الفهرس 
Review of Literature 2-Only 14 pages are availabe for public view
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Abstract
Epizootiological investigation of 29 current IBD outbreaks during 2014-2015 at 21-43 days of age showed that the infectious bursal disease virus (IBDV) affected vaccinated flocks and causes acute IBD and mortality ranged between 3.3-6.2% (average 4.75 %) in commercial broilers farms, 8-12.5 % (average 10.25 %) in native ballade varieties, and 7.5-10 % (average 8.75 %) in commercial layer replacement pullets inspite of the routinely applied vaccination program.
Pathogenicity study with 6 different vvIBDV local field isolates designated as ”Lay/Egy.Giza/98”,” Lay/Egy.Sharkia/03”, ”Br/Egy.Kalubia/07”,” Br/Egy. Ismalia /010” and ”Br/Egy.Giza /014” and ”Br/Egy. Menoufiyia /015” indicated that the isolates are highly virulent pathotypes producing 20%, 15%, 15%, 20%, 20% and 70% mortality respectively in susceptible commercial male layer chickens at 49 day-old age.
All VVIBD viruses which isolated from 1998 until 2015 are still pathogenic and cause bursal atrophy.
The two local field isolates vvIBDV ”Br/Egy.Ismalia/010” and vvIBDV ”Br/Egy. Menoufiyia /015” cause more severe bursal atrophy in comparable with other local field isolates and that were represented by BI and MSI.
The mortality % in commercial male layer chickens challenged with vvIBDV ”Br/Egy. Menoufiyia /015” local field isolate was 70% while it was 20% in commercial male layer chickens challenged with vvIBDV ”Br/Egy.Ismalia/010” and the difference between the two isolates in mortality % may be interpreted on the basis of being the commercial male layer chickens produced from a commercial hatchery and they have been expected to carry variable levels of MDA against IBD viruses because they were acquired from non SPF vaccinated parents so they may interfere to a great or less extent with the IBD challenge viruses causing finally variable degree in mortality %.
Laboratory vaccination experiment designed to evaluate the degree of protection against vvIBDV infection by vaccination with HVT-IBD vector vaccine in broiler chickens challenged with 3 different vvIBDV local field isolates at 35-days of age ”Lay./Giza.Egypt/98, ”Br./Kalubia.Egypt/07 and ”Br./Menofiya.Egypt/015 in which There was no mortality in all vaccinated groups while the mortality rate was 1/10 (10%) in non vaccinated group challenged with ”Br./Kalubia.Egypt/07 isolate and non vaccinated group challenged with ”Br./Menofiya.Egypt/015 isolate so HVT-IBD vector vaccine could protect 100% of vaccinated broiler chickens against mortality versus 10% in non-vaccinated challenged chickens with vvIBDV local field isolate ”Br./Kalubia.Egypt/07 or ”Br./Menofiya.Egypt/015” .
Broiler chickens vaccinated with HVT-IBD vector vaccine also protected from gross bursal lesion and bursal atrophy when challenged at 35-days of age with our three different isolates ”Lay./Giza.Egypt/98, ”Br./Kalubia.Egypt/07 and ”Br./Menofiya.Egypt/015.
There was partial protection of vaccinated challenged broiler chickens represented by BI and MSI versus to non-vaccinated control chickens at 7-days post challenge, respectively.
Vaccination with HVT-IBD vector vaccine protect against mortality and reduce its level than the non-vaccinated groups.