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COST ACTION 920 |
Inventory of QMRA Studies in Europe |
Data sheet
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Pathogen |
Salmonella |
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Country or region |
Denmark |
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Transmission route |
From |
All major animal sources |
To |
Humans |
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Specific product(s) |
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End-point(s) |
Number of registered cases from various sources |
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Reports or publications
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Bibliographic reference |
Hald, T., D. Vose and H.C. Wegener: Quantifying the contribution of animal-food sources to human salmonellosis in Denmark in 1999. In: Salmonella in pork - Epidemiology, control and the public health impact. Ph.D. thesis ISBN 87-988315-2-6, Royal Veterinary and Agricultural University, Copenhagen, Denmark. (Also Submitted to Int. J. Food Microbiol.) |
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Abstract |
In order to get a better understanding of the
mechanisms behind the dynamics in the occurrence of Salmonella infections
in humans, a quantitative risk assessment model was developed. The model
quantifies the importance of the major animal-food sources of domestic and
sporadic cases of human salmonellosis. Data from the national Salmonella
surveillance of animals, foods and humans in Denmark in 1999 was used for
demonstration. For modelling purposes, we applied a statistical technique called
Bayesian Monte Carlo, which combines Bayesian inference and Monte Carlo
simulation.
First, the number of domestic and sporadic cases caused by different Salmonella types was estimated based on the observed data, i.e. the registered number of cases of human salmonellosis. The principle was then to compare the occurrence of these estimated number of cases with the prevalence of the Salmonella types isolated from the different animal-food sources, weighted by the amount of food source consumed. However, the number of people being infected by a particular Salmonella type in a particular food source may depend on additional factors related to the Salmonella type and/or food source in question. Therefore, we introduced a multiparameter prior, which accounted for the presumed but undefined differences between Salmonella serotypes and food sources with respect to causing human Salmonella infections. A Poisson likelihood function was used for the probability of observing the actual number of human cases given the prevalence in the various food sources and the amount of food consumed. The maximum likelihood estimators (MLEs) were determined for the unknown parameters and uniform priors were constructed centred around the MLEs. The joint posterior distribution was estimated by the Bayesian Monte Carlo technique. Based on the final multidimensional model, the number of human cases attributable to each food source was estimated. The most important sources were found to be table eggs, where to approximately 54% (90% C.I.: 51.4 – 56.1%) of the cases could be attributed. This was followed by domestically produced pork and imported poultry, which comprised around 9% (90% C.I.: 8.1 – 9.7%) and 8% (90% C.I.: 6.5 – 9.9%) of the cases, respectively. Sources such as domestically produced beef, broiler meat and duck meat had only a minor impact (< 3% each). We believe that the described method may prove to be an alternative to the "traditional" stable-to-table risk assessment, which often involves making a large number of assumptions with very variable plausibility. |
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Status |
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Availability |
ISBN 87-988315-2-6 |
Project group
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Institute |
Danish Veterinary Institute
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Contact person |
tih@vetinst.dk |
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Partners |
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