How to cite this article: Vet. Res. (2009) 40:57
DOI: 10.1051/vetres/2009040

Establishing a cost-effective national surveillance system for Bluetongue using scenario tree modelling

Daniela C. Hadorn¹, Vanessa Racloz^{1, 2}, Heinzpeter Schwermer¹ and Katharina D.C. Stärk<sup>1, 3

1</sup>  Federal Veterinary Office, Schwarzenburgstrasse 155, CH-3003 Bern, Switzerland
²  Swiss Tropical Institute, Basel, Switzerland
³  Royal Veterinary College, London, United Kingdom

Received 19 January 2009; accepted 13 July 2009; published online 17 July 2009

Abstract - Vector-borne diseases pose a special challenge to veterinary authorities due to complex and time-consuming surveillance programs taking into account vector habitat. Using stochastic scenario tree modelling, each possible surveillance activity of a future surveillance system can be evaluated with regard to its sensitivity and the expected cost. The overall sensitivity of various potential surveillance systems, composed of different combinations of surveillance activities, is calculated and the proposed surveillance system is optimized with respect to the considered surveillance activities, the sensitivity and the cost. The objective of this project was to use stochastic scenario tree modelling in combination with a simple cost analysis in order to develop the national surveillance system for Bluetongue in Switzerland. This surveillance system was established due to the emerging outbreak of Bluetongue virus serotype 8 (BTV-8) in Northern Europe in 2006. Based on the modelling results, it was decided to implement an improved passive clinical surveillance in cattle and sheep through campaigns in order to increase disease awareness alongside a targeted bulk milk testing strategy in 200 dairy cattle herds located in high-risk areas. The estimated median probability of detection of cases (i.e. sensitivity) of the surveillance system in this combined approach was 96.4%. The evaluation of the prospective national surveillance system predicted that passive clinical surveillance in cattle would provide the highest probability to detect BTV-8 infected animals, followed by passive clinical surveillance in sheep and bulk milk testing of 200 dairy cattle farms in high-risk areas. This approach is also applicable in other countries and to other epidemic diseases.

Key words: national surveillance system / cost-effective / scenario tree modelling / Bluetongue / Switzerland

Corresponding author: Daniela.Hadorn@bvet.admin.ch

© INRA, EDP Sciences 2009