Research synthesis in veterinary science: Narrative reviews, systematic reviews and meta-analysis

A scoping review of antimicrobial resistance in the Australian dairy cattle industry

INTRODUCTION

Quantification of antimicrobial resistance (AMR) is beneficial to inform policies and direct prudent antimicrobial use.

AIM

This study aimed to assess the current published evidence of AMR from passive and active ad hoc surveillance activities within the Australian dairy cattle industry.

METHODS

Following a scoping review framework 373 articles published before January 2023 were retrieved using the keyword search function from two online databases (PubMed® and Web of Science™ Core Collection). The duplicate articles were removed and the title, abstract, and full text of the remaining articles were reviewed following the study objectives and inclusion criteria (location, subject/theme, and data). Data from the remaining articles were extracted, summarised, interpreted and the study quality assessed using the Grades of Recommendations, Assessment, Development, and Evaluation guidelines.

RESULTS

A total of 29 articles dating from the 1960 s until 2022 were identified to meet the study criteria (passive: n = 15; active: n = 14). Study characteristics such as sampling type, sampling method, and AMR assessment were all common characteristics from both passive and active surveillance articles, being milk samples, individual sampling, and phenotypic assessment respectively. Passive surveillance articles had a wider range in both the type of bacteria and the number of antimicrobials investigated, while active surveillance articles included a higher number of bacterial isolates and sampling from healthy populations. There was an overall low level of clinical AMR across all articles. Higher prevalence of non-wildtype Escherichia coli, Salmonella spp., and Staphylococcus spp., although limited in data, was suggested for commonly used Australian veterinary antimicrobials for these bacteria. The prevalence of phenotypic AMR varied due to the health and age status of the sampled animals. The articles reviewed in this study suggest the prevalence of AMR genes was higher for commonly used antimicrobials, although genes were not always related to the phenotypic AMR profile.

CONCLUSIONS

Published evidence of AMR in the Australian dairy cattle industry is limited as demonstrated by only 29 articles included in this review following selection criteria screening. However, collectively these articles provide insight on industry AMR prevalence. For example, the suggestion of non-wildtype bacteria within the Australian dairy cattle indicating a risk of emerging or increasing industry AMR. Therefore, further surveillance is required to monitor the development of future AMR risk within the industry. Additionally, evidence suggesting that animals varying in health and age differ in prevalence of AMR imply a requirement for further research into animal population demographics to reduce potential bias in data collated in both national and global surveillance activities.

Food Security of Temporary Foreign Farm Workers under the Seasonal Agricultural Worker Program in Canada and the United States: A Scoping Review

Temporary foreign farm workers (TFWs) are among the most vulnerable and exploitable groups. Recent research shows alarming rates of food insecurity among them. This review explores research focussing on food security of TFWs in Canada and the United States, summarizes findings, and identifies research gaps. Online databases, including MEDLINE, Web of Science, Scopus, Google Scholar, and government and nongovernment websites, and websites of migrant worker-supporting organizations were searched for peer-reviewed and non-peer-reviewed papers and reports published between 1966 and 2020 regarding food security of TFWs. Articles reviewed were analyzed to determine publication type, country, year, target population, and main findings. Content analysis was performed to identify major themes. Of 291 sources identified, 11 met the inclusion criteria. Most articles (n = 10) were based on studies conducted in the United States. The prevalence of food insecurity among TFWs ranged between 28% and 87%. From the content analysis, we formulated 9 themes, representing a diversity of perspectives, including access to resources, income, housing and related facilities, food access, dietary pattern and healthy food choices, and migrant's legal status. Instruments reported for the measurement of food security include USDA Household Food Security Survey Module (HFSSM; n = 8, 72.7%), the modified version of the USDA HFSSM (n = 1, 9%), hunger measure (n = 1, 9%), the modified CDC's NHANES (n = 1, 9%), and 24-h recall, diet history, and/or food-frequency questionnaire (n = 3, 27.3%). Factors impacting food security of TFWs working under the Seasonal Agricultural Worker Programs (SAWPs) in North America are understudied. There is a need to advance research looking particularly at policies and regulatory and administrative aspects of the SAWPs to improve the food security of this cohort. There is also a need for qualitative studies that explore lived experiences and perspectives of TFWs and key informants. Longitudinal studies may be useful to examine various factors, including policy-related, contributing to food insecurity of TFWs over time.

The normative grounds for NICE decision-making: a narrative cross-disciplinary review of empirical studies

The National Institute for Health and Care Excellence (NICE) is the UK's primary health care priority-setter, responsible for advising the National Health Service on its adoption of health technologies. The normative basis for NICE's advice has long been the subject of public and academic interest, but the existing literature does not include any comprehensive summary of the factors observed to have substantively shaped NICE's recommendations. The current review addresses this gap by bringing together 29 studies that have explored NICE decision-making from different disciplinary perspectives, using a range of quantitative and qualitative methods. It finds that although cost-effectiveness has historically played a central role in NICE decision-making, 10 other factors (uncertainty, budget impact, clinical need, innovation, rarity, age, cause of disease, wider societal impacts, stakeholder influence and process factors) are also demonstrably influential and interact with one another in ways that are not well understood. The review also highlights an over-representation in the literature of appraisals conducted prior to 2009, according to methods that have since been superseded. It suggests that this may present a misleading view of the importance of allocative efficiency to NICE's current approach and illustrates the need for further up-to-date research into the normative grounds for NICE's decisions.

Development of an efficient search filter to retrieve systematic reviews from PubMed

Objective:

Locating systematic reviews is essential for clinicians and researchers when creating or updating reviews and for decision-making in health care. This study aimed to develop a search filter for retrieving systematic reviews that improves upon the performance of the PubMed systematic review search filter.

Methods:

Search terms were identified from abstracts of reviews published in Cochrane Database of Systematic Reviews and the titles of articles indexed as systematic reviews in PubMed. Both the precision of the candidate terms and the number of systematic reviews retrieved from PubMed were evaluated after excluding the subset of articles retrieved by the PubMed systematic review filter. Terms that achieved a precision greater than 70% and relevant publication types indexed with MeSH terms were included in the filter search strategy.

Results:

The search strategy used in our filter added specific terms not included in PubMed's systematic review filter and achieved a 61.3% increase in the number of retrieved articles that are potential systematic reviews. Moreover, it achieved an average precision that is likely greater than 80%.

Conclusions:

The developed search filter will enable users to identify more systematic reviews from PubMed than the PubMed systematic review filter with high precision.

Age Dependence of Antimicrobial Resistance Among Fecal Bacteria in Animals: A Scoping Review

Introduction: A phenomenon of decreasing antimicrobial resistance (AMR) among fecal bacteria as food animals age has been noted in multiple field studies. We conducted a scoping review to summarize the extent, range, and nature of research activity and the data for the following question: "does AMR among enteric/fecal bacteria predictably shift as animals get older?". Methods: This review followed a scoping review methodology framework. Pertinent literature published up until November 2018 for all animals (except humans) was retrieved using keyword searches in two online databases, namely, PubMed® and the Web of Science™ Core Collection, without filtering publication date, geographic location, or language. Data were extracted from the included studies, summarized, and plotted. Study quality was also assessed using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) guidelines for all included papers. Results: The publications with detailed relevant data (n = 62) in food animals, poultry, and dogs were identified. These included longitudinal studies (n = 32), cross-sectional studies of different age groups within one food animal production system or small-animal catchment area (n = 16), and experimental or diet trials (n = 14). A decline in host-level prevalence and/or within-host abundance of AMR among fecal bacteria in production beef, dairy cattle, and swine was reported in nearly two-thirds (65%) of the identified studies in different geographic locations from the 1970's to 2018. Mixed results, with AMR abundance among fecal bacteria either increasing or decreasing with age, have been reported in poultry (broiler chicken, layer, and grow-out turkey) and dogs. Conclusions: Quantitative synthesis of the data suggests that the age-dependent AMR phenomenon in cattle and swine is observed irrespective of geographic location and specific production practices. It is unclear whether the phenomenon predates or is related to antimicrobial drug use. However, almost 50% of the identified studies predate recent changes in antimicrobial drug use policy and regulations in food animals in the United States and elsewhere.

Topics and trends in Mountain Livestock Farming research: a text mining approach

Pasture-based and small-scale livestock farming systems are the main source of livelihood in the mountain primary sector, ensuring socioeconomic sustainability and biodiversity in rural communities throughout Europe and beyond. Mountain livestock farming (MLF) has attracted substantial research efforts from a wide variety of scientific communities worldwide. In this study, the use of text mining and topic modelling analysis drew a detailed picture of the main research topics dealing with MLF and their trends over the last four decades. The final data corpus used for the analysis counted 2 679 documents, of which 92% were peer-reviewed scientific publications. The number of scientific outputs in MLF doubled every 10 years since 1980. Text mining found that milk, goat and sheep were the terms with the highest weighed frequency in the data corpus. Ten meaningful topics were identified by topic analysis: T1-Livestock management and vegetation dynamics; T2-Animal health and epidemiology; T3-Methodological studies on cattle; T4-Production system and sustainability; T5-Methodological studies; T6-Wildlife and conservation studies; T7-Reproduction and performance; T8-Dairy/meat production and quality; T9-Land use and its change and T10-Genetic/genomic studies. A hierarchical clustering analysis was performed to explore the interrelationships among topics, and three main clusters were identified: the first focused on sustainability, conservation and socioeconomic aspects (T4; T6 and T9), the second was related to food production and quality (T7 and T8) and the last one considered methodological studies on mountain flora and fauna (T1; T2; T3; T5 and T10). The 10 topics identified represent a useful and a starting source of information for further and more detailed analysis (e.g. systematic review) of specific research or geographical areas. A truly holistic and interdisciplinary research approach is needed to identify drivers of change and to understand current and future challenges faced by livestock farming in mountain areas.

Veterinarian barriers to knowledge translation (KT) within the context of swine infectious disease research: an international survey of swine veterinarians

Background

Food animal veterinarians face commodity specific and urgent global challenges yet conditions preventing use of best available knowledge have been sparsely studied. The American Association of Swine Veterinarians (AASV) membership (N = 1289) was surveyed online to benchmark their information priorities and their motivations and sources for keeping current with infectious disease research, and to describe their reported time, skill, access, and process as barriers to knowledge translation (KT).

Results

Respondents (n = 80) were mostly from Canada (n = 40) and the U.S.A (n = 31) and demographics approximated the AASV’s. Colleagues are the first choice for information on difficult cases (49%, 95%CI: 38–61). Half of respondents (53%, 95%CI: 41–64) spend an hour or less per week keeping up with infectious disease research. The majority reported moderate or less than moderate efficiency (62%, 95%CI: 51–72), and moderate or greater stress (59%, 95%CI: 48–70) with their process for keeping up. Journal article methods sections are commonly not read, almost a third (32%, 95% CI: 22–43) reported either they do not evaluate statistical methods or that they had poor confidence to do so, and half (52, 95%CI: 41–63) could not explain ‘confounding bias’. Approximately half (55%, 95%CI: 41-69) with direct oversight of swine herds had full access to 2 or fewer academic journals. Approximately a third of respondents (34%, 95%CI: 24–46) selected only formats involving single research studies (either full text or summaries) as preferred reading materials for keeping current over expert summaries of the body of evidence.

Conclusion

KT barriers are considerable and a source of stress for many swine veterinarians. Sub-optimal efficiency with keeping up and low confidence to appraise aspects of research are concerns. Results are consistent with previous literature and illustrate need for improved KT infrastructure and for additional training in statistical methods and interpretation of primary research. Further evaluation is warranted of why approximately a third of veterinarians in this study, for the purpose of keeping up, preferentially choose to review individual research studies over choices that would include an expert summary of the body of evidence. Consideration of reasons for this preference will be important in the planning of KT infrastructure improvements.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12917-020-02617-8.

Dry-off and dairy cow udder health and welfare: Effects of different milk cessation methods

The cessation of milking at the end of lactation is a routine management practice in dairy herds, and the importance of the dry period for milk production and udder health, has long been recognized. Among countries and herds, drying-off practices differ and include various milk cessation methods, such as changes in milking frequency and in feeding, the use of antibiotic dry cow therapy and teat sealants, and changes in housing. Published studies reporting methods of stopping milk production are scarce, and there are no uniform recommendations on optimal procedures to dry cows off for good udder health, cow welfare, and milk production. This review describes methods to stop mik production to prepare cows for the dry period and their effects on mammary involution, udder health, and dairy cow welfare. Milk yield at dry-off (the final milking at the end of lactation) is important for rapid involution, which stimulates the immune system and promotes good udder health and cow welfare. Based on the findings of this review, gradual cessation of milking over several days before the final milking can effectively reduce milk yield at dry-off and accelerate mammary gland involution while maximizing cow comfort and welfare. Data from this review indicate a target production level of 15 kg/day of milk or less at dry-off.

Critically Appraised Topics (CATs) in Veterinary Medicine: Applying Evidence in Clinical Practice

Critically appraised topics (CATs) are evidence syntheses that provide veterinary professionals with information to rapidly address clinical questions and support the practice of evidence-based veterinary medicine (EBVM). They also have an important role to play in both undergraduate and post-registration education of veterinary professionals, in research and knowledge gap identification, literature scoping, preparing research grants and informing policy. CATs are not without limitations, the primary one relating to the rapid approach used which may lead to selection bias or restrict information identified or retrieved. Furthermore, the narrow focus of CATs may limit applicability of the evidence findings beyond a specific clinical scenario, and infrequently updated CATs may become redundant. Despite these limitations, CATs are fundamental to EBVM in the veterinary profession. Using the example of a dog with osteoarthritis, the five steps involved in creating and applying a CAT to clinical practice are outlined, with an emphasis on clinical relevance and practicalities. Finally, potential future developments for CATs and their role in EBVM, and the education of veterinary professionals are discussed. This review is focused on critically appraised topics (CATs) as a form of evidence synthesis in veterinary medicine. It aims to be a primary guide for veterinarians, from students to clinicians, and for veterinary nurses and technicians (hereafter collectively called veterinary professionals). Additionally, this review provides further information for those with some experience of CATs who would like to better understand the historic context and process, including further detail on more advanced concepts. This more detailed information will appear in pop-out boxes with a double-lined surround to distinguish it from the information core to producing and interpreting CATs, and from the boxes with a single line surround which contain additional resources relevant to the different parts of the review.

Systematic reviews and meta-analyses in animal health, performance, and on-farm food safety: a scoping review

Systematic reviews and meta-analyses are used to summarize and interpret evidence for clinical decision-making in human health. The extent of the application of these methods in veterinary medicine and animal agriculture is unknown. The goal of this scoping study was to ascertain trends in the publication of systematic reviews and meta-analyses examining animal health, animal performance, and on-farm food safety. Online databases were searched for reviews published between 1993 and 2018 that focused on relevant outcomes in domestic livestock, companion animals, or wildlife species. In total 1787 titles and abstracts underwent data characterization. Dairy cattle, fish, and pigs were the most common target commodity groups. Few articles investigated both health and performance outcomes (only health: n = 418; only performance: n = 701; both health and performance: n = 103). Most of the reviews (67.6%, n = 1208/1787) described a meta-analysis but did not state in the title or abstract that a systematic review was also conducted, which is potentially problematic. Adherence to reporting guidelines is recommended for all systematic reviews and meta-analyses. For research areas with many reviews, an evidence repository is recommended. For less well-reviewed areas, additional investigation may be necessary to identify the reasons for the lack of synthesis research.

Using campaigns to improve perceptions of the value of adult vaccination in the United States: Health communication considerations and insights

Vaccines have much relevance and promise for improving adult health in the United States, but to date, overall use and uptake remain far below desired levels. Many adults have not received recommended vaccinations and many healthcare providers do not strongly and actively encourage their use with patients. This has led some public health and medical experts to conclude that adult vaccines are severely undervalued by the U.S. public and healthcare providers and to call for campaigns and communication-based efforts to foster increased appreciation, and in turn, higher adult immunization rates. A narrative integrative review that draws upon the vaccine valuation and health communication literatures is used to develop a framework to guide campaign and communication-based efforts to improve public, provider, and policymakers' assessment of the value of adult vaccination. The review does this by: (1) distinguishing social psychological value from economic value; (2) identifying the implications of social psychological value considerations for adult vaccination-related communication campaigns; and (3) using five core health communication considerations to illustrate how social psychological notions of value can be integrated into campaigns or communication that are intended to improve adult vaccination value perceptions and assessments, and in turn, motivate greater support for and uptake of recommended adult vaccines.

Invited review: A systematic literature review and meta-analysis of mortality and culling in dairy cattle

Dairy industries and individual farmers are concerned about mortality and culling of dairy animals. This is because the timing and fates of animals that exit dairy farms have important animal welfare and economic consequences that reflect the conditions under which they are farmed and the efficiency of their production systems. Reports from a few countries have indicated increased incidence of mortality, and occasionally culling, of dairy animals in recent decades, and these changes have been associated with intensification of production systems. Dairy industries and farmers need benchmarks for culling and mortality against which they can compare themselves, as well as improved understanding of the extent of any change and of any associated factors. We reasoned that a systematic literature review and meta-analysis of scientific articles published between 1989 and 2014 would allow us to determine whether these reports were universal, to quantify any change over time, and to investigate whether production systems or study factors were associated with culling and mortality. From 3,275 articles retrieved from databases and manual searching of cited articles, 118 articles were appraised independently by 2 assessors, and 51 articles representing 54 studies were determined to be eligible for review and meta-analysis. We estimated that both the annual incidence risk (IR) and incidence density of mortality of cows had increased significantly from 0.02 per cow and 2.32 per 100 cow-years, to 0.04 per cow and 3.75 per 100 cow-years, an increase per decade of 0.02 per cow and 1.42 per 100 cow-years, respectively. We also estimated that the annual IR of culling attributed to low production had declined significantly from 0.07 to 0.05 and that the IR of perinatal, but not neonatal, mortality had increased significantly from 0.04 to 0.06 per decade. We found no evidence of change in overall annual IR of culling of cows over time or any association between study design factors and the IR or incidence density of culling or mortality. These findings provide benchmarks for describing culling and mortality, and should encourage farmers and researchers in countries with modern dairy industries to discover and implement management strategies to reduce the animal welfare and economic costs associated with these changes.

Improving the peer review of narrative literature reviews

As the size of the published scientific literature has increased exponentially over the past 30 years, review articles play an increasingly important role in helping researchers to make sense of original research results. Literature reviews can be broadly classified as either “systematic” or “narrative”. Narrative reviews may be broader in scope than systematic reviews, but have been criticised for lacking synthesis and rigour. The submission of more scientific manuscripts requires more researchers acting as peer reviewers, which requires adding greater numbers of new reviewers to the reviewing population over time. However, whereas there are many easily accessible guides for reviewers of primary research manuscripts, there are few similar resources to assist reviewers of narrative reviews. Here, I summarise why literature reviews are valued by their diverse readership and how peer reviewers with different levels of content expertise can improve the reliability and accessibility of narrative review articles. I then provide a number of recommendations for peer reviewers of narrative literature reviews, to improve the integrity of the scientific literature, while also ensuring that narrative review articles meet the needs of both expert and non-expert readers.

On the benefits of systematic reviews for wildlife parasitology

Systematic reviews and meta-analyses are widely accepted as the best means to synthesise quantitative or qualitative scientific evidence. Many scientific fields have embraced these more rigorous review techniques as a means to bring together large and complex bodies of literature and their data. Unfortunately, due to perceived difficulties and unfamiliarity with processes, other fields are not using these options to review their literature. One way to provide guidance for a specific field is to examine critically recent reviews and meta-analyses and to explain the advantages and disadvantages of the various review techniques. In this paper, we examine review papers in the emerging field of wildlife parasitology and compare five different literature review types-configurative narrative review, aggregative scoping review, aggregative literature review, aggregative meta-analysis, and aggregative systematic review. We found that most literature reviews did not adequately explain the methodology used to find the literature under review. We also found that most literature reviews were not comprehensive nor did they critically appraise the literature under review. Such a lack severely reduces the reliability of the reviews. We encourage all authors to consider using systematic reviews in the future, and for authors and peer-reviewers to be aware of the limitations of non-systematic reviews.