title: Incidence, duration, and prevalence of Escherichia coli O157:H7 fecal shedding by feedlot cattle during the finishing period.
abstract: The objective was to describe variability in prevalence, incidence, and duration of fecal shedding of naturally occurring E. coli O157:H7 by a group of feedlot cattle over time. One hundred steers, randomly assigned to 10 pens, were fed a high-concentrate finishing diet for 136 days (19 weeks). Rectal feces from each animal were tested for E. coli O157:H7 every week for 19 weeks. E. coli O157:H7 was recovered from each animal that completed the study and was detected from at least one animal every week. Average pen prevalence of cattle shedding E. coli O157:H7 varied significantly over time (P < 0.0001) and across pens (P < 0.0001), ranging from 1 to 80%. Pairwise comparisons of mean pen prevalence of E. coli O157:H7 between weeks and estimation of the predicted probability of an incident case of E. coli O157:H7 over time allowed the definition of three distinct phases--namely, the preepidemic, epidemic, and postepidemic periods. Average pen prevalence varied significantly over time (P < 0.01) and across pens (P < 0.001) for all time periods. The odds of an incident case were significantly greater during epidemic and postepidemic periods relative to the preepidemic period (P = 0.0002 and P = 0.03, respectively). Duration of infection was significantly longer for first or second infections that began during epidemic or postepidemic periods relative to the preepidemic period (P < 0.001). Both incidence and duration of shedding peaked during the epidemic period. Pen-level prevalence of cattle shedding E. coli O157:H7 was affected by both incidence and duration of shedding and could be explained by time- or pen-dependent risk factors, or both.
authors: Department of Veterinary and Biomedical Sciences, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, P.O. Box 830905, Lincoln, Nebraska 68583-0905, USA.
authors: M L
authors: ML
authors: Khaitsa
authors: D R
authors: DR
authors: Smith
authors: J A
authors: JA
authors: Stoner
authors: A M
authors: AM
authors: Parkhurst
authors: S
authors: S
authors: Hinkley
authors: T J
authors: TJ
authors: Klopfenstein
authors: R A
authors: RA
authors: Moxley
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D015169:Colony Count, Microbial; D004783:Environmental Microbiology; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D015994:Incidence; D008297:Male; D015995:Prevalence; D011897:Random Allocation; D012007:Rectum / Q000382:microbiology; D012307:Risk Factors; D013997:Time Factors