Department of Basic Veterinary Sciences, School of Veterinary Medicine, The University of the West Indies (St. Augustine), Mount Hope, Republic of Trinidad and Tobago.
Department of Comparative Biomedical Sciences, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Italy.
Transbound Emerg Dis. 2020 Nov;67(6):2775-2788. doi: 10.1111/tbed.13637. Epub 2020 Jun 13.
Avian coronaviruses, including infectious bronchitis virus (IBV) and turkey coronavirus (TCoV), are economically important viruses affecting poultry worldwide. IBV is responsible for causing severe losses to the commercial poultry sector globally. The objectives of this study were to identify the viruses that were causing outbreaks of severe respiratory disease in chickens in Trinidad and Tobago (T&T) and to characterize the strains. Swab samples were collected from birds showing severe respiratory signs in five farms on the island of Trinidad. Samples were tested for the presence of IBV, as well as avian influenza virus (AIV), Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) by real-time reverse transcription polymerase chain reaction (qRT-PCR). All samples from the five farms tested negative for AIV, NDV and aMPV; however, samples from clinically affected birds in all five of the farms tested positive for IBV. Genetic data revealed the presence of TCoV in chickens on two of the farms. Interestingly, these two farms had never reared turkeys. Phylogenetic analysis showed that IBV S1 sequences formed two distinct clusters. Two sequences grouped with vaccine strains within the GI-1 lineage, whereas three sequences grouped together, but separately from other defined lineages, forming a likely new lineage of IBV. Pairwise comparison revealed that the three unique variant strains within the distinct lineage of IBV were significantly different in their S1 nucleotide coding regions from viruses in the closest lineage (16% difference) and locally used vaccine strains (>20% difference). Results also suggested that one of the samples was a recombinant virus, generated from a recombination event between a Trinidad virus of the GI-1 lineage and a Trinidad virus of the newly defined lineage. Many amino acid differences were also observed between the S1 coding regions of the circulating field and vaccine strains, indicating that the IBV vaccines may not be protective. Vaccine-challenge studies are however needed to prove this.
禽类冠状病毒，包括传染性支气管炎病毒（IBV）和火鸡冠状病毒（TCoV），是影响全球家禽业的具有经济重要性的病毒。IBV 是导致全球商业家禽业严重损失的罪魁祸首。本研究的目的是确定导致特立尼达和多巴哥（T&T）鸡群暴发严重呼吸道疾病的病毒，并对其株系进行特征描述。从特立尼达岛上五个农场出现严重呼吸道症状的禽类中采集拭子样本。通过实时逆转录聚合酶链反应（qRT-PCR）检测样本中是否存在 IBV、禽流感病毒（AIV）、新城疫病毒（NDV）和禽偏肺病毒（aMPV）。五个农场的所有样本均检测到 AIV、NDV 和 aMPV 均为阴性；然而，来自五个农场临床受影响禽类的样本均检测到 IBV 阳性。遗传数据显示，有两个农场的鸡群中存在 TCoV。有趣的是，这两个农场从未饲养过火鸡。系统进化分析显示，IBV S1 序列形成了两个不同的簇。两个序列与 GI-1 谱系内的疫苗株聚集在一起，而三个序列聚集在一起，但与其他定义的谱系分开，形成了一个可能的 IBV 新谱系。两两比较表明，独特谱系内的三个独特变异株在 S1 核苷酸编码区与最接近谱系中的病毒（16%的差异）和当地使用的疫苗株（>20%的差异）有显著不同。结果还表明，其中一个样本是重组病毒，是由 GI-1 谱系中的特立尼达病毒与新定义谱系中的特立尼达病毒之间的重组事件产生的。在循环现场和疫苗株的 S1 编码区之间还观察到许多氨基酸差异，表明 IBV 疫苗可能无法提供保护。然而，需要进行疫苗接种挑战研究来证明这一点。
