МОДЕЛЮВАННЯ ЧИСЕЛЬНОСТІ ГРИЗУНІВ У ЛІСОВИХ БІОТОПАХ ЗАХІДНОГО ПОДІЛЛЯ (НА ПРИКЛАДІ MYODES GLAREOLUS)

Monitoring and predicting the dynamics of abundance of species living in natural habitats is an important component stability analysis of ecosystem as well as dynamics and direction of change of biotic communities under global climate change and pressure of the alien species. The aim of the work was to build a matrix model and study the state of stabilisation of the dynamics of the bank vole population within the Leslie model. The object of the study was the population dynamics of Myodes glareolus Schreber, 1780 = Clethrionomys glareolus auct. The study is based on materials obtained during 2017–2019. This period covered one phase of the long-term population dynamics of the bank vole, named “population growth”. The research was carried out according to generally accepted methods. A total of 6400 trap-days were processed, and 358 forest fistulas were collected and studied. The intensity of harmful activity of rodents is due to the variability of the number of animals in the population. The quantitative population changes are the result of three factors: births, deaths, and migrations. The main condition for the existence of the species is the stability of the population, which is determined by the action of thecompensatory mechanisms. The growth phase of the bank vole lasted all three years of the research, the quantitative indicators were respectively: 2017 – 1.8 individuals per 100 trap-days; 2018 – 2.0 individuals per 100 trap-days; 2019 – 2.7 individuals per 100 trap-days. Low levels of the abundance in the spring of each year of the study, namely at the beginning of the breeding season (3.7 – 2.6 – 8.9 individuals per 100 trap-days). Favourable for the abundance growth was the sex ratio of the population (approximately 1:1), with some rise in the share of females, which decreases on the period of spring 2018 to autumn 2019). Some decrease in the share of immature individuals (4.5 – 3.9 – 3.1 %) is an indirect confirmation of the stability of puberty of animals with subsequent replenishment of the "stock", which led to accelerated reproduction and, consequently, provided prerequisites for further population growth. The causal mechanisms of population control established by us, without a doubt, can serve as a basis for further prognosis, of the number of pests in natural habitats. To predict population changes, the Leslie model, which is widely used in mathematical analyses of the abundance of both plant and animal groups, was chosen. The algorithm for building a matrix model, detailed in the article, has five following steps. The exponential nature of the actual and projected growth of the bank vole population during the five-year cycle (2017–2019 with a prognosis until 2023) revealed in the analysis can be explained not so much by the power of the species' reproductive potential as by the lack of the significant changes in habitat, caused by constant weather conditions, low individual mortality from predators and non-communicable diseases or other accidents. The application of the matrix model allowed to confirm the key role of the main compensatory mechanisms of population dynamics, as they contribute to the stabilisation of the population and, as a consequence, are an important condition for the existence of the species.

Experimental Mycobacterium microti Infection in Bank Voles (Myodes glareolus)

Voles are maintenance hosts of Mycobacterium microti. In line with the goal to eradicate tuberculosis (TB) in livestock, the role of this mycobacteria needs to be assessed since it might interfere with current M. bovis/M. caprae surveillance strategies. To better understand the pathogenesis of TB in voles, an experimental infection model was set up to reproduce M. microti infection in laboratory Bank voles (Myodes glareolus). Two infection routes (intragastric and intraperitoneal) and doses (105 and 106 CFU/0.1 mL) were assessed. Voles were culled at different post-infection time points. Serology, histopathology, acid-fast bacilli staining, qPCR, and mycobacterial culture from tissues were performed. In addition, qPCR from feces and oral swabs were conducted to assess bacterial shedding. The model allowed us to faithfully reproduce the disease phenotype described in free-ranging voles and characterize the pathogenesis of the infection. Most animals showed multifocal and diffuse granulomatous lesions in the liver and spleen, respectively. Less frequently, granulomas were observed in lungs, lymph nodes, muscles, and salivary gland. Mycobacterial DNA was detected in feces from a few animals but not in oral swabs. However, one contact uninfected vole seroconverted and showed incipient TB compatible lesions, suggesting horizontal transmission between voles.

Chronic Background Radiation Correlates With Sperm Swimming Endurance in Bank Voles From Chernobyl

Sperm quantity and quality are key features explaining intra- and interspecific variation in male reproductive success. Spermatogenesis is sensitive to ionizing radiation and laboratory studies investigating acute effects of ionizing radiation have indeed found negative effects of radiation on sperm quantity and quality. In nature, levels of natural background radiation vary dramatically, and chronic effects of low-level background radiation exposure on spermatogenesis are poorly understood. The Chernobyl region offers a unique research opportunity for investigating effects of chronic low-level ionizing radiation on reproductive properties of wild organisms. We captured male bank voles (Myodes glareolus) from 24 locations in the Chernobyl exclusion zone in 2011 and 2015 and collected information on sperm morphology and kinetics. The dataset is limited in size and there overall was a relatively weak correlation between background radiation and sperm quality. Still, some correlations are worth discussing. First, mid-piece segments of spermatozoa tended to be smaller in bank vole males from areas with elevated background radiation levels. Second, we demonstrated a significant positive relationship between background radiation dose rates and the proportion of static spermatozoa among males within and among study locations after 10 as well as 60 min of incubation. Our results provide novel evidence of damaging effects of low dose ionizing radiation on sperm performance in wild rodent populations, and highlight that this topic requires further study across the natural gradients of background radiation that exist in nature.

Identification of hepatozon spp. In the population of target rods of the Chernobyl radiation and ecological biosphere reserve

The ecosystems that have developed in the exclusion zone after the accident at the Chernobyl nuclear power plant in 1986 have a number of features. Parasites, as part of an ecosystem, can act as indicators of the processes taking place in it. Mouse rodents play an important role in the preservation and transmission of pathogens of some, including zoonotic, diseases in the wild. Therefore, the study of parasites in murine rodents, especially those transmitted transmissively, makes it possible to understand the characteristics of the distribution and the level of threat of their transmission to other susceptible animals, including agricultural, small domestic animals and humans. We carried out a study of blood smears taken from murine rodents for the presence of pathogens of transmissible parasitic diseases. According to the results of the studies, the pathogen Hepatozoon spp. Was detected for the first time in Ukraine. in the population of murine rodents. Creating an exclusion zone is one of the most obvious and long-lasting consequences of the Chernobyl Nuclear Power Plant (CNPS) accident. Because of 90-95% of this territory lacks systematic human activity and regime equal to the reserve. Ecosystems formed in the exclusion zone are affected a number of key factors as radioactive contamination, succession, wills and climate change. Spatial heterogeneity of density, radionuclide composition and physical chemical forms of precipitation are a characteristic feature of radioactive pollution in the Chernobyl Zone. Much of the aquatic and terrestrial ecosystems in the Chernobyl Zone as of 1986 was an artificial or semi-artificial systems that were under the regulatory control of man. The removal of regulatory control has led to the inclusion of natural influences mechanisms. That is, a significant part of ecosystems is in a state far from equilibrium, where the processes of succession are active. The testamentary effect is the result of a radical economic contraction activities and the creation of a strict security regime. Given this dynamics ecosystems in the Exclusion Zone has a unique character. Parasites are part of the ecosystem, so they can act as indicators of the processes occurring in it. Mouse-like rodents play an important role in the preservation of agents some infectious diseases in the wild. It is known that rodents are reservoirs hosts at least 60 zoonotic diseases, playing an important role in their transmission and distribution. Not the last role in it is played by features biology and way of life of these animals. Study of parasites in murine rodents, especially those that transmitted transmissively, will make it possible to understand the peculiarities of distribution and the level of threat of their transmission to other susceptible animals, including agricultural, small pets and humans. The object of our study was blood smears taken from murine rodents: Apodemus agrarius, Apodemus flavicollis, Myodes glareolus and Apodemus spp. Catching mice for further sampling conducted at 3 three landfills. Mouse-like rodents are significantly affected by pathogens of infectious diseases, including those transmitted through blood-sucking arthropods. Therefore, the study of the presence and prevalence of transmissible agents in murine rodents is important in order to prevent the disease in other species of animals or humans. The purpose of the study was to study the role of rodents Chornobyl Excusion Zone as a reservoir of blood-borne diseases. The study was conducted during 2020-2021. Blood smears from rodents Apodemus agrarius, Apodemus flavicollis, Myodes glareolus and Apodemus spp, which were selected during the expedition from three landfills and transferred to the Department of Pharmacology, Parasitology and Tropical Veterinary Medicine of NULES of Ukraine, where they conducted further research. Blood smears were stained by the method of Romanowski-Gimza, Leuko-Diff and examined under an immersion microscope system. A total of 117 blood smears were collected from 117 murine rodents from three landfills. According to the results of microscopic examination in blood smears revealed parasites, which morphologically we attributed to Hepatozoon spp. This agent was detected in Ukraine for the first time. Agents had an oval body shape with a large nucleus and were located in the cytoplasm of leukocytes (mostly neutrophils, rarely lymphocytes). In total, hepatozoan agents were detected in blood smears from 13 studied animals, which was 11.11%. And the invasion of Hepatozoon spp. was found in murine rodents of the first landfill, in 7 rodents. The smallest of the murine rodents of the second landfill was found only in blood smears from 2 animals. In addition to hepatozoons in murine rodents, we also found agents of other diseases, such as Babesia spp., Rickettsia spp., Borrelia spp. and Trypanosoma spp.

Sex and age differences in skull size in Myodes glareolus from Slovakia

The results of a craniometric analysis of the bank vole (Myodes glareolus) were evaluated in this study. Twenty cranial variables were measured and evaluated on 149 skulls (78 males, 71 females) with respect to sex and age. The main aim of this study was to test the sexual dimorphism in skull size. Overall, our results showed that on average, the values for adult and subadult females of M. glareolus were higher than for males. Results presented here thus reveal sexual differences in the measured cranial traits, most expressed for the length of the mandible and the height of the mandible. The effect size was very large for the length of the first upper molar. Comparison of our results with those from other countries confirmed that there are regional differences. These findings highlight the need for craniometric analysis of species also at the regional level.

Host in reserve: the role of common shrews (Sorex araneus) as a stable supplementary source of tick hosts in small mammal communities influenced by rodent population cycles

In recent decades, warming temperatures and changes in land use are supposed to have enabled several tick species to expand their distribution limit northwards. The progression of ticks to new areas may introduce new and emerging tick-borne pathogens as well as increase existing diseases. Aside from climatic conditions, ticks are dependent on hosts for survival, and rodents often act as important hosts for ticks and as pathogen reservoirs. At northern latitudes, rodents often undergo multi-annual population cycles, and the periodic absence of hosts may inhibit the further progression of ticks. We investigated the potential role of common shrews (Sorex araneus) to serve as a stable host source to immature life stages of a generalist tick Ixodes ricinus and a specialist tick I. trianguliceps, during decreasing abundances of bank voles (Myodes glareolus). We tested whether ticks would have a propensity to parasitize a certain host type dependent on host population size and composition in two high latitude locations in southern Norway, by comparing tick burdens on trapped animals. We found that I. ricinus larvae showed an equal propensity to parasitize both host types as the host population composition changed, but voles had a higher level of parasitism by nymphs (p< 0.004). An overall larger host population size favored the parasitism of voles by larvae (p= 0.027), but not by nymphs (p= 0.074). I. trianguliceps larvae showed a higher propensity to parasitize shrews, regardless of host population size or composition (p= 0.004), while nymphs parasitized shrews more as vole abundance increased (p= 0.002). The results indicate that common shrews may have the potential to act as a replacement host during periods of low rodent availability, but long-term observations encompassing complete rodent cycles may determine whether shrews are able to maintain tick range expansion despite low rodent availability.

Biomolecular Investigation of Bartonella spp. in Wild Rodents of Two Swiss Regions

Rodents represent a natural reservoir of several Bartonella species, including zoonotic ones. In this study, small wild rodents, collected from two sites in rural areas of Switzerland, were screened for Bartonella spp. using molecular detection methods. In brief, 346 rodents were trapped in two rural sites in the Gantrisch Nature Park of Switzerland (Plasselb, canton of Fribourg, and Riggisberg, canton of Bern). Pools of DNA originating from three animals were tested through a qPCR screening and an end-point PCR, amplifying the 16S-23S rRNA gene intergenic transcribed spacer region and citrate synthase (gltA) loci, respectively. Subsequently, DNA was extracted from spleen samples belonging to single animals of gltA positive pools, and gltA and RNA polymerase subunit beta (rpoB) were detected by end-point PCR. Based on PCR results and sequencing, the prevalence of infection with Bartonella spp. in captured rodents, was 21.10% (73/346): 31.78% in Apodemus sp. (41/129), 10.47% in Arvicola scherman (9/86), 17.05% in Myodes glareolus (22/129), and 50% in Microtus agrestis (1/2). A significant association was observed between Bartonella spp. infection and rodent species (p < 0.01) and between trapping regions and positivity to Bartonella spp. infection (p < 0.001). Similarly, prevalence of Bartonella DNA was higher (p < 0.001) in rodents trapped in woodland areas (66/257, 25.68%) compared to those captured in open fields (9/89, 10.11%). Sequencing and phylogenetic analysis demonstrated that the extracted Bartonella DNA belonged mainly to B. taylorii and also to Candidatus “Bartonella rudakovii”, B. grahamii, B. doshiae, and B. birtlesii. In conclusion, the present study could rise public health issues regarding Bartonella infection in rodents in Switzerland.

Puumala Virus Variants Circulating in Forests of Ardennes, France: Ten Years of Genetic Evolution

In Europe, Puumala virus (PUUV) transmitted by the bank vole (Myodes glareolus) is the causative agent of nephropathia epidemica (NE), a mild form of haemorrhagic fever with renal syndrome. In France, very little is known about the spatial and temporal variability of the virus circulating within bank vole populations. The present study involved monitoring of bank vole population dynamics and PUUV microdiversity over a ten-year period (2000–2009) in two forests of the Ardennes region: Elan and Croix-Scaille. Ardennes region is characterised by different environmental conditions associated with different NE epidemiology. Bank vole density and population parameters were estimated using the capture/marking/recapture method, and blood samples were collected to monitor the overall seroprevalence of PUUV in rodent populations. Phylogenetic analyses of fifty-five sequences were performed to illustrate the genetic diversity of PUUV variants between forests. The pattern of the two forests differed clearly. In the Elan forest, the rodent survival was higher, and this limited turn-over resulted in a lower seroprevalence and diversity of PUUV sequences than in the Croix-Scaille forest. Uncovering the links between host dynamics and virus microevolution is improving our understanding of PUUV distribution in rodents and the NE risk.

The Invasive Bank Vole (Myodes glareolus): A Model System for Studying Parasites and Ecoimmunology during a Biological Invasion

The primary driver of the observed increase in emerging infectious diseases (EIDs) has been identified as human interaction with wildlife and this increase has emphasized knowledge gaps in wildlife pathogens dynamics. Wild rodent models have proven excellent for studying changes in parasite communities and have been a particular focus of eco-immunological research. Helminth species have been shown to be one of the factors regulating rodent abundance and indirectly affect disease burden through trade-offs between immune pathways. The Myodes glareolus invasion in Ireland is a unique model system to explore the invasion dynamics of helminth species. Studies of the invasive population of M. glareolus in Ireland have revealed a verifiable introduction point and its steady spread. Helminths studies of this invasion have identified enemy release, spillover, spillback and dilution taking place. Longitudinal studies have the potential to demonstrate the interplay between helminth parasite dynamics and both immune adaptation and coinfecting microparasites as M. glareolus become established across Ireland. Using the M. glareolus invasion as a model system and other similar wildlife systems, we can begin to fill the large gap in our knowledge surrounding the area of wildlife pathogen dynamics.