Verdugo Cristobal, Cardona Carol J, Carpenter Tim E
Center for Animal Disease Modeling and Surveillance (CADMS), Department of Medicine and Epidemiology, One Shields Avenue, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Prev Vet Med. 2009 Feb 1;88(2):109-19. doi: 10.1016/j.prevetmed.2008.08.007. Epub 2008 Nov 1.
The placement of sentinel birds in a commercial poultry flock infected with low pathogenic avian influenza virus (LPAIV) may be an effective way of detecting subsequent change in the isolate to a high pathogenic avian influenza virus (HPAIV). Data collected from the 2002 Chilean HPAIV outbreak, along with information from a literature review of laboratory studies involving A/chicken/Chile/176822/02 (H7N3/LP) and A/chicken/Chile/184240-1/02 (H7N3/HP) viruses, were used to construct a computer simulation model. Mortality rates of the original LPAIV-infected population and the sentinel population were compared to detect the presence of HPAIV. A total of 12 increased mortality threshold scenarios were examined, using one-day absolute (2, 3, or 4 birds) or relative (0.5, 1.0, or 1.5%) mortality thresholds, and two-day absolute (1, 2, or 3 birds) or relative (0.25, 0.50, or 1.00%) mortality thresholds, to indicate the change from LPAIV to HPAIV in the sentinel and original populations, respectively. Results showed that following a one-day approach, threshold mortalities occurred on average at 7.35, 7.82, and 8.17 (0.5, 1.0, or 1.5%) and 6.21, 6.38, and 6.45 (2, 3, or 4 birds) days after the first infectious case for the original and sentinel populations, respectively. The two-day approach delayed the occurrence of threshold mortalities, on average, to 7.64, 8.05, and 8.62 (0.25, 0.50, or 1.00%) and 6.86, 6.78, and 7.23 (1, 2, or 3 birds) days after the first infectious case for the original and sentinel populations, respectively. Although, significant (p<0.10) differences were observed among different combinations of detection times for the original and sentinel populations, the use of sentinel birds has a maximum mean advantage, over monitoring mortality exclusively in the original population, of 1.96 and 1.84 days for one- and two-day threshold moralities, respectively. Additionally, the early warning system based on a sentinel vs. original population presented a decrease of the probabilities of a false alarm, from 0.04-0.45 to <0.01-0.10%. These findings may be used by decision makers to evaluate the risk of not depopulating a flock infected with a H5 or H7 LPAIV strain and the benefit of using sentinel birds as an early warning system of a change to HPAIV.
在感染低致病性禽流感病毒（LPAIV）的商业家禽群中放置哨兵鸡，可能是检测后续毒株转变为高致病性禽流感病毒（HPAIV）的有效方法。从2002年智利HPAIV疫情收集的数据，以及对涉及A/鸡/智利/176822/02（H7N3/LP）和A/鸡/智利/184240 - 1/02（H7N3/HP）病毒的实验室研究文献综述中获取的信息，被用于构建一个计算机模拟模型。比较原始LPAIV感染群体和哨兵群体的死亡率，以检测HPAIV的存在。总共检查了12种增加死亡率阈值的情况，使用单日绝对（2、3或4只鸡）或相对（0.5%、1.0%或1.5%）死亡率阈值，以及两日绝对（1、2或3只鸡）或相对（0.25%、0.50%或1.00%）死亡率阈值，分别指示哨兵群体和原始群体中从LPAIV到HPAIV的转变。结果表明，采用单日方法时，原始群体和哨兵群体在首例感染病例后的平均阈值死亡率分别出现在7.35、7.82和8.17天（0.5%、1.0%或1.5%）以及6.21、6.38和又6.45天（2、3或4只鸡）。两日方法将阈值死亡率的出现平均推迟到原始群体和哨兵群体在首例感染病例后的7.64、8.05和8.62天（0.25%、0.50%或1.00%）以及6.86、6.78和7.23天（1、2或3只鸡）。尽管在原始群体和哨兵群体的不同检测时间组合之间观察到显著（p<0.10）差异，但使用哨兵鸡相对于仅监测原始群体的死亡率，在单日和两日阈值死亡率情况下分别具有最大平均优势，为1.96天和1.84天。此外，基于哨兵群体与原始群体的早期预警系统使误报概率降低，从0.04 - 0.45降至<0.01 - 0.10%。这些发现可供决策者评估不对感染H5或H7 LPAIV毒株的鸡群进行扑杀的风险，以及使用哨兵鸡作为HPAIV转变的早期预警系统的益处。
