title: Saltelli Global Sensitivity Analysis and Simulation Modelling to Identify Intervention Strategies to Reduce the Prevalence of Escherichia coli O157 Contaminated Beef Carcasses.
abstract: BACKGROUND
  Strains of Shiga-toxin producing Escherichia coli O157 (STEC O157) are important foodborne pathogens in humans, and outbreaks of illness have been associated with consumption of undercooked beef. Here, we determine the most effective intervention strategies to reduce the prevalence of STEC O157 contaminated beef carcasses using a modelling approach.
  
  
  METHODS
  A computational model simulated events and processes in the beef harvest chain. Information from empirical studies was used to parameterise the model. Variance-based global sensitivity analysis (GSA) using the Saltelli method identified variables with the greatest influence on the prevalence of STEC O157 contaminated carcasses. Following a baseline scenario (no interventions), a series of simulations systematically introduced and tested interventions based on influential variables identified by repeated Saltelli GSA, to determine the most effective intervention strategy.
  
  
  RESULTS
  Transfer of STEC O157 from hide or gastro-intestinal tract to carcass (improved abattoir hygiene) had the greatest influence on the prevalence of contaminated carcases. Due to interactions between inputs (identified by Saltelli GSA), combinations of interventions based on improved abattoir hygiene achieved a greater reduction in maximum prevalence than would be expected from an additive effect of single interventions. The most effective combination was improved abattoir hygiene with vaccination, which achieved a greater than ten-fold decrease in maximum prevalence compared to the baseline scenario.
  
  
  CONCLUSIONS
  Study results suggest that effective interventions to reduce the prevalence of STEC O157 contaminated carcasses should initially be based on improved abattoir hygiene. However, the effect of improved abattoir hygiene on the distribution of STEC O157 concentration on carcasses is an important information gap-further empirical research is required to determine whether reduced prevalence of contaminated carcasses is likely to result in reduced incidence of STEC O157 associated illness in humans. This is the first use of variance-based GSA to assess the drivers of STEC O157 contamination of beef carcasses.
authors.affiliation: Graham Centre for Agricultural Innovation, NSW Department of Primary Industries and Charles Sturt University, Pugsley Place, Wagga Wagga, NSW 2650, Australia.|School of Animal and Veterinary Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Brookes
authors.affiliation: NSW Department of Primary Industries, Wollongbar, NSW, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Jordan
authors.affiliation: School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Victoria 3001, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Davis
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Camden, NSW 2570, Australia.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Ward
authors.affiliation: Graham Centre for Agricultural Innovation, NSW Department of Primary Industries and Charles Sturt University, Pugsley Place, Wagga Wagga, NSW 2650, Australia.|School of Animal and Veterinary Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
authors.forename: Jane
authors.initials: J
authors.lastname: Heller
mesh_terms: D003198:Computer Simulation; D019453:Escherichia coli O157 / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000517:prevention & control*; D015995:Prevalence; D000069466:Red Meat / Q000382:microbiology*; D018570:Risk Assessment