鸡传染性支气管炎研究进展(下))

4.3 基因分型按病毒基因结构产生基因分型.具体方法包括测序、RT-PCR检测基因组中特异性部分指纹(Rnase T1 fingerprinting)或是酶切图谱(RFLP)[49,50,52].基因信息是客观的,为流行病学研究提供本质的信息.基因分型在田间应用的局限是:IBV毒株(部分)基因组信息直接翻译为抗原型是不可能的,同一血清型或保护型的分离物可能在某些基因上有明显的不同(Cavanagh 1992)[53,54],而不同血清型或保护型可能在基因组上有非常高的相似性(Williams 1992; Cavanagh 1992; Capua 1998; Minta 1998)[55,56].一些研究(Lin 1991; Kwon 1993; Keeler 1998;步志高1999)[57,58,59,60]报道了在基因型和血清型之间有很高的关系,而另外一些则发表在基因和血清型和/或保护型之间存在矛盾(Clewley 1981; Kusters1987; Capua 1998; Hein 1998; Minta 1998).同样,用两种不同的基因分型方法对某一毒株分型,可能会产生互相矛盾的结果(Capua 1998).特别是利用基因型来对近期分离物进行关于这些IBV真实抗原型的确切信息时,需要进行常规血清学实验(Jia 1995; Hein 1998; Keeler1998)来验证[58,37].     

Enhancement of infectious bovine keratoconjunctivitis by modified-live infectious bovine rhinotracheitis virus vaccine

The effects of a modified-live infectious bovine rhinotracheitis virus vaccine (administered ocularly or intranasally) on experimentally induced infectious bovine keratoconjunctivitis were evaluated. The modified-live infectious bovine rhinotracheitis virus vaccine was administered to 13 male Holstein calves (intranasally in 4 and ocularly in 9; day 0). Five calves were not vaccinated and served as controls. Calves were examined daily and, starting on day 4, Moraxella bovis was administered ocularly to all 18 calves once daily for 4 days. The eyes of all calves were assigned a clinical score, and the ocular secretions were evaluated for presence of infectious bovine rhinotracheitis virus and M bovis daily until day 19. The severity of the ocular lesions was estimated by scoring the lesions clinically and by determining the protein concentration, myeloperoxidase activity, and WBC count in the tears. By day 5, conjunctivitis, chemosis, and epiphora were observed in all of the calves vaccinated ocularly. The calves vaccinated intranasally developed conjunctival plaques, but did not develop chemosis or photophobia. All of the calves developed keratitis after inoculation with M bovis. The median lesion scores were greater in both groups of vaccinated calves than in the controls. Corneal perforations developed exclusively in the vaccinated calves. The frequency of M bovis isolation from ocular secretions was significantly (P less than 0.05) greater in the vaccinated calves than in the controls. The tears from the intranasally vaccinated calves contained the highest myeloperoxidase activity and WBC count. The mean protein concentration in the tears of vaccinated calves was not significantly different from that in tears of controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

鸡传染性法氏囊病超强毒Gx株感染性分子克隆的构建

本研究以鸡传染性法氏囊病超强毒Gx株(野毒株)基因组为模板,用蛋白酶K法提取病毒基因组核酸dsRNA,在cDNA克隆的5'端上游引入了T7启动子序列,采用Long-accurateRT-PCR(LA-PCR)一步法扩增并克隆了病毒基因组A节段与B节段全长cDNA。序列测定结果表明,基因组A节段全长共3267个核苷酸,包括5'及3'端的非编码区和两个部分重叠的开放阅读框,基因组B节段全长共2843个核苷酸,包括5'及3'端的非编码区和一个开放阅读框。将IBDV-Gx株的A节段全长基因组及B节段全长基因组分别克隆入pMD18-T载体,构建成pMD-A、pMD-B两个带有T7启动子的重组质粒。两个重组质粒线性化后,进行体外转录,然后共电转染于鸡胚成纤维细胞37℃培养72h并传代。收获的细胞传代培养物分别用RT-PCR、间接免疫荧光、蚀斑试验等方法进行鉴定,结果用RT-PCR扩增出了VP3及VP5基因片段,间接免疫荧光检测到了特异性的荧光抗体,蚀斑试验结果表明蚀斑形成单位为3×103PFU/mL。     

鸡传染性法氏囊病的免疫接种对策

鸡传染性法氏囊(简称IBD)是一种高度接触性传染性且对生产危害极大的免疫抑制性疾病.3～6周龄的雏鸡最易感染,且发病迅速,病情较重.另外,由于法氏囊发炎,使其免疫功能受到破坏,因而雏鸡经接种MD、ND等疫苗后不能产生理想的免疫反应,甚至免疫失败.据统计,IBD发病率一般为80%～95%,高的可达100%,死亡率为20%～35%.有的高达50%,呈尖峰式死亡曲线.     

警惕肾型传支病

信鸽的肾型传支病就是指信鸽的传染性支气管炎。通过对病鸽的病例采集、实验室检测以及病理鉴定,我们发现近两年来在各地发生的信鸽传染性支气管炎是由冠状病毒引发的一种高度接触性传染病。     

控制传染性支气管炎

众所周知,传染性支气管炎（Infectious Bronchitis,IB）病毒很容易发生变异。最新的检测方法（RT-PCR和基因序列测定法）能够检出IB病毒基因组中极小的变化。问题是在实际生产中控制传染性支气管炎是否需要一种新型疫苗以应对每一种新出现的IB变异株？或者现有的疫苗是否足以产生充足的交叉保护力可抗击这些新出现的血清型或变异株（保护型）呢？     

鸡腺胃型传染性支气管炎的诊治

鸡腺胃型传染性支气管炎病原为冠状病毒,多发于20-80日龄,最早的发生于10日龄,主要表现病鸡生长停滞、消瘦死亡,腺胃肿大出血、胸腺、法氏囊肿大萎缩,本病病程长,有的达20-50天,并发或继发感染其它疾病会加重病情。该病1994年在我县首次报导,并分离鉴定出病原,1996年在周边其它县市也曾发现此病,此后曾一度停息,近年来,该病重又卷土重来,并有不断上升的趋势,笔者曾先后接诊数十例,现将诊疗情况总结如下,供业界同仁参考。