Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia,
School of Veterinary Medicine, Wollo University, Dessie, Ethiopia.
Avian Dis. 2022 Oct;66(3):1-9. doi: 10.1637/aviandiseases-D-22-00022. Epub 2022 Sep 9.
Population-level sampling based on qPCR detection of infectious laryngotracheitis virus (ILTV) in poultry dust can be used to assess ILT vaccination outcomes following mass administration in drinking water. We report on the field application of this approach to assess the success of vaccine administration and its use in ILT outbreak control in meat chickens. In Study 1, dust samples were collected from 26 meat chicken flocks at 0, 4, 7, 14, and 21 days post drinking water vaccination (DPV) given between 7 to 13 days of age with the Serva or A20 live attenuated ILT vaccines. Unexpectedly, ILTV DNA was detected in dust samples collected prior to vaccination in 22/26 flocks. Typing revealed that the detected ILTV was different from the vaccine virus. To determine whether the detected ILTV DNA was from active infection or carryover of a noninfectious virus, Study 2 was implemented in 14 additional flocks with dust samples collected at 0, 7, 14, and 21 DPV and tracheal swabs collected from 15 birds/flock at 0 and 21 DPV. The results indicated that there was active infection with ILTV in those flocks before vaccination. This approach contributed to a statewide control program resulting in the eradication of ILT from South Australia as confirmed by negative ILTV test results for dust samples from 50 flocks and the absence of clinical ILT. These findings show that ILTV infection prior to vaccination is common in outbreak situations and that dust samples must be collected at 0 and 7 DPV for meaningful interpretation of vaccination outcomes and ILTV status. Comparatively low-cost dust testing during an outbreak, coupled with typing information, greatly assisted with decision making and control strategies during a major outbreak, including confirmation of the absence of infection in the final stages.
基于 qPCR 检测禽传染性喉气管炎病毒（ILTV）的人群水平采样可用于评估饮水途径大规模接种疫苗后 ILT 的免疫效果。我们报告了该方法在评估疫苗接种效果及其在肉鸡传染性喉气管炎暴发控制中的应用。在研究 1 中，在 7-13 日龄龄时，用 Serva 或 A20 活减毒 ILT 疫苗给 26 个肉鸡群进行饮水免疫，分别于免疫后 0、4、7、14 和 21 天（DPV）采集粉尘样本。出乎意料的是，在 22/26 个鸡群的粉尘样本中，在免疫前就检测到了 ILTV DNA。基因分型显示，检测到的 ILTV 与疫苗病毒不同。为了确定检测到的 ILTV DNA 是来自于活性感染还是非感染性病毒的残留，在另外 14 个鸡群中开展了研究 2，分别在 0、7、14 和 21 DPV 采集粉尘样本，在 0 和 21 DPV 采集 15 只鸡/群的气管拭子。结果表明，在免疫前，这些鸡群中就存在 ILTV 的活性感染。该方法为全州范围的控制计划做出了贡献，南澳大利亚州成功根除了 ILT，这从 50 个鸡群的粉尘样本 ILTV 检测结果均为阴性和无临床传染性喉气管炎的情况得到证实。这些发现表明，在暴发情况下，免疫前的 ILTV 感染很常见，为了有意义地解释免疫效果和 ILTV 状态，必须在 0 和 7 DPV 采集粉尘样本。在暴发期间进行相对低成本的粉尘检测，结合基因分型信息，极大地帮助了在重大暴发期间做出决策和实施控制策略，包括在最后阶段确认感染的消除。
