Nili Hassan, Asasi Keramat
Avian Medicine Department, School of Veterinary Medicine, Shiraz University, P.O. Box 1731, Shiraz 71345, Iran.
Avian Pathol. 2002 Jun;31(3):247-52. doi: 10.1080/03079450220136567.
Since 1998, an epidemic of avian influenza has occurred in the Iranian poultry industry. The agent was pathotyped as non-highly pathogenic and subtyped as an H9N2 avian influenza virus. Therefore it did not require eradication. However, frequent incidences of high mortality were observed commonly on broiler farms. No other species of bird were affected. The circulation of the virus and mixed infection with other respiratory pathogens, particularly infectious bronchitis virus and Mycoplasma gallisepticum, were incriminated in the high mortality on poultry farms and resulting great economic losses. Clinical signs in both field and experimental studies included swelling of the periorbital tissues and sinuses, nasal and ocular discharge, and severe respiratory distress. However, in the experimental study, the mortality rate was much lower than in the natural outbreak. Gross lesions identified included extensive congestion of the respiratory tissues, and exudation with cast formation in the tracheal bifurcation, which extended to the secondary bronchi. Severe necrotizing tracheatis was the predominate histological lesion. Ultrastructurally, orthomyxovirus-like particles were identified in the inoculum used for the experimental study. An inactivated H9N2 avian influenza vaccine prevented mortality in experimentally challenged chickens.
自1998年以来，伊朗家禽业爆发了禽流感疫情。病原体被鉴定为非高致病性，并被亚型化为H9N2禽流感病毒。因此，无需扑杀。然而，肉鸡养殖场经常出现高死亡率。没有其他鸟类受到影响。病毒的传播以及与其他呼吸道病原体的混合感染，特别是传染性支气管炎病毒和鸡毒支原体，被认为是家禽养殖场高死亡率的原因，并导致了巨大的经济损失。现场和实验研究中的临床症状包括眶周组织和鼻窦肿胀、鼻和眼分泌物以及严重的呼吸窘迫。然而，在实验研究中，死亡率远低于自然爆发。发现的肉眼病变包括呼吸组织广泛充血，气管分叉处有渗出物并形成铸型，延伸至二级支气管。严重的坏死性气管炎是主要的组织学病变。在实验研究中使用的接种物中，超微结构鉴定出了正粘病毒样颗粒。一种灭活的H9N2禽流感疫苗可预防实验性攻毒鸡的死亡。
