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.

Identification of Common Subpopulations of Non-Sorbitol-Fermenting, β-Glucuronidase-Negative Escherichia coli O157:H7 from Bovine Production Environments and Human Clinical Samples

“…The human isolates comprised previously examined strains from the United States and Australia (16,17) as well as strains from sporadic cases and outbreaks collected by the CDC, the NPHL, and the University of Wisconsin (10). The bovinederived isolates originated from previous studies of dairy herds (8,10,17,18,32), as well as longitudinal studies of production feedlots (15). Collectively, the strains comprise a set of 1,429 isolates, each of which was tested by LSPA-6.…”

“…Additional human clinical isolates (CDC241 to CDC265) were derived from the Centers for Disease Control and Prevention (CDC; N. Strockbine). Strains in the Moxley 60, Moxley 387, Moxley W00, Moxley W01, and Moxley S01 collections were isolated from bovine feces and environmental sampling (rope) devices (35) (15,33). Human clinical isolates of O157:H7 strains were derived from the Nebraska Public Health Laboratory (NPHL).…”

Risk Factors and Control Measures for Bacterial Contamination in the Bovine Meat Chain: A Review on Salmonella and Pathogenic E.coli

“…The duration of faecal shedding in cattle can last up to 19 weeks (Khaitsa et al, 2003). On a clinical basis, pathogenic E. coli strains are grouped in 3 classes namely those rarely associated to diseases either in animals or in humans (i.e VTEC-2), strains associated to disease in both animals and humans (i.e EHEC-2) and finally strains such as EHEC-1 and VTEC-1 reported to be highly infectious for humans but rarely in animals (Mainil & Daube, 2005).…”

Rectoanal Junction Colonization of Feedlot Cattle by Escherichia coli O157:H7 and Its Association with Supershedders and Excretion Dynamics

“…Reducing the prevalence of E. coli O157:H7 excretion by market-ready cattle has so far been the mainstay of preslaughter approaches to risk mitigation. A number of epidemiological studies have investigated factors that are associated with higher shedding prevalence within populations of cattle (1,14,16). Yet, gaps in our knowledge of how or why cattle excrete E. coli O157:H7 to various degrees remain.…”

“…Yet, gaps in our knowledge of how or why cattle excrete E. coli O157:H7 to various degrees remain. A critical aspect of bovine E. coli O157:H7 epidemiology that needs to be addressed is the large amount of variation in prevalence between different groups of cattle, e.g., between herds, saleyard lots, or feedlot pens (16,18,20). Studies on the patterns of individual animal excretion of E. coli O157:H7 and subsequent population transmission dynamics are needed in order to design more-effective control strategies.…”