الفهرس 
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Abstract
In Egypt the poultry industry has been severely affected by continuous outbreaks of Avian influenza H5N1 and H9N2 resulting in severe losses to investors in the field of poultry and death of human beings who come in contact with infected birds. Many efforts to control highly pathogenic H5N1 avian influenza virus in poultry have failed despite increased biosecurity, quarantine and vaccination, therefore in this study 150 samples from chicken flocks as, broiler, layer, breeder and this flocks suspected to be suffering from AI disease were collected from Alexandria, El-Behera, El-Gharbia, Marsa Matrough and Kafr El-Sheikh governorates and examined for epidemiological survey and the spread of AI virus in these provinces. 150 poultry flocks including 142 broiler, 6 layer and 2 breeder flocks were collected from governorates mentioned and tested through isolation and identification of AI via RT-PCR ,SPF eggs inoculation , HA tests and sequencing of H9 gene to determine mutation incidence and Phylogenetic analysis of some local AIV isolates. The total incidence of AIV(70.4% ) 100 out of 142 for matrix gene and (56.3%) 80 out of 142 for H9 gene within all tested broiler flocks.as the following: AI virus was detected among broiler flocks in Alexandria, El-Behera, El- Gharbia, Marsa Matrough and Kafr El-Sheikh at a percentage of 38.9%, 66.7%, 47.4%, 30% and 20 % respectively in examined broiler flocks with atotal incidence of 56.3% . AI virus was detected among layer flocks by RT-PCR test in El-Behera at percentage of 25% for H9 infection, it was negative in Alexandria (0%) and El-Gharbia (0%) among examined layer flocks . The total incidence of AIV 16.7% for H9 infection within all tested layer flocks. AI (H9) virus was negative for the two tested farm in El-Behera at a percentage of (0%). Total incidence of AIV (0%) 0 out of 2 within all tested breeder flocks. 50 flocks were isolated on SPF eggs from the 81 positive flocks for H9 .those flocks including broilers and layer.Their HA titer log2 were ranging from 0 to 11. After isolation we have got 20 positive flocks for H9 were found .out of them 8 isolate (according to HA activity and cycle of RT-PCR) were selected for sequencing later Sequencing and phylogenetic tree of hemagglutinin (HA) gene of 8 positive AIV H9N2 isolates from broiler farms two isolate collected at 2012 from El-Behera,Three isolate were collected at 2013 from El-Gharbia, El-Behera and Alexandria And three isolate were collected at 2014 from El-Gharbia, Marsa matrouh and El-Behera and the results were as the following: Phylogenetic tree showed that all HA gene sequences of eight H9N2 samples was belonging to the isolate are G1- like HA lineage present in the Middle East. The seven isolates found to be have an identity with each other ranging from 92.9 _ 98.3% and in comparison to Israel 2008 strain it was 86.2_89% and with the original Egyptian strain of 2.4%.