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Twenty five broiler chicks were 28days old, chicken were infected by oculonasal route each with of 106 EID50 of local identified NDV local isolate (NDV/chicken/EG-QU/ NRC/2015). Clinical signs begin at the 2 nd dpi and at the 3 rd dpi: marked depression with sleepy appearance, severe respiratory signs and marked decrease in feed intake, greenish lose dropping, beasty vent with greenish diarrhea, sudden high mortalities with death of 7birds in rate of 46.7%. At the 4 th and 5 th dpi same severe signs where greenish diarrhea was obvious with respiratory sounds were detected with death of 2birds (13.3%) in each. At 6 th dpi death of 1bird (6.67%). The morbidity rate was 14/15(93.3%). while mortalities reach 80% in 4days. Post mortem examination of dead chickens in the infected group showed congested muscles, dehydrated, anorexic bird, hemorrhages on the tips of periventricular glands, liver congestion, greenish intestinal contents, greenish content of proventriculus and gizzard, severe necrosis and ulceration on cecal tonsils, and catarrhal tracheitis. NDV cloacal shedding was detected in cloacal swabs from infected chickens at 3(66.7%), 7(100%) and 10(66.7%) dpi by RT-PCR. Histopathological examination reveals the detection of showing necrosis of intestinal villi, hemorrhage and lymphocytic infiltration in intestinal sections. Cecal tonsils showed lymphocytic necrosis with areas of hemorrhage. Trachea showing Necrosis of lamina epithelialis, edema and hemorrhage in submucosa. Severe hemorrhage with severe lymphocytic depletion in spleen. Conclusion: It can be concluded that the local identified NDV strain related to genotype VII is highly pathogenic to 28day old commercial broiler chickens

N ewcastle disease, caused by the Newcastle disease virus is a highly infectious disease affecting poultry and wild birds in the whole world. It has been known as the avian paramyxovirus type 1 (APMV-1) and classified in the family Paramyxoviridae, subfamily Avulavirinae, and genus Metaavulavirus (Seal et al., 2000). The NDV is a nonsegmented negative-sense RNA virus which encoding six proteins; nucleoprotein (NP), phosphoprotein (P), matrix (M), fusion (F), hemagglutinin-neuraminidase (HN), and large polymerase (L) of 15,186-15,198 nucleotides (Rima et al., 2019).Newcastle disease virus virulence is mainly determined by the cleavage site in the F protein, where the cleavage site motif 112 R/K-R-Q-R/K-R↓F 117 that is cleaved by a variety of proteases is indivative for velogenic and mesogenic strains of NDV resulting in systemic infection. While 112 G/E-K/ R-Q-G/E-R↓L 117 motif is cleaved by specific respiratory

The present study was conducted to investigate the pathogeneicity of Newcastle Disease Virus (NDV) genotype VII.1.1 "NDV-CHICKEN-EGY-ALEX-NRC-2020" strain in combination with Infectious Bursal Disease Virus (IBDV) "IBDV/Egypt/Qalubia/17" and/or some commercial immunostimulants (Lector ® and Orego ® ) in commercial broiler chickens. The pathogenicity studies parameters included the effects on protection, growth performance and clinico-pathological changes. The results indicated that, immunostimulants can keep maternal immunity longer where lector ® was the best; the decline in HI titers also indicates that bird groups not contract ND natural infection. The results of performance parameters after immunostimulants administration and challenged with IBDV at 14-days of age and NDV GenotypeVII.1.1 at 21-days of age in broiler chickens proved that administration of Lector ® and Orego ® solution had positive effect on average body weight gain and feed conversion rates than control non medicated groups; where the Lector medicated groups showed higher rates of average weight followed by Orego ® medicated groups. Regarding signs and mortality in infected groups IBD signs varied from mild in lector ® , moderate in Orego ® while sever signs were in non-medicated group. The mortalities began at 5 th day post-challenge (pch) in non-medicated groups with total 10-20%; while the mortalities in NDV began at 3 rd day pch in group non-medicated with 50% to reach 100% mortality rate in 7 th pch. At necropsy both IBD and NDV infection lesions were found in dead birds of all challenged groups. Chicken groups challenged by IBDV or NDV after treatment with Lector showed milder histopathological changes than Orego solution and non-treated groups showed the most sever lesions. Chicken groups challenged with both virulent IBDV and NDV either treatment with Lector ® or Orego ® solution or non-treated showed no marked difference in histopathological lesions. The results of total and differential leucocytes indicated that lector had a great high effect in WBCs levels specially lymphocytes and monocytes. In conclusion the used immunostimulants are of low value against IBD and ND virulent viruses challenge. In conclusion, is recommended to apply a strict hygienic measures and suitable vaccination programmes to protect chickens against both IBD and NDV infection as the current control and prevention regimes, including vaccines and vaccination protocol are not adequate against either single or mixed infection infections with IBD and/or ND.