Centre for Epidemiology & Risk Analysis, Veterinary Laboratories Agency-Weybridge, New Haw, Addlestone, Surrey KT15 3NB, UK.
J Food Prot. 2010 Mar;73(3):488-94. doi: 10.4315/0362-028x-73.3.488.
The Zoonoses Action Plan (ZAP) Salmonella Programme was established by the British Pig Executive to monitor Salmonella prevalence in quality-assured British pigs at slaughter by testing a sample of pigs with a meat juice enzyme-linked immunosorbent assay for antibodies against group B and C(1) Salmonella. Farms were assigned a ZAP level (1 to 3) depending on the monitored prevalence, and ZAP 2 or 3 farms were required to act to reduce the prevalence. The ultimate goal was to reduce the risk of human salmonellosis attributable to British pork. A mathematical model has been developed to describe the ZAP sampling protocol. Results show that the probability of assigning a farm the correct ZAP level was high, except for farms that had a seroprevalence close to the cutoff points between different ZAP levels. Sensitivity analyses identified that the probability of assigning a farm to the correct ZAP level was dependent on the sensitivity and specificity of the test, the number of batches taken to slaughter each quarter, and the number of samples taken per batch. The variability of the predicted seroprevalence was reduced as the number of batches or samples increased and, away from the cutoff points, the probability of being assigned the correct ZAP level increased as the number of batches or samples increased. In summary, the model described here provided invaluable insight into the ZAP sampling protocol. Further work is required to understand the impact of the program for Salmonella infection in British pig farms and therefore on human health.
英国猪业执行委员会（British Pig Executive）制定了动物传染病行动计划（Zoonoses Action Plan，ZAP）沙门氏菌计划，以通过对屠宰场的猪进行肉汁酶联免疫吸附试验，检测针对 B 群和 C 群（1）沙门氏菌的抗体，监测质量保证体系下的英国猪的沙门氏菌流行率。根据监测到的流行率，农场被分配 ZAP 级别（1 至 3），ZAP 级别为 2 或 3 的农场需要采取措施降低流行率。最终目标是降低归因于英国猪肉的人类沙门氏菌病的风险。已开发出一种数学模型来描述 ZAP 抽样方案。结果表明，除了血清流行率接近不同 ZAP 级别之间的临界值的农场外，为农场分配正确 ZAP 级别的概率很高。敏感性分析表明，为农场分配正确 ZAP 级别的概率取决于测试的灵敏度和特异性、每季度屠宰的批次数量以及每批采集的样本数量。随着批次或样本数量的增加，预测血清流行率的变异性降低，并且远离临界值时，随着批次或样本数量的增加，被分配正确 ZAP 级别的概率增加。总之，这里描述的模型为 ZAP 抽样方案提供了宝贵的见解。需要进一步研究该计划对英国养猪场中沙门氏菌感染的影响，从而对人类健康产生影响。
