Newcastle disease virus (NDV) is an economic threat to the poultry industry
worldwide. In this study, we aimed to investigate the incidence of NDV in the vaccinated
Egyptian poultry flocks through histopathological and molecular investigation. One
hundred and nine broiler chicken flocks were examined during the period from January
2021 to December 2022from seven different Egyptian governorates (El-Beheira, ElFayoum, El-Gizza, El-Gharbia, El-Menofia, El-Qalyubia, and El-Sharqia). History, clinical
signs, and gross examination of the affected flocks were recorded. Brain, nostril, trachea,
lung, heart, proventriculus, duodenum, liver, pancreas, thymus, spleen, bursa, cecal tonsil,
and kidney were collected for histopathological examination and only the tracheal tissues
for Real-time polymerase chain reaction (RT-PCR). The most observed gross lesion in the
examined samples was the hemorrhage in the proventriculus. Histopathologically,
cerebral spongiosis, brain vasculitis, rhinitis, tracheitis, pneumonia, pericarditis,
hemorrhage in the proventriculus, enteritis, perihepatitis, necrotizing pancreatitis,
lymphoid depletion of the immune organs, and proliferation of lymphoid tissue in kidney.
Furthermore, lymphoid proliferation was detected in the lung, proventriculus, and liver.
From the examined samples, only forty- three samples were found to be positive by RTPCR, which represented 39.5% of the total samples. From our results, we can conclude
that NDV circulates in the vaccinated broiler flocks in Egypt. Therefore, reconsidering the
immune status, vaccination programs, and surveillance of newly emerged strains are
essential to reduce the incidence of ND in Egypt.