Quantitative decision making in animal health surveillance: Bovine
Tuberculosis Surveillance in Belgium as case study
Abstract
Introduction: Despite eradication and control measures applied across
Europe, bovine tuberculosis (bTB) remains a constant threat. In Belgium,
after several years of bTB disease freedom status, routine movement
testing, as currently practiced, revealed itself inadequate to detect
some sporadic breakdown herds. The aim of this study was to strike the
balance between cost and effectiveness of different surveillance system
components to identify sustainable alternatives for early detection and
substantiation of freedom of bTB while maintaining acceptance of these
amongst the different animal health stakeholders. Methods: Stochastic
iteration model was built to simulate, first, the expected current
surveillance system performance in terms of sensitivity and specificity
of detection. These results were then descriptively compared to observed
field results. Secondly, the cost and effectiveness of simulated
alternative surveillance components were quantified. To measure impact
of key assumptions (i.e. regarding diagnostic tests and true
prevalence), sensitivity analysis was performed. Results: Discrepancies
between the predicted and observed performance of bTB surveillance in
Belgium were observed. Secondly, simulated alternatives revealed that
targeted IFN-γ as well serological testing with Antibody ELISA towards
risk herds would enable increasing the overall cost and effectiveness of
the Belgian bTB surveillance system. Sensitivity analysis showed that
results remained constant despite modification of some key assumptions.
Discussion: Performance of current bTB surveillance system performance
in Belgium was questionable. This exercise highlighted that not only
sensitivity, but specificity is a key driver for surveillance
performance. The quantitative and participative conceptual framework
revealed itself a useful tool to allow evidence-based decision making
regarding future tuberculosis surveillance in Belgium, as required by
the international standards.