Control of Common Vole (Microtus arvalis) in Alfalfa Crops Using Reduced Content of Anticoagulants

The common vole, Microtus arvalis, which is prone to cyclic overpopulation, poses a significant threat to sustainable alfalfa production by either chewing shoots periodically or gnawing and damaging roots permanently. In areas with established vole colonies, the density of alfalfa plants was shown to decrease 55.3–63.4%. Simultaneously, the number of alfalfa shoots decreased by 60.9–71.7%. These experiments were conducted in compliance with an EPPO standard method in alfalfa fields at three geographically remote sites. The experiment tested the efficacy of the most widely used acute rodenticide zinc phosphide (2%), and anticoagulants applied at significantly reduced doses of active ingredients, i.e., bromadiolone (25 ppm) and brodifacoum (25 ppm), as well as a combination of these active ingredients at a low concentration (10 + 10 ppm). Three weeks after treatment, zinc phosphide and brodifacoum achieved the highest average efficacy, at 98.5% and 92.05%, respectively, while the average efficacy of the anticoagulant combination and bromadiolone was 87.2% and 75.5%, respectively. The achieved efficacy of baits based on brodifacoum and the combination of brodifacoum and bromadiolone in controlling common voles indicates their possible utilization in the field. Baits with 25 ppm of brodifacoum and the combination of bromadiolone and brodifacoum (10 + 10 ppm) showed satisfactory results and their introduction could significantly improve pest management programs for rodent control. At the same time, the use of anticoagulant rodenticides with reduced contents of active ingredients would significantly reduce their exposure to non-target animals, especially predators and vultures. By further improving the palatability of tested baits for target rodent species, their efficacy and safety of application would be significantly improved.

Differential temperature effects on photoperiodism in female voles: An explanation for species-specific declines in vole populations

Many mammalian species use photoperiod as a predictive cue to time seasonal reproduction. In addition, metabolic effects on the reproductive axis may also influence seasonal timing, especially in female small, short-lived mammals. To get a better understanding of how annual cycling environmental cues impact reproductive function and plasticity in small, short-lived herbivores with different geographic origins, we investigated the mechanisms underlying integration of temperature in the photoperiodic-axis regulating female reproduction in a Northern vole species (tundra vole, Microtus oeconomus) and in a Southern vole species (common vole, Microtus arvalis). We show that photoperiod and temperature interact to determine appropriate physiological responses; there is species-dependent annual variation in the sensitivity to temperature for reproductive organ development. In common voles, temperature can overrule photoperiodical spring-programmed responses, with reproductive organ mass being higher at 10°C than at 21°C, whereas in autumn they are less sensitive to temperature. These findings are in line with our census data, showing an earlier onset of spring reproduction in cold springs, while reproductive offset in autumn is synchronized to photoperiod. The reproductive organs of tundra voles were relatively insensitive to temperature, whereas hypothalamic gene expression was generally upregulated at 10°C. Thus, both vole species use photoperiod, whereas only common voles use temperature as a cue to control spring reproduction, which indicates species-specific reproductive strategies. Due to global warming, spring reproduction in common voles will be delayed, perhaps resulting in shorter breeding seasons and thus declining populations, as observed throughout Europe.

Cross-Context Responses to Novelty in Rural and Urban Small Mammals

The Anthropocene is the era of urbanization. The accelerating expansion of cities occurs at the expense of natural reservoirs of biodiversity and presents animals with challenges for which their evolutionary past might not have prepared them. Cognitive and behavioral adjustments to novelty could promote animals’ persistence under these altered conditions. We investigated the structure of, and covariance between, different aspects of responses to novelty in rural and urban small mammals of two non-commensal rodent species. We ran replicated experiments testing responses to three novelty types (object, food, or space) of 47 individual common voles (Microtus arvalis) and 41 individual striped field mice (Apodemus agrarius). We found partial support for the hypothesis that responses to novelty are structured, clustering (i) speed of responses, (ii) intensity of responses, and (iii) responses to food into separate dimensions. Rural and urban small mammals did not differ in most responses to novelty, suggesting that urban habitats do not reduce neophobia in these species. Further studies investigating whether comparable response patters are found throughout different stages of colonization, and along synurbanization processes of different duration, will help illuminate the dynamics of animals’ cognitive adjustments to urban life.

Linking Zoonosis Emergence to Farmland Invasion by Fluctuating Herbivores: Common Vole Populations and Tularemia Outbreaks in NW Spain

The expansion and intensification of agriculture are driving profound changes in ecosystems worldwide, favoring the (re)emergence of many human infectious diseases. Muroid rodents are a key host group for zoonotic infectious pathogens and frequently invade farming environments, promoting disease transmission and spillover. Understanding the role that fluctuating populations of farm dwelling rodents play in the epidemiology of zoonotic diseases is paramount to improve prevention schemes. Here, we review a decade of research on the colonization of farming environments in NW Spain by common voles (Microtus arvalis) and its public health impacts, specifically periodic tularemia outbreaks in humans. The spread of this colonizing rodent was analogous to an invasion process and was putatively triggered by the transformation and irrigation of agricultural habitats that created a novel terrestrial-aquatic interface. This irruptive rodent host is an effective amplifier for the Francisella tularensis bacterium during population outbreaks, and human tularemia episodes are tightly linked in time and space to periodic (cyclic) variations in vole abundance. Beyond the information accumulated to date, several key knowledge gaps about this pathogen-rodent epidemiological link remain unaddressed, namely (i) did colonizing vole introduce or amplified pre-existing F. tularensis? (ii) which features of the “Francisella—Microtus” relationship are crucial for the epidemiology of tularemia? (iii) how virulent and persistent F. tularensis infection is for voles under natural conditions? and (iv) where does the bacterium persist during inter-epizootics? Future research should focus on more integrated, community-based approaches in order to understand the details and dynamics of disease circulation in ecosystems colonized by highly fluctuating hosts.

Spatial and Temporal Dynamics and Molecular Evolution of Tula orthohantavirus in German Vole Populations

Tula orthohantavirus (TULV) is a rodent-borne hantavirus with broad geographical distribution in Europe. Its major reservoir is the common vole (Microtus arvalis), but TULV has also been detected in closely related vole species. Given the large distributional range and high amplitude population dynamics of common voles, this host–pathogen complex presents an ideal system to study the complex mechanisms of pathogen transmission in a wild rodent reservoir. We investigated the dynamics of TULV prevalence and the subsequent potential effects on the molecular evolution of TULV in common voles of the Central evolutionary lineage. Rodents were trapped for three years in four regions of Germany and samples were analyzed for the presence of TULV-reactive antibodies and TULV RNA with subsequent sequence determination. The results show that individual (sex) and population-level factors (abundance) of hosts were significant predictors of local TULV dynamics. At the large geographic scale, different phylogenetic TULV clades and an overall isolation-by-distance pattern in virus sequences were detected, while at the small scale (<4 km) this depended on the study area. In combination with an overall delayed density dependence, our results highlight that frequent, localized bottleneck events for the common vole and TULV do occur and can be offset by local recolonization dynamics.

Close species of rodent superfamily Muroidei in the fauna of Ukraine: taxonomy, biogeography, diagnostics, and ecomorphology

The results of the revision of the species composition and related knowledge of taxonomy, biogeography, diagnostics, variability and ecomorphology of polytypic groups of murine rodents, superfamily Muroidei, are presented. These are 5 former "large" species: "wood mice", "common mice", water voles, "shrub voles" and "common voles". Each of these groups is represented in the fauna of Ukraine and neighboring countries by 2–3 species. The two most difficult for revision and for background monitoring of fauna are "forest mice" and "common voles", each of which is represented in the fauna of the region by three morphologically very similar species of different kinship, among which one (the most genetically distant) is widely sympatric to the other two species that are allospecies. Among "forest mice", such species are Sylvaemus uralensis (= microps) against the pair S. sylvaticus + S. witherbyi (= S. falzfeini), and among the "common voles" it is Microtus levis (= rossiaemeridionalis) against the pair M. arvalis + M. obscurus. The other three pairs of species are generally more diverged (at least in terms of habitats and ecology, and in some cases morphology) and clearly less sympatric species. In the group of "common" mice, Mus "musculus" (s.l.), there is a pair of synanthropic and exanthropic forms — M. musculus and M. spicilegus (= M. sergii), which usually do not interact in nature, and therefore poorly diverged in morphology. In the group of "water voles" there is an allopatric pair, represented by the Carpathian-Roztochchian (essentially mountainous, associated with meadows) as well as plain hydrophilic forms, Arvicola scherman and A. amphibius (= A. terrestris). In the group of "shrub voles" there is a sympatric pair of species, one of them has limited distribution in the Carpathians (Terricola tatricus), but the other (T. subterraneus), being sympatric to the first in the Carpathians, also forms numbered populations in lowland forests, as in the forest zone as in the bairak steppe zone. Morphological differentiation between them is generally high, but the Eastern Carpathian form of Terricola tatricus is the smallest in a row of mountain forms of Terricola (multiplex, tatricus, zykovi), which was the reason for its long-term non-recognition in the fauna of Ukraine. For all species, descriptions are presented, including 5 standard parts for this series of publications: general remarks, taxonomy (including nomenclature), distribution (including biotopes), diagnostics (including variability), ecomorphology.Key words: small mammals, habitats, dominance, abundance of species.

Helminth fauna of Microtus cf. arvalis (Rodentia, Cricetidae) in Russia and adjacent countries

Kirillova NYu, Kirillov AA, Ruchin AB, Trukhachev MV. 2020. Helminth fauna of Microtus cf. arvalis (Rodentia, Cricetidae) in Russia and adjacent countries. Biodiversitas 21: 1961-1979. The helminth fauna of voles of the Microtus cf. arvalis group is reviewed focusing on the Russian fauna and that of adjacent territories. In total, 61 helminth species have been recorded in these rodents: Trematoda-14, Cestoda-21, Nematoda-25, Acanthocephala-1. The diversity of the helminth community of the common vole is due to the wide species range and abundance of this rodent. M. arvalis is the final host for most of the parasites recorded from this host species. Only 10 cestodes and trematodes species use common voles as intermediate and paratenic hosts. The core of this voles’ helminth fauna is formed by common species that parasitize many different rodent species. The helminth fauna of the common vole has been most intensively studied in Russia, where 45 species of parasitic worms have been recorded in rodents. The similarity of the helminth fauna of the common vole from different study regions is determined by both the geographical proximity of the research areas and the broad distribution of most of the M. cf. arvalis helminth species.

In Vivo Characterization of a Bank Vole-Derived Cowpox Virus Isolate in Natural Hosts and the Rat Model

Cowpox virus (CPXV) belongs to the genus Orthopoxvirus in the Poxviridae family and is endemic in western Eurasia. Based on seroprevalence studies in different voles from continental Europe and UK, voles are suspected to be the major reservoir host. Recently, a CPXV was isolated from a bank vole (Myodes glareolus) in Germany that showed a high genetic similarity to another isolate originating from a Cotton-top tamarin (Saguinus oedipus). Here we characterize this first bank vole-derived CPXV isolate in comparison to the related tamarin-derived isolate. Both isolates grouped genetically within the provisionally called CPXV-like 3 clade. Previous phylogenetic analysis indicated that CPXV is polyphyletic and CPXV-like 3 clade represents probably a different species if categorized by the rules used for other orthopoxviruses. Experimental infection studies with bank voles, common voles (Microtus arvalis) and Wistar rats showed very clear differences. The bank vole isolate was avirulent in both common voles and Wistar rats with seroconversion seen only in the rats. In contrast, inoculated bank voles exhibited viral shedding and seroconversion for both tested CPXV isolates. In addition, bank voles infected with the tamarin-derived isolate experienced a marked weight loss. Our findings allow for the conclusion that CPXV isolates might differ in their replication capacity in different vole species and rats depending on their original host. Moreover, the results indicate host-specific differences concerning CPXV-specific virulence. Further experiments are needed to identify individual virulence and host factors involved in the susceptibility and outcome of CPXV-infections in the different reservoir hosts.