الفهرس 
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Abstract
The aim of these study was Isolation of AIV and NDV from chickens broilers and layers ) in Damietta and Dakahlia province using embryonated chicken eggs. ,Identification of genome of viral isolates using qRT-PCR., Study the molecular epidemiology of the isolated AI & ND viruses based on sequencing of HA gene and F gene, respectively. , Investigation of pathogenesis of the field isolate (NDV GVII .1.1) in 4 weeks turkey poults by using QRT-PCR and histological examination. and evaluation the seroconversion rate in infected turkey poults by HI test . A total of 250 live and freshly dead chickens (5 birds from each flock) were collected from 50 flocks from Dakahlia and Damietta Provinces during 2019-2020, mainly broiler of different breeds [Arbor Acres (n:19); Ross (n: 9) and Cobb (n:7); and Sasso native breed (n: 8)] with different ages ranged from (24-42 days). Additionally, layer flocks (4 Hyline Brown and 3 Hisex) aged 200-300 days suspected to be infected with avian influenza and Newcastle viruses . The isolation of the suspected viruses were carried on ECE then HA test was done for identification of haemagglutinating viruses. The results revealed that 21 flocks (19 broilers (90.47%), 2 layers (9.52%) were positive HA after first ,2nd and 3rd passage in ECE.