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Impact of Dust "A Pathogen Cloud" During Loading of Feedlot Cattle for Transportation to the Harvest Facility on the Prevalence of E. coli O157:H7 and Salmonella spp.

Miller, Mark
Texas Tech University
Start date
End date
During the loading of cattle at the feedyard it is a common occurrence for a dust cloud to form. This dust cloud could conceivably a source of cross-contamination as animals pass through it during loading.

The objective of this study was to determine if a dust cloud created during the loading of cattle resulted in significant cross-contamination of E. coli O157 and/or Salmonella during cattle transport.

More information
Findings: Our results indicated that there was a quantitative increase in the number of Salmonella and E. coli O157 after the animals were subjected to the dust cloud. Salmonella increased on the hides of animals from 0.7 to 2.5 logs after the dust cloud when compared to samples taken from the hides immediately after the animals were removed from the pen. We also recovered Salmonella spp. from the dust samples collected from the air in the loading area thus indicating that the air is a potential source of the cross-contamination.

E. coli O157 numbers increased after exposure to the dust cloud on every day of sampling. We also recovered E. coli O157 from the dust on sampling day 1. Only 6% of the pen samples were positive for E. coli O157 while 26% of loading area samples was positive indicating that the loading area could also be a source of contamination.

The loading area samples show the number of positive samples was not different before and after sampling. Thus, indicating that both pathogens persist in the dirt area of the loading area from day to day and can be a source of contamination of the carcass. All isolates are currently being subjected to PFGE to determine the genetic relatedness among hide, pen, loading and air samples.

Our observations indicate that the loading areas and the dust cloud generated during loading can be primary factors in increasing pathogen loads on the animals before and after shipping. Control measures should be investigated to prevent increases in pathogen loads and ultimately to reduce pathogen loads on carcasses and in ground beef.

Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project number
Prevention and Control
Escherichia coli