Application of integrated production and economic models to estimate the impact of Schmallenberg virus for various sheep production types in the UK and France

摘要

Objective The present study aimed to estimate and compare the economic impact of Schmallenberg virus (SBV) in different sheep production holdings using partial budget and gross margin analyses in combination with production models. Participants The sheep production types considered were lowland spring lambing, upland spring lambing and early lambing flocks in the UK, and grass lamb flocks of the Centre and West of France, extensive lambing flocks and dairy sheep flocks in France. Methodology Two disease scenarios with distinct input parameters associated with reproductive problems were considered: low and high impact. Sensitivity analyses were performed for the most uncertain input parameters, and the models were run with all of the lowest and highest values to estimate the range of disease impact. Results The estimated net SBV disease cost per year and ewe for the UK was ￡19.65–￡20.85 for the high impact scenario and ￡6.40–￡6.58 for the low impact scenario. No major differences were observed between the different production types. For France, the net SBV disease cost per year and ewe for the meat sheep holdings was ￡15.59–￡17.20 for the high impact scenario and ￡4.75–￡5.26 for the low impact scenario. For the dairy sheep, the costs per year and ewe were ￡29.81 for the high impact scenario and ￡10.34 for the low impact scenario. Conclusions The models represent a useful decision support tool for farmers and veterinarians who are facing decisions regarding disease control measures. They allow estimating disease impact on a farm accounting for differing production practices, which creates the necessary basis for cost effectiveness analysis of intervention strategies, such as vaccination. Overview The SBV disease cost was calculated in three steps. First, the most typical and frequent production types of sheep in the UK and France were identified and modelled in Microsoft Excel. These production models simulated the farm population dynamics for a 1 year cycle using a static model, meaning that animal inputs and outputs (e.g. number of lambs finished or number of ewes bought for replacement) were recorded at the end of the cycle. Secondly, gross margin models were developed based on the production models. This was done by adding price level data and other economic parameters (such as veterinary costs) to the outcome of the production models in order to calculate the annual gross benefit of each system. To validate these models, the annual gross margins obtained for each system were compared with published gross margins. Thirdly, SBV disease effects were included in the production and gross margin models by adjusting respective parameters (e.g. proportion of lambs stillborn) or adding new ones (e.g. disposal costs for lambs that died because of SBV). These models were then run with and without disease, and the differences obtained were used to estimate the extra costs and extra benefits of SBV disease in a partial budget analysis. Two SBV disease scenarios—namely high and low impact scenarios—were investigated. Values for the disease parameters for each scenario were obtained from the existing literature and by expert opinion consultation. Sensitivity analyses were conducted to assess the variability of the disease impact for different combinations of the two most important disease parameter values. The methodology used is based on a concept article available on request (H?sler B. and others, unpublished observations). Sheep production models Available benchmarking data and expert opinion were used to identify the most common and representative sheep farm types in the UK and France. In total, three production types were identified for the UK and three for France (Table?1). View this table: In this window In a new window