The effects of pre-hatch elevated corticosterone and post-hatch restrictive food availability on the HPA axis development of mallard ducks (Anas platyrhynchos).

Environmental changes can be stressors (altered habitat and food supply, climate change, etc.) to wild animals. Stressors trigger the hypothalamic pituitary adrenal (HPA) axis to release corticosterone (CORT) which modifies energy homeostasis. During nesting, stressed females can deposit increased concentrations of CORT into eggs, altering egg viability and offspring characteristics, constituting a significant mechanism regulating population productivity in subsequent generations. In this study, increased maternal disposition of CORT was mimicked through a 15 ng/g in ovo injection of CORT into mallard duck eggs. Growth and HPA axis function were measured during post-hatch development. For growth, changes in mass were compared at hatch, 7 weeks and 11 weeks. The HPA axis was assessed at seven weeks by measuring CORT at baseline, followed by restraint stress, dexamethasone (negative feedback) and ACTH (maximal adrenal capacity) challenges. At eleven weeks of age, ducks were subjected to a 6-day 25% feed reduction to simulate a poor quality environment to evaluate response to a chronic stressor by comparing CORT at baseline and after restraint stress. Growth and CORT concentration did not differ between treatments at seven weeks or after feed restriction (11 weeks). The CORT dosage administered did not appear to affect HPA axis development in ducklings. Mallards are a highly adaptable species and may have overcome any early alterations to their phenotype. Further research is needed to determine the effects of increased maternal CORT on growth and the development of the HPA axis in ducks. SUMMARY STATEMENT: This study examines how maternal stress (simulated through elevated corticosterone in ovo) and post-hatch chronic stressors (food restriction) affect the development of the HPA axis in a precocial bird.

Feather corticosterone during non-breeding correlates with multiple measures of physiology during subsequent breeding in a migratory seabird.

Carry-over effects in migratory birds are likely mediated by physiological processes that are activated in response to environmental variation. Such processes affect body condition and/or reproductive success, and can include corticosterone (CORT) because this hormone responds to environmental stressors and influences energy balance. Few studies have considered how CORT levels during non-breeding relate to a broader physiological profile during subsequent breeding, and fewer still have considered measures other than body condition. To explore CORT's potential role in carry-over effects, we investigated the relationship between CORT and foraging ecology of northern gannets (Morus bassanus) during the non-breeding period, and tested for associations between these factors and variation in a suite of physiological and biochemical metrics during subsequent breeding. Northern gannets are the largest seabird top predator in the North Atlantic and were among the hardest hit by the Deepwater Horizon oil blowout in the Gulf of Mexico in 2010. We used light-level geolocators to confirm winter origins of individuals in our study. No interrelationships were found among levels of CORT from feathers grown during non-breeding (CORTf) and variation in foraging ecology, measured by stable isotopes of carbon (δ13C) and nitrogen (δ15N) from the same feathers. CORTf was correlated negatively with hematocrit and positively with triglyceride measured during subsequent incubation, and explained more variation in these variables than did body mass during incubation. These findings provide support for the hypothesis that energy management, measured using CORTf, during non-breeding carries over to influence physiological measures other than body condition. Gannets that previously wintered within the Gulf of Mexico in the years following the Deepwater Horizon oil blowout had higher levels of CORTf compared to birds that wintered along the Atlantic coast, suggesting an increased energetic cost associated with visiting the Gulf of Mexico. Our results indicate that CORT during non-breeding is associated with a broader physiological profile during subsequent breeding than previously reported in birds.

Injecting epidemiology into population viability analysis: avian cholera transmission dynamics at an arctic seabird colony.

Infectious diseases have the potential to spread rapidly and cause high mortality within populations of immunologically naïve hosts. The recent appearance of avian cholera, a highly virulent disease of birds caused by the bacterium Pasteurella multocida, at remote Arctic seabird colonies is an emerging conservation concern. Determining disease risk to population viability requires a quantitative understanding of transmission potential and the factors that regulate epidemic persistence. Estimates of the basic (R0 ) and real-time (Rt ) reproductive number are critical in this regard - enumerating the number of secondary infections caused by each primary infection in a newly invaded host population and the decline in transmission rate as susceptible individuals are removed via mortality or immunized recovery. Here, we use data collected at a closely monitored common eider (Somateria mollissima) breeding colony located in the Canadian Arctic to examine transmission and host population dynamics. Specifically, we infer epidemic curves from daily mortality observations and use a likelihood-based procedure to estimate changes in the reproductive number over a series of annual outbreaks. These data are interpreted in relation to concurrent changes in host numbers to assess local extinction risk. Consistent with expectations for a novel pathogen invasion, case incidence increased exponentially during the initial wave of exposure (R0  = 2·5; generation time = 6·5 days ± 1·1 SD). Disease conditions gradually abated, but only after several years of smouldering infection (Rt  ≈ 1). In total, 6194 eider deaths were recorded during outbreaks spanning eight consecutive breeding seasons. Breeding pair abundance declined by 56% from the pre-outbreak peak; however, a robust population of >4000 pairs remained intact upon epidemic fade-out. Overall, outbreak patterns were consistent with herd immunity acting as a mitigating factor governing in the extent and duration of mortality. Disease mortality is frequently modelled as a form of stochastic catastrophe in wildlife population assessments, whereas our approach gives shape to the functional response between transmission and host population dynamics. We conclude that increased emphasis on integrating epidemiological and population processes is essential to predicting the conservation impact of emerging infectious diseases in wildlife.

Evidence for the exchange of blood parasites between North America and the Neotropics in blue-winged teal (Anas discors).

Blue-winged teal (Anas discors) are abundant, small-bodied dabbling ducks that breed throughout the prairies of the northcentral USA and central Canada and that winter in the southern USA and northern Neotropics. Given the migratory tendencies of this species, it is plausible that blue-winged teal may disperse avian pathogens, such as parasites causing avian malaria, between spatially distant areas. To test the hypothesis that blue-winged teal play a role in the exchange of blood parasites between North America and areas further south, we collected information on migratory tendencies of this species and sampled birds at spatially distant areas during breeding and non-breeding periods to diagnose and genetically characterize parasitic infections. Using a combination of band recovery data, satellite telemetry, molecular diagnostics, and genetic analyses, we found evidence for (1) migratory connectivity of blue-winged teal between our sampling locations in the Canadian prairies and along the US Gulf Coast with areas throughout the northern Neotropics, (2) parasite acquisition at both breeding and non-breeding areas, (3) infection of blue-winged teal sampled in Canada and the USA with Plasmodium parasite lineages associated with the Neotropics, and (4) infection of blue-winged teal with parasites that were genetically related to those previously reported in waterfowl in both North America and South America. Collectively, our results suggest that blue-winged teal likely play a role in the dispersal of blood parasites between the Neotropics and North America, and therefore, the targeting of this species in surveillance programs for the early detection of Neotropical-origin avian pathogens in the USA may be informative.

Feather corticosterone reveals effect of moulting conditions in the autumn on subsequent reproductive output and survival in an Arctic migratory bird.

For birds, unpredictable environments during the energetically stressful times of moulting and breeding are expected to have negative fitness effects. Detecting those effects however, might be difficult if individuals modulate their physiology and/or behaviours in ways to minimize short-term fitness costs. Corticosterone in feathers (CORTf) is thought to provide information on total baseline and stress-induced CORT levels at moulting and is an integrated measure of hypothalamic-pituitary-adrenal activity during the time feathers are grown. We predicted that CORTf levels in northern common eider females would relate to subsequent body condition, reproductive success and survival, in a population of eiders nesting in the eastern Canadian Arctic during a capricious period marked by annual avian cholera outbreaks. We collected CORTf data from feathers grown during previous moult in autumn and data on phenology of subsequent reproduction and survival for 242 eider females over 5 years. Using path analyses, we detected a direct relationship between CORTf and arrival date and body condition the following year. CORTf also had negative indirect relationships with both eider reproductive success and survival of eiders during an avian cholera outbreak. This indirect effect was dramatic with a reduction of approximately 30% in subsequent survival of eiders during an avian cholera outbreak when mean CORTf increased by 1 standard deviation. This study highlights the importance of events or processes occurring during moult on subsequent expression of life-history traits and relation to individual fitness, and shows that information from non-destructive sampling of individuals can track carry-over effects across seasons.

Experimental relationships between levels of corticosterone in plasma and feathers in a free-living bird.

Integrated measures of corticosterone (CORT), such as from feathers (CORTf), have intuitive appeal because they incorporate both the duration and amplitude of glucocorticoid secretion. An association between CORTf and plasma CORT has never been shown in wild birds, and it is unclear as to when and whether these measures should be correlated, given that they are fundamentally different yet related measures of physiology. We hypothesized that CORTf should correlate with instantaneous measurements of plasma CORT when the latter reflect sustained changes in the activity of the hypothalamic-pituitary-adrenal (HPA) axis. To test this, we experimentally manipulated levels of plasma CORT in wild nestling tree swallows (Tachycineta bicolor) using 5 day time-release CORT pellets, and measured plasma CORT and growth parameters before, during and at the end of hormone manipulation (days 7, 9 and 11 post-hatch, respectively). CORTf and plasma CORT were significantly positively related only when the latter was at its highest and most variable among individuals (day 9). A similar relationship was expected at day 11, but plasma CORT had returned to near-original levels. Nestlings with higher CORTf were smaller, lighter and less likely to fledge, but we did not detect seasonal effects on CORTf. Our results clearly demonstrate that CORTf from free-living birds can reflect plasma CORT, but correlations may not always be expected, especially if elevations in plasma CORT are relatively modest and of short duration. Our work suggests that CORTf is best used to study the activity of the HPA axis over relatively long time frames and can be used effectively to advance avian ecology.

Isolation and characterization of Brachyspira spp. including "Brachyspira hampsonii" from lesser snow geese (Chen caerulescens caerulescens) in the Canadian Arctic.

Brachyspira is associated with diarrhea and colitis in pigs, and control of these pathogens is complicated by their complex ecology. Identification of wildlife reservoirs of Brachyspira requires the discrimination of colonized animals and those simply contaminated through environmental exposure. Lesser snow geese (Chen caerulescens caerulescens) were sampled in the Canadian arctic during the summer of 2011, and cloacal swabs were cultured on selective media. Brachyspira isolates were obtained from 15/170 (8.8 %) samples, and 12/15 isolates were similar to isolates previously recovered from pigs, including "Brachyspira hampsonii", a recently characterized species associated with dysentery-like disease in pigs in North America. A pilot inoculation study with one strongly ß-hemolytic B. hampsonii isolate resulted in fecal shedding of the isolate by inoculated pigs for up to 14 days post-inoculation, but no severe clinical disease. Results of this study indicate that lesser snow geese can be colonized by Brachyspira strains that can also colonize pigs. Millions of lesser snow geese (C. caerulescens caerulescens) travel through the major pork-producing areas of Canada and the USA during their annual migration, making them a potential factor in the continental distribution of these bacteria.

BAITING AND BANDING: EXPERT OPINION ON HOW BAIT TRAPPING MAY INFLUENCE THE OCCURRENCE OF HIGHLY PATHOGENIC AVIAN INFLUENZA (HPAI) AMONG DABBLING DUCKS.

A Eurasian lineage highly pathogenic avian influenza virus (HPAIV) of the clade 2.3.4.4b (Goose/Guangdong lineage) was detected in migratory bird populations in North America in December 2021, and it, along with its reassortants, have since caused wild and domestic bird outbreaks across the continent. Relative to previous outbreaks, HPAIV cases among wild birds in 2022 exhibited wider geographic extent within North America and higher levels of mortality, suggesting the potential for population-level impacts. Given the possible conservation implications of HPAIV in wild birds, natural resource managers have sought guidance on actions that may mitigate negative effects of disease among North American bird populations, including modification of existing management practices. Banding of waterfowl is a critical tool for population management for several harvested species in North America, but some banding techniques, such as bait trapping, can lead to increased congregation of waterfowl, potentially altering HPAIV transmission. We used an expert opinion exercise to assess how bait trapping of dabbling ducks in Canada may influence HPAIV transmission and wild bird health. The expert group found that it is moderately likely that bait trapping of dabbling ducks in wetlands will significantly increase the transmission of HPAIV among individual ducks, but there is a low probability that this will result in significant population-level effects on North American dabbling ducks. Considering the lack of empirical work studying how capture and handling methods may change transmission of HPAIV among waterfowl, as well as the importance of bait trapping for waterfowl management in North America, future work should focus on filling knowledge gaps pertaining to the influence of baiting on HPAIV occurrence to better inform banding procedures and management decision making.

Site-specific spatiotemporal occurrence and molecular congener distributions of naphthenic acids in Athabasca oil sands wetlands of Alberta, Canada.

The Athabasca oil sands region (AOSR) of Alberta, Canada is notable for its considerable unconventional petroleum extraction projects, where bitumen is extracted from naturally-occurring oil sands ore. The large scale of these heavy crude oil developments raises concerns because of their potential to distribute and/or otherwise influence the occurrence, behaviour, and fate of environmental contaminants. Naphthenic acids (NAs) are one such contaminant class of concern in the AOSR, so studies have examined the occurrence and molecular profiles of NAs in the region. We catalogued the spatiotemporal occurrence and characteristics of NAs in boreal wetlands in the AOSR over a 7-year period, using derivatized liquid chromatography-tandem mass spectrometry (LC-MS/MS). Comparing median concentrations of NAs across these wetlands revealed a pattern of NAs suggesting NAs in surface waters derived from oil sands deposits. Opportunistic wetlands that formed adjacent to reclaimed overburden and other reclamation activities had the highest concentrations of NAs and consistent patterns suggestive of bitumen-derived inputs. However, similar patterns in the occurrence of NAs were also observed in undeveloped natural wetlands located above the known surface-mineable oil sands deposit that underlies the region. Intra-annual sampling results along with inter-annual comparisons across wetlands demonstrated that differences in the spatial and temporal NA concentrations were dependent on local factors, particularly when naturally occurring oil sands ores were observed in the wetland or drainage catchment.

Genomic and transcriptomic characterization of delta SARS-CoV-2 infection in free-ranging white-tailed deer (Odocoileus virginianus).

White-tailed deer (WTD) are susceptible to SARS-CoV-2 and represent an important species for surveillance. Samples from WTD (n = 258) collected in November 2021 from Québec, Canada were analyzed for SARS-CoV-2 RNA. We employed viral genomics and host transcriptomics to further characterize infection and investigate host response. We detected Delta SARS-CoV-2 (B.1.617.2) in WTD from the Estrie region; sequences clustered with human sequences from October 2021 from Vermont, USA, which borders this region. Mutations in the S-gene and a deletion in ORF8 were detected. Host expression patterns in SARS-CoV-2 infected WTD were associated with the innate immune response, including signaling pathways related to anti-viral, pro- and anti-inflammatory signaling, and host damage. We found limited correlation between genes associated with innate immune response from human and WTD nasal samples, suggesting differences in responses to SARS-CoV-2 infection. Our findings provide preliminary insights into host response to SARS-CoV-2 infection in naturally infected WTD.

Characterization of neurotropic HPAI H5N1 viruses with novel genome constellations and mammalian adaptive mutations in free-living mesocarnivores in Canada.

The GsGd lineage (A/goose/Guangdong/1/1996) H5N1 virus was introduced to Canada in 2021/2022 through the Atlantic and East Asia-Australasia/Pacific flyways by migratory birds. This was followed by unprecedented outbreaks affecting domestic and wild birds, with spillover into other animals. Here, we report sporadic cases of H5N1 in 40 free-living mesocarnivore species such as red foxes, striped skunks, and mink in Canada. The clinical presentations of the disease in mesocarnivores were consistent with central nervous system infection. This was supported by the presence of microscopic lesions and the presence of abundant IAV antigen by immunohistochemistry. Some red foxes that survived clinical infection developed anti-H5N1 antibodies. Phylogenetically, the H5N1 viruses from the mesocarnivore species belonged to clade 2.3.4.4b and had four different genome constellation patterns. The first group of viruses had wholly Eurasian (EA) genome segments. The other three groups were reassortant viruses containing genome segments derived from both North American (NAm) and EA influenza A viruses. Almost 17 percent of the H5N1 viruses had mammalian adaptive mutations (E627 K, E627V and D701N) in the polymerase basic protein 2 (PB2) subunit of the RNA polymerase complex. Other mutations that may favour adaptation to mammalian hosts were also present in other internal gene segments. The detection of these critical mutations in a large number of mammals within short duration after virus introduction inevitably highlights the need for continually monitoring and assessing mammalian-origin H5N1 clade 2.3.4.4b viruses for adaptive mutations, which potentially can facilitate virus replication, horizontal transmission and posing pandemic risks for humans.

Predicting weekly variation of Culex tarsalis (Diptera: Culicidae) West Nile virus infection in a newly endemic region, the Canadian prairies.

West Nile virus (WNV) spread across most of North America within a short time period after its incursion into the Western Hemisphere. The Canadian prairies had the highest human incidence of WNV disease in Canada, particularly in 2007. Statistical modeling and geographic information systems can be used to develop a predictive model and facilitate the mobilization of targeted disease management strategies. Using data collected between 2005 and 2008, we constructed models integrating abiotic and biotic factors to predict the WNV infection rate in female Culex tarsalis Coquillett, the primary vector of WNV in the Canadian prairies. During the study period, the highest mean Cx. tarsalis infection rate was during week 34 (late August). The Cx. tarsalis infection rate increased with increasing Cx. tarsalis abundance and mean temperature lagged from 1 to 8 wk, but decreased with increasing mean precipitation lagged from 2 to 6 wk. Furthermore, precipitation was a 'distorter variable' that altered the association between Cx. tarsalis abundance and the WNV infection rate. Our model clarified how weather influenced the Cx. tarsalis infection rate in the Canadian prairies, a newly and highly WNV endemic region of North America. An understanding of the role of lagged weather variables was essential for providing sufficient lead time to predict WNV occurrence, and for implementing disease control and prevention strategies. Furthermore, it is a useful tool for assessing the potential effects of future climate change on WNV in areas near its northern distributional limit.

Identification of Metabolomic Biomarkers of Long-Term Stress Using NMR Spectroscopy in a Diving Duck.

Human-induced environmental changes that act as long-term stressors pose significant impacts on wildlife health. Energy required for maintenance or other functions may be re-routed towards coping with stressors, ultimately resulting in fluctuations in metabolite levels associated with energy metabolism. While metabolomics approaches are used increasingly to study environmental stressors, its use in studying stress in birds is in its infancy. We implanted captive lesser scaup (Aythya affinis) with either a biodegradable corticosterone (CORT) pellet to mimic the effects of a prolonged stressor or a placebo pellet. 1D 1H nuclear magnetic resonance (NMR) spectroscopy was performed on serum samples collected over 20 days after implant surgery. We hypothesized that CORT pellet-induced physiological stress would alter energy metabolism and result in distinct metabolite profiles in ducks compared with placebo (control). Quantitative targeted metabolite analysis revealed that metabolites related to energy metabolism: glucose, formate, lactate, glutamine, 3-hydroxybutyrate, ethanolamine, indole-3- acetate, and threonine differentiated ducks with higher circulatory CORT from controls on day 2. These metabolites function as substrates or intermediates in metabolic pathways related to energy production affected by elevated serum CORT. The use of metabolomics shows promise as a novel tool to identify and characterize physiological responses to stressors in wild birds.

Investigating SARS-CoV-2 Susceptibility in Animal Species: A Scoping Review.

In the early stages of response to the SARS-CoV-2 pandemic, it was imperative for researchers to rapidly determine what animal species may be susceptible to the virus, under low knowledge and high uncertainty conditions. In this scoping review, the animal species being evaluated for SARS-CoV-2 susceptibility, the methods used to evaluate susceptibility, and comparing the evaluations between different studies were conducted. Using the PRISMA-ScR methodology, publications and reports from peer-reviewed and gray literature sources were collected from databases, Google Scholar, the World Organization for Animal Health (OIE), snowballing, and recommendations from experts. Inclusion and relevance criteria were applied, and information was subsequently extracted, categorized, summarized, and analyzed. Ninety seven sources (publications and reports) were identified which investigated 649 animal species from eight different classes: Mammalia, Aves, Actinopterygii, Reptilia, Amphibia, Insecta, Chondrichthyes, and Coelacanthimorpha. Sources used four different methods to evaluate susceptibility, in silico, in vitro, in vivo, and epidemiological analysis. Along with the different methods, how each source described "susceptibility" and evaluated the susceptibility of different animal species to SARS-CoV-2 varied, with conflicting susceptibility evaluations evident between different sources. Early in the pandemic, in silico methods were used the most to predict animal species susceptibility to SARS-CoV-2 and helped guide more costly and intensive studies using in vivo or epidemiological analyses. However, the limitations of all methods must be recognized, and evaluations made by in silico and in vitro should be re-evaluated when more information becomes available, such as demonstrated susceptibility through in vivo and epidemiological analysis.

Understanding and strengthening wildlife and zoonotic disease policy processes: A research imperative.

The COVID-19 pandemic highlights the urgency and importance of monitoring, managing and addressing zoonotic diseases, and the acute challenges of doing so with sufficient inter-jurisdictional coordination in a dynamic global context. Although wildlife pathogens are well-studied clinically and ecologically, there is very little systematic scholarship on their management or on policy implications. The current global pandemic therefore presents a unique social science research imperative: to understand how decisions are made about preventing and responding to wildlife diseases, especially zoonoses, and how those policy processes can be improved as part of early warning systems, preparedness and rapid response. To meet these challenges, we recommend intensified research efforts towards: (i) generating functional insights about wildlife and zoonotic disease policy processes, (ii) enabling social and organizational learning to mobilize those insights, (iii) understanding epistemic instability to address populist anti-science and (iv) anticipating evolving and new zoonotic emergences, especially their human dimensions. Since policy processes for zoonoses can be acutely challenged during the early stages of an epidemic or pandemic, such insights can provide a pragmatic, empirically-based roadmap for enhancing their robustness and efficacy, and benefiting long-term decision-making efforts.

SARS-CoV-2 wildlife surveillance surrounding mink farms in British Columbia, Canada.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect many wild and domestic animal species. Farmed American mink (Neovison vison) are particularly susceptible to infection. Outbreaks of SARS-CoV-2 were detected in farmed mink on three mink farms in British Columbia (BC), Canada between December 2020 and May 2021. In BC, mink farm density and proximity to wildlife habitats increase transmission risks from infected farmed mink. The objective of this study is to investigate the risk of SARS-CoV-2 spreading to and from wildlife in the area surrounding infected mink farms in BC, Canada, as well as to compare the effectiveness of physical and camera trapping surveillance methodologies. Methods: A combination of physical and camera trapping was used on and around three BC mink farms with active SARS-CoV-2 infections between January 22, 2021, and July 10, 2021. Samples from trapped animals, including escaped farmed mink, were tested for SARS-CoV-2. Camera images from one mink farm were reviewed to determine species and proximity to the mink barn. Results: Seventy-one animals of nine species were captured and sampled. Three captured mink tested positive for SARS-CoV-2 by polymerase chain reaction and serology; the remaining samples were negative for SARS-CoV-2. Genotyping of the three positive mink indicated these were domestic (vs. wild) mink. A total of 440 animals of 16 species were photographed at the one farm where cameras were deployed. Conclusion: Detection of SARS-CoV-2 in escaped farmed mink is concerning and demonstrates the potential for transmission from farmed mink to wildlife, particularly given the observation of wildlife known to be susceptible to SARS-CoV-2 near infected mink farms. Combined use of physical and camera trapping contributed to the breadth of the results and is strongly recommended for future surveillance.

Genetic and Antigenic Characterization of Avian Avulavirus Type 6 (AAvV-6) Circulating in Canadian Wild Birds (2005-2017).

We describe for the first time the genetic and antigenic characterization of 18 avian avulavirus type-6 viruses (AAvV-6) that were isolated from wild waterfowl in the Americas over the span of 12 years. Only one of the AAvV-6 viruses isolated failed to hemagglutinate chicken red blood cells. We were able to obtain full genome sequences of 16 and 2 fusion gene sequences from the remaining 2 isolates. This is more than double the number of full genome sequences available at the NCBI database. These AAvV-6 viruses phylogenetically grouped into the 2 existing AAvV-6 genotype subgroups indicating the existence of an intercontinental epidemiological link with other AAvV-6 viruses isolated from migratory waterfowl from different Eurasian countries. Antigenic maps made using HI assay data for these isolates showed that the two genetic groups were also antigenically distinct. An isolate representing each genotype was inoculated in specific pathogen free (SPF) chickens, however, no clinical symptoms were observed. A duplex fusion gene based real-time assay for the detection and genotyping of AAvV-6 to genotype 1 and 2 was developed. Using the developed assay, the viral shedding pattern in the infected chickens was examined. The chickens infected with both genotypes were able to shed the virus orally for about a week, however, no significant cloacal shedding was detected in chickens of both groups. Chickens in both groups developed detectable levels of anti-hemagglutinin antibodies 7 days after infection.

Effects of two pesticides on northern leopard frog (Lithobates pipiens) stress metrics: Blood cell profiles and corticosterone concentrations.

Amphibians are declining globally. Exposure to pesticides has been implicated in decreasing amphibian immune function, thus increasing their susceptibility to parasites and disease and thereby negatively affecting individuals and populations. Amphibians are likely exposed to neonicotinoids because these widely used insecticides are highly soluble in water and because amphibian freshwater habitats are often embedded in agroecosystems. Herein, we investigate the effects of long-term exposure to two individual neonicotinoids (clothianidin or thiamethoxam) at either low or high concentrations (2.5 or 250 µg/L) on northern leopard frog (Lithobates pipiens) blood cell profiles and concentrations of corticosterone, an energy-mediating hormone associated with stress. Larval frogs from Gosner stage 25 to 46 were exposed to pesticide and control treatments in outdoor mesocosms. Corticosterone concentrations were measured after 6 d of exposure, and blood cell profiles were assessed once frogs reached Gosner stage 46 (following 8 w of exposure). No significant changes were found in erythrocyte counts, leukocyte counts, monocyte to leukocyte ratios or corticosterone concentrations between treatments. However, exposure to either 2.5 or 250 µg/L of clothianidin, or 250 µg/L of thiamethoxam decreased neutrophil to lymphocyte ratios and neutrophil to leukocyte ratios, and exposure to 2.5 µg/L of clothianidin or 250 µg/L of thiamethoxam decreased eosinophil to leukocyte ratios. Our results indicate that long-term exposure to neonicotinoids can alter leukocyte profiles, indicative of a stress response. Future studies should investigate whether chronic exposure to neonicotinoids affect multiple measures of stress differently or influences the susceptibility of amphibians to parasites and pathogens. Our work underscores the importance of continued use of multiple measures of stress for different amphibian species when undertaking ecotoxicological assessments.

Herd immunity drives the epidemic fadeout of avian cholera in Arctic-nesting seabirds.

Avian cholera, caused by the bacterium Pasteurella multocida, is a common and important infectious disease of wild birds in North America. Between 2005 and 2012, avian cholera caused annual mortality of widely varying magnitudes in Northern common eiders (Somateria mollissima borealis) breeding at the largest colony in the Canadian Arctic, Mitivik Island, Nunavut. Although herd immunity, in which a large proportion of the population acquires immunity to the disease, has been suggested to play a role in epidemic fadeout, immunological studies exploring this hypothesis have been missing. We investigated the role of three potential drivers of fadeout of avian cholera in eiders, including immunity, prevalence of infection, and colony size. Each potential driver was examined in relation to the annual real-time reproductive number (Rt) of P. multocida, previously calculated for eiders at Mitivik Island. Each year, colony size was estimated and eiders were closely monitored, and evaluated for infection and serological status. We demonstrate that acquired immunity approximated using antibody titers to P. multocida in both sexes was likely a key driver for the epidemic fadeout. This study exemplifies the importance of herd immunity in influencing the dynamics and fadeout of epidemics in a wildlife population.

Waterfowl occurrence and residence time as indicators of H5 and H7 avian influenza in North American Poultry.

Avian influenza (AI) affects wild aquatic birds and poses hazards to human health, food security, and wildlife conservation globally. Accordingly, there is a recognized need for new methods and tools to help quantify the dynamic interaction between wild bird hosts and commercial poultry. Using satellite-marked waterfowl, we applied Bayesian joint hierarchical modeling to concurrently model species distributions, residency times, migration timing, and disease occurrence probability under an integrated animal movement and disease distribution modeling framework. Our results indicate that migratory waterfowl are positively related to AI occurrence over North America such that as waterfowl occurrence probability or residence time increase at a given location, so too does the chance of a commercial poultry AI outbreak. Analyses also suggest that AI occurrence probability is greatest during our observed waterfowl northward migration, and less during the southward migration. Methodologically, we found that when modeling disparate facets of disease systems at the wildlife-agriculture interface, it is essential that multiscale spatial patterns be addressed to avoid mistakenly inferring a disease process or disease-environment relationship from a pattern evaluated at the improper spatial scale. The study offers important insights into migratory waterfowl ecology and AI disease dynamics that aid in better preparing for future outbreaks.