Field studies evaluating the effects of multiple concurrent preharvest interventions for Escherichia coli O157 are logistically and economically challenging; however, modeling techniques may provide useful information on these effects while also identifying crucial information
gaps that can guide future research. We constructed a risk assessment model with data obtained from a systematic search of scientific literature. Parameter distributions were incorporated into a stochastic Monte Carlo modeling framework to examine the impacts of different combinations of preharvest
and harvest interventions for E. coli O157 on the risk of beef carcass contamination. We estimated the risk of E. coli O157 carcass contamination conditional on preharvest fecal prevalence estimates, inclusion of feed additive(s) in the diet, vaccination for E. coli O157,
transport and lairage effects, hide intervention(s), and carcass intervention(s). Prevalence parameters for E. coli O157 were assumed to encompass potential effects of concentration; therefore, concentration effects were not specifically evaluated in this study. Sensitivity analyses
revealed that fecal prevalence, fecal-to-hide transfer, hide-to-carcass transfer, and carcass intervention efficacy significantly affected the risk of carcass contamination (correlation coefficients of 0.37, 0.56, 0.58, and −0.29, respectively). The results indicated that combinations
of preharvest interventions may be particularly important for supplementing harvest interventions during periods of higher variability in fecal shedding prevalence (i.e., summer). Further assessments of the relationships among fecal prevalence and concentration, hide contamination, and subsequent
carcass contamination are needed to further define risks and intervention impacts for E. coli O157 contamination of beef.
"oneragan and Brashears , 2005 ) . Although interventions to reduce carcass contamination during processing are crit - ical to reducing human exposure to E . coli O157 , pre - har - vest interventions to reduce faecal prevalence and faecal to hide transfer were also important when multiple interven - tions were assessed in a risk assessment model ( Dodd et al . , 2011 ) . Risk assessment and prediction models suggest that a reduction in cattle shedding of E . coli O157 during the pre - harvest stage will reduce the burden of human E . coli O157 illnesses ( Rotariu et al . , 2012 ; Matthews et al . , 2013 ; Smith et al . , 2013 ) . Direct - fed microbials are defined by the US Food and Drug administra"
[Show abstract][Hide abstract] ABSTRACT: Human illness due to infections with Escherichia coli O157 is a serious health concern. Infection occurs through direct contact with infected animals or their faeces, through contaminated food or water and/or through person-to-person transmission. A reduction in faecal E. coli O157 shedding in cattle might reduce the burden of human infections. We used systematic review and meta-analysis to assess the efficacy of direct-fed microbials (DFM), compared with placebo or no treatment, fed during the pre-harvest stage of production in reducing faecal E. coli O157 shedding in beef cattle during field trials. Four electronic databases, Nebraska Beef Reports and review article reference lists were searched. A total of 16 publications assessing faecal shedding at the end of the trial and/or throughout the trial period were included. The majority of publicly disseminated trials evaluated the prevalence of E. coli O157 faecal shedding; only two evaluated the concentration of organisms in faeces. The prevalence of faecal E. coli O157 shedding in cattle is significantly reduced by DFM treatments (summary effect size for all DFM – OR = 0.46; CI = 0.36–0.60). The DFM combination Lactobacillus acidophilus (NP51) and Propionibacterium freudenreichii (NP24) was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period compared with the group of other DFM, although this difference was not statistically significant. Furthermore, we found that the combination [NP51 and NP24] treatment was more efficacious in reducing the prevalence of faecal E. coli O157 shedding at the time of harvest and throughout the trial period when fed at the dose of 109 CFU/animal/day than any lesser amount, although this difference was not statistically significant. Feeding beef cattle DFM during the pre-harvest stage of production reduces the prevalence of E. coli O157 faecal shedding and might effectively reduce human infections.
Zoonoses and Public Health 04/2014; 62(2). DOI:10.1111/zph.12112 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to characterize the epidemiology of Salmonella carried by dairy cows culled from herds in the Texas High Plains. Feces were collected from a convenience sample of 706 animals culled from nine dairy farms. In addition, individually paired fecal and hide samples were collected from 70 healthy milking cows on three of the dairies. Samples were cultured for Salmonella using routine methods; isolates were serotyped and subjected to a panel of antimicrobial drugs to determine susceptibility. Salmonella was recovered from 32.6% of culled cows. Whole-herd use of a vaccine containing siderophore receptors and porin proteins was associated (p=0.05) with reduced Salmonella prevalence in that the prevalence among herds that practiced whole-herd vaccination was 8.0% compared to 36.8% among herds that did not use this vaccine. The majority (88.6%) of isolates were pansusceptible or resistant to one drug. Of the 3.1% of isolates resistant to more than four drugs, all were Salmonella Newport and were recovered from one dairy. Various serotypes were recovered from individual fecal and hide samples. Salmonella Montevideo was recovered more frequently (p<0.01) from hide samples, whereas Salmonella Cerro was recovered more frequently (p<0.01) from feces. Salmonella was recovered from at least one cow on all dairies. While our study was not a priori designed to address herd-level factors, we found evidence that the whole-herd use of a siderophore receptor and porin protein-containing vaccine might be a useful aid in the control of Salmonella in groups of cattle. As this is a nonrandomized evaluation of an intervention, other herd-level factors that may be correlated with vaccine use, such as biosecurity, might have been responsible for the observed association.
[Show abstract][Hide abstract] ABSTRACT: Our primary objective was to determine the efficacy of a siderophore receptor and porin proteins-based vaccine (VAC) and a Lactobacillus acidophilus-based direct-fed microbial (DFM) against fecal shedding of Escherichia coli O157:H7 in commercial feedlot cattle fed a corn grain-based diet with 25% distiller's grains. Cattle projected to be on a finishing diet during the summer were randomly allocated into 40 study pens within ten blocks based on allocation dates. Blocks were complete; each of the four pens within a block was randomly assigned one treatment: control, VAC, DFM, or VAC+DFM. The DFM was fed (10(6)CFU/animal/day of Lactobacillus) throughout the study periods (84-88 days) and cattle were vaccinated at enrollment and again three weeks later. Fresh fecal samples (30/pen) from pen floors were collected weekly for four consecutive weeks (study days 52-77). Two concurrent culture procedures were used to enable estimates of E. coli O157:H7 shedding prevalence and prevalence of high shedders. From 4800 total samples, 1522 (31.7%) were positive for E. coli O157:H7 and 169 (3.5%) were considered high shedders. Pen-level linear mixed models were used for data analyses. There were no significant interactions among treatments and time of sampling. However, vaccinated pens had lower (P<0.01) overall prevalence of E. coli O157:H7 (model-adjusted mean ±SEM=17.4±3.95%) and lower (P<0.01) prevalence of high shedders (0.95±0.26%) than unvaccinated pens (37.0±6.32% and 4.19±0.81%, respectively). There was no evidence of a DFM effect on either measure of E. coli O157:H7 shedding. Results indicate that a two-dose regimen of the vaccine significantly reduces fecal prevalence of E. coli O157:H7 (vaccine efficacy of 53.0%) and prevalence of E. coli O157:H7 high shedders (vaccine efficacy of 77.3%) in commercial feedlot cattle reared in the summer on a finishing diet with 25% distiller's grains.
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