Estimation de la vraie incidence de la campylobactériose, listériose, salmonellose et shigellose en Belgique

(eng) Foodborne diseases (FBD’s) are known to cause important morbidity and mortality with a significant socio-economic impact worldwide. The incidence of certain diseases causing gastroenteritis disorders such as campylobacteriosis, listeriosis, salmonelosis and shighellosis are underestimated in Belgium. This underestimation (UE) results from under- ascertainment (UA) and under-reporting (UR) of the number of cases. The objectives of this study are: 1) to quantify the UE of campylobacteriosis, listeriosis, salmonellosis and shigellosis reported cases in Belgium through designing of multiplication factors (MFs) and; 2) to estimate the true incidence of these FBDs in Belgium in 2014 by using the previously MFs. Methods: To quantify UA and UR of the selected FBDs, adapted Delphi and Cooke’s methods of expert elicitation were used. Selected Belgian experts firstly answered to 12 calibrations questions, allowing to weight their future answers based on their performance, then experts answered to the target questions, i.e. directly linked with the parameters of interest. Finally, they received anonymous answers of the whole panel of experts and had the possibility to adapt their answers. Final probabilities of UA and UE were calculated based on a performance weight (PM) and equal weight (EW) schemes using Excalibur software. True incidence was estimated by multiplying reported incidence in 2014 by the previously calculated MFs. Results: 10 experts contributed at the whole study. We observed a major difference between the multiplication factors using the EW or PW approach; this has implications for estimating the true incidence for each pathogen. MFs based respectively on the EW and the PW are estimated for the camplylobacteriosis at 50.5 vs 23.9, for the listeriosis at 25.9 vs 8.4, for the salmonellosis at 30.6 vs 22.6 and for the shigellosis at 66.4 vs 53.8. The true incidence (per 100 000 inhabitants) based respectively on the EW and the PW are estimated for the camplylobacteriosis at 3671.12 vs 1735.49, for the listeriosis at 13.97 vs 4.55, for the salmonellosis at 796.55 vs 589.44 and for the shigellosis at 238.08 vs 192.82. Conclusion: The limited number of experts and a wide variability in their responses result in a high degree of uncertainty of the multipliers. Despite these limitations, the panel of experts, by the method of elicitation, agrees that there is an UE of reported cases of Campylobacter, Listeria, Salmonella and Shigella in Belgium. Key-words: foodborne pathogen, expert elicitation, true incidence