title: Risk factors for the presence of high-level shedders of Escherichia coli O157 on Scottish farms.
abstract: Escherichia coli O157 infections are the cause of sporadic or epidemic cases of often bloody diarrhea that can progress to hemolytic uremic syndrome (HUS), a systematic microvascular syndrome with predominantly renal and neurological complications. HUS is responsible for most deaths associated with E. coli O157 infection. From March 2002 to February 2004, approximately 13,000 fecal pat samples from 481 farms with finishing/store cattle throughout Scotland were examined for the presence of E. coli O157. A total of 441 fecal pats from 91 farms tested positive for E. coli O157. From the positive samples, a point estimate for high-level shedders was identified using mixture distribution analysis on counts of E. coli O157. Models were developed based on the confidence interval surrounding this point estimate (high-level shedder, greater than 10(3) or greater than 10(4) CFU g(-1) feces). The mean prevalence on high-level-shedding farms was higher than that on low-level-shedding farms. The presence of a high-level shedder on a farm was found to be associated with a high proportion of low-level shedding, consistent with the possibility of a higher level of transmission. Analysis of risk factors associated with the presence of a high-level shedder on a farm suggested the importance of the pathogen and individual host rather than the farm environment. The proportion of high-level shedders of phage 21/28 was higher than expected by chance. Management-related risk factors that were identified included the type of cattle (female breeding cattle) and cattle stress (movement and weaning), as opposed to environmental factors, such as water supply and feed.
authors.affiliation: Centre for Infectious Diseases, University of Edinburgh, Edinburgh, United Kingdom. margo.chase@ed.ac.uk
authors.forename: Margo E
authors.initials: ME
authors.lastname: Chase-Topping
authors.forename: Iain J
authors.initials: IJ
authors.lastname: McKendrick
authors.forename: Michael C
authors.initials: MC
authors.lastname: Pearce
authors.forename: Peter
authors.initials: P
authors.lastname: MacDonald
authors.forename: Louise
authors.initials: L
authors.lastname: Matthews
authors.forename: Jo
authors.initials: J
authors.lastname: Halliday
authors.forename: Lesley
authors.initials: L
authors.lastname: Allison
authors.forename: Dave
authors.initials: D
authors.lastname: Fenlon
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Low
authors.forename: George
authors.initials: G
authors.lastname: Gunn
authors.forename: Mark E J
authors.initials: ME
authors.lastname: Woolhouse
mesh_terms: D000383:Agriculture; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D003625:Data Collection; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D011795:Surveys and Questionnaires