الفهرس 
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Abstract
Avian influenza (AI) is an highly contagious notafiable disease of birds caused by the influenza virus type A that are members of the family Orthomyxoviridae affecting many variety of birds, mammals and man. The disease was first identified in Italy at 1878, after that time the disease was reported to be worldwide. AI causing significant economic losses all over the world. (OIE. 200) This present work aims to: Provide an actual picture about the endemic status of AI infection in Egyptian and how to control it through: 1- The isolation of local AIV isolates from the infected flocks.2- The identification and characterization of the AIV isolates. 3- Phylogenetic analysis of the isolated AI viruses 4- Comparative relatedness between the local field AIV isolates and the vaccinal strains contained in the different AI vaccines. 5- Evaluation the immune response of chickens vaccinated with avian influenza vaccines. 6- Studying the comparative efficacy of inactivated and recombinant of AI vaccines by using local classical and variant HPAI isolates as challenged virus. from this study, it was found that: 1) During the outbreaks of AI in Egypt since 2011 till 2013, large number of backyard chickens and ducks and broilers in the farm suffered from major clinical signs of AI outbreaks. The clinical examination was performed at the site which revealed early signals for presence of avian influenza virus.2) After preparation of collected samples and inoculated in SPF ECE, we found all isolates cause mortality for embryonated chicken eggs with a maximum time 48 hours and when tested collected AF by rapid HA test from died inoculated eggs all slides give positive haemagglutination. All isolates give positive results when tested by agar gel precipitation test. 3) from serological identification of isolates from 2011 to 2013 give positive results when tested with H5N1 and H5N2 antisera but give negative results with ND and EDS antisera. The results of HI test for different isolates D2296/ D, D2296/C, D2296/ B , D2296/E , D2296/F , D2296/G and D2296/H AIV groups with H5N1 antisera were 6, 8, 7, 7, 9, 8 and 8 log2 respectively, while, were5, 7, 6, 5, 7, 7, 6 and 7 log2 against H5N2 antisera, respectively4) The results of the HA titers for each AIV group were 7 ,8 ,6 ,7 ,8 ,7 and 6 for D2296/D, D2296/C, D2296/ B , D2296/E , D2296/F, D2296/G and D2296/H AIV groups, respectively. 5) The results of Titration of different isolates in Embryonated chicken eggs was expressed as EID50 and ranging from (109.6 to 1013.2) EID50 for all AI isolates. 6) The IVPI value of the different isolates of AIV ranged from 2.25 - 2.63. So, all of them considered to be a highly pathogenic AIV for chicken. 7) The results of genetic identification of all isolates from 2011 to 2013 by RT-PCR using set of primer specific for H5AI give positive reaction. 8) The phayelogenetic analysis and sequencing identity of the Egyptian AI isolates and different vaccinal strains was: a) It was found the isolates (D2296/2/C and D2296/2/D) from 2011 were identical with each other. These isolates fell into Egyptian group C cluster C reference strain which represented the classical 2.2.1 referenced AI stains.b) The isolates of 2012 (D2296/2/B and D2296/2/E) were also grouped together with Egyptian group C cluster C with about 97% identity with each other and ( 97%) identity with isolates from 2011.c) The isolates from 2013 (D2296/2/F, D2296/2/G and D2296/2/H) were divided into two groups, first group contain (D2296/2/F and D2296/2/G) which were 99% identity to each other and also related to group C cluster C of Egyptian referenced strain which also more identical to AI isolates from 2011 with 98% while The second group from isolates of 2013 (2296/2/H) were showed the closed relation to the group E cluster B reference AI strains which represent the variant 2.2.1.1 referenced AI stainsd) H5N1Egy/pr8-1 strain: A /chicken / Egypt /A-18-H / 09 was identical to the D2296/ C, D2296/D, D2296/ B , D2296/E , D2296/F , D2296/G and D2296/H AIV isolate by 93.2%, 93.2%, 92.7%, 94%, 92.7%, 92.7% and 95.3% respectively.e) The degree of identity between the D2296/ C, D2296/D, D2296/B , D2296/E , D2296/F , D2296/G and D2296/H AIV isolate and H5N2 strain: A / Chicken / Mexico / 232 / 94 were 74% ,74% ,75% ,75% ,75% ,74% and 75% respectively.f) The degree of identity between the H5 insert of rHVT vaccine (A/swan/Hungary/4999/2006) and D2296/C, D2296/D, D2296/D, D2296/E, D2296/F, D2296/G and D2296/H AIV isolate were 94.4%, 94.4%, 94.4%, 94.4%, 94%, 95.3% and 95.7% respectively.9) The results HI titre of different types of vaccine (inactivated H5N1 vaccine, inactivated H5N2 and rHVT-H5) were tested by using 2 local challenge isolates classical strain D2296/E AI, variant strain D2296/H AI isolates and homologous antigen. a) The mean HI titre of inactivated H5N1 vaccine when tested with homologous Ag is 8.6 but mean HI titre become lower when tested with classical D2296/E and variant D2296/H AI isolates were 5.14 and 5.5 respectively.b) The tested serum samples of vaccinated chickens with inactivated H5N2 vaccine gave mean HI titre 8.92, 1.92 and 1.18 when tested with homologous Ag, classical and variant AI isolates.c) The HI titre of serum from vaccinated chickens with rHVT-H5 was given low mean HI titer 6.04 and 5.84 when examined by classical D2296/E and variant D2296/H AI isolates. 10) 109.8 and 106.8 EID50 were the challenge dose for classical D2296/E and variant D2296/H AI isolate which used in challenge test for measuring protective efficacy of different vaccines. 11) The results of vaccinated chicken with inactivated H5N1, inactivated H5N2 and rHVT-H5 by using local field classical (D2966/E) and variant (D2296/G) AI isolates as challenge virus.a) The mean protection% of vaccinated chickens by inactivated H5N1 vaccine is 91.7% and 92.4% when challenging by classical D2296/E and variant D2296/H AI isolate respectively. While challenged chickens vaccinated with inactivated Mexican H5N2 vaccine were given mean protection% is 82.2% and 80.3% when challenged by classical and variant AI isolates respectively. b) Challenging for the vaccinated chickens with rHVT-H5 vaccine by D2296/E and D2296/G AI isolates were given mean protection% 89% and 88.5%.c) from The results , we found the protection efficacy of vaccinated chickens weren’t depend only on the type of challenge virus even classical or variant but also on the challenge dose of the virus and the quality of the vaccine used.