免疫抑制性病毒多重感染在鸡群疫病发生和流行中的作用

Effect of Multiple Immunosuppressive Viral Infections on Pathogenesis and Epidemiology in Chicken Flocks

根据近几年各地大型鸡场不同类型病鸡的实验室鉴别诊断结果,结合国内外的研究进展,本文对不同免疫抑制性病毒多重感染在鸡群疫病发生和流行中的作用做了全面的分析和探索。现有资料表明,不同的免疫抑制性病毒的亚临床感染在规模化畜禽群体中是非常普遍的,但往往只有在同一个体发生二重或多重感染时,在它们的相互作用下对个体和群体造成的免疫抑制和其它病理反应才比较明显。在此基础上,本文提出了"条件致病性病毒"的概念,并对其含义和内涵作了讨论。这一观念的引入,可能有助于理解和解释高密度饲养鸡群中疫病的复杂性及其控制的艰难性。鸡群中的免疫抑制性病毒的多重感染造成一部分个体处于"不完全免疫状态",使许多已经多次强化免疫的鸡场中仍有部分个体成为A类病病毒侵袭的对象并成为新的传染源,也容易造成在"免疫选择压"作用下病毒的抗原变异。此外,同一个个体的多重病毒感染,为病毒间通过基因重组产生新病毒创造了条件。

Based on literatures and our laboratory diagnosis for many samples from different chicken flocks with different symptoms and lesions from different areas nationwidely during the last 4 years,this article analyzed the roles of multiple immunosuppressive viral infections in pathogenesis and epizootiology in chicks flocks.Many reports has been demonstrated that the subclinic infections of immunosuppressive viruses in chickens and pigs are very common,however,immunosuppression and other pathogenic changes could become very clear and severe only when dual or multiple viral infections and their interactions happened.According to the above,a concept of'opportunistically pathogenic viruses'or'opportunistic viral infections'was suggested and discussed.Hopefully,the new concept will help to understand the complicacy in diagnosis and difficulty in controlling of poultry diseases recently.The multiple immunosuppressive viral infections produced some immuneincompetent individuals which became the target and further infectionsources in whole flocks even extensively vaccinated against some dangerous virus infections such as Newcastle disease.Also,the incompleteimmune status could set up a immune selective pressure which will help viruses to make antigenic evolutions.Besides,multiple infections in the same birds will create a opportunity for recombination between different viruses and help new viral variants to appear.