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Estimating the best way forward: Expert and farmer evaluations of environmental interventions to reduce human exposure t

Estimating the best way forward: Expert and farmer evaluations of environmental interventions to reduce human exposure to E. coli O157. Paul Cross, Dan Rigby & Gareth Edwards-Jones RELU funded ‘Reducing Escherichia coli O157 risk in rural communities’ . Uncertainty & O157 Management.

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Estimating the best way forward: Expert and farmer evaluations of environmental interventions to reduce human exposure t

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  1. Estimating the best way forward: Expert and farmer evaluations of environmental interventions to reduce human exposure to E. coli O157 Paul Cross, Dan Rigby & Gareth Edwards-Jones • RELU funded ‘Reducing Escherichia coli O157 risk in rural communities’

  2. Uncertainty & O157 Management Uncertainty regarding: How people become infected (sporadic infection) Effectiveness of measures Likelihood of measures being adopted

  3. Is there a problem? Many potential measures + Absence of hard (e.g. RCT) evidence on measures to reduce risk + A (perceived) need to act = a problem

  4. Managing Uncertainty Identify all possible interventions Elicit ‘expert’ opinion on interventions Aim: Identify best candidate interventions Ideally = highly effective + highly practical

  5. Managing Uncertainty Which experts? • Experts (effectiveness) • Inter alia; Public Health, Veterinary Microbiology (Food), Microbiology (Agricultural/Environmental/Clinical), Risk Assessment, Business, Land Management • Farmers (practicality) • Members of farmers unions in Wales and Scotland. • Farmers’ markets How to elicit their views? • Novel method: Best Worst Scaling

  6. Best-Worst Scaling • Market research tool • Possible to carry out • over distance; no face to face; anonymous • Multiple choice based • Scaled, fine resolution results • Allows respondents to rank long lists without the associated cognitive gymnastics (bite-sized chunks)

  7. Best-Worst Scaling

  8. Best-Worst Scaling analysis Take all the “most effective” & “least effective” choices 5 item set we gain information on 7of the 10 paired combinations Respondent chooses the two measures with the maximum difference in performance (best and worst) Maximises the ability to predict peoples choices

  9. Intervention generation • Literature review • Non-systematic • Published and grey literature included • Project members • Opportunity for experts to add interventions to list

  10. Respondent sample • Results of the expert elicitation Experts (Effectiveness) Round 1 • Contacted 53 experts • 31(75%) completed survey • Reduced initial list of 99 to 30 Round 2 • Contacted 70 experts • 41 (60%) completed survey of 30 interventions Famers (Practicality) Round 3 • 50 in Wales • 50 in Scotland

  11. CV scores: a measure of agreement? Experts had higher CV scores than farmers for ‘effectiveness’ (p<0.001) and ‘practicality’ (p<0.01) Farmer CV mean scores were very similar between Scotland and Wales. The mean confidence interval for the practicality assessment was 0.86 for farmers and 1.46 for experts (p<0.001) and for effectiveness was 0.94 and 1.35 respectively (p=0.002).

  12. Effectiveness scores Vaccination Double fencing

  13. Is there consensus? • Vaccination (Intervention 19)

  14. Is there consensus? Reducing stocking densities by 50%

  15. Is there consensus? P &E Scores are widely distributed indicating poor agreement amongst respondents 16. HACCP for manure handling

  16. Practicality scores Hand washing Reduce cattle stocking densities by 50%.

  17. Scottish and Welsh farmers (practicality)

  18. Best-Worst Scaling 2 x 2 plots Low practicality/ High effectiveness High practicality/ High effectiveness 19: Vaccination of cattle 1: Hand washing 27: Reduce cattle by 50% 12: Septic tank leakage Low practicality/ low effectiveness High practicality/ low effectiveness

  19. Method suitability Best suited to the evaluation of large sets of standalone measures Best suited to the evaluation of multidimensional measures (effectiveness and practicality) Smaller multi-level sets of measures, identify the ‘best’ bundles (ACA, CBC)

  20. Future • Applications in other areas • E.g. Cryptosporidium, Salmonella, anti-microbial resistant genes • Modelling of interventions • % reduction in disease prevalence • Development of MACCs • % reduction/cost

  21. Participating institutions Health Protection Agency; Health Protection Scotland; University of Glasgow: School of Veterinary Medicine; Scottish Agricultural Ccollege; Veterinary Laboratory Agency; Scottish Infection Research Network; HPS Colindale; FSA: Microbiological Safety Division; Bioss Scotland; Wageningen University and Research Centre; Liverpool John Moores University: Centre for Public Health; NFUScotland; NFUCymru; Farmers Union Wales; Office of the Chief Veterinary Officer Wales; Meat Promotion Wales; Quality Meat Scotland; Countryside Council Wales

  22. Acknowledgements Thank you

  23. Top interventions by effectiveness and practicality

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