Swayne D E, Pantin-Jackwood M
Southeast Poultry Research Laboratory, Agricultural Research Service, US Department of Agriculture, Athens, GA 30605, USA.
Dev Biol (Basel). 2006;124:61-7.
Historically, the pathogenicity of avian influenza (AI) viruses has been based on lethality for the major domesticated poultry species, the chicken. All AI viruses are categorised as either low (LP) and high pathogenicity (HP), but, within each category, pathobiological changes vary with host species and virus strain. Typically, AI viruses that are HP produce a similar severe, systemic disease with high mortality in chickens and a similar pathobiology in other galliforme birds, but usually either produce no infection or mild disease in ducks. The newer H5 and the H7 HPAI viruses have shifted to increased virulence for chickens as evidenced by shorter mean death times (MDT). Furthermore, the Asia H5N1 HPAI viruses have changed from producing inconsistent respiratory infections in ducks to some strains being HP (Hong Kong 2002 viruses) with virus in internal organs and brain, and excretion of large virus quantities from respiratory, and to a lesser extent, intestinal tracts. However, the quantities of virus shed per bird are still 1 % of that produced in chickens. With 2003-2004 Asian H5N1 AI viruses, the isolates have been highly lethal for young ducks but this virulence is age dependent. Across all bird species, the ability to produce severe disease and death is associated with high virus replication titres in the host, especially in specific tissues such as brain and heart.
从历史上看，禽流感（AI）病毒的致病性一直基于对主要家养禽类——鸡的致死率。所有禽流感病毒都被归类为低致病性（LP）和高致病性（HP），但在每个类别中，病理生物学变化因宿主物种和病毒株而异。通常，高致病性禽流感病毒在鸡中会引发类似的严重全身性疾病，并伴有高死亡率，在其他鸡形目鸟类中具有类似的病理生物学特征，但在鸭中通常要么不产生感染，要么引发轻微疾病。较新的H5和H7高致病性禽流感病毒对鸡的毒力有所增加，平均死亡时间（MDT）缩短就是证明。此外，亚洲H5N1高致病性禽流感病毒已从在鸭中引发不一致的呼吸道感染，转变为一些毒株具有高致病性（2002年香港病毒），病毒存在于内脏器官和大脑中，并从呼吸道以及在较小程度上从肠道排出大量病毒。然而，每只鸭排出的病毒量仍为鸡排出量的1%。对于2003 - 2004年亚洲H5N1禽流感病毒，分离株对幼鸭具有高度致死性，但这种毒力具有年龄依赖性。在所有鸟类物种中，引发严重疾病和死亡的能力与宿主中高病毒复制滴度有关，尤其是在大脑和心脏等特定组织中。
