|Elder, Robert - FORMER ARS EMPLOYEE|
Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 2001
Publication Date: March 15, 2002
Citation: Journal of the American Veterinary Medical Association. 2002. v. 220. p. 756-763. Interpretive Summary: Human infections with shiga-toxigenic Escherichia coli (STEC) O157 are frequently associated epidemiologically with direct and indirect contact with live cattle and with consumption of products of bovine origin, especially hamburger. The vehicle of STEC O157 human infection and food contamination has often been presumed to be bovine feces. We report here the frequent isolation of STEC O157 from multiple hide surfaces and the oral cavity of live finished feedlot cattle both in the presence and absence of fecal STEC O157 shedding. Fecal culture greatly underestimated true STEC O157 animal status. These findings suggest that STEC O157 may have a broad ecological niche in and on cattle beyond the distal large intestine and that non-fecal bovine contacts may be important sources of animal-to-animal transmission, food contamination, and human infections. These non-fecal sites of STEC O157 colonization and/or contamination could also serve as potential targets for both pre- and post-harvest interventions.
Technical Abstract: Objective--To determine if viable shiga-toxigenic Escherichia coli (STEC) O157 are present on various hide surfaces and in the oral cavity of finished beef feedlot cattle in pens containing natural fecal STEC O157 shedding individuals. Design--Within-animal prevalence distribution survey. Sample population--Finished cattle (n=139) from 4 different pens of a Nebraska feedyard were sampled in summer 1999. All 4 pens contained cattle known to be fecal shedding STEC O157 at estimated prevalence rates between 20 and >90%. Procedure--Seven sites were sampled from each animal: rectal feces, mouth swabs, and 5 hide surface swabs (lumbar flank, ventral neck, ventral abdominal midline [ventrum], dorsal thoracic midline [back], and distal left rear leg [hock],); 973 total samples. Samples were cultured for STEC O157 on the day of collection. Results--Viable STEC O157 were isolated from the mouth and 1 or more hide surfaces of most cattle in both the presence and absence of fecal shedding. Overall site-specific STEC O157 prevalence (in descending order) was: mouth, 74.8%; back, 73.4%; neck, 62.6%; feces, 60.4%; flank, 54.0%; ventrum, 51.1%, and hock, 41.0%. Only 5 cattle were STEC O157-negative at all 7 sites. Multiple correspondence and cluster analyses demonstrated that culture results from the feces, mouth, and back detected most STEC O157-positive cattle. Public health implications--The feces, mouth, and hide of beef cattle are potential sources of zoonotic risk as indirect vehicles of meat contamination at slaughter and as direct vehicles of human infection by contact.