Search

Extensive spread of tick-borne diseases poses a significant problem for public health and the health of the population living in endemic areas.The aim of the study was to search, analyze genetic material and identify new viral agents of the Phenuiviridae family in taiga ticks collected in Asian regions of Russia using the method of high throughput sequencing.Materials and methods. The study involved 1460 taiga ticks collected in suburban areas of the Tomsk, Yekaterinburg and Primorsky Territory. The genetic material isolated from ticks was sequenced using Illumina technology followed by phylogenetic analysis.Results and discussion. Analysis of the sequencing results made it possible to detect extended nucleotide sequences of the L-gene fragment characteristic of the Phenuiviridae family viruses. We were able to identify 20 nucleotide sequences the length of 250 bp on average in homogenates of Ixodes persulcatus ticks. Eighteen isolates have been identified as members of the genus Uukuvirus and two isolates have been assigned to the genus Phlebovirus, Phenuiviridae family. Phylogenetic analysis has shown that all isolates of the genus Uukuvirus fall under the cluster of Tacheng tick virus 2 belonging to the species Tacheng uukuvirus. They form a separate phylogenetic group which is closely related to two Romanian variants of 2019. Tacheng tick virus 2 was detected in all three surveyed regions of the Asian part of Russia. Two Tomsk isolates of phlebovirus were classified as Sara tick phlebovirus and they clustered with two isolates of phleboviruses from Karelia. Thus, the genetic material of Tacheng tick virus 2 and Sara tick phlebovirus belonging to two genera of the family Phenuiviridae was found in I. persulcatus ticks collected in three geographically different regions of the Asian part of Russia.

A comparison of the efficacy of permethrin- and cypermethrin-based textile against taiga ticks (Ixodes persulcatus) was carried out in a tick-borne viral encephalitis hotspot in the Irkutsk Region (Russia) using model samples of impregnated textiles. We demonstrated that permethrin- and cypermethrin-treated model samples have similar protective parameters in terms of maximum height reached by the tick when climbing up the treated textile (20.9–38.7 cm for cypermethrin, 27.6–39.3 cm for permethrin, depending on concentration) and knockdown time (i.e., the time until a female tick falls off the treated textile; 3.52–4.31 min for cypermethrin, 5.02–8.25 min for permethrin, depending on concentration). In contrast, when evaluating the 'biting speed' index (which is the ratio of the average attaching time of ticks contacting untreated textiles and ticks contacting treated textiles), it has been shown that permethrin-treated textiles accelerate biting. So, using permethrin-treated protective clothing against the taiga tick could be risky because it increases the likelihood of being bitten and thus getting infected. In contrast, cypermethrin-treated textiles appear to block the ability of ticks to attack warm-blooded animals and humans – after contact with cypermethrin-treated textiles none of the ticks attached to a rabbit. So cypermethrin-based textiles could be an alternative to permethrin for tick-bite protection clothing production if there is no toxic effect on humans of textile materials based on it. [ABSTRACT FROM AUTHOR]

A critical analysis of the concept of a "thermal constant of development" in acarology is presented. Thermal constants were calculated based on the range of environmental conditions in the optimal distribution areas. The obtained constants of egg development and metamorphosis of larvae and nymphs are given for the taiga tick Ixodes persulcatus Sch., 1930 and the European forest tick I. ricinus L., 1758. The significance of these parameters for analyzing the distribution patterns and ecology of these tick species is discussed. [ABSTRACT FROM AUTHOR]

This paper examines the relationship between climate warming and processes occurring in communities and populations of terrestrial small mammals, reptiles, amphibians, and arthropods. The studies have been conducted at Mirnoe Yenisei Ecological Station, Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences. The dynamics of climatic changes is determined based on meteorological data collected at seven weather stations located along an almost 1000-km stretch of the Yenisei River valley. The maximum increase in temperature over the period from 1972 to 2020 is registered in the spring months; the farther north the station is located, the stronger these changes are manifested. In the 21st century, the cyclic type of small mammal population dynamics previously observed in the study area is replaced by the fluctuating dynamics type. The abundance of small mammals in the 21st century is lower than it was in the 20th century. Statistically significant decreases in population are noted mostly for species of Siberian origin. New species have been registered in the vicinity of the Yenisei ecological station for the first time. The bank vole (Clethrionomys glareolus) and the taiga tick (Ixodes persulcatus) have appeared on the right bank of the Yenisei River; the common toad (Bufo bufo) has appeared on both river banks. [ABSTRACT FROM AUTHOR]

The presented analytical literature review makes it possible to compare the adaptive capabilities of two closely related species of ixodid ticks, Ixodes persulcatus and I. ricinus, the main hosts and vectors of the most common and epidemically significant obligate, transmissible, natural focal infections in Eurasia—ixodic tick-borne borreliosis and tick-borne encephalitis. Studies on the influence of climatic factors on the number and distribution of these ticks and the formation of their fundamental ecological niches, which determine the establishment of the boundaries of their modern ranges, have been considered. The specific adaptive features of I. persulcatus and I. ricinus, their implementation in different geographic conditions (realized ecological niches), and the prerequisites for the formation and change of the sympatric area have been characterized. It is concluded that the variety of ecosystems that ticks of the compared species can inhabit limits the possibility of obtaining, at certain times, a thermal constant of development, i.e., the sum of effective temperatures necessary for egg development and the metamorphoses of larvae and nymphs. [ABSTRACT FROM AUTHOR]

Abstract Background The common tick Ixodes ricinus and the taiga tick I. persulcatus are the main tick vectors of Borrelia spirochaetes, TBE virus (TBEV) and of several other zoonotic pathogens in the western and eastern areas, respectively of the Palaearctic region. Recently, populations of the taiga tick were, for the first time, detected in northern Sweden. This prompted us to investigate if they harbour human pathogens. Methods A total of 276 I. persulcatus ticks (136 males, 126 females and 14 nymphs) and one I. ricinus nymph was collected by the cloth-dragging method in northern Sweden in July–August 2015 and May–July 2016. In addition, 8 males and 10 females of I. persulcatus were collected from two dogs (16 and 2 ticks, respectively) in two of the localities. All ticks were microscopically and molecularly identified to developmental stage and species and screened for B. burgdorferi (sensu lato), B. miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Babesia spp. and TBEV using real-time PCR followed by species identification by sequencing the PCR-products of conventional PCR assays. Results Of the ticks collected by the cloth-dragging method, 55% (152/277) were positive for Borrelia. There was no significant difference between the proportions of Borrelia-infected nymphs (33%, 5/15) and Borrelia-infected adult ticks (56%, 147/262), and no significant difference between the proportions of Borrelia-infected males (54%, 74/136) and Borrelia-infected females (58%, 73/126). Three different Borrelia species were identified. Borrelia afzelii was the predominant species and detected in 46% of all Borrelia-infected ticks followed by B. garinii, 35%, B. valaisiana, 1%, and mixed infections of different Borrelia species, 1%; 17% of all Borrelia-infections were untypeable. One I. persulcatus female contained Rickettsia helvetica, and one nymph contained Rickettsia sp. Of the 277 ticks analysed, all were negative for A. phagocytophilum, Babesia spp., Borrelia miyamotoi, N. mikurensis and TBEV. The ticks collected from the two dogs were negative for all pathogens examined except for Borrelia spp., that was detected in 5 out of 16 ticks removed from one of the dogs. Conclusions To our knowledge, this is the first time that I. persulcatus from Sweden has been analysed for the presence of tick-borne pathogens. The examined tick populations had a low diversity of tick-borne pathogens but a high prevalence of B. burgdorferi (s.l.).

Abstract The taiga tick, Ixodes persulcatus, has previously been limited to eastern Europe and northern Asia, but recently its range has expanded to Finland and northern Sweden. The species is of medical importance, as it, along with a string of other pathogens, may carry the Siberian and Far Eastern subtypes of tick-borne encephalitis virus. These subtypes appear to cause more severe disease, with higher fatality rates than the central European subtype. Until recently, the meadow tick, Dermacentor reticulatus, has been absent from Scandinavia, but has now been detected in Denmark, Norway and Sweden. Dermacentor reticulatus carries, along with other pathogens, Babesia canis and Rickettsia raoultii. Babesia canis causes severe and often fatal canine babesiosis, and R. raoultii may cause disease in humans. We collected 600 tick nymphs from each of 50 randomly selected sites in Denmark, southern Norway and south-eastern Sweden in August–September 2016. We tested pools of 10 nymphs in a Fluidigm real time PCR chip to screen for I. persulcatus and D. reticulatus, as well as tick-borne pathogens. Of all the 30,000 nymphs tested, none were I. persulcatus or D. reticulatus. Our results suggest that I. persulcatus is still limited to the northern parts of Sweden, and have not expanded into southern parts of Scandinavia. According to literature reports and supported by our screening results, D. reticulatus may yet only be an occasional guest in Scandinavia without established populations.

The paper presents an analytical review of the literature on the influence of abiotic factors on the Borrelia and virus inextricably linked with the life cycles of Ixodes persulcatus and I. ricinus ticks. They are the causative agents of the most common and epidemiologically significant of Eurasian, obligate, transmissive, natural focal infections–Lyme disease and tick-borne encephalitis. It is concluded that these microorganisms are generally well adapted to the gradient of the variability of temperature, humidity and other environmental conditions that are important for the reproduction of all phases of carrier development in the body, as well as for their vertical and horizontal transmission. The circulation of Borrelia and tick-borne encephalitis virus, as well as other obligate-transmissible pathogens, is under the control of environmental factors that act through carriers. [ABSTRACT FROM AUTHOR]

Aim. Evaluate the degree of epidemic risk of emergence of tick-borne encephalitis (TBE) and ixodes ticks’ borreliosis (ITB) in municipalities (MPs) of Irkutsk region with various natural-climate conditions. Materials and methods. Morbidity was compared for TBE and ITB during 2001 - 2015 in MPs of Irkutsk region located to the north or south of the 55th parallel, i.e. in the conditions of different severity of sharply continental climate. 5-year average data were analyzed. Results. ITB morbidity was 2 - 3 times higher than TBE for all the 5-year periods in the north of the region, whereas in the south -differences were not present. Moreover, in MPs located to the north of the 55th parallel in 2001 - 2015 a decrease of TBE and ITB morbidity did not occur, as in the south of the region. Conclusion. The lack of population morbidity reduction by TBE and ITB in the north and prevalence of the latter nosoform requires enhancement of a complex of prophylaxis measures in these MPs with an accent in development of non-specific means, including acaricidic treatment, enhancement of operations of centers of express diagnostics of transmissible infections, familiarizing of the population with the use of protective suits during periods of high activity of ticks.

The current research is aimed at studying the changes in a ratio of symmetrical to asymmetrical forms based on the counting bilateral characters in Ixodes persulcatus samples in various living conditions. Phenotypic variation was described with the following indices: (of) for a dispersion of the number of bristles at the left and right side; (Sa) for actual and (St) for theoretical number of symmetrical specimens with the supposition of an independent manifestation of such characters at the both sides of a body; and the difference between Sa and St. 4 bilateral characters were studied on the coxae of the fourth leg of the ticks collected by dragging off the plants outside Irkutsk (299 specimens) and Bratsk (156 specimens). The both territories are characterized by an excess of Sa and St. The σd2 value was proved to be higher among the ticks outside Bratsk where they live in a difficult environment. Given that no differences were revealed in the average values of «Sa-St» index, being characteristic of a subdivision of samples, the observed difference in of values may be considered as a prove of an increased instability during ontogeny under adverse circumstances.

Microbiological monitoring of the six districts of the Krasnoyarsk Territory was conducted in order to prove the existence of natural foci of human granulocytic anaplasmosis (HGA) and monocytic ehrlichiosis (HME) on its territory. Two-round PCR method was used for the detection of Anaplasma and Ehrlichia DNA. 374 samples from mites were analyzed with two-round PCR for the presence of Anaplasma and Ehrlichia DNA: 341 specimens of Ixodes persulcatus and 33 specimens of Haemaphysalis concinna. Ticks were collected from vegetation on the flag in the 6 districts of the Krasnoyarsk Territory: Yeniseisky, Achynsky, Sharypovsky, Ilansky, Minusinsky and Ermakovsky, belonging to different climate zones and have landscaped, geo-botanical and faunal features. The study showed that 5.6 % of taiga ticks infected with E. muris, 2,1 % with A. phagocytophilum. In 0.3 % of carriers we identified mixtinfected E. muris and A. phagocytophilum. These data indicate presence of HGA and HME foci in the central, western and southern parts of the Krasnoyarsk Territory.

Performed was analysis of long-term dynamics of tick-borne encephalitis (TBE) morbidity, the taiga ticks abundance, number of bites to which urban residents had been subjected, imago virus carriage. All these indices were shown to change in a cyclic manner. Worsening of TBE epidemiological situation was prognosticated in Siberia for the period of 2009-2010. Plans of preventive measures, optimally combining both specific and non-specific ones, should be elaborated for the areas with the highest risk of TBE infection for humans, taking into consideration increased epidemiological danger of the region, presence of mixed infections in ticks, social structure of the population.

Background: The tick species Ixodes ricinus and I. persulcatus are of exceptional medical importance in the western and eastern parts, respectively, of the Palaearctic region. In Russia and Finland the range of I. persulcatus has recently increased. In Finland the first records of I. persulcatus are from 2004. The apparent expansion of its range in Finland prompted us to investigate if I. persulcatus also occurs in Sweden. Methods: Dog owners and hunters in the coastal areas of northern Sweden provided information about localities where ticks could be present. In May-August 2015 we used the cloth-dragging method in 36 localities potentially harbouring ticks in the Bothnian Bay area, province Norrbotten (NB) of northern Sweden. Further to the south in the provinces Västerbotten (VB) and Uppland (UP) eight localities were similarly investigated. Results: Ixodes persulcatus was detected in 9 of 36 field localities in the Bothnian Bay area. Nymphs, adult males and adult females (n = 46 ticks) of I. persulcatus were present mainly in Alnus incana - Sorbus aucuparia - Picea abies - Pinus sylvestris vegetation communities on islands in the Bothnian Bay. Some of these I. persulcatus populations seem to be the most northerly populations so far recorded of this species. Dog owners asserted that their dogs became tick-infested on these islands for the first time 7-8 years ago. Moose (Alces alces), hares (Lepus timidus), domestic dogs (Canis lupus familiaris) and ground-feeding birds are the most likely carriers dispersing I. persulcatus in this area. All ticks (n = 124) from the more southern provinces of VB and UP were identified as I. ricinus. Conclusions: The geographical range of the taiga tick has recently expanded into northern Sweden. Increased information about prophylactic, anti-tick measures should be directed to people living in or visiting the coastal areas and islands of the Baltic Bay. [ABSTRACT FROM AUTHOR]

Investigation of the spatial-temporal variability of characteristics with alternative variation in females of taiga tick from three district of the Irkutsk Region showed all samplings to be phenotypically heterogenous. Based on these results estimated was L.A.Zhivotovsky criterion of identity between separate imago collections. Similarity index for geographically remote populations was about 0.9. This index was higher in intrapopulational groups collected from one territory in different seasons. The elucidated variability creates the basis for selection of morphologic tags of vector transmitting capacity and ticks life cycle duration and other questions of their biology investigation which includes usage of collection materials accumulated previously.