الفهرس 
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Abstract
The poultry industry in Egypt has been severely affected by continuous outbreaks of Avian influenza H5N1, 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 and in humans have failed despite increased biosecurity, quarantine and vaccination. Also, co-circulation of the AIV H5N1 and H9N2 in commercial chicken flocks in Egypt complicating the respiratory problems in affected flocks and poses concern for potential reassortment.
So epidemiological studies on AI viruses H5N1 and H9N2 subtypes in Alexandria and EL Behera governorates, Egypt from Dec. to Jan. 2015 were carried out. Sixty one poultry flocks including 50 broiler, 7 layer and 4 duck flocks were investigated through isolation of the virus in specific pathogen free (SPF) eggs and identification by hemagglutination test (HA) and RRT-PCR. Then partial sequencing of hemagglutinin (HA) gene of 4 H5N1 and 3 H9N2 selected isolates was done. Finally, three commercially available vaccines (H5N1, H5N2 inactivated oil emulsion vaccine and Vectormune AI® vectored one) were evaluated in commercial chicks. There were five groups, group1 vaccinated with (Vectormune AI®) alone; group 2 (Vectormune AI® & inactivated H5N2) group 3 (inactivated H5N2); group 4 (inactivated H5N1) and group 5 was kept as non vaccinated group.
The result revealed the following: H5N1 HPAIV was detected with a percentage of 12%, 28.6% and 50% in broiler, layer and duck flocks respectively with a total incidence of 16.4% in all species. While H9N2 LPAIV was recorded only in broiler flocks with a percentage of 12% and total incidence 9.8%.
Sequencing and phylogenetic tree of H5 gene showed that HA gene sequences belonged to highly diverse clade 2.2.1 virus while H9 AIV related to G1-like lineage circulating in Middle East.
The four isolates of H5N1 found to have amino acid sequence identity with each other ranging from 99.6 - 100% and in comparison to the original Egyptian strains from 2006 to 2008 was 95.8 - 97.3% and with other Egyptian strains from 2009 to 2014 was 96.5- 98.8%.
The three isolates of H9N2 were identical with each other by 97.2 - 98.3%. , with other Egyptian strains of 2011 - 2014 by 95.7 - 100%, while Hong Kong strains in 1997 were identical by 87.8 - 93.6% and Israel strains isolated in 2007 – 2011 were identical with the three isolates from 89.8% to 97.6%
Considering the result of the evaluation of the commercial vaccines against HPAIV H5N1 in the commercial chicks in the experimental trial, the clinical protection percent of group 1, 2, 3, 4 and 5 were 80%, 80%, 20%, 40% and zero% respectively.
The challenged groups 1 and 2 showed no clinical signs on survival birds while the other groups 3, 4 and 5 explained typical clinical signs and post mortem lesions of highly pathogenic avian influenza virus
Also, the first two groups have the highest HI titer and the lowest tracheal shedding at 2 and 5 dpi when compared with other groups. Experimentally the rHVT-H5 vaccine appeared very protective for commercial chickens when used in one day-old chickens alone and providing high level of protection with reduction of virus shedding, so it is recommended to be used in.