title: Effects of seasonality and a diet of brassicas on the shedding of Escherichia coli O157 in sheep.
abstract: Sheep flocks were tested for Escherichia coli O157 from pooled fecal samples while they grazed on pasture in winter, brassicas in spring, and on pasture during the summer. The winter pasture study reported an average individual prevalence of 3.1% (95% confidence interval [CI]: 0.6-5.6%) and an average farm-level prevalence of 10.4% (95% CI: 2.1-18.8%) over the 3-year study period. The spring brassica study reported a prevalence of 0% and the summer pasture study had an individual prevalence of 6.3% (95% CI: 2.1-12.1%) and a farm prevalence of 36.8% (95% CI: 15.8-57.8%). Analysis showed significant differences between the shedding of E. coli O157 in sheep grazing on brassicas in spring when compared to sheep grazing on pasture in the summer (p<0.01) and in winter (p=0.044; odds ratio [OR]=0.106). Furthermore, sheep excreted a lower prevalence of E. coli O157 in winter while grazing on pasture (p=0.017; OR=0.199). E. coli O157 isolates were characterized using polymerase chain reaction for the presence of known virulence factors; all carried the eae and stx2 gene and 10/11 positive flocks possessed the stx2c gene, suggesting that sheep are a potential source of human infection.
authors: School of Medicine and Dentistry, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom.
authors: Eilidh M
authors: EM
authors: Fraser
authors: Marion
authors: M
authors: MacRae
authors: Iain D
authors: ID
authors: Ogden
authors: Ken J
authors: KJ
authors: Forbes
authors: Norval J C
authors: NJ
authors: Strachan
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics; D000821:Animal Feed; D000822:Animal Husbandry; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D057138:Bacterial Shedding; D001937:Brassica; D004197:Disease Reservoirs / Q000662:veterinary; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics; D005243:Feces / Q000382:microbiology; D006801:Humans; D015995:Prevalence; D012606:Scotland / Q000453:epidemiology; D012621:Seasons; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology* / Q000382:microbiology; D022641:Shiga Toxin 2 / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D022641:Shiga Toxin 2; D037521:Virulence Factors; C073819:eaeA protein, E coli