Munsick Tristram R, Peck Dannele E, Ritten John P, Jones Randall, Jones Michelle, Miller Myrna M
Department of Agricultural & Applied Economics, University of Wyoming, Laramie, WY, United States.
Agricultural Producer, Big Horn Basin, WY, United States.
Front Vet Sci. 2017 Oct 11;4:166. doi: 10.3389/fvets.2017.00166. eCollection 2017.
Recurring outbreaks of bluetongue virus in domestic sheep of the US Intermountain West have prompted questions about the economic benefits and costs of vaccinating individual flocks against bluetongue (BT) disease. We estimate the cost of a BT outbreak on a representative rangeland sheep operation in the Big Horn Basin of the state of Wyoming using enterprise budgets and stochastic simulation. The latter accounts for variability in disease severity and lamb price, as well as uncertainty about when an outbreak will occur. We then estimate the cost of purchasing and administering a BT vaccine. Finally, we calculate expected annual net benefit of vaccinating under various outbreak intervals. Expected annual net benefit is calculated for both a killed virus (KV) vaccine and modified-live virus vaccine, using an observed price of $0.32 per dose for modified-live and an estimated price of $1.20 per dose for KV. The modified-live vaccine's expected annual net benefit has a 100% chance of being positive for an outbreak interval of 5, 10, or 20 years, and a 77% chance of being positive for a 50-year interval. The KV vaccine's expected annual net benefit has a 97% chance of being positive for a 5-year outbreak interval, and a 42% chance of being positive for a 10-year interval. A KV vaccine is, therefore, unlikely to be economically attractive to producers in areas exposed less frequently to BT disease. A modified-live vaccine, however, requires rigorous authorization before legal use can occur in Wyoming. To date, no company has requested to manufacture a modified-live vaccine for commercial use in Wyoming. The KV vaccine poses less risk to sheep reproduction and less risk of unintentional spread, both of which facilitate approval for commercial production. Yet, our results show an economically consequential tradeoff between a KV vaccine's relative safety and higher cost. Unless the purchase price is reduced below our assumed $1.20 per dose, producer adoption of a KV vaccine for BT is likely to be low in the study area. This tradeoff between cost and safety should be considered when policymakers regulate commercial use of the two vaccine types.
美国中西部山区家养绵羊反复爆发蓝舌病病毒，引发了关于给单个羊群接种蓝舌病（BT）疫苗的经济效益和成本的问题。我们使用企业预算和随机模拟方法，估算了怀俄明州大角盆地一个具有代表性的牧场绵羊养殖中蓝舌病爆发的成本。随机模拟考虑了疾病严重程度和羔羊价格的变异性，以及爆发时间的不确定性。然后，我们估算了购买和接种蓝舌病疫苗的成本。最后，我们计算了在不同爆发间隔下接种疫苗的预期年度净收益。使用观察到的每剂单价0.32美元的单价疫苗和估计每剂1.20美元的灭活病毒（KV）疫苗价格，计算了单价疫苗和灭活病毒疫苗的预期年度净收益。单价疫苗的预期年度净收益在爆发间隔为5年、10年或20年时为正的概率为100%，在50年间隔时为正的概率为77%。KV疫苗的预期年度净收益在5年爆发间隔时为正的概率为97%，在10年间隔时为正的概率为42%。因此，对于较少接触蓝舌病的地区的生产者来说，KV疫苗在经济上不太可能具有吸引力。然而，单价疫苗在怀俄明州合法使用之前需要严格的授权。到目前为止，没有公司申请在怀俄明州生产用于商业用途的单价疫苗。KV疫苗对绵羊繁殖的风险较小，无意传播的风险也较小，这两者都有助于商业生产的批准。然而，我们的结果表明，在KV疫苗的相对安全性和较高成本之间存在经济上的权衡取舍。除非购买价格降至我们假设的每剂1.20美元以下，否则在研究区域生产者采用KV疫苗预防蓝舌病的可能性可能较低。在政策制定者规范这两种疫苗的商业使用时，应考虑成本与安全性之间的这种权衡。
