Quantitative risk assessment of human infection from E coli O157 associated with recreational use of animal pasture

Norval James Colin Strachan, Iain D Ogden, G. M. Dunn

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39 Citations (Scopus)


A quantitative microbial risk assessment incorporating Monte Carlo simulations is described which estimates the probability of Escherichia coli O157 infection of humans by visiting pasture previously grazed by cattle. The risk assessment is performed for a number of scenarios including a variation in the grazing period prior to the human visit, the duration of visit (8-h day or 24-h camp) and the level of E. toll O157 shed by the cattle. Assuming the cattle have been on the field for 28 days, followed directly by a human visit, and the proportion of animals shedding the organism are as described in previous surveys 5 +/- 1% (Synge, B.A., Gunn, G.J., Ternent, H.E., Hopkins, G.F., Thomson-Carter, F., Foster, G., Chase-Topping, M., McKendrick, L, 2001). Prevalence and factors affecting the shedding of verocytotoxin producing Escherichia toll O157 in beef cattle in Scotland. In; Concerted Action CT98-3935 Veroctotoxigenic E. toll in Europe, 5. Epidemiology of Verocytotoxigenic E. toll, Dublin, pp. 98-103.). a probability of infection of 0.1% is attained for 8- and 24-h periods when the cattle are shedding approximately 10(3) and 10(4) CFU g(-1), respectively. Monte Carlo simulations demonstrated that risk mitigation strategies of removing cattle from the pasture 4 weeks prior to the human visit in addition to physical removal of faeces showed significant reductions in potential infection rates. (C) 2002 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)39-51
Number of pages13
JournalInternational Journal of Food Microbiology
Issue number1-2
Publication statusPublished - 2002


  • quantitative risk assessment
  • Monte Carlo simulations
  • Escherichia coli O157
  • environmental pathogens
  • risk mitigation
  • dairy herds
  • prevalence
  • cattle
  • slurry
  • sheep
  • farms
  • beef
  • fate
  • land


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