The abattoir and the fallen stock surveys constitute the active surveillance component aimed at improving the detection of scrapie across the EU. Previous studies have suggested the occurrence of significant differences in the operation of the surveys throughout Europe. Del Rio Vilas et al assessed the presence of heterogeneity between the observed prevalence estimates of 18 EU countries by means of a meta-analysis and showed a large residual variability indicating an inconsistent approach to the surveys across the EU. The study of these differences merits attention as they inform discrepancies in the performance of the surveys between countries. In the absence of sufficient covariate information to explain the observed variability across countries, we can model, still under the general context of the meta-analysis, the unobserved heterogeneity in our data. Countries could be grouped into clusters representing the underlying subpopulations relative to the risk of scrapie between the two surveys in each country.
Objective
In the present study we assessed the standardisation of the active surveillance of scrapie throughout time across the EU and identified countries with similar underlying characteristics allowing comparisons between them.