الفهرس 
AbstractOnly 14 pages are availabe for public view
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Abstract
Seventy four chicken, turkey and pigeon flocks were investigated for the presence of NDV using RT-PCR F-protein gene assay, 26 flocks tested positive for NDV. As a preliminary step for the exclusion of lentogenic vaccinal strain positive RTPCR samples were tested by real time reverse transcriptase polymerase chain reaction (rRTPCR) using a probe specific to velogenic strains. Nineteen samples tested positive for vNDV while seven samples tested negative. Twelve samples out of the positive samples were isolated on SPF ECE from eight different Egyptian governorates. Partial sequencing of the F-Protein gene revealed that all isolated strain have multiple basic A.A at the F-Protein cleavage site possessing the velogenic motif (112.RRQKR*F.117). Phylogenetic analysis of the F-protein 375 b.p. hypervariable region (nt 47– 422), revealed that all isolates are belonging to genotype VIId with (99%-100%) amino acid identity matrix with the Israelian (Turkey-Israel-111-2011) and Chinese (Chicken-China-SDYT03-2011) strain, Genotype VII. Single pure NDV isolated strain was selected APMV1/chicken/EG-BH/POD.CU/2015 (EG.BH/2015) after testing negative for AI common gene, IB, and IBD virus. Titration of the selected strain reveals MDT of (44 hr.) and 107.5 ELD50/ 0.1 ml. In vivo vaccination protection study was done using different vaccination programs for protection against challenge with the locally isolated (EG.BH/2015). Commercial broiler chicks were divided in to 13 different vaccination groups including positive and negative non-vaccinated control groups. Results revealed that all groups showed 100% protection rate against mortality (except in groups no. VI, VII and XI), and the tracheal viral shedding was significantly decreased but not completely prevented in neither of the vaccinated groups. group no.1 and 2 were showing a significantly high mean HI titer than other groups and least viral shedding following infection, while groups no. 3, 7, and 11 are showing a significantly lower mean HI titer and protection rate than other groups. Possible causes of these results were discussed in details.