Weber Maarten F, Nielen Mirjam, Velthuis Annet G J, van Roermund Herman J W
Animal Health Service, PO Box 9, 7400 AA Deventer, The Netherlands.
Vet Res. 2008 Mar-Apr;39(2):12. doi: 10.1051/vetres:2007050. Epub 2008 Jan 29.
A bulk milk quality assurance programme for Mycobacterium avium subsp. paratuberculosis (Map) in dairy herds was simulated with a stochastic simulation model (JohneSSim). The aim of this study was to evaluate the epidemiological and economic effects of preventive management measures and various test schemes in a simulated population of closed Dutch dairy herds over a 20-year period. Herds were certified as ;low-Map bulk milk' if, with a certain probability, the concentration of Map in bulk milk did not exceed a maximum acceptable concentration of 10(3) Map organisms per litre (based on pasteurisation studies). The programme started with an initial assessment; test-negative herds entered a surveillance procedure and test-positive herds a control procedure. The simulations showed that herd examinations by ELISA for the initial assessment, surveillance and control procedures effectively ensure the quality of ;low-Map bulk milk': > 75% of simulated herds were certified and > 96% of certified herds produced bulk milk with < 10(3) Map/L if the initial herd-level prevalence was 30%. Preventive management measures only had a minor effect on bulk milk quality of certified herds. Culling based on biennial faecal culture was more effective than culling based on annual ELISA. Average total discounted costs for 20-year participation in a programme consisting of initial assessment by ELISA, surveillance by biennial ELISA and control by biennial faecal culture were 16 Euro x 10(3) per herd. In conclusion, this study shows that a bulk milk quality assurance programme for closed Dutch dairy herds is feasible and provides information on the cost-effectiveness of different programmes. The concepts of this study equally apply to other countries because mechanisms of paratuberculosis infection, disease, and testing are comparable in other dairy cattle populations.
利用随机模拟模型（JohneSSim）模拟了奶牛群中副结核分枝杆菌（Map）的原料奶质量保证计划。本研究的目的是评估在一个模拟的荷兰封闭奶牛群中，为期20年的预防管理措施和各种检测方案的流行病学和经济影响。如果原料奶中Map的浓度以一定概率不超过每升10³个Map菌体的最大可接受浓度（基于巴氏杀菌研究），则牛群被认证为“低Map原料奶”牛群。该计划始于初始评估；检测呈阴性的牛群进入监测程序，检测呈阳性的牛群进入控制程序。模拟结果表明，通过ELISA对初始评估、监测和控制程序进行牛群检测，可有效确保“低Map原料奶”的质量：如果初始牛群水平患病率为30%，则超过75%的模拟牛群获得认证，超过96%的认证牛群生产的原料奶中Map/L<10³。预防管理措施对认证牛群的原料奶质量影响较小。基于两年一次粪便培养的扑杀比基于年度ELISA的扑杀更有效。参与由ELISA进行初始评估、两年一次ELISA进行监测和两年一次粪便培养进行控制的计划20年的平均总贴现成本为每头牛群16×10³欧元。总之，本研究表明，荷兰封闭奶牛群的原料奶质量保证计划是可行的，并提供了不同计划成本效益的信息。本研究的概念同样适用于其他国家，因为副结核感染、疾病和检测机制在其他奶牛群体中具有可比性。
