الفهرس 
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Abstract
Newcastle disease (ND) has been regarded as one of the most important devastating diseases of poultry industry because of its worldwide distribution and the severe economic losses in domestic poultry.
At the last years, there were several outbreaks in the vaccinated poultry flocks in spite of application of intensive vaccination programs. The definitely reason is unknown.
In atrial to investigate the genetic diversity of currently circulating viruses, forty five chicken flocks suspected to be infected with NDV in Sharkia Governorate were submitted for clinical, PM examination as well as virus isolation. RT-PCR and partial gene sequencing of M-F region were also carried out.
The examined birds showed respiratory signs in form of sneezing, coughing, nasal discharge or nervous signs which were manifested by torticollis, opisthotonos, leg paralysis and/or digestive troubles such as greenish diarrhea. Cyanosis of comb and wattles were observed. There are decreasing in egg production among layer flocks up to50%. The postmortem examination revealed several congestions (brain, trachea, liver and lungs), hemorrhages (proventriculus, intestine, cecal tonsils) and elliptical ulcer in the intestine also were observed. There were thickening in air sacs and greenish content in the intestine. The mortality rates were ranged from (8-70%).