Department of Animal Medicine, Production and Health, University of Padua, Viale dell'Università, 16, 35020, Legnaro (PD), Italy.
Department of Poultry Diseases, Faculty of Veterinary Science, University of Thessaly, Trikalon 224, 43100, Karditsa, Greece.
Poult Sci. 2019 Dec 1;98(12):6388-6392. doi: 10.3382/ps/pez473.
Infectious bronchitis (IB), caused by infectious bronchitis virus (IBV), account for severe economic losses in the poultry industry. The continuous emergence of a multitude of IBV variants poses many challenges for its diagnosis and control, and live attenuated vaccines, despite their routine use, still plays a significant role in driving IBV evolution, further complicating the epidemiological scenario. Unfortunately, the impact of different vaccination strategies on IB control, epidemiology, and diagnosis has rarely been investigated. This work presents the results of a large-scale diagnostic survey performed in Poland to study IBV molecular epidemiology and how vaccination may affect the viral circulation in the field. To this purpose, 589 samples were collected between May 2017 and January 2019, tested by reverse transcription-PCR for IBV and sequenced. Vaccine and field strains were discriminated based on genetic and anamnestic information. The most commonly detected lineages were 793B (79%) and variant 2 (17.4%), with sporadic detections of QX, Mass, and D274-like strains. Most of the detected strains had a vaccine origin: 46.3% matched one of the applied vaccines, while 36.5% were genetically related to vaccines not implemented in the respective protocol. Besides their practical value for the proper planning of vaccination protocols in Poland, these results suggest that only a fraction (17.2%) of the circulating strains are field ones, imposing a careful assessment of the actual IBV field menaces. Moreover, phenomena like vaccine spreading and persistence seem to occur commonly, stressing the need to further study the epidemiological consequences of the extensive use of live vaccines.
传染性支气管炎（IB）由传染性支气管炎病毒（IBV）引起，给家禽养殖业造成了严重的经济损失。大量 IBV 变异株的不断出现给其诊断和控制带来了诸多挑战，而活疫苗尽管常规使用，但仍在推动 IBV 进化方面发挥着重要作用，使流行病学情况进一步复杂化。不幸的是，不同疫苗接种策略对 IB 控制、流行病学和诊断的影响很少被研究。本工作介绍了在波兰进行的一项大规模诊断调查的结果，该调查旨在研究 IBV 的分子流行病学以及疫苗接种如何影响田间病毒的传播。为此，在 2017 年 5 月至 2019 年 1 月期间收集了 589 个样本，通过逆转录-PCR 对 IBV 进行了检测，并对其进行了测序。基于遗传和病史信息区分了疫苗株和田间株。检测到的最常见的谱系是 793B（79%）和变异 2（17.4%），零星检测到 QX、Mass 和 D274 样株。大多数检测到的毒株具有疫苗起源：46.3%与应用的疫苗之一相匹配，而 36.5%在遗传上与未在相应方案中实施的疫苗相关。除了对波兰适当规划疫苗接种方案具有实际价值外，这些结果表明，只有一小部分（17.2%）的流行株是田间株，需要仔细评估 IBV 田间威胁的实际情况。此外，疫苗传播和持续存在等现象似乎很常见，这强调了需要进一步研究活疫苗广泛使用的流行病学后果。
