Evaluation of the impact of regulatory measures for rabies prevention by modelling: example of the waiting period issue before dog importations into rabies-free areas
Résumé
Rabies introductions in rabies-free areas, especially through dog movements, pose a threat by exposing local animal and human populations. Waiting period (WP) before importation of a dog (after its identification and vaccination and eventually serological testing to ensure that specific antibodies are linked to the vaccine and not to a rabies infection), is one of the possible regulatory measures and is required for dogs entering the European Union (EU) from high risk areas. The impact of the WP can be studied through modelling, which allows the production of quantitative data even though rabies introductions in the EU occur rarely in reality. In a quantitative risk assessment framework, two modelling strategies were tested to represent event sequences between the selection of a dog and its release while incubating rabies in a rabies-free area: (i) stochastic scenario tree modelling and (ii) individual-based modelling. Results of the two models were similar, but not the same, illustrating the impact of the model structure. When considering dogs imported into the EU from countries requiring antibody titration (in compliance with regulations), the models predicted a mean annual number of virus introductions of 0.11 for model (i) and 0.03 for model (ii) when applying a 3-month WP. The risk increased (×2-4) to 0.26 introductions each year for model (i) and 0.15 for model (ii) when reducing this WP to 1 month. This approach emphasizes the impact of the structure of the model and its parameterization on the results. Such models could represent an informative tool, particularly for the policy-makers, in the context of decision-making in order to eventually update regulations.