PREZODE is a global One Health initiative, involving scientists, communities, governments and practitioners, to prevent zoonotic epidemics and pandemics.

Abstract Animal personality influences organismal interactions and individual habitat use. Rodents are zoonoses reservoirs and often exposed to several pathogens simultaneously, potentially resulting in interdependence of infections and susceptibility to infection. Still, entire pathogen communities are rarely investigated, even though, given rodents ubiquity in human settlements, understanding the link between animal personality and pathogenesis is an important public health issue. We investigated the association of animal personality with pathogen communities in wild rodents, analysing ectoparasite occurrence and pathogenic bacteria of 93 individuals belonging to 3 species from urban and forest areas around Potsdam, Germany. Individual personality was quantified using a combination of open-field and dark-light test. Rodents were then euthanised and screened for pathogens in the spleen through 16 S rRNA amplicon sequencing, and ectoparasites were collected. We detected 6 pathogenic bacteria and 3 ectoparasite taxa. Host species and sampling time explained most of the variation in pathogen associations, but within each genus, 7–9% of the variation was explained by animal personality. Active rodents were more likely infected by Bartonella than less active ones. Bold animals had lower tick infestation probabilities. Thus, animal personality contributes to the distribution and prevalence of pathogens in wild rodents, and should be considered in epidemiology and disease management.

Understanding the spatial ecology of invasive species is essential for effective management, particularly when ecological damage and sanitary risks are involved. GPS tracking offers valuable insights but remains challenging for semi-aquatic rodents. Here, we describe an exploratory glue-on GPS tagging protocol for coypu ( Myocastor coypus ), applied without anaesthesia and adapted from techniques used on Eurasian beavers ( Castor fiber ). The method is rapid to deploy, minimizes handling time, and limits animal disturbance. We tested this approach on 15 individuals, with contrasted outcomes, allowing us to assess both feasibility and constraints. While successful deployments yielded usable movement data, tag loss and performance issues were observed, likely related to species-specific behaviour such as burrow use and frequent immersion in water. We provide a detailed description of the protocol, field performance, and discuss limitations and recommendations for future applications. We do not draw ecological inference, but share practical methodological insights to inform future GPS studies on coypu and similar species.

Invasive species can disrupt native epidemiological processes, potentially leading to the emergence of zoonotic pathogens. The relatively recent appearance and spread of the bank vole (Clethrionomys glareolus) in Ireland provides a unique model system to study these phenomena. The depauperate small mammal community in Ireland, combined with baseline data, allows us to identify the invasion gradient of C. glareolus and its effects on rodent-borne pathogens over time. A total of 498 C. glareolus and 584 Apodemus sylvaticus were sampled, via removal trapping, across nine sites in Ireland in 2016 and 2017, with six sites revisited in 2021 and 2022. 16S rRNA metabarcoding identified 10 putative pathogenic Operational Taxonomic Units (OTUs) present in these rodents, relating to four bacterial taxa, Bartonella spp., Mycoplasma coccoides, Mycoplasma haemomuris and Mycoplasma penetrans, and one family of protozoans, Sarcocystidae. Several epidemiological processes were found to be correlated with the C. glareolus invasion; firstly, C. glareolus in Ireland exhibited patterns consistent with the enemy release hypothesis, compared to native populations in France, and the native A. sylvaticus in Ireland. Secondly, a potential dilution effect, with reduced prevalence of M. haemomuris in A. sylvaticus at the C. glareolus invasion core compared to the invasion front, was observed. Finally, C. glareolus had increased prevalence of Sarcocystidae at the invasion front when compared to the invasion core, depending on the time and stage of invasion. These findings further our understanding of pathogen dynamics during biological invasions, demonstrating that invaders affect native host-pathogen communities differently as they advance through various stages of establishment.

Despite advances in understanding infectious diseases, the persistence and re-emergence of wildlife pathogens continue to raise public and veterinary health concerns. This study investigates the relationship between biodiversity and rodent-borne diseases in Europe, focusing on habitat alterations and their impact on rodent diversity. We present host-pathogen data from 21 temperate forest sites and eight urban green spaces throughout five European countries, environments where rodents are abundant and human/domestic animals-wildlife interactions are likely to occur. From 2020 to 2022, 3766 specimens comprising 15 different small mammal species were analyzed. Samples were screened for bacteria via 16S rRNA sequencing or PCR, and for viral antibodies using immunofluorescent assays. Pathogens from several genera, including Bartonella, Borrelia, Mycoplasma, Anaplasma, Neoehrlichia, Leptospira, Orthohantavirus, and Orthopoxvirus, were detected at non-negligible prevalence in 11 host species. Host community composition differed between habitats, with more urban adapters in parks than in forests. Pathogen richness increased with an increase in host species diversity, supporting the "host-diversity begets parasite-diversity" hypothesis, though not with anthropization. The absence of some vector-transmitted parasites in urban areas suggests a shift in pathogen community driven by human impact. Host species and intrinsic factors were dominant explanatory variables for Mycoplasma species and Sarcocystidae, while extrinsic environmental and climatic factors influenced variations in several vector-transmitted pathogens. Apodemus sylvaticus and Clethrionomys glareolus served as important connector hosts in urban spaces and temperate forests, respectively. These results improve our understanding of the complex local host-pathogen system, aiding future management decisions and supporting the public health sector.

The emergence of infectious diseases associated with land-use changes is well-documented. However, the presence and dynamics of zoonotic pathogens in small mammals within European forests, whether from rural development or urban greening, remain underexplored. To describe zoonotic hazards in these ecosystems, and to assess the influence of biotic and abiotic factors on their distribution, we analyzed 1549 individuals from 18 small mammal species sampled across forest types representing different levels of anthropization using both targeted and broad-spectrum serological and molecular methods. We detected nine bacteria and five Apicomplexa that are potentially pathogenic to humans. Zoonotic pathogen richness and community composition varied significantly across host species, sites, and sampling periods. Richness was lower in forested urban parks, possibly due to the absence of vectors or intermediate hosts within cities. It was higher in urban adapter species, even within a given forested habitat, emphasizing the important role of specific life-history traits. Pathogen community structure was shaped by forest anthropization and host ecology, with marked differences between urban and rural forested environments and between urban adapter and dweller species within forested urban parks. The seroprevalence of key pathogens (e.g., Bartonella, Orthopoxvirus, Neoehrlichia mikurensis, and Sarcocystidae) showed spatial, temporal, and host-specific variation. Epidemiological differences between sites often exceeded those between habitat types, in particular when comparing protected and managed forests, highlighting the importance of local ecological context. Nevertheless, some patterns reflected the influence of forest anthropization and species urban adaptation strategies for certain zoonotic agents. High anthropization in forests was associated with elevated Bartonella prevalence, driven by urban-adapter species rather than forest dwellers, emphasizing local ecological interactions between hosts and pathogens. Besides, higher levels of Orthopoxvirus seroprevalence were associated with adapter species in protected forests where they might be more abundant. Altogether, these findings underscore the need for integrated and multipathogen wildlife surveillance to anticipate and mitigate disease risks at the human-environment-animal interface.

The "dilution effect" hypothesis suggests that high host diversity can reduce the prevalence of certain zoonotic pathogens. Despite growing interest, its generality and practical relevance remain debated. In particular most previous studies have focused on large scale analyses or meta-analyses, limiting their potential use for zoonotic outbreak prevention. Here, we present an extensive field-based study of small mammals and their multiple pathogens to assess diversity-disease relationships at a local scale, revealing pathogen-specific patterns. While no significant association was detected between the prevalence of some pathogens and host diversity, others such as Orthopoxvirus and a strain of Mycoplasma haemomuris exhibited dilution effect patterns, whereas another Mycoplasma haemomuris strain and Mycoplasma coccoides displayed amplification effects. Crucially, we demonstrate that these contrasting outcomes are consistently explained by the host competence-abundance relationship. Our findings underscore the importance of host community composition and highlight the need to consider multiple pathogens when evaluating the ecological mechanisms underpinning the diversity-disease relationships. ### Competing Interest Statement The authors have declared no competing interest. The raw data have been deposited on Zenodo and are available at . BiodivERsA, https://ror.org/05cvqmv08

The emergence of infectious diseases associated with land-use changes is well-documented. However, zoonotic risks originating from European forests, whether from rural development or urban greening, remain underexplored. To assess and mitigate zoonotic hazards in these ecosystems, we analyzed 1,549 individuals from 18 small mammal species sampled along a forest anthropization gradient using both targeted and broad-spectrum serological and molecular methods. We detected nine bacteria and several Apicomplexa that are potentially pathogenic to humans. Zoonotic pathogen richness and community composition varied significantly across host species, sites and sampling periods. Richness was lower in forested urban parks, possibly due to the absence of vectors or intermediate hosts within cities. It was higher in urban adapter species, even within a given forested habitat, emphasizing the important role of specific life-history traits. Pathogen community structure was similarly shaped by forest anthropization and host ecology, with marked differences between urban and rural forested environments and between urban adapter and dweller species within forested urban parks. The (sero-)prevalence of key pathogens (e.g., Bartonella, Orthopoxvirus, Neoehrlichia mikurensis , Sarcocystidae) showed spatial, temporal, and host-specific variation. Site-level differences often exceeded those between general habitat types, highlighting the importance of local ecological context. Nevertheless, some patterns reflected the influence of forest anthropization and species urban adaptation strategies for certain zoonotic agents. Forest anthropization had a positive impact on Bartonella prevalence, for urban adapter species within parks, emphasizing a potential dilution effect of these pathogens. Besides, higher levels of Orthopoxvirus seroprevalence were associated with adapter species, in protected forests where they might be more abundant. Altogether, these findings underscore the need for integrated and multi-pathogen wildlife monitoring to anticipate and mitigate disease risks at the human– environment–animal interface. ### Competing Interest Statement The authors have declared no competing interest. 2018-2019 BiodivERsA joint call, BiodivERsA3 ERA-Net COFUND programme

The Usutu virus, a neurotropic Orthoflavivirus transmitted by mosquitoes, was first identified in South Africa in 1959 and has progressively spread across Europe over the past two decades. This virus follows an enzootic cycle between mosquitoes and birds, leading to periodic outbreaks that have caused significant bird mortality. Although primarily an avian pathogen, Usutu virus can occasionally infect humans and other mammals who act as incidental or dead-end hosts. The repeated avian epizootics observed in Europe in the last two decades raise concerns about potential zoonotic risks, even though human infections remain rare. In most cases, human infection is either asymptomatic or results in mild symptoms. However, in some instances, Usutu virus has been linked to severe neurological conditions, including encephalitis and meningoencephalitis. The Occitanie region in the south of France is particularly vulnerable to this threat due to its ecosystem, which harbors both competent mosquito vectors and numerous avian hosts that act as amplifying hosts for the virus. We investigated the urban circulation of Usutu virus in the city of Montpellier, where the first human case of infection by this virus in France was previously identified. To assess the presence of Usutu virus, we conducted a repeated cross-sectional study using serological (ELISA, microneutralization) and molecular (RT-qPCR) analyses of captive avifauna, including a longitudinal study of captive birds at the Montpellier zoological park between 2016 and 2024. Additionally, in 2024, we completed our study with avian cloacal swabs, pigeon droppings, rat blood, mosquito faeces, and environmental water samples (dPCR). Our findings revealed active circulation of the Usutu virus in the urban environment over multiple years. Furthermore, we demonstrated the feasibility of detecting the virus in droppings and environmental waters, highlighting the potential of environmental surveillance as a non-invasive and large-scale method. This study contributes to a better understanding of Usutu virus circulation and highlights its established presence in urban areas.

In a rapidly urbanizing world, research on dietary habits of wildlife is essential to understand how plastic behaviors may guide evolutionary trajectories of endangered animal species. Bats are very sensitive to habitat destruction and land-use change, although some species have shown the capacity for adaptation to urban life. In this study, we tested to what extent urban insectivorous bats modify their feeding strategies in a recently human-modified tropical insular ecosystem. Using a DNA metabarcoding approach on fecal samples collected in seven roosts, we analyzed the dietary niche of free-tailed bats ( Mormopterus francoismoutoui ) endemic to Reunion Island. Our results revealed a wide dietary niche, including 174 arthropod species in 12 orders, among which lepidopterans were predominant. We identified several crop pests and disease vectors, highlighting the central role of this bat species for agroecology and epidemiology concerns. Our study also highlighted potential sex- and reproduction-related dietary strategies. Moreover, we found that agriculture areas, inferred from land cover surrounding bat roosts, were associated with higher relative abundance of Lepidoptera in the diet of bats. In contrast, bats roosting in urban areas increased their consumption of Blattodea. As Reunion free-tailed bats roost and thrive in human-modified landscapes, understanding the consequences of this dietary plasticity for bat health and fitness will be necessary for urban evolutionary research and conservation actions. ### Competing Interest Statement The authors have declared no competing interest. French National Research Agency, ANR JCJC SEXIBAT Université de la Réunion - BIOST, MOLOSS-EAT

As human activities drive biodiversity decline, effective biomonitoring is more crucial than ever to track species distribution changes and inform conservation and restoration actions. Environmental DNA (eDNA) metabarcoding has emerged as a promising tool for the simultaneous detection of multiple taxa. However, while substrates play a crucial role in eDNA studies, limited research has compared substrate performance for terrestrial vertebrate detection, leaving a critical gap in empirical knowledge for large-scale application. This study evaluates and compares the effectiveness of three easy-to-collect substrates: soil, leaf swabs, and spider webs, for broad terrestrial vertebrate eDNA monitoring. Specifically, we examined taxonomic richness overlaps among substrates, their effects on wild vertebrate detection probabilities, and within-sample PCR repeatability. We analysed 120 samples from the Landes Forest, an intensively managed temperate forest in Western France, and included additional control samples from the Montpellier zoo to validate our detection capabilities. Using metabarcoding with 12S-V5 and 16S mam primers, we identified 63 taxa at the genus or species level. Our findings highlight the advantages of substrates that passively accumulate airborne DNA (leaf swabs and spider webs) over soil, and position spider webs as a suitable choice for maximising detection probabilities in rapid eDNA surveys, emphasising their potential for efficient, scalable biomonitoring. Further research is needed to identify factors affecting eDNA detectability from these substrates, aiming to standardise procedures and move from proof-of-concept to broad use by researchers and managers.

Communication Leveraging Small Biodiversity Reserves to Prevent Zoonotic Disease: Insights from Dilution Effect and Pathogen Adaptation Theories Audrey Arnal 1,2,3, Rodolphe Elie Gozlan 4, Nathalie Charbonnel 5, Marie Bouilloud 1,5, Andrea Chaves 6,7, Manon Lounnas 1,2, Michel Gauthier-Clerc 8, Ana L. Vigueras-Galván 2,3, Céline Arnathau 1,2, David Roiz 1,2, Ana I. Bento 9, Serge Morand 10,11,12, Chris Walzer 13,14, Gerardo Suzán 2,15, Rosa Elena Sarmiento Silva 2,3,*,† and Benjamin Roche 1,2,3,† 1 MIVEGEC, Université de Montpellier, IRD, CNRS, 34394 Montpellier, France 2 International Joint Laboratory IRD/UNAM ELDORADO, Merida 97000, Mexico 3 Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Ciudad de México 04510, Mexico 4 ISEM, University of Montpellier, CNRS, IRD, 34090 Montpellier, France 5 CBGP, INRAE, CIRAD, IRD, Institut Agro, Université de Montpellier, 34398 Montpellier, France 6 Centro Nacional de Innovaciones Biotecnológicas (CENIBiot), CeNAT, Conare, San José 1174-1200, Costa Rica 7 Escuela de Biología, Universidad de Costa Rica, San José 11501-206, Costa Rica 8 Faculté des Sciences, Université de Genève, 30 Quai Ernest-Ansermet, CH-1211 Geneve, Switzerland 9 Department of Public and Ecosystem Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA 10 IRL Health DEEP, CNRS, Kasetsart University, Mahidol University Bangkok 10900, Thailand 11 Faculty of Veterinary Technology, Kasetsart University, Bangkok 10900, Thailand 12 Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand 13 Wildlife Conservation Society Southern Boulevard, Bronx, NY 10460, USA 14 Research Institute of Wildlife Ecology, University of Veterinary Medicine, 1210 Vienna, Austria 15 Departamento de Etología, Fauna Silvestre y Animales de Laboratorio, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Ciudad de México 04360, Mexico * Correspondence: rosass@unam.mx; Tel.: +52-554-449-7749 † Co-last authors. Received: 22 February 2025; Revised: 12 March 2025; Accepted: 12 March 2025; Published: 2 April 2025 Abstract: In today’s landscape of zoonotic pathogen outbreaks, the dilution effect theory, i.e., the theory that greater biodiversity can help curb pathogen transmission among wildlife, has gained significant attention. However, the positive link between animal diversity and pathogen richness urges us to apply this concept with caution. It is crucial to explore how conservation biology can safeguard human health by preventing the emergence of zoonotic diseases. By investigating the implications of conservation strategies on animal communities and pathogen transmission as well as the adaptive capabilities of pathogens, we propose that biodiversity conservation based on small reserves can effectively reduce pathogen spread in wildlife, provided certain measurable conditions are met. Given the urgent need to tackle both zoonoses disease emergence and biodiversity loss, these interventions should be prioritized and implemented without delay.

IntroductionInter- and transdisciplinary research (ITDR) is increasingly promoted to address “wicked problems”, particularly in health sectors adopting approaches like Ecohealth. Our Ecohealth-inspired project on rodent-borne diseases, initiated just before the COVID-19 pandemic, provided an opportunity to evaluate ITDR implementation.MethodsWe employed a recently developed semi-quantitative evaluation method to measure our project’s success in achieving ITDR and analyzed factors influencing this achievement.ResultsThe project showed strengths in system description, team task allocation, and data sharing, but had lower scores in engaging societal actors throughout the project cycle.DiscussionWe identified the underexplored influence of problem wickedness as a critical determinant of ITDR success. Addressing rodent-borne diseases, a less wicked problem, limited engagement potential but enabled constructive dialog with local actors. These insights are vital for addressing variably wicked problems in a polycrisis era. We propose recommendations to strengthen researchers’ capacities, particularly in Ecohealth.

Urbanization significantly impacts wild populations, favoring urban dweller species over those that are unable to adapt to rapid changes. These differential adaptative abilities could be mediated by the microbiome, which may modulate the host phenotype rapidly through a high degree of flexibility. Conversely, under anthropic perturbations, the microbiota of some species could be disrupted, resulting in dysbiosis and negative impacts on host fitness. The links between the impact of urbanization on host communities and their gut microbiota (GM) have only been scarcely explored. In this study, we tested the hypothesis that the bacterial composition of the GM could play a role in host adaptation to urban environments. We described the GM of several species of small terrestrial mammals sampled in forested areas along a gradient of urbanization, using a 16S metabarcoding approach. We tested whether urbanization led to changes in small mammal communities and in their GM, considering the presence and abundance of bacterial taxa and their putative functions. This enabled to decipher the processes underlying these changes. We found potential impacts of urbanization on small mammal communities and their GM. The urban dweller species had a lower bacterial taxonomic diversity but a higher functional diversity and a different composition compared to urban adapter species. Their GM assembly was mostly governed by stochastic effects, potentially indicating dysbiosis. Selection processes and an overabundance of functions were detected that could be associated with adaptation to urban environments despite dysbiosis. In urban adapter species, the GM functional diversity and composition remained relatively stable along the urbanization gradient. This observation can be explained by functional redundancy, where certain taxa express the same function. This could favor the adaptation of urban adapter species in various environments, including urban settings. We can therefore assume that there are feedbacks between the gut microbiota and host species within communities, enabling rapid adaptation.

Rodents are recognized as the main reservoirs of Leptospira spp. Rats, in particular, serve as hosts for the widely predominant Leptospira interrogans serovar Icterohaemorrhagiae, found worldwide. Several studies have shown the importance of other reservoirs, such as mice or hedgehogs, which harbor other leptospires' serovars. Nevertheless, our knowledge of circulating Leptospira spp. in reservoirs other than rats remains limited. In this context, we proposed an eco-health approach to assess the health hazard associated with leptospires in urban green spaces, where contacts between human/small mammals and domestic animals are likely. We studied the prevalence, the diversity of circulating strains, and epidemiology of pathogenic Leptospira species in small terrestrial mammal communities (rodents and shrews), between 2020-2022, in two parks in Lyon metropolis, France. Our study showed a significant carriage of Leptospira spp. in small terrestrial mammals in these parks and unveiled a global prevalence rate of 11.4%. Significant variations of prevalence were observed among the small mammal species (from 0 to 26.1%), with Rattus norvegicus exhibiting the highest infection levels (26.1%). We also observed strong spatio-temporal variations in Leptospira spp. circulation in its reservoirs. Prevalence seems to be higher in the peri-urban park and in autumn in 2021 and 2022. This is potentially due to differences in landscape, abiotic conditions and small mammal communities' composition. Our study suggests an important public health relevance of rats and in a lesser extent of other rodents (Apodemus spp., Clethrionomys glareolus and Mus musculus) as reservoirs of L. interrogans, with rodent species carrying specific serogroups/serovars. We also emphasize the potential hazard associated between the shrew Crocidura russula and L. kirschneri. Altogether, these results improve our knowledge about the prevalence of leptospirosis in an urban environment, which is an essential prerequisite for the implementation of prevention of associated risks.

Rodents are major reservoirs of pathogens that can cause disease in humans and livestock. It is therefore important to know what pathogens naturally circulate in rodent populations, and to understand the factors that may influence their distribution in the wild. Here, we describe the occurrence and distribution patterns of a range of endemic and zoonotic pathogens circulating among rodent communities in northern France. The community sample consisted of 713 rodents, including 11 host species from diverse habitats. Rodents were screened for virus exposure (hantaviruses, cowpox virus, Lymphocytic choriomeningitis virus, Tick-borne encephalitis virus) using antibody assays. Bacterial communities were characterized using 16S rRNA amplicon sequencing of splenic samples. Multiple correspondence (MCA), multiple regression and association screening (SCN) analyses were used to determine the degree to which extrinsic factors (study year and site; host habitat, species, sex and age class) contributed to pathogen community structure, and to identify patterns of associations between pathogens within hosts. We found a rich diversity of bacterial genera, with 36 known or suspected to be pathogenic. We revealed that host species is the most important determinant of pathogen community composition, and that hosts that share habitats can have very different pathogen communities. Pathogen diversity and co-infection rates also vary among host species. Aggregation of pathogens responsible for zoonotic diseases suggests that some rodent species may be more important for transmission risk than others. Moreover, we detected positive associations between several pathogens, including Bartonella , Mycoplasma species, Cowpox virus (CPXV) and hantaviruses, and these patterns were generally specific to particular host species. Altogether, our results suggest that host and pathogen specificity is the most important driver of pathogen community structure, and that interspecific pathogen-pathogen associations also depend on host species.

Major advances in the understanding of infectious diseases have been achieved in the last decades. However, the persistence and re-emergence of pathogens continue to raise public and veterinary health concerns, of which the recent COVID-19 pandemic may be one of the most dramatic examples. Understanding the impact of habitat alterations and concomitant biodiversity loss on pathogen transmission and emergence from wildlife remains challenging. Here, we aim to elucidate the interlinkages between biodiversity and rodent-borne diseases at local and European scales. We present recently collected host-pathogen data from 21 temperate forest sites and eight urban green spaces throughout five European countries, environments where rodents are abundant and human/domestic animals – wildlife interactions are likely to occur. 3766 specimens were analyzed during the period from 2020 to 2022 comprising 15 different small mammal species. Different organ tissues of each specimen were screened for bacteria by either 16S rRNA amplicon sequencing or specific PCR. The presence of antibodies to different families of viruses was screened using immunofluorescent assays. A multitude of pathogens of zoonotic potential from several genera including Bartonella, Borrelia, Mycoplasma, Anaplasma, Neoehrlichia, Leptospira , Orthohantavirus and Orthopoxvirus were detected at non-negligible prevalence in 11 different terrestrial mammal species. A shift in host community composition was observed along the anthropization gradient with more urban adapters in more anthropized sites. Pathogen richness increased with an increase in host species diversity, following the “host-diversity begets parasite-diversity” hypothesis. The absence of some vector-transmitted parasites in urban areas suggests a shift in pathogen community along the anthropization gradient. Host species and host intrinsic factors were dominant explanatory variables for endoparasitic Mycoplasma species and Sarcocystidae , while extrinsic environmental and climatic factors where influential in explaining variations in occurrences of several vector-transmitted pathogens. Apodemus sylvaticus and Clethrionomys glareolus were important connector host species in respectively urban green spaces and temperate forests. Increased host diversity, but not anthropization, correlated with a richer pathogen community. These results ultimately lead to an increased understanding of the complex host-pathogen system at the local landscape that can aid future management decisions and support the public health sector. ### Competing Interest Statement The authors have declared no competing interest.

Abstract Evidence for divergent selection and adaptive variation across the landscape can provide insight into a species' ability to adapt to different environments. However, despite recent advances in genomics, it remains difficult to detect the footprints of climate‐mediated selection in natural populations. Here, we analysed ddRAD sequencing data (21,892 SNPs) in conjunction with geographic climate variation to search for signatures of adaptive differentiation in twelve populations of the bank vole (Clethrionomys glareolus) distributed across Europe. To identify the loci subject to selection associated with climate variation, we applied multiple genotype‐environment association methods, two univariate and one multivariate, and controlled for the effect of population structure. In total, we identified 213 candidate loci for adaptation, 74 of which were located within genes. In particular, we identified signatures of selection in candidate genes with functions related to lipid metabolism and the immune system. Using the results of redundancy analysis, we demonstrated that population history and climate have joint effects on the genetic variation in the pan‐European metapopulation. Furthermore, by examining only candidate loci, we found that annual mean temperature is an important factor shaping adaptive genetic variation in the bank vole. By combining landscape genomic approaches, our study sheds light on genome‐wide adaptive differentiation and the spatial distribution of variants underlying adaptive variation influenced by local climate in bank voles.

Background Seoul virus (SEOV) is an orthohantavirus primarily carried by rats. In humans, it may cause hemorrhagic fever with renal syndrome (HFRS). Its incidence is likely underestimated and given the expansion of urban areas, a better knowledge of SEOV circulation in rat populations is called for. Beyond the need to improve human case detection, we need to deepen our comprehension of the ecological, epidemiological, and evolutionary processes involved in the transmission of SEOV. Methodology / Principal findings We performed a comprehensive serological and molecular characterization of SEOV in Rattus norvegicus in a popular urban park within a large city (Lyon, France) to provide essential information to design surveillance strategies regarding SEOV. We sampled rats within the urban park of ‘La Tête d’Or’ in Lyon city from 2020 to 2022. We combined rat population genetics, immunofluorescence assays, SEOV high-throughput sequencing (S, M, and L segments), and phylogenetic analyses. We found low structuring of wild rat populations within Lyon city. Only one sampling site within the park (building created in 2021) showed high genetic differentiation and deserves further attention. We confirmed the circulation of SEOV in rats from the park with high seroprevalence (17.2%) and high genetic similarity with the strain previously described in 2011 in Lyon city. Conclusion/Significance This study confirms the continuous circulation of SEOV in a popular urban park where the risk for SEOV transmission to humans is present. Implementing a surveillance of this virus could provide an efficient early warning system and help prepare risk-based interventions. As we reveal high gene flow between rat populations from the park and the rest of the city, we advocate for SEOV surveillance to be conducted at the scale of the entire city.

Despite its central role in host fitness, the gut microbiota may differ greatly between individuals. This variability is often mediated by environmental or host factors such as diet, genetics, and infections. Recently, particular attention has been given to the interactions between gut bacteriota and helminths, as these latter could affect host susceptibility to other infections. Further studies are still required to better understand the three-way interactions between gut bacteriota, helminths and other parasites, especially because previous findings have been very variable, even for comparable host-parasite systems. In our study, we used the V4 region of the 16S rRNA gene to assess the variability of gut bacteriota diversity and composition in wild populations of a small mammal, the bank vole Myodes glareolus. Four sites were sampled at a regional geographical scale (100 km) along a North-South transect in Eastern France. We applied analyses of community and microbial ecology to evaluate the interactions between the gut bacteriota, the gastro-intestinal helminths and the pathogenic bacteria detected in the spleen. We identified important variations of the gut bacteriota composition and diversity among bank voles. They were mainly explained by sampling localities and reflected the North/South sampling transect. In addition, we detected two main enterotypes, that might correspond to contrasted diets. We found geographic variations of the Firmicutes/Bacteroidetes ratio, that correlated positively with body mass index. We found positive correlations between the specific richness of the gut bacteriota and of the helminth community, as well as between the composition of these two communities, even when accounting for the influence of geographical distance. The helminths Aonchotheca murissylvatici, Heligmosomum mixtum and the bacteria Bartonella sp were the main taxa associated with the whole gut bacteriota composition. Besides, changes in the relative abundance of particular gut bacteriota taxa were specifically associated with other helminths ( Mastophorus muris, Catenotaenia henttoneni, Paranoplocephala omphalodes and Trichuris arvicolae) or pathogenic bacteria. Especially, infections with Neoehrlichia mikurensis, Orientia sp, Rickettsia sp and P. omphalodes were associated with lower relative abundance of the family Erysipelotrichaceae (Firmicutes), while coinfections with higher number of bacterial infections were associated with lower relative abundance of a Bacteroidales family (Bacteroidetes). These results emphasize complex interlinkages between gut bacteriota and infections in wild animal populations. They remain difficult to generalize due to the strong impact of the environment on these interactions, even at regional geographical scales. Abiotic features, as well as small mammal community composition and within host parasite coinfections, should now be considered to better understand the spatial variations observed in the relationships between gut bacteriota, gastro-intestinal helminths and bacterial infections.