A stakeholder-informed approach to the identification of criteria for the prioritization of zoonoses in Canada

BACKGROUND

Zoonotic diseases account for over 60% of all communicable diseases causing illness in humans and 75% of recently emerging infectious diseases. As limited resources are available for the control and prevention of zoonotic diseases, it is necessary to prioritize diseases in order to direct resources into those with the greatest needs. The selection of criteria for prioritization has traditionally been on the basis of expert opinion; however, details of the methods used to identify criteria from expert opinion often are not published and a full range of criteria may not be captured by expert opinion.

METHODOLOGY/PRINCIPAL FINDINGS

This study used six focus groups to identify criteria for the prioritization of zoonotic diseases in Canada. Focus groups included people from the public, animal health professionals and human health professionals. A total of 59 criteria were identified for prioritizing zoonotic diseases. Human-related criteria accounted for the highest proportion of criteria identified (55%), followed by animal-related criteria (26%) then pathogen/disease-related criteria (19%). Similarities and differences were observed in the identification and scoring of criteria for disease prioritization between groups; the public groups were strongly influenced by the individual-level of disease burden, the responsibility of the scientific community in disease prioritization and the experiences of recent events while the professional groups were influenced by the societal- and population-level of disease burden and political and public pressure.

CONCLUSIONS/SIGNIFICANCE

This was the first study to describe a mixed semi-quantitative and qualitative approach to deriving criteria for disease prioritization. This was also the first study to involve the opinion of the general public regarding disease prioritization. The number of criteria identified highlights the difficulty in prioritizing zoonotic diseases. The method presented in this paper has formulated a comprehensive list of criteria that can be used to inform future disease prioritization studies.

A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes

Pasteurization of milk ensures safety for human consumption by reducing the number of viable pathogenic bacteria. Although the public health benefits of pasteurization are well established, pro-raw milk advocate organizations continue to promote raw milk as "nature's perfect food." Advocacy groups' claims include statements that pasteurization destroys important vitamins and that raw milk consumption can prevent and treat allergies, cancer, and lactose intolerance. A systematic review and meta-analysis was completed to summarize available evidence for these selected claims. Forty studies assessing the effects of pasteurization on vitamin levels were found. Qualitatively, vitamins B12 and E decreased following pasteurization, and vitamin A increased. Random effects meta-analysis revealed no significant effect of pasteurization on vitamin B6 concentrations (standardized mean difference [SMD], -2.66; 95% confidence interval [CI], -5.40, 0.8; P = 0.06) but a decrease in concentrations of vitamins B1 (SMD, -1.77; 95% CI, -2.57, -0.96; P < 0.001), B2 (SMD, -0.41; 95% CI, -0.81, -0.01; P < 0.05), C (SMD, -2.13; 95% CI, -3.52, -0.74; P < 0.01), and folate (SMD, -11.99; 95% CI, -20.95, -3.03; P < 0.01). The effect of pasteurization on milk's nutritive value was minimal because many of these vitamins are naturally found in relatively low levels. However, milk is an important dietary source of vitamin B2, and the impact of heat treatment should be further considered. Raw milk consumption may have a protective association with allergy development (six studies), although this relationship may be potentially confounded by other farming-related factors. Raw milk consumption was not associated with cancer (two studies) or lactose intolerance (one study). Overall, these findings should be interpreted with caution given the poor quality of reported methodology in many of the included studies.

A systematic review of vaccinations to reduce the shedding of Escherichia coli O157 in the faeces of domestic ruminants

The objective of this study was to conduct a systematic review and meta-analysis of the published literature to evaluate the efficacy of vaccines in reducing faecal shedding of Escherichia coli O157 in ruminants. A systematic search of eight databases and land-grant university research reports using an algorithm adapted from a previous systematic review of pre-harvest interventions against E. coli O157 was conducted to locate all reports of in vivo trials of E. coli O157 vaccines in ruminants published between 1990 and 2010. All located references were screened by two independent reviewers, and data were extracted from all relevant papers, with treatment effect measured in odds ratios. For trials with a faecal prevalence outcome that did not involve mixing of treated and untreated cattle in the same pen, efficacy was explored using random-effects meta-analysis. Funnel plots were used to evaluate publication bias, and random-effects meta-regression was performed to explore heterogeneity. The search located 20 relevant manuscripts which detailed 24 trials and 46 treatment comparisons; all but one trial involved cattle. There were 9 deliberate challenge trials (19 comparisons), and 15 natural exposure trials (27 comparisons). For Type III protein vaccines, there were 9 natural exposure trials detailing 17 comparisons, and meta-analysis of 8 comparisons revealed that vaccine treatment resulted in a statistically significant reduction in E. coli O157 faecal prevalence [odds ratio (OR)=0.38, 95% confidence interval (CI)=0.29, 0.51]. Siderophore receptor and porin protein (SRP) vaccines (three trials/four comparisons) also reduced faecal prevalence (OR=0.42, 95% CI=0.20, 0.61); however, none of the bacterin vaccine trials (n=3, six comparisons) resulted in a statistically significant reduction in prevalence. The results suggest that Type III protein and SRP vaccines significantly reduce faecal shedding in cattle; however, caution should be taken in interpreting the results because of the heterogeneity in the results.

Escherichia coli O157:H7 genetic diversity in bovine fecal samples

Escherichia coli O157:H7 causes foodborne illness in humans; cattle are considered a primary reservoir for the organism, and transmission is often through contaminated food products or water. The objective of this study was to determine the genetic diversity of E. coli O157:H7 within a single individual bovine fecal sample based on pulsed-field gel electrophoresis (PFGE) typing. Fecal samples (n=601) were collected from dairy and beef cattle at three separate facilities, and E. coli O157:H7 was isolated by enrichment, immunomagnetic separation, and plating on selective medium. The prevalence of E. coli O157:H7 was 46 (7.7%) of 601. From each positive fecal sample, up to 10 putative colonies were tested, and isolates from samples with at least seven positive colonies were subtyped using PFGE and tested for six major virulence genes by multiplex PCR. A total of 254 E. coli O157:H7 isolates from 27 samples met these criteria and were included in PFGE analysis. Fifteen PFGE subtypes (<100% Dice similarity) were detected among the 254 isolates, and there were no common subtypes between the three locations. Seven (26%) of 27 fecal samples had E. coli O157:H7 isolates with different PFGE subtypes (mean=2.1) within the same sample. The virulence gene profiles of different isolates from the same sample were always identical, regardless of the number of PFGE types. The results of this study suggest that determining the PFGE pattern of a single isolate from a bovine sample may not be sufficient when comparing isolates from feces, hides, or carcasses, because multiple PFGE subtypes are present.

Seasonality in human salmonellosis: assessment of human activities and chicken contamination as driving factors

This study used integrated surveillance data to assess the seasonality in retail chicken contamination and of human activities and their role on the seasonality of human endemic salmonellosis. From June 2005 to May 2008, reported cases of salmonellosis were followed-up comprehensively using a standardized questionnaire, and 616 retail chicken breasts were systematically tested for Salmonella, in one Canadian community. Poisson regression was used to model seasonality of human cases, Salmonella in retail chicken, and to assess the relationship between these and selected meteorological variables. The case-case approach was used to compare the activities of salmonellosis cases that occurred during the summer peak to the other cases. There were 216 human endemic salmonellosis cases (incidence rate: 14.7 cases/100,000 person-years), predominantly of Typhimurium and Enteritidis serotypes (28.4% and 20.8%, respectively). The monthly distribution of cases was associated with ambient temperature (p < 0.001) with a significant seasonal peak in June (p = 0.03) and July (p = 0.0005), but it was not associated with precipitation (p = 0.38). Several activities reported by cases tended to be more frequent during summer. Particularly, attending a barbeque and gardening within the 3 days before the disease onset were two significant risk factors for salmonellosis in June or July compared with the salmonellosis cases that occurred in the other months. Out of all chicken samples, 185 (30%) tested positive for Salmonella spp., Kentucky being the dominant serotype (44.3% of positive samples). The monthly proportion of positive chicken samples showed no seasonal variations (p = 0.30) and was not associated with the monthly count of human cases (p = 0.99). In conclusion, even though evidence generally supports chicken as a primary vehicle of Salmonella to humans, the contamination of retail chicken was not driving the seasonality in human salmonellosis. Attending a barbeque or gardening during the hotter months of the year should be further assessed for their risk.

Comparison of outcomes and other variables between conference abstracts and subsequent peer-reviewed papers involving pre-harvest or abattoir-level interventions against foodborne pathogens

Accuracy in the reporting of studies in conference abstracts is important because the majority of studies in such abstracts are never further detailed in peer-reviewed publications, and data from such abstracts may be used in systematic reviews. Previous research on interventional studies in human biomedicine indicates that there is no guarantee of consistency between a conference abstract and paper in the reporting of results and other key variables. However, no research has been done to determine if this lack of reporting consistency in abstracts and papers extends to interventional studies in pre-harvest/harvest-level food safety. The goal of this study was to compare outcome results and other key variables between conference abstracts and subsequent peer-reviewed publications describing studies of pre-harvest and abattoir-level interventions against foodborne pathogens, and to determine whether the agreement in the results or key variables was associated with the time to full publication. A systematic search identified 59 conference abstracts with matching peer-reviewed papers (matches), and data on variables including outcome measures and results, pathogens, species, interventions, overall efficacy of intervention, sample size and housing were extracted from both the conference abstracts and the papers. The matching of variables between abstracts and papers was described, and logistic regression used to test for associations between variable matching and time to publication. Sample size was only provided for both abstract and paper in 24 matches; the same sample size was reported in 20 of these matches. Most other variables were reported in the majority of abstracts/papers, and with the exception of outcomes and intervention effect, the reporting of variables was relatively consistent. There was no significant difference in the numbers of authors, with the first author the same in 78.3% of matches. Of 231 outcome measures reported in both abstracts and papers, nearly one third (77% or 32.2%) had different results, with 32 changing direction of effect. More than a quarter of matches involved at least one significant change in outcome result. The overall conclusion on the efficacy of the intervention changed in 10.7% of matches. There was a significant association between increased time to publication and differences in the number of authors, and having fewer outcome measures in the abstract reported in the paper. These results suggest that data from conference abstracts should be considered with caution.

Quality of reporting of clinical trials of dogs and cats and associations with treatment effects

BACKGROUND

To address concerns about the quality of reporting of randomized controlled trials, and the potential for biased treatment effects in poorly reported trials, medical journals have adopted a common set of reporting guidelines, the Consolidated Standards of Reporting Trials (CONSORT) statement, to improve the reporting of randomized controlled trials.

HYPOTHESIS

The reporting of clinical trials involving dogs and cats might not be ideal, and this might be associated with biased treatment effects.

ANIMALS

Dogs and cats used in 100 randomly selected reports of clinical trials.

METHODS

Data related to methodological quality and completeness of reporting were extracted from each trial. Associations between reporting of trial features and the proportion of positive treatment effects within trials were evaluated by generalized linear models.

RESULTS

There were substantive deficiencies in reporting of key trial features. An increased proportion of positive treatment effects within a trial was associated with not reporting: the method used to generate the random allocation sequence (P < .001), the use of double blinding (P < .001), the inclusion criteria for study subjects (P = .003), baseline differences between treatment groups (P = .006), the measurement used for all outcomes (P = .002), and possible study limitations (P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

Many clinical trials involving dogs and cats in the literature do not report details related to methodological quality and aspects necessary to evaluate external validity. There is some evidence that these deficiencies are associated with treatment effects. There is a need to improve reporting of clinical trials, and guidelines, such as the CONSORT statement, can provide a valuable tool for meeting this need.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that might not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A 2-day consensus meeting was held on November 18-19, 2008 in Chicago, IL, to achieve the objective. Before the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Before the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items would need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional subitem was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

A qualitative exploration of the perceptions and information needs of public health inspectors responsible for food safety

Background

In Ontario, local public health inspectors play an important frontline role in protecting the public from foodborne illness. This study was an in-depth exploration of public health inspectors' perceptions of the key food safety issues in public health, and their opinions and needs with regards to food safety information resources.

Methods

Four focus group discussions were conducted with public health inspectors from the Central West region of Ontario, Canada during June and July, 2008. A questioning route was used to standardize qualitative data collection. Audio recordings of sessions were transcribed verbatim and data-driven content analysis was performed.

Results

A total of 23 public health inspectors participated in four focus group discussions. Five themes emerged as key food safety issues: time-temperature abuse, inadequate handwashing, cross-contamination, the lack of food safety knowledge by food handlers and food premise operators, and the lack of food safety information and knowledge about specialty foods (i.e., foods from different cultures). In general, participants reported confidence with their current knowledge of food safety issues and foodborne pathogens. Participants highlighted the need for a central source for food safety information, access to up-to-date food safety information, resources in different languages, and additional food safety information on specialty foods.

Conclusions

The information gathered from these focus groups can provide a basis for the development of resources that will meet the specific needs of public health inspectors involved in protecting and promoting food safety.

Analysis of trends in the full publication of papers from conference abstracts involving pre-harvest or abattoir-level interventions against foodborne pathogens

Study results are often presented as abstracts at scientific conferences before publication as full articles in peer-reviewed journals. Given the current emphasis on evidence-based decision-making, it is vital that the peer-reviewed literature represents as broad and un-biased a selection of studies as possible. While the proportion of abstracts published as full papers in the peer-reviewed literature has been extensively studied in human healthcare, no such studies have been published in the field of food safety. The goal of this study was to estimate the proportion published and average time to publication for conference abstracts involving studies of pre-harvest or abattoir interventions to reduce foodborne pathogens. Abstracts were obtained by hand-searching available proceedings between 1995 and 2004 from 10 conferences. Included abstracts were limited to those detailing non-observational, controlled in vivo trials where outcome(s) were measured in livestock, carcasses or eggs. Data on abstract type (<or=500 words, >500 words), species, intervention, study type, sample size, number housed together and outcomes were recorded. Four databases (Agricola, CAB, Web of Science, Scholar's Portal) were searched for published papers corresponding to the conference abstracts using author and intervention/pathogen terms. Time to publication and overall median time to publication were estimated. Chi-squared, logistic regression and survival analyses were used to test for significant differences in proportion published and time to publication between variable levels. Of the 149 abstracts identified, 68 (45.6%) were published in peer-reviewed journals within 4 years. The median time to publication was 13.5 months (range: 0, 72). Abstracts shorter than 1 page were significantly more likely to be published (OR=2.2, 95% CI=1.0, 4.8), and abstracts involving pork or pigs were significantly less likely to be published that those involving poultry (OR=0.4: 0.2, 0.8). Abstracts reporting at least one positive outcome were more likely to be published (OR=2.608: 1.097, 6.196) and were published faster (HR=2.3: 1.1, 4.7). Time to publication decreased with the number of positive outcomes reported (HR=1.1: 1.0, 1.3). Sample size could only be determined for 46% of abstracts, with a median sample size of 9 (range 1-378), and housing was sufficiently described to determine sample size in 35% of pre-slaughter studies. The potential effects of this bias on systematic reviews and uses of interventions could be significant, and thus improvements may be warranted in the proportion of conference abstracts resulting in papers in the peer-reviewed literature.

The association between proximity to animal feeding operations and community health: a systematic review

BACKGROUND

A systematic review was conducted for the association between animal feeding operations (AFOs) and the health of individuals living near AFOs.

METHODOLOGY/PRINCIPAL FINDINGS

The review was restricted to studies reporting respiratory, gastrointestinal and mental health outcomes in individuals living near AFOs in North America, European Union, United Kingdom, and Scandinavia. From June to September 2008 searches were conducted in PUBMED, CAB, Web-of-Science, and Agricola with no restrictions. Hand searching of narrative reviews was also used. Two reviewers independently evaluated the role of chance, confounding, information, selection and analytic bias on the study outcome. Nine relevant studies were identified. The studies were heterogeneous with respect to outcomes and exposures assessed. Few studies reported an association between surrogate clinical outcomes and AFO proximity. A negative association was reported when odor was the measure of exposure to AFOs and self-reported disease, the measure of outcome. There was evidence of an association between self-reported disease and proximity to AFO in individuals annoyed by AFO odor.

CONCLUSIONS/SIGNIFICANCE

There was inconsistent evidence of a weak association between self-reported disease in people with allergies or familial history of allergies. No consistent dose response relationship between exposure and disease was observable.

The REFLECT statement: reporting guidelines for randomized controlled trials in livestock and food safety: explanation and elaboration

Concerns about the completeness and accuracy of reporting of randomized clinical trials (RCTs) and the impact of poor reporting on decision-making have been documented in the medical field over the past several decades. Experience from RCTs in human medicine would suggest that failure to report critical trial features can be associated with biased estimated effect measures, and there is evidence to suggest similar biases occur in RCTs conducted in livestock populations. In response to these concerns, standardized guidelines for reporting RCTs were developed and implemented in human medicine. The Consolidated Standards of Reporting Trials (CONSORT) statement was first published in 1996 with a revised edition published in 2001. The CONSORT statement consists of a 22-item checklist for reporting a RCT and a flow diagram to follow the number of participants at each stage of a trial. An explanation and elaboration document not only defines and discusses the importance of each of the items, but also provides examples of how this information could be supplied in a publication. Differences between human and livestock populations necessitate modifications to the CONSORT statement to maximize its usefulness for RCTs involving livestock. These have been addressed in an extension of the CONSORT statement titled the REFLECT statement: Methods and processes of creating reporting guidelines for randomized control trials for livestock and food safety. The modifications made for livestock trials specifically addressed the common use of group housing and group allocation to intervention in livestock studies, the use of a deliberate challenge model in some trials, and common use of non-clinical outcomes, such as contamination with a foodborne pathogen. In addition, the REFLECT statement for RCTs in livestock populations proposed specific terms or further clarified terms as they pertained to livestock studies.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A two-day consensus meeting was held on November 18-19, 2008 in Chicago, Ill, United States of America, to achieve the objective. Prior to the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Prior to the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety (LFS) and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional sub-item was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A two-day consensus meeting was held on November 18-19, 2008 in Chicago, IL, United States of America, to achieve the objective. Prior to the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock-production specialists, journal editors, assistant editors, and associate editors. Prior to the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines For Randomized Control Trials) statement for livestock and food safety (LFS) and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional sub-item was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

Methodological quality and completeness of reporting in clinical trials conducted in livestock species

Randomized controlled trials (RCTs) are the gold standard for evaluating efficacy of treatments under real world conditions and, as such, it is important that they are conducted with methodological rigour to prevent biased results. Many medical journals have adopted a standard checklist for reporting of RCTs, the CONSORT statement. The objective of this study was to evaluate clinical trials in livestock populations to assess methodological quality and completeness of reporting and to investigate the association between these criteria and treatment effects. A total of 100 clinical trials published between 2006 and 2008 in the English language were randomly selected. For each trial, 2 reviewers independently completed a checklist based on the CONSORT statement and a different 2 reviewers completed a standard template describing the outcomes used and the statistical significance of all reported treatment effects. Disagreements among reviewers were resolved by consensus. The results showed that there were substantive deficiencies in the reporting of many of trial features, both related to methodological quality and completeness of reporting. Details on key features such as randomization, double blinding, and the number of subjects lost to follow-up were reported in only 67, 4, and 62% of trials, respectively. Reporting of random allocation to treatment group was associated with a lower proportion of positive treatments effects within trials, as was reporting of inclusion/exclusion criteria for study subjects, details on the intervention, animal signalment, significance tests of baseline differences for at least one variable, and the methods used to measure all outcomes. The results suggest that there are deficiencies in the current reporting of important features of RCTs conducted in livestock species and that these deficiencies may be associated with biased treatment effects. The creation and adoption of standards for trial reporting in livestock could aid authors, reviewers, and editors in ensuring that necessary trial details are reported in all published trials.

The influence of veterinary epidemiology on public health: past, present and future

This paper summarizes a presentation given at the Association for Veterinary Epidemiology and Preventive Medicine sponsored Calvin W. Schwabe symposium honouring the lifetime achievements of Dr. S. Wayne Martin. While the concepts were amalgamated from many sources, the examples were primarily selected to represent areas where Wayne Martin has been an active researcher and educator. The purpose was to describe the impact of veterinary epidemiology on public health in the past and present and to consider the future of veterinary epidemiology in public health. Veterinary medicine contributes to public health not only in the area of zoonotic disease prevention and control, but also through contributions to animal health, comparative and basic medical research, and population and environmental health. Veterinary epidemiologists contribute to both research in public health and the practice of public health through a wide range of methodological approaches and via the networks of trained epidemiologists working in the area. The contributions of veterinary epidemiologists have resulted in significant improvements in human health. There are considerable challenges and opportunities facing veterinary epidemiologists working in the public health area in the future. Meeting these needs will require continued integration between veterinary and human public health research and practice, and enhanced communication of both content and context expertise.

Pre-harvest Interventions to Reduce the Shedding of E. coli O157 in the Faeces of Weaned Domestic Ruminants: A Systematic Review

Our objective was to use formal systematic review methods to evaluate the efficacy of interventions to reduce faecal shedding of Escherichia coli O157 in post-weaned ruminants by increasing animal resistance. The methodology consisted of an extensive search to identify all potentially relevant research, screening of titles and abstracts for relevance to the research question, quality assessment of relevant research, extraction of data from research of sufficient quality, and qualitative summarization of results. The interventions evaluated included probiotics, vaccination, antimicrobials, sodium chlorate, bacteriophages and other feed additives. There was evidence of efficacy for the probiotic combination Lactobacillus acidophilus NP51 (NPC 747) and Propionibacterium freudenreichii and for sodium chlorate in feed or water. The effectiveness of vaccination varied among studies and among vaccine protocols and there was no consistent evidence to suggest that antibiotic use was associated with a decrease in faecal shedding of E. coli O157, or that current industry uses of antimicrobials were associated with increased faecal shedding. There were an insufficient number of studies available to address the effectiveness of bacteriophages and several other feed additives. In general, few of the primary studies evaluated the interventions under commercial housing conditions with a natural disease challenge, there were inconsistencies in the results among study designs and in some cases among studies within study designs, and a relatively large proportion of publications were excluded based on quality assessment criteria. Few studies reported on associations between the proposed intervention and production parameters, such as average daily gain and feed: gain ratio. While the results suggest that some interventions may be efficacious, there are knowledge gaps in our understanding of the efficacy of pre-harvest interventions to increase animal resistance to E. coli O157 that require further targeted research.