Abstract
Epidemiological studies on AI viruses H5N1 and H9N2 subtypes in Alexandria and EL Behera governorates in Egypt during late 2013 to 2015 were carried out. Sixty one poultry flocks were investigated through isolation in specific pathogen free (SPF) eggs and identification by hemagglutination test (HA) and RRT-PCR, followed by partial sequencing of hemagglutinin (HA) gene of 4 H5N1 and 3 H9N2 selected isolates. moreover, three commercially available vaccines (H5N1, H5N2 inactivated oil emulsion vaccine and rHVT–H5 vectored one) were evaluated in commercial chicks. There were five groups, group1 vaccinated with (rHVT–H5) alone; group 2 (rHVT–H5 & inactivated H5N2) group 3 (inactivated H5N2); group 4 (inactivated H5N1) and group 5 was kept as positive control group. The data revealed the following: H5N1 HPAIV was detected with a percentage of 12%, 28.5% and 50% in broiler, layer and duck flocks respectively with a total percentage of 12% in all species. While H9N2 LPAIV was recorded only in broiler flocks with a percentage of 12% and total percentage 10%. Sequencing and phylogenetic tree of H5 gene showed that HA gene sequences belonged to highly diverse clade 2.2.1 virus while that of H9 related to G1-like lineage circulating in Middle East. Considering the result of the experimental trial the clinical protection percent of group 1, 2, 3, 4 and 5 were 80%, 80%, 20%, 40% and zero% respectively, in addition to the first two groups have the higest HI titre and the lowest tracheal sheding at 5 dpi when compared with other groups. 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 continuous surveillance for avian influenza viruses is important. 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 areas with high infection pressure for optimal protection.

Key words: AI viruses - H5N1 - H9N2 - inactivated oil emulsion vaccine- rHVT–H5 vectored vaccine