Body size and early marine conditions drive changes in Chinook salmon productivity across northern latitude ecosystems.

Disentangling the influences of climate change from other stressors affecting the population dynamics of aquatic species is particularly pressing for northern latitude ecosystems, where climate-driven warming is occurring faster than the global average. Chinook salmon (Oncorhynchus tshawytscha) in the Yukon-Kuskokwim (YK) region occupy the northern extent of their species' range and are experiencing prolonged declines in abundance resulting in fisheries closures and impacts to the well-being of Indigenous people and local communities. These declines have been associated with physical (e.g., temperature, streamflow) and biological (e.g., body size, competition) conditions, but uncertainty remains about the relative influence of these drivers on productivity across populations and how salmon-environment relationships vary across watersheds. To fill these knowledge gaps, we estimated the effects of marine and freshwater environmental indicators, body size, and indices of competition, on the productivity (adult returns-per-spawner) of 26 Chinook salmon populations in the YK region using a Bayesian hierarchical stock-recruitment model. Across most populations, productivity declined with smaller spawner body size and sea surface temperatures that were colder in the winter and warmer in the summer during the first year at sea. Decreased productivity was also associated with above average fall maximum daily streamflow, increased sea ice cover prior to juvenile outmigration, and abundance of marine competitors, but the strength of these effects varied among populations. Maximum daily stream temperature during spawning migration had a nonlinear relationship with productivity, with reduced productivity in years when temperatures exceeded thresholds in main stem rivers. These results demonstrate for the first time that well-documented declines in body size of YK Chinook salmon were associated with declining population productivity, while taking climate into account.

Evaluating injuries and illnesses that occurred during the Yukon Quest International sled dog race, 2018-2020.

Introduction: The purpose of this study was to evaluate medical record data from the 2018-2020 Yukon Quest International Sled Dog race to examine injury patterns and risk factors for dogs competing in multi-day ultra-endurance events. Specifically, we summarized injuries and illnesses that resulted in canine athletes being removed ("dropped") from competition, and in orthopedic injuries diagnosed in both dropped and finished dogs. Methods: The records of 989 dogs that started the race were examined, but only records from dogs in teams that went on to finish the race were included, for a total of 711 records. Results and discussion: Three hundred and sixty five dogs (51.3%) were noted to have at least one abnormal finding in their veterinary medical record during the race. Orthopedic injuries were most common, and 291 injuries were ultimately diagnosed in 234 dogs (32.9%). Ultimately, 206 dogs (29%) were dropped from competition, for any reason. The most common reasons for dropping dogs were orthopedic injuries (156 dogs; 188 injuries), gastrointestinal illness (22 dogs), and cardiorespiratory disease (7 dogs). Most orthopedic injuries in dropped dogs occurred in the thoracic limb (n = 121 dogs; 151 injuries). Of those, injuries to the shoulder were most common (n = 77), followed by injuries to the carpus (n = 59), and injury to the pelvic limb (n = 32). Carpal injuries were the most prevalent injury diagnosed in dogs that went on to finish the race (71 of 85 injuries). Carpal injuries were the most prevalent injuries overall in 2018 (51%) and 2019 (52%). In 2020, shoulder injuries were most prevalent (27%), suggesting that trail conditions may have differed between years. The majority of dogs with an orthopedic injury ultimately were removed from competition (156 of 234, or 66.6%), but the likelihood of finishing the race with an injury depended on the type of injury sustained; 71 of 130 dogs (54.6%) with a carpal injury went on to finish the race, whereas only 9 of 86 dogs with a shoulder injury (10.5%) went on to finish. The results of this study can assist mushers and veterinarians in preparing for races, and in decision making during endurance sled dog races.

Snow depth influences harvest of a boreal ungulate more than socio-economic factors: Implications for food security in a changing climate.

Climate change may affect the ability of hunters to harvest wildlife and, hence, threaten food security of local people. However, few studies have investigated the relative influence of environmental conditions on wildlife harvest rates. We harnessed a 24-year dataset of harvest dates for a boreal ungulate in a region where climate change is having pronounced impacts on snow depth, precipitation, and temperatures to investigate the effect of weather on harvest rates. We used generalized linear models and a model selection framework to examine the influence of weather covariates (snow depth, mean daily temperature, precipitation) and socio-economic factors (gasoline and red meat prices, employment rates, and moose [Alces americanus] harvest) on harvest rates of bison (Bison bison) in Yukon, Canada, at two temporal scales: annual and daily. At an annual scale, snow depth was the only covariate that was important in explaining bison harvest. No socioeconomic variables improved our model beyond the null. At the daily scale, snow depth and mean daily temperature influenced bison harvest rates, with a 1 SD increase resulting in a 14 % and 9 % increase in daily harvest rates, respectively. Increased snow depth facilitates ease of travel in remote, roadless areas by snowmobile to locate bison and truncates movements of bison, resulting in increased harvest rates. Decreased snow depth due to climate change will impact hunter access to boreal ungulates and food security for northern people. More broadly, our data suggests that in some socioecological systems, environmental covariates have a greater influence on wildlife harvest rates than socioeconomic factors and need to be considered in future studies to better understand and predict harvest rates.

Applying Machine Learning to investigate metal isotope variations at the watershed scale: A case study with lithium isotopes across the Yukon River Basin.

Constraining the multiple climatic, lithological, topographic, and geochemical variables controlling isotope variations in large rivers is often challenging with standard statistical methods. Machine learning (ML) is an efficient method for analyzing multidimensional datasets, resolving correlated processes, and exploring relationships between variables simultaneously. We tested four ML algorithms to elucidate the controls of riverine δ7Li variations across the Yukon River Basin (YRB). We compiled (n = 102) and analyzed new samples (n = 21), producing a dataset of 123 river water samples collected across the basin during the summer including δ7Li and extracted environmental, climatological, and geological characteristics of the drainage area for each sample from open-access geospatial databases. The ML models were trained, tuned, and tested under multiple scenarios to avoid issues such as overfitting. Random Forests (RF) performed best at predicting δ7Li across the basin, with the median model explaining 62 % of the variance. The most important variables controlling δ7Li across the basin are elevation, lithology, and past glacial coverage, which ultimately influence weathering congruence. Riverine δ7Li has a negative dependence on elevation. This reflects congruent weathering in kinetically-limited mountain zones with short residence times. The consistent ranking of lithology, specifically igneous and metamorphic rock cover, as a top feature controlling riverine δ7Li modeled by the RFs is unexpected. Further study is required to validate this finding. Rivers draining areas that were extensively covered during the last glacial maximum tend to have lower δ7Li due to immature weathering profiles resulting in short residence times, less secondary mineral formation and therefore more congruent weathering. We demonstrate that ML provides a fast, simple, visualizable, and interpretable approach for disentangling key controls of isotope variations in river water. We assert that ML should become a routine tool, and present a framework for applying ML to analyze spatial metal isotope data at the catchment scale.

Adult spawners: A critical period for subarctic Chinook salmon in a changing climate.

Concurrent, distribution-wide abundance declines of some Pacific salmon species, including Chinook salmon (Oncorhynchus tshawytscha), highlights the need to understand how vulnerability at different life stages to climate stressors affects population dynamics and fisheries sustainability. Yukon River Chinook salmon stocks are among the largest subarctic populations, near the northernmost extent of the species range. Existing research suggests that Yukon River Chinook salmon population dynamics are largely driven by factors occurring between the adult spawner life stage and their offspring's first summer at sea (second year post-hatching). However, specific mechanisms sustaining chronic poor productivity are unknown, and there is a tremendous sense of urgency to understand causes, as declines of these stocks have taken a serious toll on commercial, recreational, and indigenous subsistence fisheries. Therefore, we leveraged multiple existing datasets spanning parent and juvenile stages of life history in freshwater and marine habitats. We analyzed environmental data in association with the production of offspring that survive to the marine juvenile stage (juveniles per spawner). These analyses suggest more than 45% of the variability in the production of juvenile Chinook salmon is associated with river temperatures or water discharge levels during the parent spawning migration. Over the past two decades, parents that experienced warmer water temperatures and lower discharge in the mainstem Yukon River produced fewer juveniles per spawning adult. We propose the adult spawner life stage as a critical period regulating population dynamics. We also propose a conceptual model that can explain associations between population dynamics and climate stressors using independent data focused on marine nutrition and freshwater heat stress. It is sobering to consider that some of the northernmost Pacific salmon habitats may already be unfavorable to these cold-water species. Our findings have immediate implications, given the common assumption that northern ranges of Pacific salmon offer refugia from climate stressors.

Challenging Health Service Delivery Models to Improve Access to Physical Therapy in Rural, Remote and Northern Communities.

Effective rural, remote and northern physical therapy services are an important component of health care. Providing these services with limited financial and human resources can present many challenges. Indigenous communities also have unique needs that must be considered when providing health care. Most current service delivery models are based in Western medicine practices and most often, do not account for the local, political, cultural and spiritual needs of communities. In this perspective article, I discuss the challenges of providing these services in rural Yukon to many small First Nation communities. Relationship building is paramount to effective and meaningful health care programs, and this means a change in current practice approaches. We need to challenge the delivery models and be open to other ways of knowing, beyond the Western biomedical approach that is the foundation of our profession. It is imperative that physical therapists, health care providers and funders seek new and innovative ways to provide services to the rural, remote and northern communities while ensuring a culturally humble approach.

Subarctic soil carbon losses after deforestation for agriculture depend on permafrost abundance.

The northern circumpolar permafrost region is experiencing considerable warming due to climate change, which is allowing agricultural production to expand into regions of discontinuous and continuous permafrost. The conversion of forests to arable land might further enhance permafrost thaw and affect soil organic carbon (SOC) that had previously been protected by frozen ground. The interactive effect of permafrost abundance and deforestation on SOC stocks has hardly been studied. In this study, soils were sampled on 18 farms across the Yukon on permafrost and non-permafrost soils to quantify the impact of land-use change from forest to cropland and grassland on SOC stocks. Furthermore, the soils were physically and chemically fractionated to assess the impact of land-use change on different functional pools of SOC. On average, permafrost-affected forest soils lost 15.6 ± 21.3% of SOC when converted to cropland and 23.0 ± 13.0% when converted to grassland. No permafrost was detected in the deforested soils, indicating that land-use change strongly enhanced warming and subsequent thawing. In contrast, the change in SOC at sites without permafrost was not significant but had a slight tendency to be positive. SOC stocks were generally lower at sites without permafrost under forest. Furthermore, land-use change increased mineral-associated SOC, while the fate of particulate organic matter (POM) after land-use change depended on permafrost occurrence. Permafrost soils showed significant POM losses after land-use change, while grassland sites without permafrost gained POM in the topsoil. The results showed that the fate of SOC after land-use change greatly depended on the abundance of permafrost in the pristine forest, which was driven by climatic conditions more than by soil properties. It can be concluded that in regions of discontinuous permafrost in particular, initial conditions in forest soils should be considered before deforestation to minimize its climate impact.

The Yukon's experience with COVID-19: Travel restrictions, variants and spread among the unvaccinated.

The Yukon's experience with coronavirus disease 2019 (COVID-19) has been an interesting one; the territory successfully implemented travel restrictions to limit importing the virus and rolled out vaccines quickly compared to most Canadian jurisdictions. However, the Yukon's first wave of COVID-19 in June and July 2021 overwhelmed the healthcare system due to widespread transmission in unvaccinated children, youth and adults, despite high vaccination uptake overall and mandatory masking. This experience highlights the importance of continued support for public vaccination programs, widespread vaccine uptake in paediatric populations, and the judicious relaxation of non-pharmaceutical interventions in all Canadian jurisdictions as they reopen while more contagious variants emerge.

Wildfires trigger multi-decadal increases in sedimentation rate and metal loading to subarctic montane lakes.

We evaluated how two large wildfires affected the sedimentation rate and accumulation of lead (Pb), mercury (Hg), and cadmium (Cd) in sediment of four subarctic montane lakes in the Yukon, Canada. The wildfires occurred 60 and 20 years (1958, 1998) before sediment collection in 2018. Site-specific fire exposure was inferred from the charcoal accumulation histories in the lake sediments and the burned catchment area was determined from historical fire maps. The two major wildfires caused a two to five-fold increase in sedimentation rates and a two to eight-fold increase in sediment metal accumulation rates in Little Fox Lake. The mass accumulation rates of metals in Little Fox Lake sediment increased by a maximum of 2.7-4.7 mg Pb m-2 yr-1, 19-29 µg Hg m-2 yr-1 and 37-114 µg Cd m-2 yr-1 following wildfires. Modelling using elemental ratios of lithogenic sources suggested a large proportion of the Pb and Hg accumulating in post-fire sediment was from remobilized legacy anthropogenic pollution. In contrast, Cd fluxes were consistent with variation in catchment weathering. Impacts of wildfires were visible but more muted in the sediment of Little Braeburn Lake, whereas Fox Lake and Grayling Lake sediments showed little to no wildfire impact and served as a reference for external (long-range) metal deposition. Major changes to lake sediment geochemistry in Little Fox Lake were caused by the lack of vegetation and soil recovery in the catchment following the severe 1998 fire. Wildfire impacts were persistent in the lake more than 20 years after the last fire, with no sign of a return to pre-fire Pb, Hg, and Cd accumulation rates. This study shows that wildfires in northern montane catchments can significantly increase the rate of metal accumulation in affected lakes, thereby impeding recovery from reductions in anthropogenic air emissions of these metals.

Food in the cold: exploring food security and sovereignty in Whitehorse, Yukon.

Harsh weather patterns that are unpredictable owing to climate change, remoteness, dependence on food imports and limited local food production place Arctic and Subarctic food systems under serious pressure. The model of food sovereignty provides a surprisingly interesting contribution to address the food insecurity in these regions; it promotes long-term stable provision of healthy foods (sustainable) that are accessible to all (equity) and fosters local food production-consumption patterns (localisation). This study aims to deepen the understanding of food insecurity in the Subarctic regions and explores the possibilities for a food sovereignty approach at both individual and regional level. The study focuses on Whitehorse, capital of Yukon, Canada, and uses a cross-sectional online survey among residents of Whitehorse and semi-structured in-depth interviews with food-systems experts in Yukon. The findings indicated a need for affordable year-round local food production. Application of food sovereignty has provided the opportunities for local food procurement, innovation hubs, and several types of greenhouses including hydroponics and vertical farming, to work towards a more localised food system, thereby improving food security and sovereignty in Yukon. The findings constitute the scientific knowledge base for the formulation of prospective scenarios in the spirit of the food sovereignty theory.

Pleistocene mitogenomes reconstructed from the environmental DNA of permafrost sediments.

Traditionally, paleontologists have relied on the morphological features of bones and teeth to reconstruct the evolutionary relationships of extinct animals.1 In recent decades, the analysis of ancient DNA recovered from macrofossils has provided a powerful means to evaluate these hypotheses and develop novel phylogenetic models.2 Although a great deal of life history data can be extracted from bones, their scarcity and associated biases limit their information potential. The paleontological record of Beringia3-the unglaciated areas and former land bridge between northeast Eurasia and northwest North America-is relatively robust thanks to its perennially frozen ground favoring fossil preservation.4,5 However, even here, the macrofossil record is significantly lacking in small-bodied fauna (e.g., rodents and birds), whereas questions related to migration and extirpation, even among well-studied taxa, remain crudely resolved. The growing sophistication of ancient environmental DNA (eDNA) methods have allowed for the identification of species within terrestrial/aquatic ecosystems,6-12 in paleodietary reconstructions,13-19 and facilitated genomic reconstructions from cave contexts.8,20-22 Murchie et al.6,23 used a capture enrichment approach to sequence a diverse range of faunal and floral DNA from permafrost silts deposited during the Pleistocene-Holocene transition.24 Here, we expand on their work with the mitogenomic assembly and phylogenetic placement of Equus caballus (caballine horse), Bison priscus (steppe bison), Mammuthus primigenius (woolly mammoth), and Lagopus lagopus (willow ptarmigan) eDNA from multiple permafrost cores spanning the last 40,000 years. We identify a diverse metagenomic spectra of Pleistocene fauna and identify the eDNA co-occurrence of distinct Eurasian and American mitogenomic lineages.

High egg retention in Chinook Salmon Oncorhynchus tshawytscha carcasses sampled downstream of a migratory barrier.

Barriers in rivers have the potential to severely decrease functional connectivity between habitats. Failure to pass barriers and reach natal spawning habitat may compromise individual reproductive success, particularly for semelparous, philopatric species that rely on free-flowing rivers to reach natal habitat during their once-in-a-lifetime spawning migrations. To investigate the consequences of in-river barriers on fish spawning success, we quantified egg retention and spawning effort (caudal fin wear) in female Chinook Salmon Oncorhynchus tshawytscha carcasses collected downstream of the Whitehorse Hydro Plant on the upper Yukon River and at a nearby free-flowing tributary (Teslin River) from 2018 to 2020 (~2900 km migrations). Previous studies have demonstrated that a large proportion of fish attempting to reach spawning locations upstream of the hydro plant fail to pass the associated fishway. We estimated nearly all female salmon failing to pass the hydro plant attempted spawning in non-natal habitat downstream, but that these females retained ~34% of their total fecundity compared to ~6% in females from the free-flowing river. Females downstream of the hydro plant also had lower wear on their caudal fin, a characteristic that was correlated with increased egg deposition. Egg retention did not vary across years with different run sizes, and we propose that egg retention downstream of the hydro plant was not driven by density-dependent mechanisms. Findings from this work indicate that female Chinook Salmon can still deposit eggs following failed fish passage and failure to reach natal spawning sites, though egg retention rates are considerably higher and uncertainties remain about reproductive success. We encourage researchers to incorporate carcass surveys into fish passage evaluations for semelparous species to fully account for consequences of failed passage.

Herbivory changes soil microbial communities and greenhouse gas fluxes in a high-latitude wetland.

Herbivory can have strong impacts on greenhouse gas fluxes in high-latitude ecosystems. For example, in the Yukon-Kuskokwim (Y-K) Delta in western Alaska, migratory goose grazing affects the magnitude of soil carbon dioxide (CO2) and methane (CH4) fluxes. However, the underlying drivers of this relationship are unclear, as few studies systematically tease apart the processes by which herbivores influences soil biogeochemistry. To examine these mechanisms in detail, we conducted a laboratory incubation experiment to quantify changes in greenhouse gas fluxes in response to three parameters altered by herbivores in situ: temperature, soil moisture content, and nutrient inputs. These treatments were applied to soils collected in grazing lawns and nearby ungrazed habitat, allowing us to assess how variation in microbial community structure influenced observed responses. We found pronounced differences in both fungal and prokaryotic community composition between grazed and ungrazed areas. In the laboratory incubation experiment, CO2 and CH4 fluxes increased with temperature, soil moisture, and goose fecal addition, suggesting that grazing-related changes in the soil abiotic environment may enhance soil C losses. Yet, these abiotic drivers were insufficient to explain variation in fluxes between soils with and without prior grazing. Differences in trace gas fluxes between grazed and ungrazed areas may result both from herbivore-induced shifts in abiotic parameters and grazing-related alterations in microbial community structure. Our findings suggest that relationships among herbivores and soil microbial communities could mediate carbon-climate feedbacks in rapidly changing high-latitude ecosystems.

Long term safety and efficacy of the Yukon Choice Flex sirolimus-eluting coronary stent-a real-world data from India.

In-stent restenosis and stent thrombosis are the major concerns while choosing a coronary stent. This single-centre, retrospective study evaluated the one and three-year clinical outcomes following implantation of Yukon Choice Flex (YCF) sirolimus-eluting stent. A total of 168 consecutive patients with 217 lesions underwent stenting with YCF stent. The presentation was with acute coronary syndrome in 158 (94%) patients. At 3 years, 9 (5.3%) patients died due to cardiac cause. Myocardial infarction, and definite stent thrombosis occurred in 10 (6%) and 4 (2.4%) patients respectively. Redo stenting and coronary artery bypass surgery was performed in 3 (1.8%) and 1 (0.6%) patient respectively. The use of YCF sirolimus eluting stent was associated with a favourable safety and efficacy profile at one and three-years of follow-up in a high-risk population.

Micropropagation and Cryopreservation of Yukon Draba (Draba yukonensis), a Special Concern Plant Species Endemic to Yukon Territory, Canada.

Yukon Draba (Draba yukonensis) is a small, short-lived perennial mustard species that is endemic to southwestern Yukon in Canada. This plant has been categorized as a species of Special Concern. It faces the threat of habitat loss due to natural and man-made causes and a population that is unevenly distributed to a few large and several small subpopulations in the area. It will therefore be judicious to undertake investigations on the conservation of this species to save it from further deterioration which may lead to its extinction. In this study, a protocol was developed for in vitro propagation and cryopreservation of Yukon Draba. The micropropagation protocol was optimized using shoot tips which enabled clonal propagation and in vitro storage of the species. Shoots grew best in the medium containing MS basal salts and had the highest multiplication with the addition of 2 µM 6-benzylaminopurine or 5 µM Kinetin with 3% sucrose. The addition of 10 µM Indole Butyric Acid (IBA) produced the highest number of adventitious roots on the shoots and the longest root length was observed at 2 µM IBA. The rooted plantlets were transferred to greenhouse and the highest survival (87.5%) was observed for the plantlets treated with a lower concentration of IBA (2 µM). Cryopreservation protocol was developed using the droplet-vitrification method for in vitro shoot tips. Two-week-old shoots had the highest survival and regrowth following exposure to plant vitrification solution 3 (PVS3) for 30 min, prior to direct immersion of the droplets into the liquid nitrogen. The optimized protocols for the micropropagation and cryopreservation may be useful for the long-term germplasm conservation and reintroduction of this species in its natural habitat.

Diphtheria Antitoxin and Tales of Mercy in Northern Health Care.

This article examines the history of diphtheria in the Yukon and the Mackenzie district of the Northwest Territories in the first half of the 20th century. This analysis follows the traces of this now largely forgotten disease and its treatment to illuminate the constraints - intrinsic and constructed - on the provision of health care commensurate with the expectations and needs of northern Indigenous peoples. While diphtheria was never the most serious infectious disease, nor a major cause of death compared with tuberculosis or influenza at this time, examining its history offers significant insight into the creation of medical and public health infrastructures in Canada's northern territories, and the ways in which those infrastructures served, and failed to serve, different northern populations.

Cannabis use prior to legalisation among alcohol consumers in the Canadian Yukon and Northwest territories.

Although rates of substance use are higher in the Canadian territories than the provinces, there is little research on cannabis use. This exploratory study describes cannabis use and related risk behaviours among alcohol consumers in Whitehorse (Yukon) and Yellowknife (Northwest Territories), with comparisons to data from the provinces. Prior to non-medical cannabis legalisation, respondents (n = 387) aged ≥19 were recruited from a study on alcohol labelling to complete an online cannabis survey. Logistic regression was used to compare territorial and provincial data, and correlates of cannabis use in the territories. Forty-seven percent of respondents were past 12-month cannabis consumers, and 15.5% were daily/almost daily consumers, significantly higher than in the provinces (p < 0.001 for both). Dried herb (85.7%) and edibles (58.2%) were most commonly used among consumers. Use of dried herb, edibles, solid concentrates and tinctures was significantly higher than in the provinces (all p ≤ 0.01). Twenty-four percent of respondents had ridden with a driver who had used cannabis, while 31.9% of cannabis consumers had driven within 2h of cannabis use, significantly higher than the provinces (both p < 0.001). Further research should examine the impact of legalisation on cannabis use in the territories, including rural communities.

Differential susceptibility of Yukon River and Salish Sea stocks of Chinook salmon Oncorhynchus tshawytscha to ichthyophoniasis.

Preliminary evidence suggests that Chinook salmon Oncorhynchus tshawytscha from the Yukon River may be more susceptible to Ichthyophonus sp. infections than Chinook from stocks further south. To investigate this hypothesis in a controlled environment, we experimentally challenged juvenile Chinook from the Yukon River and from the Salish Sea with Ichthyophonus sp. and evaluated mortality, infection prevalence and infection load over time. We found that juvenile Chinook salmon from a Yukon River stock were more susceptible to ichthyophoniasis than were those from a Salish Sea stock. After feeding with tissues from infected Pacific herring Clupea pallasii, Chinook salmon from both stocks became infected. The infection was persistent and progressive in Yukon River stock fish, where infections sometimes progressed to mortality, and histological examinations revealed parasite dissemination and proliferation throughout the host tissues. In Salish Sea-origin fish, however, infections were largely transient; host mortalities were rare, and parasite stages were largely cleared from most tissues after 3-4 wk. Susceptibility differences were evidenced by greater cumulative mortality, infection prevalence, parasite density, proportion of fish demonstrating a cellular response, and intensity of the cellular response among fish from the Yukon River stock. These observed differences between Chinook salmon stocks were consistent when parasite exposures occurred in both freshwater and seawater. These results support the hypothesis that a longer-standing host-pathogen relationship, resulting in decreased disease susceptibility, exists among Salish Sea Chinook salmon than among Yukon River conspecifics.

High Prevalence and Intensity of Trichinella Infection in Yukon American Black (Ursus americanus) and Grizzly (Ursus arctos) Bears.

Trichinella spp. nematodes are commonly found in bear species (Ursidae) and can pose severe health risks to humans when infective first-stage larvae are ingested in meat. Samples of tongue or masseter muscle from 22 male and 11 female American black bears (Ursus americanus; mean age 6.5 yr, range 1-16 yr) and 22 male, eight female, and one unknown sex grizzly bears (Ursus arctos; mean age 8.8 yr, range 2-28 yr), from Yukon, Canada, were tested to determine prevalence and intensity of Trichinella spp. infection. For black bears, prevalence was 20% and mean intensity was 401 larvae per gram of tissue (LPG), whereas for grizzly bears, prevalence was 71%, and mean infection intensity was 35 LPG. Isolates from all positive samples were identified as genotype Trichinella-T6 by multiplex PCR. For black bears, prevalence is the highest reported in Canada and infection intensity the highest recorded in North America. One black bear had a larval burden of 1,173 LPG, the second highest recorded in any host species. The prevalence in grizzly bears was the highest reported in Canada for this host. In total, 90% (27 of 30) of infected bears had infection burdens above the human food safety threshold of ≥1 LPG, reinforcing the importance of communicating the health risks to people consuming bear meat.

SARS-CoV-2 Surveillance System in Canada: Longitudinal Trend Analysis.

BACKGROUND: The COVID-19 global pandemic has disrupted structures and communities across the globe. Numerous regions of the world have had varying responses in their attempts to contain the spread of the virus. Factors such as public health policies, governance, and sociopolitical climate have led to differential levels of success at controlling the spread of SARS-CoV-2. Ultimately, a more advanced surveillance metric for COVID-19 transmission is necessary to help government systems and national leaders understand which responses have been effective and gauge where outbreaks occur. OBJECTIVE: The goal of this study is to provide advanced COVID-19 surveillance metrics for Canada at the country, province, and territory level that account for shifts in the pandemic including speed, acceleration, jerk, and persistence. Enhanced surveillance identifies risks for explosive growth and regions that have controlled outbreaks successfully. METHODS: Using a longitudinal trend analysis study design, we extracted 62 days of COVID-19 data from Canadian public health registries for 13 provinces and territories. We used an empirical difference equation to measure the daily number of cases in Canada as a function of the prior number of cases, the level of testing, and weekly shift variables based on a dynamic panel model that was estimated using the generalized method of moments approach by implementing the Arellano-Bond estimator in R. RESULTS: We compare the week of February 7-13, 2021, with the week of February 14-20, 2021. Canada, as a whole, had a decrease in speed from 8.4 daily new cases per 100,000 population to 7.5 daily new cases per 100,000 population. The persistence of new cases during the week of February 14-20 reported 7.5 cases that are a result of COVID-19 transmissions 7 days earlier. The two most populous provinces of Ontario and Quebec both experienced decreases in speed from 7.9 and 11.5 daily new cases per 100,000 population for the week of February 7-13 to speeds of 6.9 and 9.3 for the week of February 14-20, respectively. Nunavut experienced a significant increase in speed during this time, from 3.3 daily new cases per 100,000 population to 10.9 daily new cases per 100,000 population. CONCLUSIONS: Canada excelled at COVID-19 control early on in the pandemic, especially during the first COVID-19 shutdown. The second wave at the end of 2020 resulted in a resurgence of the outbreak, which has since been controlled. Enhanced surveillance identifies outbreaks and where there is the potential for explosive growth, which informs proactive health policy.