Evaluating control strategies for outbreaks in BHV1-free areas using stochastic and spatial simulation

Several countries within the EU have successfully eradicated bovine herpesv irus type I (BHV1), while others are still making efforts to eradicate the virus. Reintroduction of the virus into BHV1-free areas can lead to major o utbreaks - thereby causing severe economic losses. To give decisionmakers m ore insight into the risk and economic consequences of BHV1 reintroduction and into the effectiveness of various control strategies, we developed the simulation model InterIBR. InterIBR is a dynamic model that takes into acco unt risk and uncertainty and the geographic location of individual farms. S imulation of a BHV1-outbreak in the Netherlands starts with introduction of the virus on a predefined farm type, after which both within-farm and betw een-farm transmission are simulated. Monitoring and control measures are im plemented to simulate detection of the infection and subsequent control. Ec onomic consequences included in this study are related to losses due to inf ection and casts of control. In the simulated basic control strategy, dairy farms are monitored by monthly bulk-milk tests and miscellaneous farms are monitored by half-yearly serological tests. After detection, movement-cont rol measures apply, animal contacts are traced and neighbour farms are put on surveillance. Given current assumptions on transmission dynamics, we con clude that a strategy with either rapid removal or vaccination of infected cattle does not reduce the number of infected farms compared to this basic strategy - but will cost more to control. Farm type with first introduction of BHV1 has a considerable impact on the expected number of secondarily in fected farms and total costs. To limit the number of infected farms and tot al costs due to outbreaks, we suggest intensifying the monitoring program o n farms with a high frequency of cattle trade, and monthly bulk-milk testin g on dairy farms. (C) 2000 Elsevier Science B.V. All rights reserved.