الفهرس 
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Abstract
Newcastle disease causes substantial economic losses and is a perpetual threat to poultry species in Egypt and all over the world. Prevention and control of the disease require much effort and cost for biosafety and vaccination regimes. Continuous evaluation (characterization) of the causative agent is an urgent demand for controlling ND. Limited data indicates the clinico-pathological features of NDV infection in quails as compared to conventional poultry species. The present study aimed to investigate the natural occurrence and pathological characterizations of ND in quails in Egypt.
Diseased quails represented eleven flocks in Egypt were exhibited mild respiratory signs including coughing and sneezing, nervous signs in the form of torticollis and opisthotonous, and digestive disorders in the form of whitish green diarrhea. The morbidity rate and the mortality rate were less than 1%. To our knowledge, our work is one of the first in Egypt illustrating that the infected quails with ND showed a decrease in egg production and hatchability of up to 25%, besides egg deterioration, including thin-shelled, easily broken eggs and loss of pigmentation. The post mortem examination revealed several congestions (brain, liver, spleen, and muscles), an over-distended gall bladder, and greenish content in the gizzard.
Virus isolation via inoculation of pooled samples from quails (liver, brain, trachea, lung, and spleen) for three successive passages in SPF-ECEs revealed that 7 of 11 samples were positive for HA. The allantoic fluids were examined by a HIT, revealed 5/11 (45.4%) confirmed positive results against specific NDV antiserum. The dead embryos showed hemorrhage, congestion, and dwarfism.