الفهرس 
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Abstract
In order to investigate the dynamic of the epidemic occurrence and reasons of endemicity of avian influenza in Egypt. A total of 58 commercial poultry farms (49 chicken, 7 turkeys and 2 quails), 366 samples from backyard and live bird markets and 7 wild birds were collected for detection, isolation and characterization of avian influenza viruses circulating among different poultry species during 2012. We found 2 AI isolates from farms, (H5N1 was isolated from layer farm in Kaleobea government and H9N2 isolate from chicken farm in Sharkeia government. Also 2 H5N1 isolate obtained from backyard ducks .While, no influenza viruses were detected in wild birds, turkey farms or quails. Sequencing analysis of the isolates reveled that they belong to 2012 isolates with some changes in amino acid sites. To evaluate the protective immune responses of birds, 193 blood samples were obtained from different chicken farms (broiler, layer and breeder) and serum was examined using haemagglutination inhibition test. Results revealed that there were incomplete protection at the flock level which lead to silent spread of AI virus. Inactivation of H5N1 virus was studied using experimentally contaminated litter with H5N1 and exposed to physical agents (temperature and UV light) and different commercial disinfectants. The results show that virus could be inactivated within 24 hour using high temperature at 56 ◦ c. UV failed to inactivate virus after 90 min, also inactivation of virus using peroxide based new disinfectant within 24 hour.