Bighorn Sheep (Ovis canadensis) with Higher Whole Blood Selenium Levels Have Improved Survival and Altered Immune Responses.

Bighorn sheep (Ovis canadensis) are herbivorous ungulates that live in forage-poor areas of the American west. The trace minerals that herbivores derive from forage are important for immune function. Therefore, identifying trace minerals that affect immune function in bighorn sheep could provide important insights into disease susceptibility and population health in threatened populations. We sought to determine whether trace mineral composition in blood or plasma correlates to survival and determine whether immunologic parameters correlate with any trace minerals that affect survival. We used data collected from 2016 to 2018 as part of a large study on bighorn sheep in southeastern Oregon and northern Nevada, US. We measured the survival of 135 bighorn sheep during the 8-mo monitoring period, including general metrics of immune function and trace mineral levels. We found that animals with higher selenium had improved survival over the monitoring period, with higher peripheral blood mononuclear cell activity (lymphocytes and monocytes) and lower bacterial killing ability in an in vitro assay. This suggests that bighorn sheep may have altered immune function when selenium levels are low, making them more likely to die during the 8-mo monitoring period. Future work should consider whether habitat management strategies that increase selenium intake might improve disease resistance and survival in bighorn sheep in selenium-poor areas.

Cold and Hungry: Heterothermy Is Associated with Low Leptin Levels in a Bulk Grazer during a Drought.

AbstractReduced energy intake can compromise the ability of a mammal to maintain body temperature within a narrow 24-h range, leading to heterothermy. To investigate the main drivers of heterothermy in a bulk grazer, we compared abdominal temperature, body mass, body condition index, and serum leptin levels in 11 subadult Cape buffalo (Syncerus caffer caffer) during a drought year and a nondrought year. Low food availability during the drought year (as indexed by grass biomass, satellite imagery of vegetation greenness, and fecal chlorophyll) resulted in lower body condition index, lower body mass relative to that expected for an equivalent-aged buffalo, and lower leptin levels. The range of 24-h body temperature rhythm was 2°C during the nondrought year and more than double that during the drought year, and this was caused primarily by a lower minimum 24-h body temperature rhythm during the cool dry winter months. After rain fell and vegetation greenness increased, the minimum 24-h body temperature rhythm increased, and the range of 24-h body temperature rhythm was smaller than 2°C. In order of importance, poor body condition, low minimum 24-h air temperature, and low serum leptin levels were the best predictors of the increase in the range of 24-h body temperature rhythm. While the thermoregulatory role of leptin is not fully understood, the association between range of 24-h body temperature rhythm and serum leptin levels provides clues about the underlying mechanism behind the increased heterothermy in large mammals facing food restriction.

Associations between urogenital carcinoma and DECA-BDE (BDE-209) among wild California Sea lions (Zalophus californianus) and Steller Sea lions (Eumetopias jubatus).

Urogenital carcinoma (UGC) is prevalent among California sea lions (Zalophus californianus), while less is known concerning UGC among Steller sea lions (Eumetopias jubatus). Our objective was to investigate associations between UGC and polybrominated diphenyl ethers (PBDEs) among both sea lion species. Twenty-nine California sea lions and 20 Steller sea lions were lethally removed from the Columbia River Basin, Oregon, USA between 2020 and 2021, under Section 120 of the Marine Mammal Protection Act. UGC was diagnosed through gross necropsy and histopathology. Forty PBDE congeners were analyzed in blubber, including BDE-209, a potential carcinogen. Twenty (69 %) California sea lions and one (5 %) Steller sea lion were diagnosed with UGC. All cases were identified as early stage UGC, aside from one California sea lion with more advanced stage UGC. Among California sea lions, associations between PBDEs and UGC were analyzed using logistic regression. In the adjusted model, BDE-209 (log2-transformed) was associated with increased odds of UGC [Odds Ratio (OR): 4.68, 95 % confidence interval: 1.04, 21.0, OR p-value = 0.044). This is the first study to report BDE-209 concentrations in sea lion blubber. The percentages of California and Steller sea lions diagnosed with UGC were higher than expected for wild (non-stranded) sea lions. Our results suggested blubber BDE-209 was potentially associated with UGC in California sea lions in the Columbia River Basin.

The heterogeneous herd: Drivers of close-contact variation in African buffalo and implications for pathogen invasion.

Many infectious pathogens are shared through social interactions, and examining host connectivity has offered valuable insights for understanding patterns of pathogen transmission across wildlife species. African buffalo are social ungulates and important reservoirs of directly-transmitted pathogens that impact numerous wildlife and livestock species. Here, we analyzed African buffalo social networks to quantify variation in close contacts, examined drivers of contact heterogeneity, and investigated how the observed contact patterns affect pathogen invasion likelihoods for a wild social ungulate. We collected continuous association data using proximity collars and sampled host traits approximately every 2 months during a 15-month study period in Kruger National Park, South Africa. Although the observed herd was well connected, with most individuals contacting each other during each bimonthly interval, our analyses revealed striking heterogeneity in close-contact associations among herd members. Network analysis showed that individual connectivity was stable over time and that individual age, sex, reproductive status, and pairwise genetic relatedness were important predictors of buffalo connectivity. Calves were the most connected members of the herd, and adult males were the least connected. These findings highlight the role susceptible calves may play in the transmission of pathogens within the herd. We also demonstrate that, at time scales relevant to infectious pathogens found in nature, the observed level of connectivity affects pathogen invasion likelihoods for a wide range of infectious periods and transmissibilities. Ultimately, our study identifies key predictors of social connectivity in a social ungulate and illustrates how contact heterogeneity, even within a highly connected herd, can shape pathogen invasion likelihoods.

Best practice for wildlife gut microbiome research: A comprehensive review of methodology for 16S rRNA gene investigations.

Extensive research in well-studied animal models underscores the importance of commensal gastrointestinal (gut) microbes to animal physiology. Gut microbes have been shown to impact dietary digestion, mediate infection, and even modify behavior and cognition. Given the large physiological and pathophysiological contribution microbes provide their host, it is reasonable to assume that the vertebrate gut microbiome may also impact the fitness, health and ecology of wildlife. In accordance with this expectation, an increasing number of investigations have considered the role of the gut microbiome in wildlife ecology, health, and conservation. To help promote the development of this nascent field, we need to dissolve the technical barriers prohibitive to performing wildlife microbiome research. The present review discusses the 16S rRNA gene microbiome research landscape, clarifying best practices in microbiome data generation and analysis, with particular emphasis on unique situations that arise during wildlife investigations. Special consideration is given to topics relevant for microbiome wildlife research from sample collection to molecular techniques for data generation, to data analysis strategies. Our hope is that this article not only calls for greater integration of microbiome analyses into wildlife ecology and health studies but provides researchers with the technical framework needed to successfully conduct such investigations.

Population connectivity patterns of genetic diversity, immune responses and exposure to infectious pneumonia in a metapopulation of desert bighorn sheep.

Habitat fragmentation is an important driver of biodiversity loss and can be remediated through management actions aimed at maintenance of natural connectivity in metapopulations. Connectivity may protect populations from infectious diseases by preserving immunogenetic diversity and disease resistance. However, connectivity could exacerbate the risk of infectious disease spread across vulnerable populations. We tracked the spread of a novel strain of Mycoplasma ovipneumoniae in a metapopulation of desert bighorn sheep Ovis canadensis nelsoni in the Mojave Desert to investigate how variation in connectivity among populations influenced disease outcomes. M. ovipneumoniae was detected throughout the metapopulation, indicating that the relative isolation of many of these populations did not protect them from pathogen invasion. However, we show that connectivity among bighorn sheep populations was correlated with higher immunogenetic diversity, a protective immune response and lower disease prevalence. Variation in protective immunity predicted infection risk in individual bighorn sheep and was associated with heterozygosity at genetic loci linked to adaptive and innate immune signalling. Together, these findings may indicate that population connectivity maintains immunogenetic diversity in bighorn sheep populations in this system and has direct effects on immune responses in individual bighorn sheep and their susceptibility to infection by a deadly pathogen. Our study suggests that the genetic benefits of population connectivity could outweigh the risk of infectious disease spread and supports conservation management that maintains natural connectivity in metapopulations.

Chronic clinical signs of upper respiratory tract disease associate with gut and respiratory microbiomes in a cohort of domestic felines.

Feline upper respiratory tract disease (FURTD), often caused by infections etiologies, is a multifactorial syndrome affecting feline populations worldwide. Because of its highly transmissible nature, infectious FURTD is most prevalent anywhere cats are housed in groups such as animal shelters, and is associated with negative consequences such as decreasing adoption rates, intensifying care costs, and increasing euthanasia rates. Understanding the etiology and pathophysiology of FURTD is thus essential to best mitigate the negative consequences of this disease. Clinical signs of FURTD include acute respiratory disease, with a small fraction of cats developing chronic sequelae. It is thought that nasal mucosal microbiome changes play an active role in the development of acute clinical signs, but it remains unknown if the microbiome may play a role in the development and progression of chronic clinical disease. To address the knowledge gap surrounding how microbiomes link to chronic FURTD, we asked if microbial community structure of upper respiratory and gut microbiomes differed between cats with chronic FURTD signs and clinically normal cats. We selected 8 households with at least one cat exhibiting chronic clinical FURTD, and simultaneously collected samples from cohabitating clinically normal cats. Microbial community structure was assessed via 16S rDNA sequencing of both gut and nasal microbiome communities. Using a previously described ecophylogenetic method, we identified 136 and 89 microbial features within gut and nasal microbiomes respectively that significantly associated with presence of active FURTD clinical signs in cats with a history of chronic signs. Overall, we find that nasal and gut microbial community members associate with the presence of chronic clinical course, but more research is needed to confirm our observations.

Fecal Methylmercury Correlates With Gut Microbiota Taxa in Pacific Walruses (Odobenus rosmarus divergens).

OBJECTIVES: Methylmercury metabolism was investigated in Pacific walruses (Odobenus rosmarus divergens) from St. Lawrence Island, Alaska, United States. METHODS: Total mercury and methylmercury concentrations were measured in fecal samples and paired colon samples (n = 16 walruses). Gut microbiota composition and diversity were determined using 16S rRNA gene sequencing. Associations between fecal and colon mercury and the 24 most prevalent gut microbiota taxa were investigated using linear models. RESULTS: In fecal samples, the median values for total mercury, methylmercury, and %methylmercury (of total mercury) were 200 ng/g, 4.7 ng/g, and 2.5%, respectively, while in colon samples, the median values for the same parameters were 28 ng/g, 7.8 ng/g, and 26%, respectively. In fecal samples, methylmercury was negatively correlated with one Bacteroides genus, while members of the Oscillospirales order were positively correlated with both methylmercury and %methylmercury (of total mercury). In colon samples, %methylmercury (of total mercury) was negatively correlated with members of two genera, Romboutsia and Paeniclostridium. CONCLUSIONS: Median %methylmercury (of total mercury) was 10 times higher in the colon compared to the fecal samples, suggesting that methylmercury was able to pass through the colon into systemic circulation. Fecal total mercury and/or methylmercury concentrations in walruses were comparable to some human studies despite differences in seafood consumption rates, suggesting that walruses excreted less mercury. There are no members (at this time) of the Oscillospirales order which are known to contain the genes to methylate mercury, suggesting the source of methylmercury in the gut was from diet and not in vivo methylation.

Diet and gut microbiome enterotype are associated at the population level in African buffalo.

Studies in humans and laboratory animals link stable gut microbiome "enterotypes" with long-term diet and host health. Understanding how this paradigm manifests in wild herbivores could provide a mechanistic explanation of the relationships between microbiome dynamics, changes in dietary resources, and outcomes for host health. We identify two putative enterotypes in the African buffalo gut microbiome. The enterotype prevalent under resource-abundant dietary regimes, regardless of environmental conditions, has high richness, low between- and within-host beta diversity, and enrichment of genus Ruminococcaceae-UCG-005. The second enterotype, prevalent under restricted dietary conditions, has reduced richness, elevated beta diversity, and enrichment of genus Solibacillus. Population-level gamma diversity is maintained during resource restriction by increased beta diversity between individuals, suggesting a mechanism for population-level microbiome resilience. We identify three pathogens associated with microbiome variation depending on host diet, indicating that nutritional background may impact microbiome-pathogen dynamics. Overall, this study reveals diet-driven enterotype plasticity, illustrates ecological processes that maintain microbiome diversity, and identifies potential associations between diet, enterotype, and disease.

Co-infection best predicts respiratory viral infection in a wild host.

The dynamics of directly transmitted pathogens in natural populations are likely to result from the combined effects of host traits, pathogen biology, and interactions among pathogens within a host. Discovering how these factors work in concert to shape variation in pathogen dynamics in natural host-multi-pathogen systems is fundamental to understanding population health. Here, we describe temporal variation in incidence and then elucidate the effect of hosts trait, season and pathogen co-occurrence on host infection risk using one of the most comprehensive studies of co-infection in a wild population: a suite of seven directly transmitted viral and bacterial respiratory infections from a 4-year study of 200 free-ranging African buffalo Syncerus caffer. Incidence of upper respiratory infections was common throughout the study-five out of the seven pathogens appeared to be consistently circulating throughout our study population. One pathogen exhibited clear outbreak dynamics in our final study year and another was rarely detected. Co-infection was also common in this system: The strongest indicator of pathogen occurrence for respiratory viruses was in fact the presence of other viral respiratory infections. Host traits had minimal effects on odds of pathogen occurrence but did modify pathogen-pathogen associations. In contrast, only season predicted bacterial pathogen occurrence. Though a combination of environmental, behavioural, and physiological factors work together to shape disease dynamics, we found pathogen associations best determined infection risk. Our study demonstrates that, in the absence of very fine-scale data, the intricate changes among these factors are best represented by co-infection.

Human practices promote presence and abundance of disease-transmitting mosquito species.

Humans alter the environment at unprecedented rates through habitat destruction, nutrient pollution and the application of agrochemicals. This has recently been proposed to act as a potentially significant driver of pathogen-carrying mosquito species (disease vectors) that pose a health risk to humans and livestock. Here, we use a unique set of locations along a large geographical gradient to show that landscapes disturbed by a variety of anthropogenic stressors are consistently associated with vector-dominated mosquito communities for a wide range of human and livestock infections. This strongly suggests that human alterations to the environment promote the presence and abundance of disease vectors across large spatial extents. As such, it warrants further studies aimed at unravelling mechanisms underlying vector prevalence in mosquito communities, and opens up new opportunities for preventative action and predictive modelling of vector borne disease risks in relation to degradation of natural ecosystems.

Bighorn sheep gut microbiomes associate with genetic and spatial structure across a metapopulation.

Studies in laboratory animals demonstrate important relationships between environment, host traits, and microbiome composition. However, host-microbiome relationships in natural systems are understudied. Here, we investigate metapopulation-scale microbiome variation in a wild mammalian host, the desert bighorn sheep (Ovis canadensis nelsoni). We sought to identify over-represented microbial clades and understand how landscape variables and host traits influence microbiome composition across the host metapopulation. To address these questions, we performed 16S sequencing on fecal DNA samples from thirty-nine bighorn sheep across seven loosely connected populations in the Mojave Desert and assessed relationships between microbiome composition, environmental variation, geographic distribution, and microsatellite-derived host population structure and heterozygosity. We first used a phylogenetically-informed algorithm to identify bacterial clades conserved across the metapopulation. Members of genus Ruminococcaceae, genus Lachnospiraceae, and family Christensenellaceae R7 group were among the clades over-represented across the metapopulation, consistent with their known roles as rumen symbionts in domestic livestock. Additionally, compositional variation among hosts correlated with individual-level geographic and genetic structure, and with population-level differences in genetic heterozygosity. This study identifies microbiome community variation across a mammalian metapopulation, potentially associated with genetic and geographic population structure. Our results imply that microbiome composition may diverge in accordance with landscape-scale environmental and host population characteristics.

Elucidating cryptic dynamics of Theileria communities in African buffalo using a high-throughput sequencing informatics approach.

Increasing access to next-generation sequencing (NGS) technologies is revolutionizing the life sciences. In disease ecology, NGS-based methods have the potential to provide higher-resolution data on communities of parasites found in individual hosts as well as host populations.Here, we demonstrate how a novel analytical method, utilizing high-throughput sequencing of PCR amplicons, can be used to explore variation in blood-borne parasite (Theileria-Apicomplexa: Piroplasmida) communities of African buffalo at higher resolutions than has been obtained with conventional molecular tools.Results reveal temporal patterns of synchronized and opposite fluctuations of prevalence and relative abundance of Theileria spp. within the host population, suggesting heterogeneous transmission across taxa. Furthermore, we show that the community composition of Theileria spp. and their subtypes varies considerably between buffalo, with differences in composition reflected in mean and variance of overall parasitemia, thereby showing potential to elucidate previously unexplained contrasts in infection outcomes for host individuals.Importantly, our methods are generalizable as they can be utilized to describe blood-borne parasite communities in any host species. Furthermore, our methodological framework can be adapted to any parasite system given the appropriate genetic marker.The findings of this study demonstrate how a novel NGS-based analytical approach can provide fine-scale, quantitative data, unlocking opportunities for discovery in disease ecology.

Correction: Multiple innate antibacterial immune defense elements are correlated in diverse ungulate species.

[This corrects the article DOI: 10.1371/journal.pone.0225579.].

Multiple innate antibacterial immune defense elements are correlated in diverse ungulate species.

In this study, we aimed to evaluate to what extent different assays of innate immunity reveal similar patterns of variation across ungulate species. We compared several measures of innate antibacterial immune function across seven different ungulate species using blood samples obtained from captive animals maintained in a zoological park. We measured mRNA expression of two receptors involved in innate pathogen detection, toll-like receptors 2 and 5 (TLR2 and 5), the bactericidal capacity of plasma, as well as the number of neutrophils and lymphocytes. Species examined included aoudad (Ammotragus lervia), American bison (Bison bison bison), yak (Bos grunniens), Roosevelt elk (Cervus canadensis roosevelti), fallow deer (Dama dama), sika deer (Cervus nippon), and Damara zebra (Equus quagga burchellii). Innate immunity varied among ungulate species. However, we detected strong, positive correlations between the different measures of innate immunity-specifically, TLR2 and TLR5 were correlated, and the neutrophil to lymphocyte ratio was positively associated with TLR2, TLR5, and bacterial killing ability. Our results suggest that ecoimmunological study results may be quite robust to the choice of assays, at least for antibacterial innate immunity; and that, despite the complexity of the immune system, important sources of variation in immunity in natural populations may be discoverable with comparatively simple tools.

West Nile Virus in Wildlife and Nonequine Domestic Animals, South Africa, 2010-2018.

West Nile virus (WNV) lineage 2 is associated with neurologic disease in horses and humans in South Africa. Surveillance in wildlife and nonequine domestic species during 2010-2018 identified WNV in 11 (1.8%) of 608 animals with severe neurologic and fatal infections, highlighting susceptible hosts and risk for WNV epizootics in Africa.

A comparative assessment of adult mosquito trapping methods to estimate spatial patterns of abundance and community composition in southern Africa.

BACKGROUND: Assessing adult mosquito populations is an important component of disease surveillance programs and ecosystem health assessments. Inference from adult trapping datasets involves comparing populations across space and time, but comparisons based on different trapping methods may be biased if traps have different efficiencies or sample different subsets of the mosquito community. METHODS: We compared four widely-used trapping methods for adult mosquito data collection in Kruger National Park (KNP), South Africa: Centers for Disease Control miniature light trap (CDC), Biogents Sentinel trap (BG), Biogents gravid Aedes trap (GAT) and a net trap. We quantified how trap choice and sampling effort influence inferences on the regional distribution of mosquito abundance, richness and community composition. RESULTS: The CDC and net traps together collected 96% (47% and 49% individually) of the 955 female mosquitoes sampled and 100% (85% and 78% individually) of the 40 species or species complexes identified. The CDC and net trap also identified similar regional patterns of community composition. However, inference on the regional patterns of abundance differed between these traps because mosquito abundance in the net trap was influenced by variation in weather conditions. The BG and GAT traps collected significantly fewer mosquitoes, limiting regional comparisons of abundance and community composition. CONCLUSIONS: This study represents the first systematic assessment of trapping methods in natural savanna ecosystems in southern Africa. We recommend the CDC trap or the net trap for future monitoring and surveillance programs.

Immune stability predicts tuberculosis infection risk in a wild mammal.

Immunity is one of the most variable phenotypic traits in animals; however, some individuals may show less fluctuation in immune traits, resulting in stable patterns of immune variation over time. It is currently unknown whether immune variation has consequences for infectious disease risk. In this study, we identified moderately stable immune traits in wild African buffalo and asked whether the stability of these traits affected bovine tuberculosis (TB) infection risk. We found that adaptive immune traits such as the level of interferon-γ (IFN-γ) released after white blood cell stimulation, the number of circulating lymphocytes and the level of antibodies against bovine adenovirus-3 were moderately repeatable (i.e. stable) over time, whereas parameters related to innate immunity either had low repeatability (circulating eosinophil numbers) or were not repeatable (e.g. neutrophil numbers, plasma bacteria killing capacity). Intriguingly, individuals with more repeatable IFN-γ and lymphocyte levels were at a significantly higher risk of acquiring TB infection. In stark contrast, average IFN-γ and lymphocyte levels were poor predictors of TB risk, indicating that immune variability rather than absolute response level better captured variation in disease susceptibility. This work highlights the important and under-appreciated role of immune variability as a predictor of infection risk.

Bovine tuberculosis disturbs parasite functional trait composition in African buffalo.

Novel parasites can have wide-ranging impacts, not only on host populations, but also on the resident parasite community. Historically, impacts of novel parasites have been assessed by examining pairwise interactions between parasite species. However, parasite communities are complex networks of interacting species. Here we used multivariate taxonomic and trait-based approaches to determine how parasite community composition changed when African buffalo (Syncerus caffer) acquired an emerging disease, bovine tuberculosis (BTB). Both taxonomic and functional parasite richness increased significantly in animals that acquired BTB than in those that did not. Thus, the presence of BTB seems to catalyze extraordinary shifts in community composition. There were no differences in overall parasite taxonomic composition between infected and uninfected individuals, however. The trait-based analysis revealed an increase in direct-transmitted, quickly replicating parasites following BTB infection. This study demonstrates that trait-based approaches provide insight into parasite community dynamics in the context of emerging infections.

A Search for Snail-Related Answers to Explain Differences in Response of Schistosoma mansoni to Praziquantel Treatment among Responding and Persistent Hotspot Villages along the Kenyan Shore of Lake Victoria.

Following a 4-year annual praziquantel (PZQ) treatment campaign, the resulting prevalence of Schistosoma mansoni was seen to differ among individual villages along the Kenyan shore of Lake Victoria. We have investigated possible inherent differences in snail-related aspects of transmission among such 10 villages, including six persistent hotspot (PHS) villages (≤ 30% reduction in prevalence following repeated treatments) located along the west-facing shore of the lake and four PZQ-responding (RESP) villages (> 30% prevalence reduction following repeated treatment) along the Winam Gulf. When taking into account all sampling sites, times, and water hyacinth presence/absence, shoreline-associated Biomphalaria sudanica from PHS and RESP villages did not differ in relative abundance or prevalence of S. mansoni infection. Water hyacinth intrusions were associated with increased B. sudanica abundance. The deeper water snail Biomphalaria choanomphala was significantly more abundant in the PHS villages, and prevalence of S. mansoni among villages both before and after control was positively correlated with B. choanomphala abundance. Worm recoveries from sentinel mice did not differ between PHS and RESP villages, and abundance of non-schistosome trematode species was not associated with S. mansoni abundance. Biomphalaria choanomphala provides an alternative, deepwater mode of transmission that may favor greater persistence of S. mansoni in PHS villages. As we found evidence for ongoing S. mansoni transmission in all 10 villages, we conclude that conditions conducive for transmission and reinfection occur ubiquitously. This argues for an integrated, basin-wide plan for schistosomiasis control to counteract rapid reinfections facilitated by large snail populations and movements of infected people around the lake.