Optimising cost-effectiveness of freedom from disease surveillance-Bluetongue Virus Serotype 8 as an example.

The aim of this study was to propose a procedure for optimising the cost-effectiveness of vector borne disease surveillance using a scenario tree model and cost-effectiveness analysis. The surveillance systems for Bluetongue Virus serotype 8 (BTV-8) implemented in Switzerland and Belgium were used as examples. In twenty four different, simulated population structures, passive surveillance and five designs of active surveillance were investigated. The influence of surveillance system design and parameters such as farmer disease awareness, veterinary disease awareness, herd and within-herd design prevalence on the overall surveillance system sensitivity were assessed. Furthermore, the cost-effectiveness of mandatory and voluntary vaccination regimes in relation to disease surveillance was investigated. Under the assumption that BTV-8 manifests clinically, freedom from disease in a population can be established with almost certainty over the period of one year using clinical surveillance alone. Additional investment in active surveillance would therefore economically only be justified, if no clinical manifestation is suspected or other surveillance objectives are to be provided such as early detection. The best cost-effectiveness is obtained by sampling more herds rather than more animals within a herd. Mandatory vaccination reduces the cost of surveillance by 0.26 € per vaccine and voluntary vaccination only marginally reduces the cost of risk-based surveillance, by reducing the population at risk. Finally, in populations with predominantly dairy cattle, bulk-tank milk testing is the method of choice to actively demonstrate freedom from disease.