Priority Setting for Food Borne Pathogens Angela Vargas Supervisors: Dr. Arie Havelaar Prof. Dr. Roger Cooke 12, June 2007 TU Delft

Overview Introduction Problem Description Methodology Paired Comparisons Probabilistic Inversion Elicitation and Analysis Results Conclusions and Recommendations

Introduction Disease Burden YLD Years Lived with a Disability YLL Years of Live Lost DALY Disability-Adjusted Life Years Cost-of-illness COI Cost-of-illness DHC Direct Health care Costs DNHC Direct Non-health care Costs INHC Indirect Non-health care Costs Fraction of cases attributable to Food Fraction of cases attributable to Food Group

Pathways Food borneEnvironmentalHuman-humanDirect animalTraveling

Food borne Transmission through food that is contaminated when it enters the kitchen or during preparation (e.g. by food handlers). Environmental Transmission through contaminated water (drinking water, recreational water), soil, air or other environmental media. Human-humanTransmission from person to person by the fecal-oral route. Direct animal Transmission by direct contact with live animals including pets, farm animals, petting zoos etc. Abroad Cases when exposure takes place by any of the above pathways during foreign travel. Pathways Description

Food Categories Beef and lamb Pork Chicken and other poultry Eggs Dairy products Fish and shellfish Fruit and vegetables Beverages Bread, grains, pastas and bakery products Other foods incl. composite foods Infected humans or animals Food Categories

Problem Description Determine the fraction of transmission route for each pathogen and the fraction of transmission due to specific food groups. The objective is to find a fast, not resource intensive and accurate method of estimation for these fractions. Estimated fractions that will sum to one Insufficient data

Methodology Paired Comparisons Compare pair wise of all items in order to determine preference. The result is a score for each item. Lighter elicitation for experts. The resulting scores sum to one. Probabilistic Inversion Experts give quantiles for the query variables. It is possible to estimate results that sum up to one. …

Paired Comparisons

Paired Comparisons Results Item nameScoreConf L.Conf U. Food Ingestion Environment Contact with sick person Direct animal contact Contamination abroad

Paired Comparisons Results Item nameScoreConf L.Conf U. Beef and lamb Pork Chicken and poultry Eggs Dairy products Fish and shellfish Fruit and vegetables Beverages Bread, grains, pasta Composite Foods Food Handlers

Probabilistic Inversion BACK u1u

IPF – One iteration

Re-Sampling w1 w2 w3 w4 w5 w6 w7 w8 … W n Re- sample

Elicitation and Analysis Specify an interval which contains the probability of occurrence with 90% certainty. A case of illness due to Bacillus cereus toxin was transmitted by ingestion of Pork: ≤ 100% ≤0% ≤ 16 experts participated in the elicitation.

Results “Seed Variables” Some probabilities are believed to be zero therefore that value was used as the true value and used as a seed variable. Additionally 50% Fit was done based on the 5%, 50% and 95% quantile of the equal weight distribution 5% and 95% Fit was done based on the 5% and 95% quantile of the equal weight distribution

Issues Data Recollection Finding the experts. Encouraging them to participate and actually answer. No opportunity to give them guidance Number of experts per pathogen ** Validation How to evaluate the quality of the estimates Results

QUESTIONS

Expert 27

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