High shedders are target for E. coli mitigation strategies

Feb 20, 2009
by WLJ
High shedders are target for E. coli mitigation strategies

High shedders within a truckload at slaughter could be a target for mitigation strategies to reduce the probability of preevisceration carcass contamination, a study by Kansas State University has found.

To quantify associations at slaughter between E. coli O157:H7 carcass contamination, fecal-positive animals and high-shedding animals within truckloads of finished cattle, researchers sampled up to 32 cattle from each of 50 truckloads arriving at a commercial abattoir in the Midwestern U.S. during a five-week summer period. Carcass swab samples collected preevisceration and fecal samples collected postevisceration were matched within animals and analyzed for the presence of E. coli O157:H7 using enrichment, immunomagnetic separation and plating on selective media. In addition, a direct plating procedure was performed on feces to identify higher-shedding animals.

The research found that preevisceration carcass prevalence was positively correlated with overall fecal, fecal IMS and fecal highshedder prevalence within truckloads of finished cattle.

In addition, research indicated that the probability of a carcass testing positive for E. coli O157:H7 was more strongly associated with truckload rather than with individual measures of fecal prevalence and the presence of a high shedder within the truckload results in high odds of carcass contamination. Results suggest that future risk assessments, surveillance and research into potential mitigation strategies could potentially focus on the presence of high shedders within a group of cattle rather than the presence or absence of E. coli in an individual.