Development of the Prevention of Suicide Behaviour in Prisons: Enhancing Access to Therapy (PROSPECT) logic model and implementation strategies.

AIMS AND METHOD: This study aimed to develop and articulate a logic model and programme theories for implementing a new cognitive-behavioural suicide prevention intervention for men in prison who are perceived to be at risk of death by suicide. Semi-structured one-to-one interviews with key stakeholders and a combination of qualitative analysis techniques were used to develop programme theories. RESULTS: Interviews with 28 stakeholders resulted in five programme theories, focusing on: trust, willingness and engagement; readiness and ability; assessment and formulation; practitioner delivering the 'change work' stage of the intervention face-to-face in a prison environment; and practitioner training, integrating the intervention and onward care. Each theory provides details of what contextual factors need to be considered at each stage, and what activities can facilitate achieving the intended outcomes of the intervention, both intermediate and long term. CLINICAL IMPLICATIONS: The PROSPECT implementation strategy developed from the five theories can be adapted to different situations and environments.

Algorithmic approach to finding people with multiple sclerosis using routine healthcare data in Wales.

BACKGROUND: Identification of multiple sclerosis (MS) cases in routine healthcare data repositories remains challenging. MS can have a protracted diagnostic process and is rarely identified as a primary reason for admission to the hospital. Difficulties in identification are compounded in systems that do not include insurance or payer information concerning drug treatments or non-notifiable disease. AIM: To develop an algorithm to reliably identify MS cases within a national health data bank. METHOD: Retrospective analysis of the Secure Anonymised Information Linkage (SAIL) databank was used to identify MS cases using a novel algorithm. Sensitivity and specificity were tested using two existing independent MS datasets, one clinically validated and population-based and a second from a self-registered MS national registry. RESULTS: From 4 757 428 records, the algorithm identified 6194 living cases of MS within Wales on 31 December 2020 (prevalence 221.65 (95% CI 216.17 to 227.24) per 100 000). Case-finding sensitivity and specificity were 96.8% and 99.9% for the clinically validated population-based cohort and sensitivity was 96.7% for the self-declared registry population. DISCUSSION: The algorithm successfully identified MS cases within the SAIL databank with high sensitivity and specificity, verified by two independent populations and has important utility in large-scale epidemiological studies of MS.

Epigenetic age estimation of wild mice using faecal samples.

Age is a key parameter in population ecology, with a myriad of biological processes changing with age as organisms develop in early life then later senesce. As age is often hard to accurately measure with non-lethal methods, epigenetic methods of age estimation (epigenetic clocks) have become a popular tool in animal ecology and are often developed or calibrated using captive animals of known age. However, studies typically rely on invasive blood or tissue samples, which limit their application in more sensitive or elusive species. Moreover, few studies have directly assessed how methylation patterns and epigenetic age estimates compare across environmental contexts (e.g. captive or laboratory-based vs. wild animals). Here, we built a targeted epigenetic clock from laboratory house mice (strain C57BL/6, Mus musculus) using DNA from non-invasive faecal samples, and then used it to estimate age in a population of wild mice (Mus musculus domesticus) of unknown age. This laboratory mouse-derived epigenetic clock accurately predicted adult wild mice to be older than juveniles and showed that wild mice typically increased in epigenetic age over time, but with wide variation in epigenetic ageing rate among individuals. Our results also suggested that, for a given body mass, wild mice had higher methylation across targeted CpG sites than laboratory mice (and consistently higher epigenetic age estimates as a result), even among the smallest, juvenile mice. This suggests wild and laboratory mice may display different CpG methylation levels from very early in life and indicates caution is needed when developing epigenetic clocks on laboratory animals and applying them in the wild.

Association between maternal depression symptoms and child telomere length.

The biological mechanisms that explain how adverse early life events influence adult disease risk are poorly understood. One proposed mechanism is via the induction of accelerated biological aging, for which telomere length is considered a biomarker. We aimed to determine if maternal depression pre- and post-partum was associated with telomere length in children at 4 years of age (n = 4299). Mothers completed structured questionnaires assessing depression during pregnancy (Edinburgh Depression Scale), at 9 months (Edinburgh Depression Scale), and at 54 months postpartum (Patient Health Questionnaire 9). Regression methods were used to investigate the relationship between telomere length (DNA from saliva) and maternal depression score recorded at each stage. Significant covariates included in the final model were: maternal age at pregnancy; child sex; child ethnicity; gestational age group, and rurality group. Child telomere length was found to be longer if their mother had a higher depression score at both postpartum time points tested (9 months of age; coefficient 0.003, SE = 0.001, P = 0.01, 54 months of age; coefficient 0.003, SE = 0.002, P = 0.02). Although these findings seem paradoxical, increased telomere length may be an adaptive response to early life stressors. We propose several testable hypotheses for these results and to determine if the positive association between depression and telomere length is a developmental adaptation or an indirect consequence of environmental factors.

Social and environmental transmission spread different sets of gut microbes in wild mice.

Gut microbes shape many aspects of organismal biology, yet how these key bacteria transmit among hosts in natural populations remains poorly understood. Recent work in mammals has emphasized either transmission through social contacts or indirect transmission through environmental contact, but the relative importance of different routes has not been directly assessed. Here we used a novel radio-frequency identification-based tracking system to collect long-term high-resolution data on social relationships, space use and microhabitat in a wild population of mice (Apodemus sylvaticus), while regularly characterizing their gut microbiota with 16S ribosomal RNA profiling. Through probabilistic modelling of the resulting data, we identify positive and statistically distinct signals of social and environmental transmission, captured by social networks and overlap in home ranges, respectively. Strikingly, microorganisms with distinct biological attributes drove these different transmission signals. While the social network effect on microbiota was driven by anaerobic bacteria, the effect of shared space was most influenced by aerotolerant spore-forming bacteria. These findings support the prediction that social contact is important for the transfer of microorganisms with low oxygen tolerance, while those that can tolerate oxygen or form spores may be able to transmit indirectly through the environment. Overall, these results suggest social and environmental transmission routes can spread biologically distinct members of the mammalian gut microbiota.

A common regulatory haplotype doubles lactoferrin concentration in milk.

BACKGROUND: Bovine lactoferrin (Lf) is an iron absorbing whey protein with antibacterial, antiviral, and antifungal activity. Lactoferrin is economically valuable and has an extremely variable concentration in milk, partly driven by environmental influences such as milking frequency, involution, or mastitis. A significant genetic influence has also been previously observed to regulate lactoferrin content in milk. Here, we conducted genetic mapping of lactoferrin protein concentration in conjunction with RNA-seq, ChIP-seq, and ATAC-seq data to pinpoint candidate causative variants that regulate lactoferrin concentrations in milk. RESULTS: We identified a highly-significant lactoferrin protein quantitative trait locus (pQTL), as well as a cis lactotransferrin (LTF) expression QTL (cis-eQTL) mapping to the LTF locus. Using ChIP-seq and ATAC-seq datasets representing lactating mammary tissue samples, we also report a number of regions where the openness of chromatin is under genetic influence. Several of these also show highly significant QTL with genetic signatures similar to those highlighted through pQTL and eQTL analysis. By performing correlation analysis between these QTL, we revealed an ATAC-seq peak in the putative promotor region of LTF, that highlights a set of 115 high-frequency variants that are potentially responsible for these effects. One of the 115 variants (rs110000337), which maps within the ATAC-seq peak, was predicted to alter binding sites of transcription factors known to be involved in lactation-related pathways. CONCLUSIONS: Here, we report a regulatory haplotype of 115 variants with conspicuously large impacts on milk lactoferrin concentration. These findings could enable the selection of animals for high-producing specialist herds.

Comparing the Pathology, Clinical, and Demographic Characteristics of Younger and Older-Onset Multiple Sclerosis.

OBJECTIVE: Older people with multiple sclerosis (MS) have a less active radiological and clinical presentation, but many still attain significant levels of disability; but what drives worsening disability in this group? METHODS: We used data from the UK MS Register to characterize demographics and clinical features of late-onset multiple sclerosis (LOMS; symptom onset at ≥50 years), compared with adult-onset MS (AOMS; onset 18-49 years). We performed a pathology study of a separate MS cohort with a later onset (n = 18, mean age of onset 54 years) versus AOMS (n = 23, mean age of onset 29 years). RESULTS: In the Register cohort, there were 1,608 (9.4%) with LOMS. When compared with AOMS, there was a lower proportion of women, a higher proportion of primary progressive MS, a higher level of disability at diagnosis (median MS impact scale 36.7 vs. 28.3, p < 0.001), and a higher proportion of gait-related initial symptoms. People with LOMS were less likely to receive a high efficacy disease-modifying treatment and attained substantial disability sooner. Controlling for age of death and sex, neuron density in the thalamus and pons decreased with onset-age, whereas actively demyelinating lesions and compartmentalized inflammation was greatest in AOMS. Only neuron density, and not demyelination or the extent of compartmentalized inflammation, correlated with disability outcomes in older-onset MS patients. INTERPRETATION: The more progressive nature of older-onset MS is associated with significant neurodegeneration, but infrequent inflammatory demyelination. These findings have implications for the assessment and treatment of MS in older people. ANN NEUROL 2024;95:471-486.

Gut microbiota of the critically endangered Saiga antelope across two wild populations in a year without mass mortality.

The Saiga are migratory antelopes inhabiting the grasslands of Eurasia. Over the last century, Saiga have been pushed to the brink of extinction by mass mortality events and intense poaching. Yet, despite the high profile of the Saiga as an animal of conservation concern, little is known of its biology. In particular, the gut microbiota of Saiga has not been studied, despite its potential importance in health. Here, we characterise the gut microbiota of Saiga from two geographically distinct populations in Kazakhstan and compare it with that of other antelope species. We identified a consistent gut microbial diversity and composition among individuals and across two Saiga populations during a year without die-offs, with over 85% of bacterial genera being common to both populations despite vast geographic separation. We further show that the Saiga gut microbiota resembled that of five other antelopes. The putative causative agent of Saiga mass die-offs, Pasteurella multocida, was not detected in the Saiga microbiota. Our findings provide the first description of the Saiga gut microbiota, generating a baseline for future work investigating the microbiota's role in health and mass die-offs, and supporting the conservation of this critically endangered species.

Effects of interventions on depression and anxiety in older people with physical health problems in the criminal justice system: a systematic review.

The demand for health care in older people involved in the criminal justice system is high. The prevalence of mental and physical health conditions for people living in prison is greater than in community populations. After systematically searching 21 databases, we found no targeted interventions to support depression or anxiety for this group of people. 24 studies (including interventions of yoga, creative-arts-based programmes, positive psychology, or mindfulness-based interventions and psychotherapy) did contain people older than 50 years, but this only represented a minority (10%) of the overall study population. No single study reported outcomes of physical health. Future interventions need to consider the needs and views of this vulnerable group. Specific gendered and coproduced interventions are required to enhance the implementation, feasibility, and acceptability of interventions that are delivered in prisons.

Collaborative evaluation of a pilot involvement opportunity: Cochrane Common Mental Disorders Voice of Experience College.

BACKGROUND: Involving consumers in systematic reviews can make them more valuable and help achieve goals around transparency. Systematic reviews are technically complex and training can be needed to enable consumers to engage with them fully. The Cochrane Common Mental Disorders group sought to engage people with lived experience of mental health problems in the Voice of Experience College, three workshops introducing them to systematic review methods and to opportunities to contribute as Cochrane consumers. We aimed to collectively evaluate the College from the perspective of both facilitators and consumers, to critically reflect on the experience, and to identify how the College could be sustained and spread to other review groups. METHODS: This study was a longitudinal qualitative and collaborative evaluation, structured around normalisation process theory. Both facilitators and consumers were involved in not only providing their perspectives but also reflecting on these together to identify key learning points. RESULTS: The workshops were positively evaluated as being engaging and supportive, largely due to the relational skills of the facilitators, and their willingness to engage in joint or two-way learning. The College suffered from a lack of clarity over the role of consumers after the College itself, with a need for greater communication to check assumptions and clarify expectations. This was not achieved due to pandemic disruptions, which nevertheless demonstrated that resources for involvement were not prioritised as core business during this period. CONCLUSIONS: Soft skills around communication and support are crucial to effective consumer engagement. Sustaining involvement requires sustained communication and opportunities to reflect together on opportunities and challenges. This requires committed resources to ensure involvement activity is prioritised. This is critical as negative experiences later in the involvement journey can undermine originally positive experiences if contributors are unclear as to what their involvement can lead to. Open discussions about this are necessary to avoid conflicting assumptions. The spread of the approach to other review groups could be achieved by flexibly adapting to group-specific resources and settings, but maintaining a core focus on collaborative relationships as the key mechanism of engagement. PATIENT AND PUBLIC CONTRIBUTION: Public contributors were collaborators throughout the evaluation process and have co-authored the paper.

Maternal transmission gives way to social transmission during gut microbiota assembly in wild mice.

BACKGROUND: The mammalian gut microbiota influences a wide array of phenotypes which are relevant to fitness, yet knowledge about the transmission routes by which gut microbes colonise hosts in natural populations remains limited. Here, we use an intensively studied wild population of wood mice (Apodemus sylvaticus) to examine how vertical (maternal) and horizontal (social) transmission routes influence gut microbiota composition throughout life. RESULTS: We identify independent signals of maternal transmission (sharing of taxa between a mother and her offspring) and social transmission (sharing of taxa predicted by the social network), whose relative magnitudes shift as hosts age. In early life, gut microbiota composition is predicted by both maternal and social relationships, but by adulthood the impact of maternal transmission becomes undetectable, leaving only a signal of social transmission. By exploring which taxa drive the maternal transmission signal, we identify a candidate maternally-transmitted bacterial family in wood mice, the Muribaculaceae. CONCLUSION: Overall, our findings point to an ontogenetically shifting transmission landscape in wild mice, with a mother's influence on microbiota composition waning as offspring age, while the relative impact of social contacts grows.

Experimental temperatures shape host microbiome diversity and composition.

Global climate change has led to more extreme thermal events. Plants and animals harbour diverse microbial communities, which may be vital for their physiological performance and help them survive stressful climatic conditions. The extent to which microbiome communities change in response to warming or cooling may be important for predicting host performance under global change. Using a meta-analysis of 1377 microbiomes from 43 terrestrial and aquatic species, we found a decrease in the amplicon sequence variant-level microbiome phylogenetic diversity and alteration of microbiome composition under both experimental warming and cooling. Microbiome beta dispersion was not affected by temperature changes. We showed that the host habitat and experimental factors affected microbiome diversity and composition more than host biological traits. In particular, aquatic organisms-especially in marine habitats-experienced a greater depletion in microbiome diversity under cold conditions, compared to terrestrial hosts. Exposure involving a sudden long and static temperature shift was associated with microbiome diversity loss, but this reduction was attenuated by prior-experimental lab acclimation or when a ramped regime (i.e., warming) was used. Microbial differential abundance and co-occurrence network analyses revealed several potential indicator bacterial classes for hosts in heated environments and on different biome levels. Overall, our findings improve our understanding on the impact of global temperature changes on animal and plant microbiome structures across a diverse range of habitats. The next step is to link these changes to measures of host fitness, as well as microbial community functions, to determine whether microbiomes can buffer some species against a more thermally variable and extreme world.

Seasonal dynamics of the wild rodent faecal virome.

Viral discovery studies in wild animals often rely on cross-sectional surveys at a single time point. As a result, our understanding of the temporal stability of wild animal viromes remains poorly resolved. While studies of single host-virus systems indicate that host and environmental factors influence seasonal virus transmission dynamics, comparable insights for whole viral communities in multiple hosts are lacking. Utilizing noninvasive faecal samples from a long-term wild rodent study, we characterized viral communities of three common European rodent species (Apodemus sylvaticus, A. flavicollis and Myodes glareolus) living in temperate woodland over a single year. Our findings indicate that a substantial fraction of the rodent virome is seasonally transient and associated with vertebrate or bacteria hosts. Further analyses of one of the most common virus families, Picornaviridae, show pronounced temporal changes in viral richness and evenness, which were associated with concurrent and up to ~3-month lags in host density, ambient temperature, rainfall and humidity, suggesting complex feedbacks from the host and environmental factors on virus transmission and shedding in seasonal habitats. Overall, this study emphasizes the importance of understanding the seasonal dynamics of wild animal viromes in order to better predict and mitigate zoonotic risks.

Contributors are representative, as long as they agree: How confirmation logic overrides effort to achieve synthesis in applied health research.

INTRODUCTION: The paradox of representation in public involvement in research is well recognized, whereby public contributors are seen as either too naïve to meaningfully contribute or too knowledgeable to represent 'the average patient'. Given the underlying assumption that expertise undermines contributions made, more expert contributors who have significant experience in research can be a primary target of criticism. We conducted a secondary analysis of a case of expert involvement and a case of lived experience, to examine how representation was discussed in each. METHODS: We analysed a case of a Lived Experience Advisory Panel (LEAP) chosen for direct personal experience of a topic and a case of an expert Patient and Public Involvement (PPI) panel. Secondary analysis was of multiple qualitative data sources, including interviews with the LEAP contributors and researchers, Panel evaluation data and documentary analysis of researcher reports of Panel impacts. Analysis was undertaken collaboratively by the author team of contributors and researchers. RESULTS: Data both from interviews with researchers and reported observations by the Panel indicated that representation was a concern for researchers in both cases. Consistent with previous research, this challenge was deployed in response to contributors requesting changes to researcher plans. However, we also observed that when contributor input could be used to support research activity, it was described unequivocally as representative of 'the patient view'. We describe this as researchers holding a confirmation logic. By contrast, contributor accounts enacted a synthesis logic, which emphasized multiplicity of viewpoints and active dialogue. These logics are incompatible in practice, with the confirmation logic constraining the potential for the synthesis logic to be achieved. CONCLUSION: Researchers tend to enact a confirmation logic that seeks a monophonic patient voice to legitimize decisions. Contributors are therefore limited in their ability to realize a synthesis logic that would actively blend different types of knowledge. These different logics hold different implications regarding representation, with the synthesis logic emphasizing diversity and negotiation, as opposed to the current system in which 'being representative' is a quality attributed to contributors by researchers. PATIENT OR PUBLIC CONTRIBUTION: Patient contributors are study coauthors, partners in analysis and reporting.

Why Am I So Exhausted?: Exploring Meeting-to-Work Transition Time and Recovery From Virtual Meeting Fatigue.

OBJECTIVE: Ineffective meetings have been well-documented as presenting considerable direct (eg, salary) and indirect costs (eg, employee burnout). We explore the idea that people need meeting recovery, or time to transition from meetings to their next task. Doing so may reduce employee burnout. METHODS: We used a quantitative survey of working adults' last meeting to determine the relationship between meeting outcomes (satisfaction and effectiveness) and meeting recovery. RESULTS: We found that meeting outcomes are related to meeting recovery and that relationship is moderated by the degree to which the meeting was relevant to the individual. Implications for theory and practice are discussed to provide concrete recommendations for researchers, managers, and consultants. CONCLUSIONS: This study explores virtual meeting fatigue with a focus on meeting quality and explores the need for recovery after workplace meetings.

Adapting a codesign process with young people to prioritize outcomes for a systematic review of interventions to prevent self-harm and suicide.

BACKGROUND: Research and clinical outcomes that matter to people with lived experience can significantly differ from those outcomes studied by researchers. To inform a future Cochrane review of suicide and self-harm prevention interventions, we aimed to work with young people with relevant lived experience to agree on priority outcomes. DESIGN: Four participatory codesign workshops were completed across two sites (New Zealand, United Kingdom) with 28 young people in total. We iteratively adapted the methods over the course of the study. RESULTS: 'Improved coping' and 'safer/more accepting environment to disclose' were the final top-rated outcomes. 'Reduction of self-harm' was considered a low priority as it could be misleading, stigmatizing and was considered a secondary consequence of other improvements. In contrast to typical research outcomes, young people emphasized the diversity of experience, the dynamic nature of improvement and holistic and asset-based framing. Methodologically, dialogue using design materials (personas) to thematically explore outcomes was effective in overcoming the initial challenge of disparate quantitative ratings. DISCUSSION: The results will directly inform the development of a Cochrane review, enabling identification of whether and how outcomes of most importance to young people are measured in trials. Rather than producing discrete measurable outcomes that could be easily added to the systematic review, the young people challenged the academic conceptualization of outcomes, with implications for future evidence synthesis and intervention research, and for future codesign. PATIENT OR PUBLIC CONTRIBUTION: Young people with lived experience were codesigners of the outcomes, and their feedback informed iterative changes to the study methods.

Synchronous Seasonality in the Gut Microbiota of Wild Mouse Populations.

The gut microbiome performs many important functions in mammalian hosts, with community composition shaping its functional role. However, the factors that drive individual microbiota variation in wild animals and to what extent these are predictable or idiosyncratic across populations remains poorly understood. Here, we use a multi-population dataset from a common rodent species (the wood mouse, Apodemus sylvaticus), to test whether a consistent "core" gut microbiota is identifiable in this species, and to what extent the predictors of microbiota variation are consistent across populations. Between 2014 and 2018 we used capture-mark-recapture and 16S rRNA profiling to intensively monitor two wild wood mouse populations and their gut microbiota, as well as characterising the microbiota from a laboratory-housed colony of the same species. Although the microbiota was broadly similar at high taxonomic levels, the two wild populations did not share a single bacterial amplicon sequence variant (ASV), despite being only 50km apart. Meanwhile, the laboratory-housed colony shared many ASVs with one of the wild populations from which it is thought to have been founded decades ago. Despite not sharing any ASVs, the two wild populations shared a phylogenetically more similar microbiota than either did with the colony, and the factors predicting compositional variation in each wild population were remarkably similar. We identified a strong and consistent pattern of seasonal microbiota restructuring that occurred at both sites, in all years, and within individual mice. While the microbiota was highly individualised, some seasonal convergence occurred in late winter/early spring. These findings reveal highly repeatable seasonal gut microbiota dynamics in multiple populations of this species, despite different taxa being involved. This provides a platform for future work to understand the drivers and functional implications of such predictable seasonal microbiome restructuring, including whether it might provide the host with adaptive seasonal phenotypic plasticity.

Scale-up of ABC care bundle for intracerebral haemorrhage across two hyperacute stroke units in one region in England: a mixed methods evaluation of a quality improvement project.

BACKGROUND: Intracerebral haemorrhage (ICH) accounts for 10%-15% of strokes in the UK, but is responsible for half of all annual global stroke deaths. The ABC bundle for ICH was developed and implemented at Salford Royal Hospital, and was associated with a 44% reduction in 30-day case fatality. Implementation of the bundle was scaled out to the other hyperacute stroke units (HASUs) in the region from April 2017. A mixed methods evaluation was conducted alongside to investigate factors influencing implementation of the bundle across new settings, in order to provide lessons for future spread. METHODS: A harmonised quality improvement registry at each HASU captured consecutive patients with spontaneous ICH from October 2016 to March 2018 to capture process and outcome measures for preimplementation (October 2016 to March 2017) and implementation (April 2017 to March 2018) time periods. Statistical analyses were performed to determine differences in process measures and outcomes before and during implementation. Multiple qualitative methods (interviews, non-participant observation and project document analysis) captured how the bundle was implemented across the HASUs. RESULTS: HASU1 significantly reduced median anticoagulant reversal door-to-needle time from 132 min (IQR: 117-342) preimplementation to 76 min (64-113.5) after implementation and intensive blood pressure lowering door to target time from 345 min (204-866) preimplementation to 84 min (60-117) after implementation. No statistically significant improvements in process targets were observed at HASU2. No significant change was seen in 30-day mortality at either HASU. Qualitative evaluation identified the importance of facilitation during implementation and identified how contextual changes over time impacted on implementation. This identified the need for continued implementation support. CONCLUSION: The findings show how the ABC bundle can be successfully implemented into new settings and how challenges can impede implementation. Findings have been used to develop an implementation strategy to support future roll out of the bundle outside the region.

Bifidobacterium castoris strains isolated from wild mice show evidence of frequent host switching and diverse carbohydrate metabolism potential.

Members of the gut microbiota genus Bifidobacterium are widely distributed human and animal symbionts believed to exert beneficial effects on their hosts. However, in-depth genomic analyses of animal-associated species and strains are somewhat lacking, particularly in wild animal populations. Here, to examine patterns of host specificity and carbohydrate metabolism capacity, we sequenced whole genomes of Bifidobacterium isolated from wild-caught small mammals from two European countries (UK and Lithuania). Members of Bifidobacterium castoris, Bifidobacterium animalis and Bifodobacterium pseudolongum were detected in wild mice (Apodemus sylvaticus, Apodemus agrarius and Apodemus flavicollis), but not voles or shrews. B. castoris constituted the most commonly recovered Bifidobacterium (78% of all isolates), with the majority of strains only detected in a single population, although populations frequently harboured multiple co-circulating strains. Phylogenetic analysis revealed that the mouse-associated B. castoris clades were not specific to a particular location or host species, and their distribution across the host phylogeny was consistent with regular host shifts rather than host-microbe codiversification. Functional analysis, including in vitro growth assays, suggested that mouse-derived B. castoris strains encoded an extensive arsenal of carbohydrate-active enzymes, including putative novel glycosyl hydrolases such as chitosanases, along with genes encoding putative exopolysaccharides, some of which may have been acquired via horizontal gene transfer. Overall, these results provide a rare genome-level analysis of host specificity and genomic capacity among important gut symbionts of wild animals, and reveal that Bifidobacterium has a labile relationship with its host over evolutionary time scales.