Swayne D E, Beck J R, Perdue M L, Brugh M, Slemons R D
USDA, Agriculture Research Service, Athens, Georgia 30605, USA.
Avian Dis. 1996 Apr-Jun;40(2):438-47.
Pathobiologic characteristics were determined for three mildly pathogenic (MP) ratite-origin avian influenza viruses (AIVs). Ratite-origin AIVs produced respiratory disease in rheas, and virus was reisolated from oropharyngeal and cloacal swabs on days 2-6 postinoculation. Inoculation of two ratite-origin AIVs in the upper respiratory tract of chickens resulted in viral infections, but the mean chicken infectious dose (CID50) for A/emu/Texas/39924/93 (H5N2) (Emu/Texas) virus was 500-fold lower than the CID50 for the A/rhea/North Carolina/39482/93 (H7N1) virus. In ovo and in vivo passage of the MP parent Emu/Texas isolate resulted in emergence of a highly pathogenic (HP) variant that had high plaquing efficiency in chicken embryo fibroblast cultures and was highly lethal in chicken pathotyping tests. This variant virus produced gross lesions in chickens similar to those reported for other HP AIVs. These findings demonstrated that ratite-origin AIVs can produce significant clinical disease in rheas and have a realistic potential for interspecies transmission to domestic poultry. Furthermore, HP variants can emerge from MP H5 ratite-origin AIVs if introduced and allowed to circulate in chicken populations.
对三种低致病性（MP）平胸鸟类源禽流感病毒（AIV）的病理生物学特征进行了测定。平胸鸟类源AIV在美洲鸵鸟中引发呼吸道疾病，接种后第2至6天可从口咽和泄殖腔拭子中再次分离出病毒。将两种平胸鸟类源AIV接种于鸡的上呼吸道可导致病毒感染，但A/鸸鹋/得克萨斯/39924/93（H5N2）（鸸鹋/得克萨斯）病毒的平均鸡感染剂量（CID50）比A/美洲鸵鸟/北卡罗来纳/39482/93（H7N1）病毒的CID50低500倍。MP亲本鸸鹋/得克萨斯分离株在鸡胚内和体内传代后出现了一种高致病性（HP）变异株，该变异株在鸡胚成纤维细胞培养物中具有高噬斑形成效率，在鸡致病型试验中具有高致死性。这种变异病毒在鸡身上产生的肉眼可见病变与其他HP AIV报道的病变相似。这些发现表明，平胸鸟类源AIV可在美洲鸵鸟中引发严重临床疾病，并具有向家禽跨物种传播的现实可能性。此外，如果引入并允许在鸡群中传播，HP变异株可从MP H5平胸鸟类源AIV中出现。
