An economic model to evaluate the mitigation programme for bovine viral diarrhoea in Switzerland

Abstract

Economic analyses are indispensable as sources of information to help policy makers make decisions about mitigation resource use. The aim of this study was to conduct an economic evaluation of the Swiss national mitigation programme for bovine viral diarrhoea virus (BVDV), which was implemented in 2008 and concludes in 2017. The eradication phase of the mitigation programme comprised testing and slaughtering of all persistently infected (PI) animals found. First, the whole population was antigen tested and all PI cattle removed. Since October 2008, all newborn calves have been subject to antigen testing to identify and slaughter PI calves. All mothers of PI calves were retested and slaughtered if the test was positive. Antigen testing in calves and elimination of virus-carriers was envisaged to be conducted until the end of 2011. Subsequently, a surveillance programme will document disease freedom or detect disease if it recurs. Four alternative surveillance strategies based on antibody testing in blood from newborn calves and/or milk from primiparous cows were proposed by Federal Veterinary Office servants in charge of the BVDV mitigation programme. A simple economic spreadsheet model was developed to estimate and compare the costs and benefits of the BVDV mitigation programme. In an independent project, the impact of the mitigation programme on the disease dynamics in the population was simulated using a stochastic compartment model. Mitigation costs accrued from materials, labour, and processes such as handling and testing samples, and recording results. Benefits were disease costs avoided by having the mitigation programme in place compared to a baseline of endemic disease equilibrium. Cumulative eradication costs and benefits were estimated to determine the break-even point for the eradication component of the programme. The margin over eradication cost therefore equalled the maximum expenditure potentially available for surveillance without the net benefit from the mitigation programme overall becoming zero. Costs of the four surveillance strategies and the net benefit of the mitigation programme were estimated. Simulations were run for the years 2008-2017 with 20,000 iterations in @Risk for Excel. The mean baseline disease costs were estimated to be 16.04 m CHF (1 Swiss Franc, CHF=0.73 € at the time of analysis) (90% central range, CR: 14.71-17.39 m CHF) in 2008 and 14.89 m CHF (90% CR: 13.72-16.08 m CHF) in 2009. The break-even point was estimated to be reached in 2012 and the margin over eradication cost 63.15m CHF (90% CR: 53.72-72.82 m CHF). The discounted cost for each surveillance strategy was found to be smaller than the margin, so the mitigation programme overall is expected to have a positive net economic benefit irrespective of the strategy adopted. For economic efficiency, the least cost surveillance alternative must be selected.