Dania Richter

Rodents, including dormice, are competent reservoir hosts for at least four genospecies of Lyme disease (LD) spirochetes. It remains unknown whether the European forest dormouse (Dryomys nitedula) may serve as reservoir hosts for LD spirochetes. Therefore, we exposed six laboratory-bred forest dormice each experimentally to LD spirochetes of the genospecies Borrelia afzelii, B. spielmanii or B. burgdorferi sensu stricto via tick bite and determined their subsequent infectivity to xenodiagnostic ticks. All forest dormice were susceptible to infection with B. afzelii and infected about 75% of the xenodiagnostic ticks feeding on them for as long as three quarters of a year. These individuals, however, seemed partially refractory to re-infection with the same Borrelia genospecies. The susceptibility of forest dormice to tick-borne B. spielmanii seemed to be limited, because only half of the tick-exposed individuals became infectious and they infected less than 10% of their xenodiagnostic ticks. Nevertheless, they remained fully susceptible to a subsequent infection with B. afzelii. Only one forest dormouse became infectious for xenodiagnostic ticks, after exposure to ticks infected with B. burgdorferi s.s., it infected less than 1% of its ticks. But yet again, these dormice appeared fully susceptible to tick-borne B. afzelii. We conclude that forest dormice were competent reservoir hosts for B. afzelii following their first exposure to these LD spirochetes. However, their reservoir competence seemed limited compared to many other small rodents.

People may be exposed to questing Ixodes ricinus ticks in urban settings, e.g. residential gardens. Little is known about the garden characteristics that support a tick population. To determine which features in and around residential gardens support or limit the occurrence and abundance of questing I. ricinus ticks, we sampled them in residential gardens in the Braunschweig region that differed in various intrinsic and extrinsic parameters. We recorded the number of questing nymphal and adult ticks on transects, and by using mixed-effects generalized linear regression models, we related their occurrence and abundance to garden characteristics, meteorological covariates, and landscape features in the vicinity. We detected questing I. ricinus ticks in about 90% of the 103 surveyed gardens. Our occurrence model (marginal R² = 0.31) predicted the highest probability of questing ticks on transects with hedges or groundcover in gardens, which are located in neighborhoods with large proportions of forest. The abundance of questing ticks was similarly influenced. We conclude that I. ricinus ticks are frequent in residential gardens in Northern Germany and likely associated with intrinsic garden characteristics on a small scale, such as hedges, as well as extrinsic factors on a local scale, such as the proportion of nearby woodland.

The Garden Dormouse (Eliomys quercinus) is an example of an endangered species with a distribution focus in Germany. Little is known about its habitat use and movements. Radio tracking is a common method used to analyze movement patterns to identify specific habitat requirements. During 11 weeks from May until September 2021, we tracked four individuals (2 females, 2 males) in the Harz Mountains National Park (~700 m a.s.l.). The study area was characterized by a predominance of rocks and spruce. Within one hour, males moved a distance of up to 173.95 m, females covered a maximum distance of 155.62 m. We analyzed whether a hiking trail cutting through the study area represented a potential barrier for the movement of these animals. Three individuals were tracked crossing the path up to 4 times a night. Raspberry bushes along the path were a potential incentive for crossing. A dense rocky cover and a well-developed shrub layer with raspberry bushes within spruce woodlands seem favorable to the presence of Garden Dormice. For the conservation of this species, it is necessary to protect similar habitats. To connect areas with populations of garden dormice, it may be important to encourage bushes with wild fruits among forest edges and pathways.

For the conservation of endangered species, a good knowledge of their biology is essential. However, due to the secluded lifestyle and nocturnal activity of the Garden Dormouse (Eliomys quercinus), comprehensive research on these small mammals is difficult, resulting in a lack of data. Little is known about the habitat requirements of Garden Dormice in forest habitats. Radio tracking was used to analyze movement patterns to identify specific features of their habitat in the Harz Mountains National Park in Germany (~700 m a.s.l.). Four individuals (2 females, 2 males) were tracked during 11 weeks from May until September 2021. Home ranges were calculated using minimum convex polygon (MCP) and fixed kernel density estimation (KDE) methods. Home range sizes (100% MCP) of males were between 0.58 ha and 7.62 ha and of females between 3.63 ha and 6.39 ha. The size of the core areas (65% KDE) was 0.25 ha - 3.08 ha for males and 1.94 ha - 6.18 ha for females. Whereas the start of their daily activity did not correlate with sunset, the end of activity was associated with sunrise. The females never switched their nesting sites, but the males used 7 -10 nesting sites. Nesting sites were located between boulders and inside deadwood piles. Deadwood is an important habitat for insects which serve as food for Garden Dormice (and other small mammals). To this species in its natural habitat it is necessary to sustain deadwood in forests.

Rats are a reservoir of human- and livestock-associated methicillin-resistant Staphylococcus aureus (MRSA). However, the composition of the natural S. aureus population in wild and laboratory rats is largely unknown. Here, 144 nasal S. aureus isolates from free-living wild rats, captive wild rats and laboratory rats were genotyped and profiled for antibiotic resistances and human-specific virulence genes. The nasal S. aureus carriage rate was higher among wild rats (23.4%) than laboratory rats (12.3%). Free-living wild rats were primarily colonized with isolates of clonal complex (CC) 49 and CC130 and maintained these strains even in husbandry. Moreover, upon livestock contact, CC398 isolates were acquired. In contrast, laboratory rats were colonized with many different S. aureus lineages—many of which are commonly found in humans. Five captive wild rats were colonized with CC398-MRSA. Moreover, a single CC30-MRSA and two CC130-MRSA were detected in free-living or captive wild rats. Rat-derived S. aureus isolates rarely harbored the phage-carried immune evasion gene cluster or superantigen genes, suggesting long-term adaptation to their host. Taken together, our study revealed a natural S. aureus population in wild rats, as well as a colonization pressure on wild and laboratory rats by exposure to livestock- and human-associated S. aureus, respectively.

As the phylogenetic organization of mammalian polyomaviruses is complex and currently incompletely resolved, we aimed at a deeper insight into their evolution by identifying polyomaviruses in host orders and families that have either rarely or not been studied. Sixteen unknown and two known polyomaviruses were identified in animals that belong to 5 orders, 16 genera, and 16 species. From 11 novel polyomaviruses, full genomes could be determined. Splice sites were predicted for large and small T antigen (LTAg, STAg) coding sequences (CDS) and examined experimentally in transfected cell culture. In addition, splice sites of seven published polyomaviruses were analyzed. Based on these data, LTAg and STAg annotations were corrected for 10/86 and 74/86 published polyomaviruses, respectively. For 25 polyomaviruses, a spliced middle T CDS was observed or predicted. Splice sites that likely indicate expression of additional, alternative T antigens, were experimentally detected for six polyomaviruses. In contrast to all other mammalian polyomaviruses, three closely related cetartiodactyl polyomaviruses display two introns within their LTAg CDS. In addition, the VP2 of Glis glis (edible dormouse) polyomavirus 1 was observed to be encoded by a spliced transcript, a unique experimental finding within the Polyomaviridae family. Co-phylogenetic analyses based on LTAg CDS revealed a measurable signal of codivergence when considering all mammalian polyomaviruses, most likely driven by relatively recent codivergence events. Lineage duplication was the only other process whose influence on polyomavirus evolution was unambiguous. Finally, our analyses suggest that an update of the taxonomy of the family is required, including the creation of novel genera of mammalian and non-mammalian polyomaviruses.

Wild rodents are important hosts for tick larvae but co-infestations with other mites and insects are largely neglected. Small rodents were trapped at four study sites in Berlin, Germany, to quantify their ectoparasite diversity. Host-specific, spatial and temporal occurrence of ectoparasites was determined to assess their influence on direct and indirect zoonotic risk due to mice and voles in an urban agglomeration. Rodent-associated arthropods were diverse, including 63 species observed on six host species with an overall prevalence of 99%. The tick Ixodes ricinus was the most prevalent species, found on 56% of the rodents. The trapping location clearly affected the presence of different rodent species and, therefore, the occurrence of particular host-specific parasites. In Berlin, fewer temporary and periodic parasite species as well as non-parasitic species (fleas, chiggers and nidicolous Gamasina) were detected than reported from rural areas. In addition, abundance of parasites with low host-specificity (ticks, fleas and chiggers) apparently decreased with increasing landscape fragmentation associated with a gradient of urbanisation. In contrast, stationary ectoparasites, closely adapted to the rodent host, such as the fur mites Myobiidae and Listrophoridae, were most abundant at the two urban sites. A direct zoonotic risk of infection for people may only be posed by Nosopsyllus fasciatus fleas, which were prevalent even in the city centre. More importantly, peridomestic rodents clearly supported the life cycle of ticks in the city as hosts for their subadult stages. In addition to trapping location, season, host species, body condition and host sex, infestation with fleas, gamasid Laelapidae mites and prostigmatic Myobiidae mites were associated with significantly altered abundance of I. ricinus larvae on mice and voles. Whether this is caused by predation, grooming behaviour or interaction with the host immune system is unclear. The present study constitutes a basis to identify interactions and vector function of rodent-associated arthropods and their potential impact on zoonotic diseases.

Wood ticks, Ixodes ricinus L., serve as vectors for various pathogens and are ubiquitous throughout Central Europe. Survival and development of I. ricinus depend on biotic and abiotic factors. We examined whether relative humidity (RH), air (T _a ) and soil temperatures (T _s ), or snow depth during November through February affect the questing activity of ticks during their subsequent season of activity. We related the number of host-seeking nymphs to meteorological parameters measured in close proximity at minutely intervals over the period of 6 years (2010–2015) in an urban park in Berlin. We defined thresholds at which associations appeared strongest. Although the annual variations in RH, T _a , and snow depth were typical of the mid-latitudes, the questing activity of nymphs during their first peak of activity (March through July) varied among the 6 years more than threefold. The accumulated hours of RH below 77% in 2 m height during November through February affected the questing activity of nymphs during the following activity peak. In contrast to T _a , accumulated hours of T _s below −1 °C in 0.02 m depth or below −4 °C in 0.05 m depth during the preceding period significantly influenced the average number of nymphs questing during spring. Our observations suggest that RH, T _s , and snow cover during the preceding months affect the questing activity of nymphal I. ricinus during their first peak of activity. Snow cover serves as an insulator between the atmosphere and soil, which not only stabilizes T _s but also appears to protect ticks from exposure to frost and frequent temperature shifts.

The reservoir competence and long life expectancy of edible dormice, Glis glis, suggest that they serve as efficient reservoir hosts for Lyme disease (LD) spirochetes. Their arboreality, however, may reduce the probability to encounter sufficient questing Ixodes ricinus ticks to acquire and perpetuate LD spirochetes. To define the potential role of this small arboreal hibernator in the transmission cycle of LD spirochetes, we examined their rate and density of infestation with subadult ticks throughout the season of activity. Of the 1081 edible dormice that we captured at five study sites in Southern Germany and inspected for ticks at 2946 capture occasions, 26 % were infested with at least one and as many as 26 subadult ticks on their ear pinnae. The distribution of ticks feeding on edible dormice was highly aggregated. Although only few individuals harbored nymphal ticks soon after their emergence from hibernation, the rate of nymphal infestation increased steadily throughout the season and reached about 35 % in September. Dormice inhabiting a site with few conspecifics seemed more likely to be infested by numerous ticks, particularly nymphs, than those individuals living in densely populated sites. Male dormice were more likely to be parasitized by numerous nymphs than were females, independent of their age and body mass. Our observation that season, population density, and sex affect the rates of ticks feeding on edible dormice suggests that the contribution of edible dormice to the transmission cycle of LD spirochetes depends mainly on their ranging behavior and level of activity.