الفهرس 
1-IntroductionOnly 14 pages are availabe for public view
 |  | from | 212 |  |  |
| | | from | 212 | | |
Abstract
The epizootiological investigation of 22 current infectious bursal disease ( IBD) outbreks among vaccinated chickens flocks during 2005-2007 revealed that all infectious bursal disease virus (IBDV) occured at 18-41 days .59.1% of these outbraks were
characterized by typical IBD lesions. On other hand 40.9% showed sub clinical form of
IBDVwithout clinical signs or high mortality. IBDV was detected in 100% of tested
bursa by agar gel precipitation test (AGPT).
Antigenic typing of IBDV from selected outbreks were carried out by monocolonal
antibodies antigen capture –enzyme linked immunsorbent assay ( AC-ELISA) which
indicating thatb 59.1% (13/22) were typed as classic and 40.1% (9/22) were variant
IBDVs. The majority of IBDV variant antigen detected (77.8%) of IBDV variant were
classified as Del/E and RS593 was (22.2%) of variant IBDV. Detection of RNA in
bursal homogenates by RT/PCR followed by nucleotide sequences indicated that
Behera/06/06 strain fall in vvIBDV ancestor which reaveld 94% similarity to (Bolivia
05 B-67 and Soll-04 and 93 % similarity to UK661. Comparison between
Behera/06/06 and Giza /2000 indicate the vvIBDV of the field in continous mutation.
Pathogenicity study of local field isolates reaveld that IBDV related to variants Del/E or
RS593 caused sever atrophy of the bursa of fabricius and low mortality percentages in
comparison to the classic vvIBDV in susceptible chickens. Finally vaccination with
intermediate plus or intermediate vaccine provide complete protection against mortality
but not against bursal atrophy.