الفهرس 
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Abstract
Servalence of IBDV infection was conduct in Egyptian farms during 2007 - 2010 , the incidence of Egyptian farms IBDV infection was found to be 85.7 and 14.3% in vaccinated and non vaccinated broilers frames respectively , while in the layer farms the incidence was 75% and 25% for the vaccinated and non vaccinated farms; respectively. Native breed farms shows slight similar incidence when compared to the broiler farms (incidence was 85.5 and 12.5 in the vaccinated and non vaccinated farms respectively. All the isolated strains were conducting by PCR, one strain was confirmed to be variant IBDV using sequencing analysis of the hypervariable region of VP2 gene and this strain showed both deletion and substitutional mutation that made this strain capable of escaping the immune system of birds vaccinated with the classical IDD vaccine. Preparation of live Tissue Culture propagated vaccine from the variant IDD strains gave protection rate of92% and 96% against wlBD and the isolated variant IBDV; respectively.