الفهرس 
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Abstract
Studies on the infectious bronchitis infection in broiler in the West Delta region This study was conducted to survey the nature of the spread of avian infectious bronchitis in broiler flocks in the West Delta region represented in the provinces of EL-Behira and Alexandria was chosen as the thirty-five broilers flocks of different breeds have already been immunized at the age of 7 days vaccine live (Hitchner + IB H120). Moreover, ranging in age from 18 to 35 days During the examination of infected broiler flocks the following was observed 1-Respiratory signs ranged from mild to severe and included mouth breathing (gasping), coughing, sneezing with mucoid nasal discharges and a swollen sinuses and eyes in some cases and reduced weight gain-2 A significant increased morbidity and mortality rates up to 33.3 % with watery and whitish diarrhea, soiled vent feathers Gross pathological examination revealed presence of- Congestion of the respiratory mucosa of the trachea with varying degree pneumonia, pericarditis, perihepatitis and airsacculitis. Renal pathological lesions include enlarged kidneys with prominent tubules with urates deposition and distention of the ureters with urates associated with cystic formation.Samples were taken from the trachea, bronchi, and kidneys in order to isolate the infectious bronchitis virus in SPF-ECE for three consecutive blind passages. The harvested allantoic fluid after the third passage was collected and tested for hemagglutinatng viruses by HA test and revealed that twenty nine flocks about (83%) out of thirty five had positive HA titer. The harvested allantoic fluid for detection of IBV by RRT-PCR and the results revealed identification of 26 positive field samples about 74.3%. Four positive isolates were selected (9, 16, 23 and 35) for further genetic analysis by S1 gene sequencing and the results revealed that all isolates had similarity relatedness to Israelian strain IS/1494/06 (EU780077) by (95.1% and 93.9% and 94.5% and 89.6% respectively and the strain D274 had the most related similarity % to the isolates of the study ranged from 77.4% to 82.9% .Three immunization experiments were conducted to estimate the breadth of the protection against the newly characterized Egyptian highly virulent and variant (1212B) of IBV and evaluation of different immunization programs using commercially available live vaccines in Egypt as following; group I vaccinated by (IB Primer and Ma5), group II vaccinated by (IB Primer and 4/91), and group III vaccinated by (Ma5 and H120) and the other two groups remained as controls. Group I (IB Primer + Ma5) recorded the highest degree of ciliary protection by 82%, followed by the second group (IB Primer + 4/91) by 56%, then the third group (Ma5 + H120) 32% in relation to control non-infected group. All the vaccinated and control positive groups secrete the challenge virus at 5dpc at different rates and the second group had the lowest rate of virus secretion. The second group (IB Primer + 4/91) recorded the highest serological response at challenge day with 80% positive random samples The impact of the three immunization programs at the rate body weight gain of vaccinated bird at the age of challenge had recorded and the third group (Ma5 + H120) had the least depressant effect with an average weight of 217 grams, followed by the first group (IB Primer + Ma5) with an average weight of 207 grams whilst the second group (IB Primer + 4/91) was the most affected with an average weight of 195 grams.