Annette M. O’Connor

Feeding management practices and feed characteristics associated with Salmonella prevalence in live and slaughtered market-weight finisher swine: A systematic review and summation of evidence from 1950 to 2005

This review summarizes evidence for associations between Salmonella prevalence in market-weight swine and changes in feeding management practices or feed characteristics. A systematic review of the topic was conducted with the goal of minimizing the impact of bias on the review conclusions. Potential interventions included feed withdrawal from swine prior to slaughter, feed acidification, heat treatment of feed, pelletized feed versus mash, course versus fine grind, and wet versus dry feeds. In the reviewed literature, Salmonella prevalence was measured either by culture or by the presence of antibodies to Salmonella. The evidentiary value of studies was assessed, and studies that failed to meet predetermined standards were excluded. 7694 potentially relevant references were identified by an extensive literature search; however, 2623 references that were not published in English were excluded, because funds for translation were not available. Of the remaining references, only 277 were considered relevant to the review topic by two independent reviewers, and assessed for methodological quality. During quality assessment, 233 references were excluded because they failed to report design features that limit the introduction of bias or were conducted in a non-target population such as gnotobiotic, neonatal, nursery, or recently weaned pigs and sows. Forty-four publications passed the quality assessment conducted by 2 independent reviewers, but only 15 of the 44 publications reported studies that tested hypotheses associated with feeding management practices and feed characteristics and Salmonella prevalence in market-weight swine. The most common study design was cross-sectional (7/15). The included studies failed to provide strong evidence of an association between any of the potential interventions and Salmonella prevalence, due to the potential for confounding, and the failure to document temporal association between the intervention and Salmonella prevalence. The strongest evidence of an association was found for feed form, i.e. the use of non-pelleted may be potential interventions associated with reduced Salmonella prevalence. The uncertainty is primarily based on studies containing moderate to low evidentiary value or insufficient numbers of tested individuals, resulting in a low degree of confidence that results could be extrapolated to the target population. Therefore, the conclusion of the review is that there should be a low level of comfort among qualified scientists that the claimed association between non-pelleted feed and reduced Salmonella prevalence is scientifically valid. There is no strong evidence regarding associations between presence of Salmonella and the other feed characteristics examined.

Issues of reporting in observational studies in veterinary medicine.

Observational studies are common in veterinary medicine; the results may be used to inform decision-making, future research, or as inputs to systematic reviews or risk assessment. To be of use, the results must be published, all of the outcomes that were assessed must be included in the publication, and the research (methods and results) must be reported in sufficient detail that the reader can evaluate the internal and external validity. In human healthcare, concerns about the completeness of reporting - and evidence that poor reporting is associated with study results - have led to the creation of reporting guidelines; these include the STROBE statement for observational studies. There is evidence from a limited body of research that there also are reporting inadequacies in veterinary observational studies. There are differences between human and veterinary observational studies that might be relevant to recommendations for reporting. Such differences include: the use of observational studies in animal populations for simultaneously estimating disease frequency and risk-factor identification; the distinction between the animal owners who consent to participate and the animals that are the study subjects; and the complexity of organizational levels inherent in animal research (in particular, for studies in livestock species). In veterinary medicine, it is common to have clustering within outcomes (due to animal grouping) and clustering of predictor variables. We argue that there is a compelling need for the scientific community involved in veterinary observational studies to use the STROBE statement, use an amended version of STROBE, or to develop and use reporting guidelines that are specific to veterinary medicine to improve reporting of these studies.

Reporting of methodological features in observational studies of pre-harvest food safety.

Observational studies in pre-harvest food safety may be useful for identifying risk factors and for evaluating potential mitigation strategies to reduce foodborne pathogens. However, there are no structured reporting guidelines for these types of study designs in livestock species. Our objective was to evaluate the reporting of observational studies in the pre-harvest food safety literature using guidelines modified from the human healthcare literature. We identified 100 pre-harvest food safety studies published between 1999 and 2009. Each study was evaluated independently by two reviewers using a structured checklist. Of the 38 studies that explicitly stated the observational study design, 27 were described as cross-sectional studies, eight as case-control studies, and three as cohort studies. Study features reported in over 75% of the selected studies included: description of the geographic location of the studies, definitions and sources of data for outcomes, organizational level and source of data for independent variables, description of statistical methods and results, number of herds enrolled in the study and included in the analysis, and sources of study funding. However, other features were not consistently reported, including details related to eligibility criteria for groups (such as barn, room, or pen) and individuals, numbers of groups and individuals included in various stages of the study, identification of primary outcomes, the distinction between putative risk factors and confounding variables, the identification of a primary exposure variable, the referent level for evaluation of categorical variable associations, methods of controlling confounding variables and missing variables, model fit, details of subset analysis, demographic information at the sampling unit level, and generalizability of the study results. Improvement in reporting of observational studies of pre-harvest food safety will aid research readers and reviewers in interpreting and evaluating the results of such studies.

Identifying questions in the American Association of Swine Veterinarian's PRRS risk assessment survey that are important for retrospectively classifying swine herds according to whether they reported clinical PRRS outbreaks in the previous 3 years

The American Association of Swine Veterinarians (AASV) Production Animal Disease Risk Assessment Program (PADRAP) is a web-based program that offers a set of risk assessment surveys being used by veterinarians who are members of the AASV. Members use PADRAP to help producers systematically assess risk factors that may be associated with clinical outcomes. As assessments are performed the completed surveys are added to the dataset maintained at the Iowa State University College of Veterinary Medicine. One of the surveys included in PADRAP is the porcine reproductive and respiratory syndrome (PRRS) Risk Assessment for the Breeding Herd. The aim of the study was to categorize questions in version 2 of the PRRS Risk Assessment for the Breeding Herd survey as important or unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. The results elucidate the relative importance of risk factors and areas of risk factors for clinical outcomes and removing unimportant questions may reduce the time required to complete the survey without affecting the quality of information obtained. Surveys from 896 sow herd sites in the United States and Canada completed between March 2005 and March 2009 were included in the analysis. The survey contained a large number of questions with a complex correlation structure among the questions. Responses for several questions were dependent upon responses to others. To address these issues, an approach was developed using a series of statistical methods including random forest, principle component analysis, logistic regression and receiver operating characteristic (ROC) analysis to classify the herds using the questions in the survey as explanatory variables. Questions were ranked by importance and systematically excluded from least important to most important. The questions excluded, without significantly affecting the performance of the model for classifying herds were identified as unimportant. Thirty-eight of the 127 questions analyzed were identified as unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. Sections of the survey where a large number of questions were identified as unimportant included (1) entry of semen into the breeding herd and (2) transportation of live animals. Sections with a high percentage of questions identified as unimportant included (1) characteristics of the site, (2) disposal of dead animals and waste management and (3) employee and visitors.

Meta-analyses including data from observational studies.

Observational studies represent a wide group of studies where the disease or condition of interest is naturally occurring and the investigator does not control allocation to interventions or exposures. Observational studies are used to test hypotheses about the efficacy of interventions or about exposure-disease relationships, to estimate incidence or prevalence of conditions, and to assess the sensitivity and specificity of diagnostic assays. Experimental-study designs and randomized controlled trials (RCTs) can also contribute to the body of evidence about such questions. Meta-analyses (either with or without systematic reviews) aim to combine information from primary research studies to better describe the entire body of work. The aim of meta-analyses may be to obtain a summary effect size, or to understand factors that affect effect sizes. In this paper, we discuss the role of observational studies in meta-analysis questions and some factors to consider when deciding whether a meta-analysis should include results from such studies. Our suggestion is that one should only include studies that are not at high risk of inherent bias when calculating a summary effect size. Study design however can be a meaningful variable in assessment of outcome heterogeneity.

The Association between Sub-Therapeutic Antibiotics and Salmonella Typhimurium in Market-Weight Swine: A Systematic Review and Summation of Evidence from 1950 to 2007

A systematic review approach was used to evaluate the association between sub‐therapeutic antibiotics in feed and Salmonella Typhimurium isolation in market‐weight finisher swine raised in modern swine production systems. Fourteen challenge trials described the efficacy of different antibiotics after challenge with S. Typhimurium. The studies identified were of limited evidentiary value for the review question because they were not relevant to the review question, i.e. conducted in artificial settings on small numbers of young pigs. None of the studies reported using blinding during outcome assessment. No antibiotic regimen was evaluated more than once. The association between sub‐therapeutic antibiotics and Salmonella outcomes in market‐weight swine raised in modern production systems cannot be summarized using the currently available literature. Many available studies fail to report critical study design features such as blinding and/or to take into account the data generated from longitudinal studies.

Updated systematic review: Associations between proximity to animal feeding operations and health of individuals in nearby communities

ObjectiveThe objective of this review was to update a systematic review of associations between living near an animal feeding operation (AFO) and human health.MethodsThe MEDLINE® and MEDLINE® In-Process, Centre for Agricultural Biosciences Abstracts, and Science Citation Index databases were searched. Reference lists of included articles were hand-searched. Eligible studies reported exposure to an AFO and an individual-level human health outcome. Two reviewers performed study selection and data extraction.ResultsThe search returned 3702 citations. Sixteen articles consisting of 10 study populations were included in the analysis. The health outcomes were lower and upper respiratory tracts, MRSA, other infectious disease, neurological, psychological, dermatological, otologic, ocular, gastrointestinal, stress and mood, and other non-infectious health outcomes. Most studies were observational and used prevalence measures of outcome. An association between Q fever risk and proximity to goat production was reported. Other associations were unclear. Risk of bias was serious or critical for most exposure-outcome associations. Multiplicity (i.e., a large number of potentially correlated outcomes and exposures assessed on the same study subjects) was common in the evidence base.ConclusionsFew studies reported an association between surrogate clinical outcomes and AFO proximity for respiratory tract-related outcomes. There were no consistent dose-response relationships between surrogate clinical outcome and AFO proximity. A new finding was that Q fever in goats is likely associated with an increased Q fever risk in community members. The review results for the non-respiratory health outcomes were inconclusive because only a small number of studies were available or the between-study results were inconsistent.Systematic review registrationPROSPERO CRD42014010521

A mixed treatment meta-analysis of antibiotic treatment options for bovine respiratory disease - An update.

Bovine respiratory disease is the most economically important disease of feedlot cattle in North America. Choice of antibiotic is a critical factor for producers and veterinarians. We previously published a mixed-treatment comparison meta-analysis that combined evidence from published trials and published estimates of comparative efficacy for 12 antibiotics registered for use in the USA. Some of the comparative efficacy estimates were based only on indirect evidence. Since the original review was published, new studies that provide direct evidence of comparative efficacy have been published. We updated the original review to include the current evidence. We also compared the results from the indirect estimates from the prior model with the observed results from randomized control trials. We repeated the original search and found that five of the new studies met the criteria for inclusion in the updated review. Four of these studies provided new data on direct comparisons of active drugs. The results from one study (performed in 2002) that compared ceftiofur pinna and enrofloxacin were inconsistent with the network and were excluded from the analysis. Three new direct comparison studies examined gamithromycin compared with tulathromycin, florfenicol, and tilmicosin. The results of our analysis suggested that the indirect estimates from the prior model provided reasonable estimates of the risk ratios revealed by the primary studies. For example, for the comparison of gamithromycin (referent) with tulathromycin, the original model predicted a risk ratio of re-treatment of 0.54 (95% credible interval 0.27-0.87). The subsequent randomized controlled trial revealed that the observed risk ratio of re-treatment was 0.59 (95% confidence interval 0.45-0.78). The results of other comparisons were also similar. For the gamithromycin (referent) to florfenicol comparison, the observed randomized trial RR was 1.17 (95% confidence interval 0.83-1.64) and the indirect estimate of RR from the prior model was 0.84 (95% credibility interval 0.48-1.3). The gamithromycin to tilmicosin (referent) observed RR from the randomized trial was 0.99 (95% confidence interval 0.67-1.47) and the indirect estimate of RR from the prior model was 1.09 (95% credible interval 0.64-1.79). The results suggested that indirect estimates provided reasonable estimates of RR when direct data were not available.

The association between proximity to animal-feeding operations and community health: a protocol for updating a systematic review

BackgroundLivestock and poultry operations that feed large numbers of animals are common. Facility capacity varies, but it is not uncommon for facilities to house 1,000 swine with multiple barns at a single site, feedlots to house 50,000 cattle, and poultry houses to house 250,000 hens. There is primary research that suggests livestock facilities that confine animals indoors for feeding can represent a health hazard for surrounding communities. In this protocol, we describe a review about the association between proximity to animal-feeding operations (AFOs) and the health of individuals in nearby communities. A systematic review of the topic was published by some members of our group in 2010. The purpose of this review is to update that review.Methods/DesignThe populations of interest are people living in communities near livestock production facilities. Outcomes of interest are any health outcome measured in humans such as respiratory disease, gastrointestinal disease, and mental health. Measures of antibiotic resistance in people from the communities compared to measures of resistance found in animals and the environment on animal-feeding operations will also be summarized. The exposure of interest will be exposure to livestock production using a variety of metrics such as distance from facilities, endotoxin levels, and measures of odor. Electronic searches will be conducted using MEDLINE and MEDLINE In-Process (via OvidSP), CAB Abstracts (via Web of Knowledge), and Science Citation Index (via Web of Knowledge). No language or date restriction will be applied. We will access the risk of bias using a pilot version of a tool developed by the Methods Groups of the Cochrane Collaboration for non-randomized interventions.We propose to conduct a meta-analysis for each health metric (e.g., combining all respiratory disease outcomes, combining all gastrointestinal outcomes). A planned subgroup analysis will be based on the domains of the risk of bias.DiscussionThis systematic review will provide synthesis of current evidence reporting the association between living near an animal-feeding operation and human health.Systematic review registrationPROSPERO CRD42014010521

Where are the food animal veterinarian shortage areas anyway

In 2010 the United States implemented the Veterinary Medicine Loan Repayment Program (VMLRP) to address perceived regional shortages in certain veterinary occupations, including food animal practice. With county as the unit of analysis, this paper describes a pair of models to evaluate factors associated with being designated a private practice shortage area in 2010. One model is used to explain food animal veterinarian location choices so as to provide an objective evaluation of comparative shortage. The other model seeks to explain the counties chosen as shortage areas. Model results are then used to evaluate the program. On the whole the program appears to perform quite well. For several states, however, VMLRP shortage designations are inconsistent with the food animal veterinarian location model. Comparative shortage is generally more severe in states that have no VMLRP designated private practice shortage counties than in states that do.