QX-like infectious bronchitis virus isolated from cases of proventriculitis in commercial broilers in England
QX-like infectious bronchitis virus isolated from cases of proventriculitis in commercial broilers in England
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DOI：
10.1136/vr.101005
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发表时间：
2012-12-08
影响因子：
2.2
通讯作者：
Jones, R. C.
中科院分区：
文献类型：
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作者：
Ganapathy, K.;Wilkins, M.;Jones, R. C.
这篇简短的通讯报道了从英国肉鸡腺胃中分离出的QX样传染性支气管炎病毒（IBV）及其在无特异性病原体（SPF）雏鸡中的致病性。这似乎是第一次报告分离出这种病毒从受影响的鸡在英国的前胃。1996年首次在中国鸡的这种组织中发现病毒（YuDong等，1998年），后来报告了更多病例，包括接种IBV疫苗的鸡群（Yu等，2001年）。我们收到了一群56日龄商业肉鸡的肾脏和前胃样本，提交的现场兽医报告了呼吸道体征、死亡率水平升高、饲料转化率差和活体重增量不佳。尸检时，报告了腺胃炎和肾脏肿胀。如前所述（Worthington等，2008），合并并处理相似组织，通过逆转录酶PCR（RT-PCR）检测IBV，并尝试进行病毒分离（VI）。肾组织上清液RT-PCR检测IBV阴性，腺胃组织RT-PCR检测IBV阳性。对腺胃进行PCR检测，aMPV、纽卡斯尔病病毒（NDV）和传染性法氏囊病病毒（IBDV）均为阴性，腺病毒为阳性。随后的IBV测序显示，它与属于IBV 793 B的疫苗株非常相似。由于鸡群在采样前两周接种了793 B型疫苗，因此很可能检测到疫苗的残留基因组。组织上清液进行VI，无论是在气管器官培养物（TOC）和鸡胚（ECE）中，在TOC中的第二和第三代，腺胃接种物引起100%纤毛停滞3天后。在ECEs中，到第三代，相同的接种物引起IBV典型的胚胎病变。对TOC培养基和第二代和第三代的尿囊液进行RT-PCR和测序。所有样品均为IBV阳性，TOC和ECE回收的病毒与IBV QX相关。对来自第三次ECE传代的病毒进行全长S1基因组测序。将S1基因的一段核苷酸序列与本实验室分离的鸡传染性支气管炎病毒QX分离株L-1148（GenBank登录号DQ 431199）进行同源性比较，结果表明该分离株S1基因的同源性为98.57%。1;（Worthington等2008），97.71%为先前在英国其他地方分离的QX样IBV（GenBank登录号EU 914939）。1;（Gough等2008）和98.57%，与原始中国QX分离物（GenBank登录号AF 193423）。经PCR检测，用于致病性研究的尿囊液对aMPV、NDV、IBDV和禽腺病毒均为阴性。这似乎是第一个QX样IBV分离自鸡前胃从一个患病的鸡群在英国。为了确定该分离株（菌株KG 3 P）的初步致病性，病毒的第三代在ECE中再传两代，并在TOC中滴定尿囊液。12只SPF鸡在日龄时鼻内接种0.1 ml 105 TOC 50/ml菌株KG 3 P。每天检查其临床体征。在感染后7天和14天（dpi），对5只鸡实施安乐死，收集组织（鼻甲、气管、肺、肾、睾丸、输卵管、前胃、胰腺、十二指肠、回肠、空肠、盲肠扁桃体和直肠），并在每个采样点合并用于RT-PCR和VI（使用TOC）。轻度至中度呼吸道...
This short communication reports on the isolation of QX-like infectious bronchitis virus (IBV) from the proventriculus of broiler chicken in England, and its pathogenesis in specific-pathogen-free (SPF) chicks. This appears to be the first report of the isolation of this virus from the proventriculus of affected chicks in the UK. The virus was first recovered from this tissue in chickens in China in 1996 (YuDong and others 1998), and later, more cases were reported, including in flocks vaccinated against IBV (Yu and others 2001). We received samples of kidney and proventriculus from a flock of 56-days-old commercial broiler chickens, where the submitting field veterinarian reported respiratory signs, increased levels of mortality, a poor feed conversion ratio and suboptimal live body weight gain. At necropsy, proventriculitis and swollen kidneys were reported. Similar tissues were pooled and processed for IBV detection by reverse-transcriptase PCRs (RT-PCR), as previously described (Worthington and others 2008), and virus isolation (VI) were attempted. RT-PCR tests on the supernatant of the pooled tissues of kidneys were negative for IBV, while the proventriculus samples were positive. The proventriculus was negative for avian metapneumovirus (aMPV), Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV), but positive for fowl adenovirus by PCR tests. Subsequent sequencing of the IBV showed that it closely resembled a vaccinal strain belonging to IBV 793B. Since the flock had been vaccinated with a 793B-type vaccine two weeks prior to the sampling, it was likely that residual genome of the vaccine was detected. The tissue supernatant was subjected to VI, both in tracheal organ cultures (TOC) and embryonated chicken eggs (ECE).By the second and third passages in TOCs, the proventriculus inocula caused 100 per cent ciliostasis by three days postinfection. In ECEs, by the third passage, the same inocula caused embryos lesions typical of IBV. The TOC medium and allantoic fluid from second and third passages were subjected to RT-PCR and sequencing. All samples were positive for IBV, and the viruses recovered by TOC and ECE were related to IBV QX. The virus from the third ECE passage was subjected to full-length S1 genome sequencing. By comparing percentage of nucleotide sequences of a segment of S1 gene, it showed 98.57 per cent similarity with an IBV QX isolate L-1148 previously isolated in this laboratory (GenBank accession number DQ431199. 1;(Worthington and others 2008), 97.71 per cent to a QX-like IBV previously isolated elsewhere in the UK (GenBank accession number EU914939. 1;(Gough and others 2008) and 98.57 per cent, with the original Chinese QX isolate (GenBank accession number AF193423). By PCR, the allantoic fluid used for pathogenicity study was negative for aMPV, NDV, IBDV and fowl adenovirus. This appears to be the first QX-like IBV isolated from the chicken proventriculus from a diseased flock in England. To establish the preliminary pathogenicity of this isolate (strain KG3P), the third passage of the virus went through another two passages in ECE, and the allantoic fluid was titrated in TOCs. Twelve SPF chicks were inoculated intranasally when day old with 0.1 ml of 105 TOC50/ml of strain KG3P. They were examined for clinical signs on a daily basis. At seven and 14 days postinfection (dpi), five birds were euthanased, and tissues (turbinate, trachea, lung, kidney, testes, oviduct, proventriculus, pancreas, duodenum, ileum, jejunum, caecal tonsils and rectum) were collected and, at each sampling point, were pooled for RT-PCR and VI (using TOC). Mild to moderate respiratory …