الفهرس 
Introduction
History of avian influenzaOnly 14 pages are availabe for public view
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Abstract
This thesis aimed to determine antibody response against AI H5 vaccines in the field, detection of MDAs in some of broiler and baladichicks,evaluate the influence of MDAs against H5N1 on the potency of different vaccination programs and to evaluate the potency of rHVT-H5 vaccine alone, killed vaccine (rg H5N3 Vietnam strain) alone and the potency of the combination between rHVT-H5 and killed vaccine. Todetermine antibody response against AI H5 vaccines in the field, 40 blood samples were collected from different vaccinated broiler and baladi farms, age of chicken, time and type of vaccine was recorded. Sera were harvested and tested by using HI test for the presence of AI H5 specific antibody. For detection of MDAs in one day old chicks 25 blood samples were collected from one day old chicks sera harvested and tested by HI test for the presence of MDAs.
Experimental trials were conducted to detect potency of different vaccination programs and also to detect effect of MDAs, 6 different groups from one day old chicks were conducted. group I vaccinated with rHVT-H5 alone at one day old, group II vaccinated with killed vaccine at 10 days old, group III vaccinated with rHVT-H5 at one day and killed vaccine at 10 day, group IV vaccinated with two doses of killed vaccine at 10 and 24 days old, group V vaccinated with killed vaccine at 21 days old and group VI served as unvaccinated control group. Blood samples were collected 1st, 2nd, 3rd, 4th, 5th, 6th WPV according to vaccination program and time of experimental trial and sera harvested and tested by HI test.
Broiler farms (47.6%)didn’t seroconvert upon vaccination (gave GMT ˂ 3) and only 23.8% gave GMT 25 (protective titer) and it appear in marketing age, in case of baladi farms 73.6% gave GMT ˂ 3 and only 0.05% (one farm) gave 25. Detection of MDAse in broiler chicks had showing that 75% of one day old chicks had HI titer ≥ 25 these moderate level can interfere with efficacy of vaccination with the killed vaccine.
Experimental trial showing that MDAs was 29in one day old chicks, its level decrease until the 3rd week of age and complete waning of MDAs occurred at 28 days old. MDAs appear to interfere with development of humoral immune response of the killed vaccine (identity 96.8 with the vaccine used in breeder chickens) when given at 10 day but it didn’t interfere with rHVT-H5 alone and the combination of rHVT-H5 and killed vaccine. rHVT-H5 with killed vaccine prime/boost showed the highest and fastest post vaccination humoral immune response, rHVT-H5 alone gave protective titer after the 4th week of age but the killed vaccine didn’t give protective titer until the end of the trial (45day).