Ssematimba Amos, Bonney Peter J, Malladi Sasidhar, Charles Kaitlyn M St, Culhane Marie, Goldsmith Timothy J, Halvorson David A, Cardona Carol J
Secure Food Systems Team, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108,
Department of Mathematics, Faculty of Science, Gulu University, P.O. Box 166, Gulu, Uganda.
Avian Dis. 2019 Mar 1;63(sp1):157-164. doi: 10.1637/11870-042518-Reg.1.
Outbreaks involving avian influenza viruses are often devastating to the poultry industry economically and otherwise. Disease surveillance is critically important because it facilitates timely detection and generates confidence that infected birds are not moved during business continuity intended to mitigate associated economic losses. The possibility of using an abnormal increase in daily mortality to levels that exceed predetermined thresholds as a trigger to initiate further diagnostic investigations for highly pathogenic avian influenza (HPAI) virus infection in the flock is explored. The range of optimal mortality thresholds varies by bird species, trigger type, and mortality thresholds, and these should be considered when assessing sector-specific triggers. The study uses purposefully collected data and data from the literature to determine optimal mortality triggers for HPAI detection in commercial upland game bird flocks. Three trigger types were assessed for the ability to detect rapidly both HPAI (on the basis of disease-induced and normal mortality data) and false alarm rate (on the basis of normal mortality data); namely, 1) exceeding a set absolute threshold on one day, 2) exceeding a set absolute threshold on two consecutive days, or 3) exceeding a multiple of a seven-day moving average. The likelihood of disease detection using some of these triggers together with premovement real-time reverse transcription PCR (rRT-PCR) testing was examined. Results indicate that the performance of the two consecutive days trigger had the best metrics (i.e., rapid detection with few false alarms) in the trade-off analysis. The collected normal mortality data was zero on 66% of all days recorded, with an overall mean of 0.6 dead birds per day. In the surveillance scenario analyses, combining the default protocol that relied only on active surveillance (i.e., premovement testing of oropharyngeal swab samples from dead birds by rRT-PCR) together with either of the mortality-based triggers improved detection rates on all days postexposure before scheduled movement. For exposures occurring within 8 days of movement, the protocol that combined the default with single-day triggers had slightly more detections than that with two consecutive days triggers. However, all assessed protocol combinations were able to detect all infections that occurred more than 10 days before scheduled movement. These findings can inform risk-based decisions pertaining to continuity of business in the commercial upland game bird industry.
涉及禽流感病毒的疫情通常会给家禽业带来巨大的经济损失及其他影响。疾病监测至关重要，因为它有助于及时发现疫情，并让人相信在旨在减轻相关经济损失的业务连续性过程中，感染禽类不会被转移。本文探讨了将每日死亡率异常增加至超过预定阈值作为启动对禽群高致病性禽流感（HPAI）病毒感染进行进一步诊断调查的触发因素的可能性。最佳死亡率阈值范围因鸟类种类、触发类型和死亡率阈值而异，在评估特定行业触发因素时应予以考虑。本研究使用特意收集的数据和文献数据来确定商业高地猎鸟禽群中检测HPAI的最佳死亡率触发因素。评估了三种触发类型检测HPAI（基于疾病导致的死亡率数据和正常死亡率数据）以及误报率（基于正常死亡率数据）的能力；即，1）一天内超过设定的绝对阈值，2）连续两天超过设定的绝对阈值，或3）超过七天移动平均值的倍数。研究了使用其中一些触发因素结合移动前实时逆转录聚合酶链反应（rRT-PCR）检测进行疾病检测的可能性。结果表明，在权衡分析中，连续两天触发因素的表现具有最佳指标（即检测迅速且误报少）。在所有记录的日子中，66%的日子收集到的正常死亡率数据为零，总体平均每天死亡0.6只鸟。在监测情景分析中，将仅依赖主动监测的默认方案（即通过rRT-PCR对死鸟的口咽拭子样本进行移动前检测）与基于死亡率的触发因素之一相结合，可提高暴露后至预定移动前所有日子的检测率。对于在移动前8天内发生的暴露，将默认方案与单日触发因素相结合的方案比与连续两天触发因素相结合的方案检测到的病例略多。然而，所有评估的方案组合都能够检测到在预定移动前10天以上发生的所有感染。这些发现可为商业高地猎鸟行业基于风险的业务连续性决策提供参考。
