Sydney School of Veterinary Science, Poultry Research Foundation, Faculty of Science, The University of Sydney, 425 Werombi Rd, Camden, 2570 NSW, Australia.
Birling Avian Laboratories, 975 The Northern Rd, Bringelly 2556, NSW, Australia.
Vaccine. 2019 Aug 14;37(35):5035-5043. doi: 10.1016/j.vaccine.2019.06.087. Epub 2019 Jul 9.
Vaccination against infectious laryngotracheitis virus (ILTV) in commercial broiler flocks in the field, which is only undertaken in the face of a local outbreak, requires mass administration techniques, usually via drinking water. This is often fraught with difficulties such as variable vaccination "reactions" and sometimes, vaccination failure. Laboratory testing of the outbreak strains however invariably shows the vaccines in use to be protective. To investigate this paradox, the dynamics of an ILT vaccine virus was examined within broiler flocks during a natural outbreak. In an initial flock, 70 birds were individually identified and had tracheal swabs collected sequentially at intervals from 1 to 26 days after vaccination and submitted for ILTV detection using qPCR. This evaluation was extended by collection of tracheal swabs from 40 to 45 random birds at 4, 7-8, 12-13 and 25-26 days post vaccination (pv) across a further 7 flocks. The results showed a very variable early uptake of vaccine virus from the drinking water (between 3% and 52% of tested birds with detectable virus in trachea at 4 days pv) and revealed that actual vaccination of the flocks relied on bird to bird transmission of the vaccine virus. In flocks with very low (<10%) initial bird uptake, successful exposure of vaccine virus to the majority of the flock can be delayed, leaving a large proportion of birds as susceptible at the likely time of possible exposure to wild virus. This may explain the cases of apparent failure of vaccination in the field. The variable bird to bird spread can be associated with reversion to virulence, this may explain the rolling vaccine reactions often observed. The variation in initial vaccine uptake may be affected by some factors involved with the administration technique and this requires further study in a larger sample size.
在商业肉鸡群中，针对传染性喉气管炎病毒（ILTV）的疫苗接种仅在当地爆发时进行，需要采用大规模管理技术，通常通过饮用水进行。这常常充满困难，例如疫苗接种“反应”的可变性，有时还会导致接种失败。然而，对爆发株的实验室检测始终表明，所使用的疫苗具有保护作用。为了研究这一矛盾，在自然爆发期间，研究了肉鸡群中 ILT 疫苗病毒的动态。在最初的一批鸡中，70 只鸡被单独标记，并在接种后 1 至 26 天内每隔一段时间采集气管拭子，并使用 qPCR 进行 ILTV 检测。通过在另外 7 个鸡群中，在接种后 4、7-8、12-13 和 25-26 天采集 40 到 45 只随机鸡的气管拭子，扩展了这项评估。结果表明，从饮用水中早期摄取疫苗病毒的情况非常多变（在接种后 4 天，有 3%至 52%的受测鸡的气管中可检测到病毒），并且表明实际的疫苗接种取决于疫苗病毒在鸡群中的传播。在初始鸡只摄取量非常低（<10%）的鸡群中，疫苗病毒成功暴露于大多数鸡群的时间可能会延迟，使很大一部分鸡在可能接触野生病毒时仍然易感。这可能解释了在现场观察到的疫苗接种失败的情况。鸡与鸡之间的传播可与毒力返祖相关，这可能解释了经常观察到的滚动疫苗反应。初始疫苗摄取量的变化可能受到与管理技术有关的一些因素的影响，这需要在更大的样本量中进一步研究。
