الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In the present study, twenty five tracheal and lung samples were collected and prepared then subjected for PCR, egg inoculation, IHC and indirect IF. Other tissue specimens(trachea, lungs, kidneys, liver, spleen) were collected then immediately fixed in 10% neutral buffered formalin for routine histopathology. selected formalin fixed tissue specimens were used for identification of viral antigens in tissues by AB- IP and indirect IF from positively infected chickens by polymerase chain reaction of IBV, H9AI and ILTV in recent outbreaks of respiratory diseases in broiler chicken in Dakhlia province during 2010 until 2014.The obtained results as follows:1-Infectious bronchitis10 samples which were positive by RRT-PCR. Two screened positive samples were amplified by RRT-PCR using specific primers for S1 gene, a segment of 400-bp was obtained. The nucleotide and deduced amino acid sequences were determined and compared among each other and with other IBV strains published in the GenBank database including vaccinal strains used in Egypt, these samples were very close to IBV-IS-1494-06. Microscopic examination of the tracheal tissues revealed deciliation, epithelial and glandular desquamation tracheitis, extensive degeneration and necrosis of the ciliated epithelial cells, infiltration of lymphocytes and heterophils, congestion and edema. 2-Avian influenza H9 Four samples from 25 were positive by RRT-PCR. One screened positive sample was amplified by RRT-PCR . this sample were grouped in Quail/Hong Kong/G1/97 lineage - strains. Microscopic examination of the tracheal tissues revealed necrosis and desquamation of the epithelial lining trachea with infiltration of lymphocytes in mucosa and edema in submucosa. Lungs showed accumulation of pale bluish mucus and heterophils in lumen of secondary bronchioles with congestion of pulmonary bloods vessels and perivascular hemorrhage.3- infectious laryngotracheitis Eleven samples showed amplification of 647 bp of ICP4 gene of ILTV. Both samples were very closely related to vaccinal strains. Microscopic examination of the tracheal tissues revealed loss of trachea lining epithelium with the presence of hemorrhagic exudate in lumen besides congestion in lamina propria and intense infiltration were seen.