Abstract of Meeting Paper

Society for Risk Analysis - Europe 1998 Annual Meeting

Quantitative Risk Assessment of Human Listeriosis from Consumption of Soft Cheese Made from Raw Milk. Prof. O. Cerf, Alfort Veterinary School, 7 Avenue Du General De Gaulle, F-94704 Maisons-Alfort Cedex, France, telephone +33 (0)1 43 96 70 34, fax +33 (0)1 43 96 71 30, e-Mail Cerf@Vet-Alfort.Fr; H. O. Mohammed, Cornell University, Ithaca (New York), USA; Stéphanie Meyer and Nawel Bemrah, Epidemiology and Animal Health Management Laboratory, Alfort Veterinary School, Maisons-Alfort, France; M. H. Cassin, Decisionalysis Risk Consulting (Uk), Cambridge, England; M. W. Griffiths, Department of Food Science, University of Guelph, Ontario, Canada; and M. Sanaa, Epidemiology and Animal Health Management Laboratory, Alfort Veterinary School, Maisons-Alfort, France

The microbial hazard Listeria monocytogenes has been identified in soft cheese made from raw milk. Quantification of the resulting risk for public health was attempted within the frame of the Codex Alimentarius Commission approach to Quantitative Risk Assessment, using a Monte Carlo simulation software. The complete process of cheese making was modeled, from milking to consumption. Using epidemiological data published on the different sources of milk contamination (environment and mastitis) and bacterial growth data, distributions were assumed for parameters of the model. Equations of Farber et al. (1996) and Buchanan et al. (1997) for populations at low, medium and high risk were used to link the ingested dose of L. monocytogenes to the occurrence of listeriosis, accounting for nutritional habits of concerned sub-populations (provided by the French Network of Public Health and CREDOC, a polling institute). The probability of milk and cheese contamination was estimated. The estimated probability of consuming a contaminated cheese serving was calculated, as well as the annual probability for the whole population of being infected. Sensitivity study of the model was done by modifying inputs and their distributions. The model was used to simulate various risk management options. Influence of factors such as the frequency of environmental milk contamination or the incidence of bovine listeriosis were studied. Thus the usefulness of simulation to demonstrate the efficiency of various management options was demonstrated, even if results should be interpreted with care, as many assumptions had to be made on data and their distributions.