الفهرس 
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Abstract
Infectious bursal disease virus (IBDV) is one of the incriminated etiological agents in both fatal and immunosuppressive disease problems affecting broiler chickens all over the world. In recent years more debate was established about the exact share of this virus in the economic losses in poultry industry in Egypt. This quarrel initiated us to point on the IBD virus infection and its role either as a potential even with regular vaccination or as increasing the susceptibility of other pathogens like avian influenza (AI) subtypes and Newcastle disease (ND) viruses.
For the aforementioned goal, forty broiler flocks at different localities in Sharkia province were investigated for clinical signs and postmortem lesions of IBD virus infection and / or concurrent infections. Alongside, the immune status of the examined birds under different circumstances was explored for the purpose of evaluation of the impact of genetic variation of the isolated IBDV on the increase liability of other viruses.
Clinical inspection among the examined birds revealed no outbreaks in the first category of study farm groups (Regularly monitored broilers), that group was subjected to regular weekly visit for seven broiler chicken farms with total of 56000 birds of various breeds and vaccination programs non-significant mortality rates (0.25%-0.7%) with sporadic sick birds. However, the second group; clinically suspected affected with IBDV (N=27) with a total population of 184000 birds which had an increase in mortality by (2%-20%) ,General signs of illness, vent picking, huddling together, perfuse watery and whitish diarrhea . the last investigated group included those exhibiting respiratory signs.