Gallardo R A, Aleuy O A, Pitesky M, Sentíes-Cué G, Abdelnabi A, Woolcock P R, Hauck R, Toro H
A Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, 1089 Veterinary Medicine Dr. VM3B, Davis, CA 95616.
B University of California, School of Veterinary Medicine, Cooperative Extension, 1089 Veterinary Medicine Dr. VM3B, Davis, CA 95616.
Avian Dis. 2016 Jun;60(2):424-9. doi: 10.1637/11294-100615-Reg.
On the basis of the data from the California Animal Health and Food Safety Laboratory System, 1444 infectious bronchitis (IB) cases were diagnosed between 1997 and 2012. Epidemiologic analyses demonstrated two major IB virus (IBV) outbreak peaks, affecting mainly 35-to-49-day-old broiler chickens. California variant 1737 (CA1737) and California variant 1999 (Cal 99) IBV types were the most prevalent genotypes during the analyzed period. To further understand the increased prevalence of these genotypes, we assessed and compared the variability of the S1 gene hypervariable region of CA1737 and Cal 99 with the variability of IBV strains belonging to the Massachusetts 41 (M41) and Arkansas (Ark) types during serial passages in embryonated chicken eggs. On the basis of the S1 nonsynonymous changes, seven different subpopulations were detected in M41. However, the predominant population of the field strain M41 before passages continued to be predominant throughout the experiment. In contrast, Ark passaging resulted in the detection of 13 different subpopulations, and the field sequence became extinct after the first passage. In IBV Cal 99, eight different subpopulations were detected; one of these became predominant after the second passage. In CA1737, 10 different subpopulations were detected. The field strain major sequence was not detected after the first passage but reappeared after the second passage and remained at low levels throughout the experiment. Compared with M41 and Ark, Cal 99 and CA1737 showed intermediate variability.
根据加利福尼亚动物健康与食品安全实验室系统的数据，1997年至2012年间共诊断出1444例传染性支气管炎（IB）病例。流行病学分析显示有两个主要的传染性支气管炎病毒（IBV）爆发高峰，主要影响35至49日龄的肉鸡。加利福尼亚变种1737（CA1737）和加利福尼亚变种1999（Cal 99）IBV类型是分析期间最普遍的基因型。为了进一步了解这些基因型流行率增加的情况，我们评估并比较了CA1737和Cal 99的S1基因高变区的变异性与属于马萨诸塞41型（M41）和阿肯色型（Ark）的IBV毒株在鸡胚连续传代过程中的变异性。基于S1非同义变化，在M41中检测到七个不同的亚群。然而，传代前田间毒株M41的优势群体在整个实验过程中仍然占主导地位。相比之下，Ark传代导致检测到13个不同的亚群，并且田间序列在第一次传代后就灭绝了。在IBV Cal 99中，检测到八个不同的亚群；其中一个在第二次传代后成为优势群体。在CA1737中，检测到10个不同的亚群。田间毒株的主要序列在第一次传代后未被检测到，但在第二次传代后重新出现，并在整个实验过程中保持在低水平。与M41和Ark相比，Cal 99和CA1737表现出中等变异性。
