الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
 |  | from | 196 |  |  |
| | | from | 196 | | |
المستخلص
Infectious bronchitis (IB) is an acute, highly contagious, upper respiratory tract disease in chickens. Clinical signs include tracheal rales, nasal exudates, coughing, and sneezing. (Ahmed, 1954).
Infectious Bronchitis Virus, one of the major viruses affecting poultry industry, causing DROP in egg production quality and quantity, in addition affect the performance of broilers and coplicate other diseases causing severe losses.
The etiologic agent of IB is infectious bronchitis virus (IBV), a member of the Coronaviridae family. The virion is enveloped with club-shaped surface projections. The viral genome is a single-stranded, positive sense, 27.5-kilobase RNA molecule. The genome codes for four major structural proteins: a spike glycoprotein, the integral membrane glycoprotein, the envelope protein, and the nucleocapsid protein that associates with the RNA genome. (Maeda, et al 1999). The extensive antigenic variability of IBV is well recognized. Many serotypes of the virus have been reported (Cavanagh and Naqi, 1997), and new, previously unrecognized serotypes, often referred to as variants, have been identified as a result of increased surveillance efforts. Identification of the serotype (s) causing disease is vital so the most appropriate vaccinal strains, if available, may be selected for control programs.(Cavanagh, et al. 2005)