Project Summary

The Role of Super-Shedders in Determining Feedlot Pen Prevalence of E. coli O157:H7

Principle Investigator(s):
Rowland Cobbold, Ph.D.
Washington State University
Completion Date:
May 2006



Due to its significance to public health, its potential impact to beef trade and production security, as well as negative public perception issues, E. coli O157:H7 is a critical problem for the beef industry. Pathogen reduction through a series of interventions at various stages of the beef production process is currently considered the most effective means to reduce the risk of final product contamination. Control of E. coli O157:H7 at the pre-slaughter/harvest level is an important component in such a risk reduction strategy.

A previous checkoff-funded study examined the phenomenon of recto-anal junction (RAJ) colonization of cattle by E. coli O157:H7. This study concluded that the RAJ does indeed appear to be a significant site for E. coli O157:H7 colonization, and that this colonization is associated with fecal excretion patterns. Tied to the phenomenon of RAJ colonization is the concept that certain cattle within feedlots are colonized by E. coli O157:H7 more frequently, persistently and in greater numbers than other cattle. These “super-shedders” appear to influence the degree of E. coli O157:H7 colonization of other cattle in their pens, as well as environmental contamination levels. While the previous study showed increased levels of E. coli O157:H7 colonization of copenned cattle, it could not confirm that the presence of super-shedders were the cause. Furthermore, increases in environmental concentrations of E. coli O157:H7 could not be tied directly to the presence of a super-shedder.

The objectives of this study were as follows:

  1. Demonstrate that the addition/removal of a super-shedder results in an increase/decrease in the prevalence, mean count and duration of E. coli O157:H7 by other cattle in that pen;
  2. Use genetic similarity profiling to confirm the transmission of E. coli O157:H7 from super-shedder cattle to other cattle in that pen; and 
  3. Demonstrate an association between the presence of a super-shedder in a pen and the prevalence and identity of O157:H7 in the pen environment.

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