Centre for Environment, Fisheries and Aquaculture Science, Barrack Rd, Weymouth DT4 8UB, UK.
Prev Vet Med. 2011 Dec 15;102(4):329-40. doi: 10.1016/j.prevetmed.2011.07.016. Epub 2011 Aug 27.
A semi-quantitative model is presented to rank freshwater rainbow trout farms within a country or region with regards to the risk of becoming infected and spreading a specified pathogen. The model was developed to support a risk-based surveillance scheme for notifiable salmonid pathogens. Routes of pathogen introduction and spread were identified through a process of expert consultation in a series of workshops. The routes were combined into themes (e.g. exposure via water, mechanical transmission). Themes were weighted based on expert opinion. Risk factors for each route were scored and combined into a theme score which was adjusted by the weight. The number of sources and consignments were used to assess introduction via live fish movements onto the farm. Biosecurity measures were scored to assess introduction on fomites. Upstream farms, wild fish and processing plants were included in assessing the likelihood of introduction by water. The scores for each theme were combined to give separate risk scores for introduction and spread. A matrix was used to combine these to give an overall risk score. A case study for viral haemorrhagic septicaemia is presented. Nine farms that represent a range of farming practices of rainbow trout farms in England and Wales are used as worked examples of the model. The model is suited to risk rank freshwater salmonid farms which are declared free of the pathogen(s) under consideration. The score allocated to a farm does not equate to a quantitative probability estimate of the farm to become infected or spread infection. Nevertheless, the method provides a transparent approach to ranking farms with regards to pathogen transmission risks. The output of the model at a regional or national level allows the allocation of surveillance effort to be risk based. It also provides fish farms with information on how they can reduce their risk score by improving biosecurity. The framework of the model can be applied to different production systems which may have other routes of disease spread. Further work is recommended to validate the allocated scores. Expert opinion was obtained through workshops, where the outputs from groups were single point estimates for relative weights of risks. More formal expert opinion elicitation methods could be used to capture variation in the experts' estimates and uncertainty and would provide data on which to simulate the model stochastically. The model can be downloaded (in Microsoft(®)-Excel format) from the Internet at: http://www.cefas.defra.gov.uk/6701.aspx.
提出了一种半定量模型，用于根据感染和传播特定病原体的风险对一个国家或地区内的淡水虹鳟养殖场进行排名。该模型是为支持有报告要求的鲑鳟鱼病原体的基于风险的监测计划而开发的。通过一系列研讨会中的专家咨询过程确定了病原体的传入和传播途径。将途径组合成主题（例如，通过水暴露、机械传播）。根据专家意见对主题进行加权。为每个途径的风险因素评分，并组合成一个主题得分，然后通过权重进行调整。使用来源和发运批次的数量来评估通过活鱼运动引入到养殖场的情况。对生物安全措施进行评分，以评估传入的病媒。上游养殖场、野生鱼类和加工厂被包括在评估通过水引入的可能性中。将每个主题的得分组合起来，为传入和传播分别给出风险得分。使用矩阵将这些得分组合起来，给出总体风险得分。展示了病毒性出血性败血症的案例研究。使用代表英格兰和威尔士虹鳟养殖场各种养殖实践的九个养殖场作为模型的实际示例。该模型适用于对已宣布无考虑病原体的淡水鲑鳟养殖场进行风险排名。分配给农场的分数并不等同于农场感染或传播感染的定量概率估计。尽管如此，该方法为农场的病原体传播风险提供了一种透明的排名方法。在区域或国家层面上输出模型允许根据风险分配监测工作。它还为养殖场提供了有关如何通过改善生物安全来降低风险评分的信息。该模型的框架可应用于具有其他疾病传播途径的不同生产系统。建议进一步开展工作以验证分配的分数。通过研讨会获得专家意见，其中小组的产出是相对风险权重的单点估计。可以使用更正式的专家意见征求方法来捕获专家估计值的变化和不确定性，并提供数据以随机模拟模型。该模型可以从互联网上下载（以 Microsoft(®)-Excel 格式）：http://www.cefas.defra.gov.uk/6701.aspx。
