A vaccine programme comprising GA08 (GI-27) and Mass (GI-1) strains prevents DMV1639 (GI-17) infectious bronchitis virus transmission among broiler chickens

Effective control of infectious bronchitis is a challenge in commercial poultry operations due to the high transmissibility of the virus. Although multiple IBV lineages are circulating in the United States, the DMV1639-type IBV strain (GI-17) is currently the major circulating variant, creating production losses in the poultry industry. This study aimed to test whether the combination of a GA08 (GI-27) and a Mass-type (GI-1) IB vaccines could significantly reduce the transmission of a DMV1639-type (GI-17) field IBV strain in 4-week-old commercial broilers. Half of the birds were directly challenged, whereas the other half of the groupmates were put in contact 24 hours later. Two replicates of the same study setup, including 10 directly challenged and 10 contact birds per group, were run. Transmission of the challenge virus was significantly reduced in vaccinates (<i>R</i> = 0.0), whereas all unvaccinated birds became infected (<i>R</i> = 9.6). Reduced transmission of the DMV1639 IB challenge virus by the combined vaccination programme in broiler chickens was also accompanied by clinical protection. These data are important because prevention of IBV transmission by vaccination will result in overall reduced viral replication and consequently in reduced likelihood of genetic changes that can lead to new variants. This is the first published evidence of the successful transmission control of a DMV1639 IBV strain in chickens.

由于传染性支气管炎病毒（Infectious Bronchitis Virus, IBV）传播能力极强，在商业家禽养殖体系中对该病实施有效防控始终是一项极具挑战性的工作。尽管美国境内目前已有多种IBV谱系流行，但DMV1639型IBV毒株（GI-17）作为当前主流的流行变异株，正给家禽养殖业造成生产损失。本研究旨在评估联合使用GA08型（GI-27）与Mass型（GI-1）两种IB疫苗，能否显著降低4周龄商业肉鸡感染DMV1639型（GI-17）野外IBV毒株后的病毒传播效率。试验中将鸡只分为两组：一半为直接攻毒组，另一半则在24小时后与攻毒鸡只进行接触暴露。本研究设置两组平行重复试验，每组均包含10只直接攻毒鸡与10只接触暴露鸡。免疫组的攻毒病毒传播效率显著降低（有效再生数<i>R</i> = 0.0），而所有未免疫鸡只均被感染（<i>R</i> = 9.6）。肉鸡联合免疫方案不仅降低了DMV1639型IBV攻毒株的病毒传播效率，同时还为鸡只提供了临床保护作用。本研究数据具有重要意义：通过疫苗接种阻断IBV传播，可整体降低病毒复制水平，进而减少引发新变异株的基因变异概率。本研究为全球首次公开报道的、可在鸡群中成功防控DMV1639型IBV毒株传播的试验证据。