Publications (13)31.72 Total impact
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Article: Assessment of the efficacy and quality of evidence for five on-farm interventions for Salmonella reduction in grow-finish swine: A systematic review and meta-analysis.
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ABSTRACT: Five on-farm practices for reduction of Salmonella shedding or sero-prevalence in grow-finish swine were selected through scoping study and expert consultation. Specific examples were selected based on supporting evidence from at least one controlled trial (CT), and availability to Canadian swine producers. Efficacy was evaluated using systematic review and meta-analysis (SR-MA) methodology. A modified Grading of Recommendations, Assessment, and Evaluation (GRADE) approach was applied to assess the quality of evidence for each intervention, and a 'summary of findings' table was developed to present findings 'at-a-glance'. MA of the small dataset of CTs investigating feeding meal, and measuring serology, yielded a significant summary estimate of efficacy (odds ratio (OR)=0.21; 95% confidence intervals (CI): 0.14, 0.31) with non-significant heterogeneity (P>0.10). MA of the dataset investigating inclusion of organic acids in the ration, measuring serology, yielded a significant summary estimate with significant heterogeneity across studies (P<0.001, I(2)=91%) precluding presentation of a single summary estimate; a range of results were reported (OR Range: 28 (1.6, 498); 0.07 (CI: 0.042, 0.33)). Pen disinfection between batches of finishers was studied in one large CT measuring both fecal culture (OR 0.84 (0.68, 1.1)) and serology (OR 0.48 (0.40, 0.58)) outcomes. The dataset investigating Salmonella spp. vaccination contained inconsistent findings (OR Range: 4.5 (1.3, 15); 0.07 (0.008, 0.68)), with significant heterogeneity across studies (P=0.005, I(2)=82), assessed measuring fecal culture. MA of the dataset investigating inclusion of in-feed tetracyclines yielded a significant OR indicating a potential harmful effect, measuring fecal culture, (OR Range: 14 (1.9, 108); 1.0 (0.43, 2.5)) with significant heterogeneity (P=0.003, I(2)=82%) across studies, suggesting some potential for withdrawal of in-feed tetracyclines to reduce Salmonella shedding. Therefore our ranking of intervention efficacy is: feeding meal>inclusion of acids in ration, feeder pen disinfection or Salmonella spp. vaccination>in-feed tetrayclines. Study design characteristics increasing risk of bias, including failure to justify sample size (19 of 31 studies) and failure to report random or systematic sampling (13 of 31studies), resulted in modified GRADE evidence rankings of 'low' for these interventions. This suggests that further research is likely to affect our findings. Field CTs investigating herd-level interventions with measurements at the herd- and individual-levels are recommended. Overall, SR-MA was a useful approach for ranking efficacy, and GRADE offered a transparent method for ranking quality of evidence, although both were limited by the small number of comparable studies available.Preventive Veterinary Medicine 08/2012; 107(1-2):1-20. · 2.05 Impact Factor -
Article: A systematic review-meta-analysis of chilling interventions and a meta-regression of various processing interventions for Salmonella contamination of chicken.
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ABSTRACT: The results of individual studies investigating the efficacy of chilling and other processing interventions on Salmonella prevalence or concentration in broiler chicken carcasses are inconsistent or contradictory. Determine efficacy of chilling on reducing Salmonella prevalence or concentration on broiler carcasses using systematic review-meta-analysis, and explore sources of heterogeneity among studies investigating various processing interventions through meta-regression. A comprehensive search included electronic search in six databases, manual search of reference lists of topic-related articles, and consultation with five topic experts to assure that all relevant intervention research was identified. STUDY INCLUSION: Primary intervention research, published in English, encompassing control, challenge, cohort, or before-and-after study designs investigating the efficacy of any chilling or other processing interventions on Salmonella prevalence or concentration in broiler chicken carcasses. RISK OF BIAS ASSESSMENT AND DATA EXTRACTION: Data pertaining to study methodology and reported results, chilling or other processing intervention parameters, populations sampled and outcomes measured were assessed for methodological soundness and extracted by two independent reviewers using pretested checklists. Random-effects meta-analyses of immersion chilling with chlorine (n=9 trials), acetic acid (n=16) and potable water (n=13) trended towards reductions in the odds or log(10)CFU/ml of Salmonella. Significant heterogeneity (P-value≤0.1 and I(2)>25%) precluded the reporting of pooled summary effect estimates. Meta-regression of all processing interventions indicated that serotype, disinfectant type and treatment time and pH were significantly associated with studies reporting reductions in concentration while study design, population sampled, study setting, publication date, intervention and disinfectant type, and treatment pH were significantly associated with studies reporting reductions in prevalence. Methodological and reporting flaws were consistently observed in relevant intervention research as well as a lack of studies conducted under commercial conditions and using Salmonella concentration outcomes. Chilling may be effective at reducing Salmonella concentration and prevalence, but significant heterogeneity precluded reporting of pooled summary effect estimates for many chilling interventions. Investigations into potential sources of heterogeneity among all processing interventions found that the use of other chemical disinfectants, such as organic acids and surfactants might result in larger reductions in Salmonella contamination than more commonly utilized oxidizing agents like chlorine.Preventive Veterinary Medicine 01/2012; 103(1):1-15. · 2.05 Impact Factor -
Article: Food-specific attribution of selected gastrointestinal illnesses: estimates from a Canadian expert elicitation survey.
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ABSTRACT: The study used a structured expert elicitation survey to derive estimates of food-specific attribution for nine illnesses caused by enteric pathogens in Canada. It was based on a similar survey conducted in the United States and focused on Campylobacter spp., Escherichia coli O157:H7, Listeria monocytogenes, nontyphoidal Salmonella enterica, Shigella spp., Vibrio spp., Yersinia enterocolitica, Cryptosporidium parvum, and Norwalk-like virus. A snowball approach was used to identify food safety experts within Canada. Survey respondents provided background information as well as self-assessments of their expertise for each pathogen and the 12 food categories. Depending on the pathogen, food source attribution estimates were based on responses from between 10 and 35 experts. For each pathogen, experts divided their estimates of total foodborne illness across 12 food categories and they provided a best estimate for each category as well as 5th and 95th percentile limits for foods considered to be vehicles. Their responses were treated as triangular probability distributions, and linear aggregation was used to combine the opinions of each group of experts for each pathogen-food source group. Across the 108 pathogen-food groups, a majority of experts agreed on 30 sources and 48 nonsources for illness. The number of food groups considered to be pathogen sources by a majority of experts varied by pathogen from a low of one food source for Vibrio spp. (seafood) and C. parvum (produce) to a high of seven food sources for Salmonella spp. Beta distributions were fitted to the aggregated opinions and were reasonable representations for most of the pathogen-food group attributions. These results will be used to quantitatively assess the burden of foodborne illness in Canada as well as to analyze the uncertainty in our estimates.Foodborne Pathogens and Disease 05/2011; 8(9):983-95. · 2.26 Impact Factor -
Article: Foodborne proportion of gastrointestinal illness: estimates from a Canadian expert elicitation survey.
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ABSTRACT: The study used a structured expert elicitation survey to derive estimates of the foodborne attributable proportion for nine illnesses caused by enteric pathogens in Canada. It was based on a similar study conducted in the United States and focused on Campylobacter, Escherichia coli O157:H7, Listeria monocytogenes, nontyphoidal Salmonella enterica, Shigella spp., Vibrio spp., Yersinia enterocolitica, Cryptosporidium parvum, and Norwalk-like virus. For each pathogen, experts were asked to provide their best estimate and low and high limits for the proportion of foodborne illness relative to total cases. In addition, they provided background information with regard to food safety experience, including self-evaluated expertise for each pathogen on a 5-point scale. A snowball approach was used to identify 152 experts within Canada. The experts' background details were summarized using descriptive statistics. Factor analysis was used to determine whether the variability in best estimates was related to self-assessed level of expertise or other background information. Cluster analysis followed by beta function fitting was undertaken on best estimates from experts who self-evaluated their expertise 3 or higher. In parallel, Monte Carlo resampling was run using triangular distributions based on each expert's best estimate and its limits. Sixty-six experts encompassing various academic backgrounds, fields of expertise, and experiences relevant to food safety provided usable data. Considerable variation between experts in their estimated foodborne attributable proportions was observed over all diseases, without any relationship to the expert's background. Uncertainty about their estimate (measured by the low and high limits) varied between experts and between pathogens as well. Both cluster analysis and Monte Carlo resampling clearly indicated disagreement between experts for Campylobacter, E. coli O157, L. monocytogenes, Salmonella, Vibrio, and Y. enterocolitica. In the absence of more reliable estimates, the observed discrepancy between experts must be explored and understood before one can judge which opinion is the best.Foodborne Pathogens and Disease 12/2010; 7(12):1463-72. · 2.26 Impact Factor -
Article: Dose-response modeling of Salmonella using outbreak data.
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ABSTRACT: Salmonella is a key human pathogen worldwide, most often associated with food poisoning incidences. There is a small number of predominant serotypes found in human cases. The role of exposure in the epidemiology of Salmonella can be explained using dose-response assessment both for infection and acute enteric illness. Dose-response studies are traditionally based on human challenge experiments but an alternative is to use outbreak data. Such data were collected from the published literature which included estimates of the dose ingested and the attack rate. Separate dose-response models for infection and illness given infection were fitted using a multi-level statistical framework. These models incorporated serotype and susceptibility as categorical covariates, and adjusted for heterogeneity in exposure. The results indicate that both the risk of infection and the risk of illness given infection increase with dose. The dose-response model incorporating data from all outbreaks had an infection ID50 of 7 CFU's and illness ID50 of 36 CFUs. This is indicative of much higher infectivity and pathogenicity compared with feeding studies of healthy human volunteers with laboratory adapted strains. No differences were found in the outbreak models between serotypes and susceptibility categories. However, for serotypes other than S. Enteritidis or S. Typhimurium, results indicate that a minor proportion of individuals exposed will not fall ill even at high doses. The dose-response relations indicate that outbreaks are associated with higher doses making it more likely to have a higher attack rate. Applications of the dose-response model in outbreak situations where either dose or attack rate is missing were successfully used to clarify the epidemiology. Finally, the dose-response models described here can be readily used in quantitative microbiological risk assessment to predict human infection and illness rates. A simple Excel spreadsheet implementing the model has been prepared and is available from the authors.International journal of food microbiology 10/2010; 144(2):243-9. · 3.01 Impact Factor -
Article: The global burden of nontyphoidal Salmonella gastroenteritis.
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ABSTRACT: To estimate the global burden of nontyphoidal Salmonella gastroenteritis, we synthesized existing data from laboratory-based surveillance and special studies, with a hierarchical preference to (1) prospective population-based studies, (2) "multiplier studies," (3) disease notifications, (4) returning traveler data, and (5) extrapolation. We applied incidence estimates to population projections for the 21 Global Burden of Disease regions to calculate regional numbers of cases, which were summed to provide a global number of cases. Uncertainty calculations were performed using Monte Carlo simulation. We estimated that 93.8 million cases (5th to 95th percentile, 61.8-131.6 million) of gastroenteritis due to Salmonella species occur globally each year, with 155,000 deaths (5th to 95th percentile, 39,000-303,000 deaths). Of these, we estimated 80.3 million cases were foodborne. Salmonella infection represents a considerable burden in both developing and developed countries. Efforts to reduce transmission of salmonellae by food and other routes must be implemented on a global scale.Clinical Infectious Diseases 02/2010; 50(6):882-9. · 9.15 Impact Factor -
Article: A multifactorial risk prioritization framework for foodborne pathogens.
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ABSTRACT: We develop a prioritization framework for foodborne risks that considers public health impact as well as three other factors (market impact, consumer risk acceptance and perception, and social sensitivity). Canadian case studies are presented for six pathogen-food combinations: Campylobacter spp. in chicken; Salmonella spp. in chicken and spinach; Escherichia coli O157 in spinach and beef; and Listeria monocytogenes in ready-to-eat meats. Public health impact is measured by disability-adjusted life years and the cost of illness. Market impact is quantified by the economic importance of the domestic market. Likert-type scales are used to capture consumer perception and acceptance of risk and social sensitivity to impacts on vulnerable consumer groups and industries. Risk ranking is facilitated through the development of a knowledge database presented in the format of info cards and the use of multicriteria decision analysis (MCDA) to aggregate the four factors. Three scenarios representing different stakeholders illustrate the use of MCDA to arrive at rankings of pathogen-food combinations that reflect different criteria weights. The framework provides a flexible instrument to support policymakers in complex risk prioritization decision making when different stakeholder groups are involved and when multiple pathogen-food combinations are compared.Risk Analysis 09/2009; 30(5):724-42. · 2.37 Impact Factor -
Article: Quantitative risk assessment of Listeria monocytogenes in ready-to-eat meats in Australia.
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ABSTRACT: Listeria monocytogenes is a food-borne pathogen that can contaminate processed meats and has caused outbreaks in several nations in which processed meats were the vehicle. Due to its ecology, the control of this organism in ready-to-eat meats is difficult. As a first step in improving risk management for this product:pathogen pair in Australia, a stochastic simulation model to predict the numbers of L. monocytogenes likely to be consumed in those products under a wide range of scenarios was developed. The predictions are based on data describing initial contamination levels of both lactic acid bacteria and L. monocytogenes, product formulation, times and temperatures of distribution and storage prior to consumption, and consumption patterns. The model was used to estimate the probable numbers of cases of listeriosis due to processed meats in Australia per year. The model predicted that processed meats could be responsible for up to approximately 40% of cases of listeriosis in Australia, a level considered credible by comparison with available epidemiological data. The reliability of the model, as well as data gaps and further research needs, is discussed.International journal of food microbiology 03/2009; 131(2-3):128-37. · 3.01 Impact Factor -
Article: A comparison of risk assessments on Campylobacter in broiler meat.
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ABSTRACT: In recent years, several quantitative risk assessments for Campylobacter in broiler meat have been developed to support risk managers in controlling this pathogen. The models encompass some or all of the consecutive stages in the broiler meat production chain: primary production, industrial processing, consumer food preparation, and the dose-response relationship. The modelling approaches vary between the models, and this has supported the progress of risk assessment as a research discipline. The risk assessments are not only used to assess the human incidence of campylobacteriosis due to contaminated broiler meat, but more importantly for analyses of the effects of control measures at different stages in the broiler meat production chain. This review paper provides a comparative overview of models developed in the United Kingdom, Denmark, the Netherlands and Germany, and aims to identify differences and similarities of these existing models. Risk assessments developed for FAO/WHO and in New Zealand are also briefly discussed. Although the dynamics of the existing models may differ substantially, there are some similar conclusions shared between all models. The continuous introduction of Campylobacter in flocks implies that monitoring for Campylobacter at the farm up to one week before slaughter may result in flocks that are falsely tested negative: once Campylobacter is established at the farm, the within-flock prevalence increases dramatically within a week. Consequently, at the point of slaughter, the prevalence is most likely to be either very low (<5%) or very high (>95%). In evaluating control strategies, all models find a negligible effect of logistic slaughter, the separate processing of positive and negative flocks. Also, all risk assessments conclude that the most effective intervention measures aim at reducing the Campylobacter concentration, rather than reducing the prevalence. During the stage where the consumer handles the food, cross-contamination is generally considered to be more relevant than undercooking. An important finding, shared by all, is that the tails of the distributions describing the variability in Campylobacter concentrations between meat products and meals determine the risks, not the mean values of those distributions. Although a unified model for risk assessment of Campylobacter in the broiler meat production would be desirable in order to promote a European harmonized approach, it is neither feasible nor desirable to merge the different models into one generic risk assessment model. The purpose of such a generic model has yet to be defined at a European level and the large variety in practices between countries, especially related to consumer food preparation and consumption, complicates a unified approach.International journal of food microbiology 01/2009; 129(2):107-23. · 3.01 Impact Factor -
Article: Estimated Numbers of Community Cases of Illness Due to Salmonella, Campylobacter and Verotoxigenic Escherichia Coli: Pathogen-specific Community Rates.
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ABSTRACT: To estimate the annual number of cases of illness due to verotoxigenic Escherichia coli (VTEC), Salmonella and Campylobacter in the Canadian population, using data from the National Notifiable Disease registry (NND), estimates of under-reporting derived from several National Studies on Acute Gastrointestinal Illness, and the literature. For each of the three pathogens (VTEC, Salmonella and Campylobacter), data were used to estimate the percentage of cases reported at each step in the surveillance system. The number of reported cases in the NND for each pathogen was then divided by these percentages. In cases where the pathogen-specific estimates were unavailable, data on acute gastrointestinal illness were used, accounting for differences between those with bloody and nonbloody diarrhea. For every case of VTEC, Salmonella and Campylobacter infection reported in the NND, there were an estimated 10 to 47, 13 to 37, and 23 to 49 cases annually in the Canadian population, respectively. The authors estimate that a significant number of infections due to VTEC, Salmonella and Campylobacter occur each year in Canada, highlighting the fact that these enteric pathogens still pose a significant health burden. Recognizing the significant amount of under-reporting is essential to designing appropriate interventions and assessing the impact of these pathogens in the population.The Canadian journal of infectious diseases & medical microbiology = Journal canadien des maladies infectieuses et de la microbiologie medicale / AMMI Canada 08/2006; 17(4):229-34. · 1.54 Impact Factor -
Article: Estimating the under-reporting rate for infectious gastrointestinal illness in Ontario.
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ABSTRACT: In Ontario, infectious gastrointestinal illness (IGI) reporting can be represented by a linear model of several sequential steps required for a case to be captured in the provincial reportable disease surveillance system. Since reportable enteric data are known to represent only a small fraction of the total IGI in the community, the objective of this study was to estimate the under-reporting rate for IGI in Ontario. A distribution of plausible values for the under-reporting rate was estimated by specifying input distributions for the proportions reported at each step in the reporting chain, and multiplying these distributions together using simulation methods. Input distributions (type of distribution and parameters) for the proportion of cases reported at each step of the reporting chain were determined using data from the Public Health Agency of Canada's National Studies on Acute Gastrointestinal Illness (NSAGI) initiative. For each case of enteric illness reported to the province of Ontario, the estimated number of cases of IGI in the community ranged from 105 to 1,389, with a median of 285, and a mean and standard deviation of 313 and 128, respectively. Each case of enteric illness reported to the province of Ontario represents an estimated several hundred cases of IGI in the community. Thus, reportable disease data should be used with caution when estimating the burden of such illness. Program planners and public health personnel may want to consider this fact when developing population-based interventions.Canadian journal of public health. Revue canadienne de santé publique 96(3):178-81. · 1.02 Impact Factor -
Article: Fuzzy risk assessment tool for microbial hazards in food systems
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ABSTRACT: A Fuzzy Risk Assessment Tool (FRAT) has been developed for early-stage risk assessment of microbial hazards in food systems. The user defines parameters to describe initial hazard level, potential changes during processing and consumer preparation as well as factors related to consumption and health impact. The inputs are defined in linguistic terms or semi-quantitative levels which are converted to fuzzy values. Interval arithmetic is used to compute exposure and risk. Four examples of microbial hazards in food systems are used to demonstrate features of the tool.Fuzzy Sets and Systems. -
Article: Dose–response modeling of Salmonella using outbreak data
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ABSTRACT: Salmonella is a key human pathogen worldwide, most often associated with food poisoning incidences. There is a small number of predominant serotypes found in human cases. The role of exposure in the epidemiology of Salmonella can be explained using dose–response assessment both for infection and acute enteric illness. Dose–response studies are traditionally based on human challenge experiments but an alternative is to use outbreak data. Such data were collected from the published literature which included estimates of the dose ingested and the attack rate. Separate dose–response models for infection and illness given infection were fitted using a multi-level statistical framework. These models incorporated serotype and susceptibility as categorical covariates, and adjusted for heterogeneity in exposure. The results indicate that both the risk of infection and the risk of illness given infection increase with dose. The dose–response model incorporating data from all outbreaks had an infection ID50 of 7 CFU's and illness ID50 of 36 CFUs. This is indicative of much higher infectivity and pathogenicity compared with feeding studies of healthy human volunteers with laboratory adapted strains. No differences were found in the outbreak models between serotypes and susceptibility categories. However, for serotypes other than S. Enteritidis or S. Typhimurium, results indicate that a minor proportion of individuals exposed will not fall ill even at high doses. The dose–response relations indicate that outbreaks are associated with higher doses making it more likely to have a higher attack rate. Applications of the dose–response model in outbreak situations where either dose or attack rate is missing were successfully used to clarify the epidemiology. Finally, the dose–response models described here can be readily used in quantitative microbiological risk assessment to predict human infection and illness rates. A simple Excel spreadsheet implementing the model has been prepared and is available from the authors.International Journal of Food Microbiology.
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Institutions
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2010
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Public Health Agency of Canada
- Laboratory for Foodborne Zoonoses
Ottawa, Ontario, Canada
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