Department of Bacteriology and Epidemiology, Wageningen Bioveterinary Research, P.O. Box 65, 8200 AB, Lelystad, The Netherlands.
Sci Rep. 2018 Jun 4;8(1):8533. doi: 10.1038/s41598-018-26954-9.
The objective of this study was to identify effective reporting thresholds for suspicions of both highly pathogenic (HPAI) and low pathogenic avian influenza (LPAI) outbreaks in layer farms. Daily mortality and egg-production data from 30 Dutch farms with no record of AI infection were analysed and thresholds set. Mortality rates above or egg-production below these thresholds for two consecutive days would trigger an alarm sign. The following thresholds were identified for mortality: (i) A mortality threshold of 0.08% or 0.13% for layers kept indoors or with free-range access respectively, (ii) a 2.9 times higher mortality than the average weekly mortality of the previous week, and iii) a moving-average threshold that could be implemented for each specific farm. For egg-production: (i) a weekly ratio lower than 0.94 in egg-production drop, and (ii) a moving-average threshold. The accuracy of these thresholds was assessed by quantifying their sensitivity, specificity and time to trigger disease detection using data from 15 infected and 31 non-infected farms. New thresholds were more sensitive and signalled infection two to six days earlier than the presently used thresholds. A high Specificity (97-100%) was obtained by combining mortality and egg production thresholds in a serial approach to trigger an alarm.
本研究的目的是确定高致病性禽流感（HPAI）和低致病性禽流感（LPAI）暴发在蛋鸡养殖场的有效报告阈值。分析了 30 个没有禽流感感染记录的荷兰养殖场的日死亡率和产蛋数据，并设定了阈值。死亡率连续两天高于或产蛋量低于这些阈值将触发警报信号。确定的死亡率阈值如下：（i）室内或有自由放养条件的蛋鸡死亡率阈值分别为 0.08%或 0.13%，（ii）死亡率比前一周的平均每周死亡率高 2.9 倍，（iii）可针对每个特定养殖场实施移动平均值阈值。对于产蛋量：（i）产蛋量下降的每周比例低于 0.94，（ii）移动平均值阈值。通过使用 15 个感染和 31 个非感染养殖场的数据来量化这些阈值的敏感性、特异性和触发疾病检测的时间，评估了这些阈值的准确性。新的阈值比目前使用的阈值更敏感，并提前两到六天发出感染信号。通过对死亡率和产蛋量阈值进行串联分析来触发警报，可以获得 97-100%的高特异性。
