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.

中文翻译：

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疫苗或野外毒株：波兰传染性支气管炎病毒分子流行病学的拼图模式。


由传染性支气管炎病毒（IBV）引起的传染性支气管炎（IB）给养禽业造成严重的经济损失。多种IBV变种的不断出现给其诊断和控制带来了许多挑战，而减毒活疫苗尽管已被常规使用，但仍然在推动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。这项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 分子流行病学以及疫苗接种如何影响该领域的病毒循环。为此，我们在 2017 年 5 月至 2019 年 1 月期间收集了 589 个样本，通过逆转录 PCR 检测 IBV 并进行测序。根据遗传和记忆信息来区分疫苗和现场毒株。最常检测到的谱系是 793B (79%) 和变体 2 (17.4%)，偶有检测到 QX、Mass 和 D274 样菌株。大多数检测到的毒株都有疫苗来源：46.3% 与所应用的疫苗之一相匹配，而 36.5% 与各自方案中未实施的疫苗有遗传相关。这些结果除了对波兰正确规划疫苗接种方案具有实用价值外，还表明只有一小部分（17.2%）的流行毒株是现场毒株，因此需要对实际 IBV 现场威胁进行仔细评估。此外，疫苗传播和持续存在等现象似乎普遍存在，强调需要进一步研究广泛使用活疫苗的流行病学后果。