Use of rope devices to describe and explain the feedlot ecology of Escherichia coli O157:H7 by time and place.

Escherichia coli O157:H7 is an important pathogen of humans, and cattle populations serve as an important reservoir for human exposure. The organism is ubiquitous to feedlot cattle populations, although the nature of its occurrence is quite dynamic. Why E. coli O157:H7 varies by time and place in fed cattle is poorly understood. This study was designed to describe and explain the occurrence of E. coli O157:H7 by pen-level factors of time and place. From each pen, we cultured seven ropes placed within pens for cattle to rub and chew (ROPES), in order to classify the pens as high or low prevalence in longitudinal studies conducted during the summer and winter feeding periods of 2 full years. We observed differences in occurrence of ROPES-positive pens by season, weeks within season, and feedyard. ROPES-positive pens clustered temporally. Factors associated with ROPES-positive pen-weeks during both the summer and winter feeding periods were feedyard, prior 7-day mean air temperature, recovery of E. coli O157...