Spatial and stochastic simulation to evaluate the impact of events and control measures on the 1997-1998 classical swine fever epidemic in The Netherlands. II. Comparison of control strategies

Using the spatial, temporal and stochastic simulation model InterCSF, sever al alternative pre-emptive slaughter strategies that could have been applie d in the Dutch Classical Swine Fever (CSF) epidemic of 1997-1998 were evalu ated. Furthermore, effects of changes in some disease-spread and disease-co ntrol parameters were studied. InterCSF simulates the spread of CSF between farms through local spread and contacts (animals, transport and persons). Disease spread is affected by control measures implemented through differen t mechanisms (e.g. depopulation of infected farms, pre-emptive slaughter, m ovement control). The starting point for the evaluation of strategies was a simulated basic scenario, which mimicked the real epidemic. Strategies wer e compared using epidemiological as well as economic results. Economic resu lts were generated by a separate model (EpiLoss) that calculated the direct losses and consequential losses for farmers and related industries. The co mparison of the different alternatives to the basic scenario led to some ge neral conclusions on the Dutch CSF-epidemic. Pre-emptive slaughter seemed t o be an effective strategy to reduce the size of an epidemic, if started at an early stage. Economically: pre-emptive slaughter was not as expensive a s expected; the resulting smaller size of the epidemic, combined with less welfare slaughter, led to much lower overall losses. Furthermore, although large movement control areas seemed effective in reducing the size of the e pidemic, Phe total losses were relatively high because of subsequent welfar e slaughter. If infection probabilities could be reduced, for example by im proved biosecurity, the resulting epidemics would be much smaller. (C) 1999 Elsevier Science B.V. All rights reserved.