 48 of I. ovatus ticks were negative for that lineage. Laboratory experiments confirmed the transmission of Hobetsu and U.S. parasites to hamsters via I. ovatus and I. persulcatus, respectively. Differences in vector capacity shown by MIRs at Nemuro, where the two species were equally likely to acquire either lineage of parasite, may explain the difference in distribution of Hobetsu throughout Japan and U.S. taxa in Nemuro. These findings are of importance in the assessment of the regional risk for babesiosis in humans.     

Demography and population models of ticks of the genus Ixodes with long-term life cycles

The most important parameters necessary for the creation of population models for threehost species with long-term life cycles are discussed with an example of ticks Ixodes persulcatus and I. ricinus. In these species, specimens of the same biological age may belong to different age cohorts and their calendar age may differ by several months or even years. Accurate estimation of the calendar age of separate individuals is dofficult; it is based on the extrapolation by its possible biological age and by belonging to the certain age cohort of a natural population. Population models that can predict simultaneous abundance of activated hungry specimens of all the three developmental stages and probability of host-finding in hyngry ticks during questing period possess the prognostic value. Daily mortality of ticks of different developmental stages and phases of each stage (questing, feeding, preparation for molting, and diapause) must also be known. The abundance of questing hungry ticks in the ecosystem is determined by the balance between recruitment of the population with new individuals, their selection by hosts, dying of ticks from starvation, and consumption of ticks by predators. At present, unfortunately, only some of these parameters are known rather sufficiently.     

Study of the heterogeneity of 16s rRNA gene and groESL operone in the dna samples of Anaplasma phagocytophilum, Ehrlichia muris, and "Candidatus Neoehrlichia mikurensis" determined in the Ixodes persulcatus ticks in the area of Urals, Siberia, and far east of Russia

A total of 3552 Ixodes persulcatus from Sverdlovsk, Chelyabinsk, Novosibirsk, Irkutsk regions and Khabarovsk Territory were examined on the Ehrlichia and Anaplasma presence by nested PCR based on the 16S rRNA gene. Both Anaplasma phagocytophilum and Ehrlichia muris DNA were found in I. persulcatus in all studied regions. A. Phagocytophilum was detected in 1.3-6.3% of ticks and E. muris - in 2.0-14.1% of ticks. Moreover, "Candidatus Neoehrlichia mikurensis" DNA was found in 8 ticks collected in Novosibirsk, Irkutsk Regions and Khabarovsk Territory. Partial nucleotide sequences of 16S rRNA gene and groESL operone (1240-1300 bp) were determined for 65 samples of A. Phagocytophilum, 17 samples of E. muris and 4 samples of "Candidatus Neoehrlichia mikurensis". Nucleotide sequences of 16S rRNA gene and groESL operone of E. muris and "Candidatus Neoehrlichia mikurensis" were shown to be highly conservative, and nucleotide sequences of groESL operone of both E. muris and "Candidatus Neoehrlichia mikurensis" differed from the sequences found previously in other species of Ixodid tick. On the basis of analysis of the 16S rRNA gene and groESL operone sequences it was concluded that all revealed samples A. Phagocytophilum could be divided into 2 groups. GroESL operone sequences of A. Phagocytophilum from the first group were identical to each other but significantly differed from the known groESL operone sequences (less than 98.2% of similarity), whereas their 16S rRNA gene sequences were identical to the sequence of widely distributed and pathogenic for human A. Phagocytophilum genetic variant (CAHU-HGEl, GenBank AF093788) or differed from it by a single nucleotide substitution. The nucleotide sequences of groESL operone of A. Phagocytophilum from the second group differed from each other by 1-4 nucleotides and were closely related (99.2-99.4% of similarity) to the sequences of groESL operone ofA. phagocytophilum isolates found in Europe in Ixodes ricinus and roe deer. The nucleotide sequences of the 16S rRNA gene of A. Phagocytophilum from the second group were most similar to the sequence of the rare A. Phagocytophilum genetic variant previously found only in China (GenBank DQ342324).     

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.