Sander J E, Jackwood M W, Rowland G N
Department of Avian Medicine, College of Veterinary Medicine, University of Georgia, Athens 30602-4875, USA.
Avian Dis. 1997 Oct-Dec;41(4):964-7.
A late-breaking infectious bronchitis virus (IBV)-associated respiratory disease was a chronic problem in Georgia broilers in 1995. The predominant virus isolated from diseased birds was the Arkansas (Ark) type of IBV. Because broilers in Georgia are currently vaccinated with the Arkansas serotype, there was concern that a phenotypic and/or genotypic change had occurred in the field virus so it could break through immunity conferred by commercial vaccines. The purpose of this study was to determine if a commercially available vaccine for IBV as currently used in the field still protected broilers against those viruses. We obtained 108 1-day-old broilers from a commercial source and assigned them randomly to 12 groups. One-half of the groups of birds were vaccinated at 1 day of age and again at 18 days of age with commercially available B1/Mass/Ark vaccine. One-half of both vaccinated and nonvaccinated groups of birds were challenged at 35 and 42 days of age with a recent IBV Ark field isolate. Serologic titers were evaluated by enzyme-linked immunosorbent assay at time of challenge and at the end of the trial. A necropsy was performed on birds at 56 days and pathogenicity was assessed. Seroconversion was statistically significant in all birds exposed to vaccine or challenge by 56 days of age. Gross airsacculitis was significantly more severe in broilers challenged without prior exposure to vaccine.
1995年，一种新出现的与传染性支气管炎病毒（IBV）相关的呼吸道疾病在佐治亚州的肉鸡中成为一个慢性问题。从患病鸡中分离出的主要病毒是阿肯色州（Ark）型IBV。由于佐治亚州的肉鸡目前接种的是阿肯色州血清型疫苗，人们担心田间病毒发生了表型和/或基因型变化，从而可能突破商业疫苗所提供的免疫力。本研究的目的是确定目前在田间使用的市售IBV疫苗是否仍能保护肉鸡抵抗这些病毒。我们从商业来源获得了108只1日龄的肉鸡，并将它们随机分为12组。一半的鸡群在1日龄时接种市售的B1/Mass/Ark疫苗，并在18日龄时再次接种。接种和未接种疫苗的鸡群中各有一半在35日龄和42日龄时用最近的IBV Ark田间分离株进行攻毒。在攻毒时和试验结束时通过酶联免疫吸附测定法评估血清滴度。在56日龄时对鸡进行剖检并评估致病性。到56日龄时，所有接触疫苗或攻毒的鸡的血清转化在统计学上具有显著意义。在未事先接触疫苗的情况下进行攻毒的肉鸡中，肉眼可见的气囊炎明显更严重。
