Disease and Mortality in Free-Ranging Leporids in Canada, 1990-2019: A Retrospective Study.

Passive surveillance of wildlife disease is a valuable tool for the identification of emerging and changing disease patterns. Free-ranging leporids play an important role in their ecosystem and in the culture and diet of Canadians; however, little is known about their health status and the zoonotic pathogens they may carry. We summarized major causes of mortality and morbidity, as well as incidental infections and lesions, of free-ranging leporids submitted to the Canadian Wildlife Health Cooperative (CWHC) between 1990 and 2019. We identified Canadian leporids as competent hosts for several zoonotic pathogens, most notably Francisella tularensis (20/569; 3.5%). Trauma was the most frequent cause of mortality or morbidity among leporids, accounting for 46.0% of cases submitted to the CWHC, followed by bacterial infections (13.7%) and emaciation (5.1%). Human-mediated mortalities, such as those involving machines (23.7%), were the most common trauma case type, with apparently healthy individuals overrepresented within this mortality group. Harvesters proved to be a valuable resource for the monitoring of diseased and infected animals, as more than half (69.6%) of the animals submitted by this group had an incidental infection or lesion. The results from this study provide a scientific understanding the cause of mortality in free-ranging leporids in Canada with relevance to public health, wildlife biologists, veterinarians, and potential future surveillance programs.

Factors associated with antimicrobial resistant enterococci in Canadian beef cattle: A scoping review.

Introduction: Antimicrobial resistance (AMR) is a global health concern, occurring when bacteria evolve to render antimicrobials no longer effective. Antimicrobials have important roles in beef production; however, the potential to introduce AMR to people through beef products is a concern. This scoping review identifies factors associated with changes in the prevalence of antimicrobial-resistant Enterococcus spp. applicable to the Canadian farm-to-fork beef continuum. Methods: Five databases (MEDLINE, BIOSIS, Web of Science, Embase, and CAB Abstracts) were searched for articles published from January 1984 to March 2022, using a priori inclusion criteria. Peer-reviewed articles were included if they met all the following criteria: written in English, applicable to the Canadian beef production context, primary research, in vivo research, describing an intervention or exposure, and specific to Enterococcus spp. Results: Out of 804 screened articles, 26 were selected for inclusion. The included articles discussed 37 factors potentially associated with AMR in enterococci, with multiple articles discussing at least two of the same factors. Factors discussed included antimicrobial administration (n = 16), raised without antimicrobials (n = 6), metal supplementation (n = 4), probiotics supplementation (n = 3), pen environment (n = 2), essential oil supplementation (n = 1), grass feeding (n = 1), therapeutic versus subtherapeutic antimicrobial use (n = 1), feeding wet distiller grains with solubles (n = 1), nutritional supplementation (n = 1) and processing plant type (n = 1). Results were included irrespective of their quality of evidence. Discussion: Comparability issues arising throughout the review process were related to data aggregation, hierarchical structures, study design, and inconsistent data reporting. Findings from articles were often temporally specific in that resistance was associated with AMR outcomes at sampling times closer to exposure compared to studies that sampled at longer intervals after exposure. Resistance was often nuanced to unique gene and phenotypic resistance patterns that varied with species of enterococci. Intrinsic resistance and interpretation of minimum inhibitory concentration varied greatly among enterococcal species, highlighting the importance of caution when comparing articles and generalizing findings. Systematic Review Registration: [http://hdl.handle.net/1880/113592].

Qiviut cortisol is associated with metrics of health and other intrinsic and extrinsic factors in wild muskoxen (Ovibos moschatus).

Glucocorticoid (GC) levels are increasingly and widely used as biomarkers of hypothalamic-pituitary-adrenal (HPA) axis activity to study the effects of environmental changes and other perturbations on wildlife individuals and populations. However, identifying the intrinsic and extrinsic factors that influence GC levels is a key step in endocrinology studies to ensure accurate interpretation of GC responses. In muskoxen, qiviut (fine woolly undercoat hair) cortisol concentration is an integrative biomarker of HPA axis activity over the course of the hair's growth. We gathered data from 219 wild muskoxen harvested in the Canadian Arctic between October 2015 and May 2019. We examined the relationship between qiviut cortisol and various intrinsic (sex, age, body condition and incisor breakage) and extrinsic biotic factors (lungworm and gastrointestinal parasite infections and exposure to bacteria), as well as broader non-specific landscape and temporal features (geographical location, season and year). A Bayesian approach, which allows for the joint estimation of missing values in the data and model parameters estimates, was applied for the statistical analyses. The main findings include the following: (i) higher qiviut cortisol levels in males than in females; (ii) inter-annual variations; (iii) higher qiviut cortisol levels in a declining population compared to a stable population; (iv) a negative association between qiviut cortisol and marrow fat percentage; (v) a relationship between qiviut cortisol and the infection intensity of the lungworm Umingmakstrongylus pallikuukensis, which varied depending on the geographical location; and (vi) no association between qiviut cortisol and other pathogen exposure/infection intensity metrics. This study confirmed and further identified important sources of variability in qiviut cortisol levels, while providing important insights on the relationship between GC levels and pathogen exposure/infection intensity. Results support the use of qiviut cortisol as a tool to monitor temporal changes in HPA axis activity at a population level and to inform management and conservation actions.

The Role of Whole Genome Sequencing in the Surveillance of Antimicrobial Resistant Enterococcus spp.: A Scoping Review.

Enterococcus spp. have arisen as important nosocomial pathogens and are ubiquitous in the gastrointestinal tracts of animals and the environment. They carry many intrinsic and acquired antimicrobial resistance genes. Because of this, surveillance of Enterococcus spp. has become important with whole genome sequencing emerging as the preferred method for the characterization of enterococci. A scoping review was designed to determine how the use of whole genome sequencing in the surveillance of Enterococcus spp. adds to our knowledge of antimicrobial resistance in Enterococcus spp. Scoping review design was guided by the PRISMA extension and checklist and JBI Reviewer's Guide for scoping reviews. A total of 72 articles were included in the review. Of the 72 articles included, 48.6% did not state an association with a surveillance program and 87.5% of articles identified Enterococcus faecium. The majority of articles included isolates from human clinical or screening samples. Significant findings from the articles included novel sequence types, the increasing prevalence of vancomycin-resistant enterococci in hospitals, and the importance of surveillance or screening for enterococci. The ability of enterococci to adapt and persist within a wide range of environments was also a key finding. These studies emphasize the importance of ongoing surveillance of enterococci from a One Health perspective. More studies are needed to compare the whole genome sequences of human enterococcal isolates to those from food animals, food products, the environment, and companion animals.

Fecal glucocorticoid metabolites reflect hypothalamic-pituitary-adrenal axis activity in muskoxen (Ovibos moschatus).

Muskoxen (Ovibos moschatus), a taxonomically unique Arctic species, are increasingly exposed to climate and other anthropogenic changes. It is critical to develop and validate reliable tools to monitor their physiological stress response in order to assess the impacts of these changes. Here, we measured fecal glucocorticoid metabolite (FGM) levels in response to the administration of adrenocorticotropic hormone (ACTH) in the winter (1 IU/kg) and summer (2 IU/kg) using two enzyme immunoassays, one targeting primarily cortisol and the other targeting primarily corticosterone. Fecal cortisol levels varied substantially within and among individuals, and none of the animals in either challenge showed an increase in fecal cortisol following the injection of ACTH. By contrast, two of six (winter) and two of five (summer) muskoxen showed a clear response in fecal corticosterone levels (i.e., maximal percentage increase as compared to time 0 levels > 100%). Increases in fecal corticosterone post-ACTH injection occurred earlier and were of shorter duration in the summer than in the winter and fecal corticosterone levels were, in general, lower during the summer. These seasonal differences in FGM responses may be related to the use of different individuals (i.e., influence of sex, age, social status, etc.) and to seasonal variations in the metabolism and excretion of glucocorticoids, intestinal transit time, voluntary food intake, and fecal output and moisture content. Results from this study support using FGMs as a biomarker of hypothalamic-pituitary-adrenal axis activity in muskoxen, advance our understanding of the physiological adaptations of mammals living in highly seasonal and extreme environments such as the Arctic, and emphasize the importance of considering seasonality in other species when interpreting FGM levels.

Salmonella spp. prevalence and antimicrobial resistance in broiler chicken and turkey flocks in Canada from 2013 to 2018.

Salmonella infections are a major human health concern. In the elderly and immunocompromised, infections can be life-threatening and may require antibiotic therapy. Where antibiotic therapy is required, antimicrobials of choice include fluoroquinolones and extended-spectrum cephalosporins (ESC). The aim of this study is to utilize data from the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) to compare the prevalence of Salmonella serovars between broiler chicken and turkey flocks across Canada, and to gain an understanding of the prevalence of resistance to antimicrobials categorized as important to human health. There were 1,596 Salmonella isolates obtained from 514 broiler chicken flocks, and 659 Salmonella isolates obtained from 217 turkey flocks (2013-2018). All isolates were obtained from pooled faecal samples. Among broiler chicken flocks, the top three serovars were Kentucky (n = 573, 36%), Enteritidis (n = 314, 20%) and Heidelberg (n = 127, 8%). Resistance to ceftriaxone among Salmonella ser. Kentucky decreased from 27% in 2013 to 22% in 2018. There was no resistance among Salmonella ser. Enteritidis reported until 2018 when one isolate from British Columbia was resistant to ampicillin, streptomycin, sulphisoxazole and tetracycline. Salmonella ser. Heidelberg resistance to ceftriaxone decreased from 19% in 2013 to 14% in 2018. Among turkey flocks the top three serovars were Uganda (n = 109, 16.5%), Hadar (n = 85, 12%) and Muenchen (n = 66, 10%). No isolates of Salmonella ser. Uganda or Salmonella ser. Muenchen were resistant to any ß-lactams. Salmonella ser. Hadar (34/81, 42%) exhibited resistance to ampicillin. There was no resistance to quinolones among turkey isolates. Emerging resistance among Salmonella ser. Enteritidis, and resistance to ß-lactams and fluoroquinolones among Salmonella ser. Kentucky from broilers are cause for concern as these classes of antimicrobials are important for treatment of salmonellosis.

A cross-sectional study of the prevalence factors associated with fluoroquinolone resistant Campylobacter jejuni in broiler flocks in Canada.

Campylobacter infections in humans are usually self-limiting; however, antibiotic intervention may be necessary in the case of severe infection. Fluoroquinolones are often the drug of choice for treatment of campylobacteriosis; however, resistance to these drugs can develop rapidly, complicating treatment protocols. Increasing resistance to fluoroquinolones in human infections has coincided with approval of use of fluoroquinolones in animals, therefore, isolation of fluoroquinolone resistant (FQr) Campylobacter in broiler flocks is concerning. This cross-sectional study utilized data collected from 2013-2018 by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) on-farm surveillance program to investigate prevalence factors associated with the isolation of FQr C. jejuni from broiler faecal samples. Mixed effects logistic regression models accounting for clustering of flocks within hatcheries, with and without a fixed effect for the presence of flock level tetracycline resistance were used to assess prevalence factors among 536 C. jejuni isolates from 158 flocks. Both models indicated that the type of bird used (Ross versus Cobb or mixed), the use of virginiamycin as a feed additive, the use of traps to control rodent populations in the barn, and the total number of birds in the barn were significant prevalence factors for increased FQr C. jejuni in a flock. In the model where flock level tetracycline resistance was included as a fixed effect, the odds of FQr C. jejuni increased by 16 (95% CI: 3.74, 68), and the magnitude of the effect of each of the identified prevalence factors was larger. Both models indicated that methods of disinfection of water lines between production cycles is important, with the use of chlorine being protective in the model where tetracycline resistance was included as a fixed effect, and the use of hydrogen peroxide being a risk factor in the model where tetracycline resistance was not included as a fixed effect. The use of hot water to wash the barn between production cycles was also a significant protective factor in the model where tetracycline resistance was not included as a fixed effect. These results indicate that biosecurity and sanitation procedures play a role in the dissemination of FQr C. jejuni in broiler flocks. Future analysis should seek to understand the effect of different disinfectant products on the isolation of FQr C. jejuni. Gaining a better understanding of the management of these critical practices may allow for the reduction of this enteric pathogen in broiler flocks in Canada.

Correction: Novel insights into serodiagnosis and epidemiology of Erysipelothrix rhusiopathiae, a newly recognized pathogen in muskoxen (Ovibos moschatus).

[This corrects the article DOI: 10.1371/journal.pone.0231724.].

Novel insights into serodiagnosis and epidemiology of Erysipelothrix rhusiopathiae, a newly recognized pathogen in muskoxen (Ovibos moschatus).

BACKGROUND: Muskoxen are a key species of Arctic ecosystems and are important for food security and socio-economic well-being of many Indigenous communities in the Arctic and Subarctic. Between 2009 and 2014, the bacterium Erysipelothrix rhusiopathiae was isolated for the first time in this species in association with multiple mortality events in Canada and Alaska, raising questions regarding the spatiotemporal occurrence of the pathogen and its potential impact on muskox populations. MATERIALS AND METHODS: We adapted a commercial porcine E. rhusiopathiae enzyme-linked immunosorbent assay to test 958 blood samples that were collected from muskoxen from seven regions in Alaska and the Canadian Arctic between 1976 and 2017. The cut-off between negative and positive results was established using mixture-distribution analysis, a data-driven approach. Based on 818 samples for which a serological status could be determined and with complete information, we calculated trends in sample seroprevalences in population time-series and compared them with population trends in the investigated regions. RESULTS: Overall, 219/818 (27.8%, 95% Confidence Interval: 24.7-31.0) samples were classified as positive for exposure to E. rhusiopathiae. There were large variations between years and regions. Seropositive animals were found among the earliest serum samples tested; 1976 in Alaska and 1991 in Canada. In Alaskan muskoxen, sample seroprevalence increased after 2000 and, in two regions, peak seroprevalences occurred simultaneously with population declines. In one of these regions, concurrent unusual mortalities were observed and E. rhusiopathiae was isolated from muskox carcasses. In Canada, there was an increase in sample seroprevalence in two muskox populations following known mortality events that had been attributed to E. rhusiopathiae. CONCLUSION: Our results indicate widespread exposure of muskoxen to E. rhusiopathiae in western Canada and Alaska. Although not new to the Arctic, we documented an increased exposure to the pathogen in several regions concurrent with population declines. Understanding causes for the apparent increased occurrence of this pathogen and its association with large scale mortality events for muskoxen is critical to evaluate the implications for wildlife and wildlife-dependent human populations in the Arctic.

Muskox status, recent variation, and uncertain future.

Muskoxen (Ovibos moschatus) are an integral component of Arctic biodiversity. Given low genetic diversity, their ability to respond to future and rapid Arctic change is unknown, although paleontological history demonstrates adaptability within limits. We discuss status and limitations of current monitoring, and summarize circumpolar status and recent variations, delineating all 55 endemic or translocated populations. Acknowledging uncertainties, global abundance is ca 170 000 muskoxen. Not all populations are thriving. Six populations are in decline, and as recently as the turn of the century, one of these was the largest population in the world, equaling ca 41% of today's total abundance. Climate, diseases, and anthropogenic changes are likely the principal drivers of muskox population change and result in multiple stressors that vary temporally and spatially. Impacts to muskoxen are precipitated by habitat loss/degradation, altered vegetation and species associations, pollution, and harvest. Which elements are relevant for a specific population will vary, as will their cumulative interactions. Our summaries highlight the importance of harmonizing existing data, intensifying long-term monitoring efforts including demographics and health assessments, standardizing and implementing monitoring protocols, and increasing stakeholder engagement/contributions.

Comparison of different approaches to antibiotic restriction in food-producing animals: stratified results from a systematic review and meta-analysis.

BACKGROUND: We have previously reported, in a systematic review of 181 studies, that restriction of antibiotic use in food-producing animals is associated with a reduction in antibiotic-resistant bacterial isolates. While informative, that report did not concretely specify whether different types of restriction are associated with differential effectiveness in reducing resistance. We undertook a sub-analysis of the systematic review to address this question. METHODS: We created a classification scheme of different approaches to antibiotic restriction: (1) complete restriction; (2) single antibiotic-class restriction; (3) single antibiotic restriction; (4) all non-therapeutic use restriction; (5) growth promoter and prophylaxis restriction; (6) growth promoter restriction and (7) other/undetermined. All studies in the original systematic review that were amenable to meta-analysis were included into this substudy and coded by intervention type. Meta-analyses were conducted using random effects models, stratified by intervention type. RESULTS: A total of 127 studies were included. The most frequently studied intervention type was complete restriction (n=51), followed by restriction of non-therapeutic (n=33) and growth promoter (n=19) indications. None examined growth promoter and prophylaxis restrictions together. Three and seven studies examined single antibiotic-class and single antibiotic restrictions, respectively; these two intervention types were not significantly associated with reductions in antibiotic resistance. Though complete restrictions were associated with a 15% reduction in antibiotic resistance, less prohibitive approaches also demonstrated reduction in antibiotic resistance of 9%-30%. CONCLUSION: Broad interventions that restrict global antibiotic use appear to be more effective in reducing antibiotic resistance compared with restrictions that narrowly target one specific antibiotic or antibiotic class. Importantly, interventions that allow for therapeutic antibiotic use appear similarly effective compared with those that restrict all uses of antibiotics, suggesting that complete bans are not necessary. These findings directly inform the creation of specific policies to restrict antibiotic use in food-producing animals.

Examination of unintended consequences of antibiotic use restrictions in food-producing animals: Sub-analysis of a systematic review.

Antimicrobial resistance is considered one of the greatest threats to global and public health today. The World Health Organization, the Food and Agriculture Organization, and the World Organisation for Animal Health, known as the Tripartite Collaboration, have called for urgent action. We have previously published a systematic review of 181 studies, demonstrating that interventions that restrict antibiotic use in food-producing animals are associated with a reduction in antibiotic resistant bacterial isolates in both animals and humans. What remains unknown, however, are whether (and what) unintended consequences may arise from such interventions. We therefore undertook a sub-analysis of the original review to address this research question. A total of 47 studies described potential consequences of antibiotic restrictions. There were no consistent trends to suggest clear harm. There may be increased bacterial contamination of food products, the clinical significance of which remains unclear. There is a need for rigorous evaluation of the unintended consequences of antibiotic restrictions in human health, food availability, and economics, given their possible widespread implications.

Insights about the Epidemiology of Dog Bites in a Canadian City Using a Dog Aggression Scale and Administrative Data.

Dog bites are a public health concern that also implicates animal welfare, with negative outcomes such as rehoming or euthanasia for the animals responsible. Previous research has shown that the severity of dog-bite injuries reflects multiple factors, including the degree of inhibition exhibited by dogs and how people behave towards dogs. This study utilizes an objective dog bite injury assessment tool: The Dunbar aggression scale. Trained officers employed by The City of Calgary systematically use the Dunbar scale whenever investigating dog-bite complaints. We analyzed The City of Calgary's administrative data on confirmed dog-bite injuries in people, 2012-2017, with a multivariable generalized ordered logistic regression model. Severe dog-bite injuries occurred more frequently in the family home than in any other setting. Young children, youths and older adults were at higher risk of more serious bites than adults. There has been a decreasing trend in the probability of a high or medium severity bite, and an increasing trend in the probability of a low severity bite since 2012. These results indicate that greater public awareness regarding dog-bite injuries is needed. Consideration should be given to campaigns targeted towards different demographics, including older adults, to provide an understanding of dog behaviour and to emphasize the need to supervise children closely in the presence of all dogs at all times, including family dogs in the home environment. Given that dog-bite injuries are not just a public health issue, but also an animal welfare issue, we endorse One Health responses in educational campaigns, policy development, and professional practice.

Antimicrobial resistance of bovine Salmonella enterica ssp. enterica isolates from the Alberta Agriculture and Forestry Disease Investigation Program (2006-2014).

The objectives of this study were to describe the antimicrobial susceptibility and serotypes of clinical Salmonella spp. isolates from Alberta cattle, to inform antimicrobial stewardship decisions for Alberta bovine veterinarians and to provide data for national surveillance. Isolates were collected from cattle and serotyped by Alberta Agriculture and Forestry from 2006 to 2014. Susceptibility testing was completed using Canadian surveillance breakpoints. There were 81 unique Salmonella isolates from 72 visits to 27 farms. The majority of isolates were S. Typhimurium (66.7%) and S. Dublin (19.8%). The prevalence of multidrug resistance was high in S. Typhimurium (89.1%) and S. Dublin (93.8%), including ceftiofur resistance (43.6% and 68.8%, respectively), while there was no resistance in other serotypes. As ceftiofur is a recommended treatment option for enteritis and septicemia caused by Salmonella in cattle, these results reinforce that obtaining bacterial culture and susceptibility results is critical for suspected cases of bovine salmonellosis in Alberta.

Antibiorésistance des isolats bovins de Salmonella enterica ssp. enterica provenant du Programme d'enquête du ministère de l'Agriculture et des Forêts de l'Alberta (2006­2014). Les objectifs de cette étude consistaient à décrire la susceptibilité antimicrobienne et les sérotypes des isolats cliniques de Salmonella spp. provenant du bétail de l'Alberta afin de fournir des données nationales de surveillance et d'informer les décisions d'antibiogouvernance des vétérinaires bovins de l'Alberta. Les isolats ont été prélevés du bétail et sérotypés par le ministère de l'Agriculture et des Forêts de l'Alberta de 2006 à 2014. Les tests de susceptibilité ont été réalisés en utilisant des points de référence de la surveillance canadienne. Il y avait 81 isolats uniques de Salmonella provenant de 72 visites à 27 fermes. La majorité des isolats étaient S. Typhimurium (66,7 %) et S. Dublin (19,8 %). La prévalence de la multirésistance aux médicaments était élevée pour S. Typhimurium (89,1 %) et S. Dublin (93,8 %), y compris la résistance au ceftiofur (43,6 % et 68,8 %, respectivement), tandis qu'il n'y avait pas de résistance pour d'autres sérotypes. Vu que le ceftiofur est une option de traitement recommandée pour l'entérite et la septicémie causées par Salmonella chez le bétail, ces résultats servent de renforcement pour confirmer qu'il est crucial d'obtenir des cultures bactériennes et des résultats de susceptibilité pour les cas suspectés de salmonellose bovine en Alberta.(Traduit par Isabelle Vallières).

Bacterial Genomics Reveal the Complex Epidemiology of an Emerging Pathogen in Arctic and Boreal Ungulates.

Northern ecosystems are currently experiencing unprecedented ecological change, largely driven by a rapidly changing climate. Pathogen range expansion, and emergence and altered patterns of infectious disease, are increasingly reported in wildlife at high latitudes. Understanding the causes and consequences of shifting pathogen diversity and host-pathogen interactions in these ecosystems is important for wildlife conservation, and for indigenous populations that depend on wildlife. Among the key questions are whether disease events are associated with endemic or recently introduced pathogens, and whether emerging strains are spreading throughout the region. In this study, we used a phylogenomic approach to address these questions of pathogen endemicity and spread for Erysipelothrix rhusiopathiae, an opportunistic multi-host bacterial pathogen associated with recent mortalities in arctic and boreal ungulate populations in North America. We isolated E. rhusiopathiae from carcasses associated with large-scale die-offs of muskoxen in the Canadian Arctic Archipelago, and from contemporaneous mortality events and/or population declines among muskoxen in northwestern Alaska and caribou and moose in western Canada. Bacterial genomic diversity differed markedly among these locations; minimal divergence was present among isolates from muskoxen in the Canadian Arctic, while in caribou and moose populations, strains from highly divergent clades were isolated from the same location, or even from within a single carcass. These results indicate that mortalities among northern ungulates are not associated with a single emerging strain of E. rhusiopathiae, and that alternate hypotheses need to be explored. Our study illustrates the value and limitations of bacterial genomic data for discriminating between ecological hypotheses of disease emergence, and highlights the importance of studying emerging pathogens within the broader context of environmental and host factors.

Antimicrobial Resistance in Escherichia coli Recovered from Feedlot Cattle and Associations with Antimicrobial Use.

The objectives of this study were to estimate the prevalence of antimicrobial resistance (AMR) and to investigate the associations between exposures to antimicrobial drugs (AMDs) and AMR in fecal non-type specific Escherichia coli (NTSEC) recovered from a large population of feedlot cattle. Two-stage random sampling was used to select individually identified cattle for enrollment, which were sampled at arrival and then a second time later in the feeding period. Advanced regression techniques were used to estimate resistance prevalences, and to investigate associations between AMD exposures in enrolled cattle and penmates and AMR identified in NTSEC recovered from the second sample set. Resistance was most commonly detected to tetracycline, streptomycin, and sulfisoxazole, and was rarely identified for critically important AMDs. All cattle were exposed to AMDs in feed, and 45% were treated parenterally. While resistance prevalence generally increased during the feeding period, most AMD exposures were not significantly associated with AMR outcomes. Exposures of enrolled cattle to tetracycline were associated with increased resistance to tetracycline and trimethoprim sulfa, while beta-lactam exposures were associated with decreased likelihood of detecting streptomycin resistance. Pen-level AMD exposure measures were not associated with resistance outcomes. These findings suggest that tetracycline treatment of feedlot cattle can be associated with modest increases in risk for recovery of resistant NTSEC, but the numerous treatments with an advanced macrolide (tulathromycin) were not associated with detectable increases in resistance in NTSEC. All cattle were exposed to in-feed treatments of tetracycline and this could limit the ability to identify the full impact of these exposures, but these exposures varied for enrolled cattle varied, providing an opportunity to evaluate a dose response. While AMD exposures were not associated with detectably increased risks for resistance to critically important AMDs, rare resistance outcomes and infrequent exposure to other important AMDs (e.g., cephalosporins) limited our ability to rigorously investigate questions regarding factors that can influence resistance to these important AMDs.

Associations between antimicrobial use and the prevalence of antimicrobial resistance in fecal Escherichia coli from feedlot cattle in western Canada.

A randomized, controlled, blinded clinical trial was performed at a research feedlot in western Canada. Auction-market-derived steers (n = 288) were randomly assigned to 1 of 3 treatments: 1) no antimicrobials on arrival; 2) oxytetracycline in the starter ration for 14 d; and 3) long-acting oxytetracycline subcutaneously on day 0. Minimal inhibitory concentrations of 7 antimicrobials were determined for 3 generic fecal E. coli isolates per animal on arrival and throughout the feeding period. There was a low prevalence of antimicrobial resistance in generic E. coli isolates from calves on arrival. There were increased proportions of cattle with resistant E. coli isolates early in the feeding period among calves in groups 2 and 3. Individual animal treatments were not associated with increased proportions of cattle with resistant E. coli isolates preslaughter. There was no difference in the proportion of animals with E. coli isolates resistant to tetracycline between the treatment groups preslaughter. However, there were significantly more animals with tetracycline resistant isolates of E. coli preslaughter than at arrival.

A retrospective diagnostic laboratory survey of antimicrobial resistance in fecal Escherichia coli isolated from spring calves in western Canada.

Diagnostic laboratory data on antimicrobial susceptibility of Escherichia coli isolated from feces of spring calves were evaluated retrospectively for the 5-year period from 1999 to 2003. The antimicrobials to which resistance was most prevalent were tetracycline, ampicillin, and trimethoprim/sulphamethoxazole. Resistance to 3 or more antimicrobials was found in 52.5% [95% confidence interval (CI): 47.9 to 56.6] of the E. coli isolates. Incomplete records reduced the usefulness of the diagnostic laboratory data for surveillance. Standardized patient information submitted by veterinary clinics would increase the value of this data for surveillance.

Microbiological baseline study of poultry slaughtered in provincially inspected abattoirs in Alberta, Canada.

Studies to determine baseline levels of microbial contaminants and foodborne bacterial pathogens are needed to evaluate the effectiveness of Hazard Analysis Critical Control Point (HACCP) programs, Good Manufacturing/Production Practices, and various interventions. In 2004 and 2005 poultry carcass rinses from provincially inspected abattoirs in Alberta, Canada, were tested to determine the levels of aerobic plate count bacteria, coliform bacteria, and generic Escherichia coli, the prevalence and levels of Campylobacter spp., and the prevalence of Salmonella spp. and Shiga toxin-producing E. coli (STEC). Samples were collected from 3 high volume and 62 low volume abbatoirs. All samples (1296) were positive for aerobic plate count bacteria, with 98.8% of samples having counts of 100 000 or less colony forming units (CFU)/cm2. Coliform bacteria were isolated from 99.7% of the 1296 carcasses and were recovered at levels of < or = 1000 CFU/cm2 for 98.3% of the samples. Generic E. coli were recovered from 99.1% of the 1296 carcasses at levels of < or = 1000 CFU/cm2 for 98.6% of the samples. Seventy five percent of 1234 samples that were tested for Campylobacter were positive; 37.5% of 1295 samples that were tested for Salmonella were positive; and only 2 of 1296 samples tested for STEC were positive (0.15%).