Pathological and Epidemiological Study on Newcastle Disease in Broiler Chicken Farms in Egypt between 2021-2022.

Newcastle disease virus (NDV) is an economic threat to the poultry industryworldwide. In this study, we aimed to investigate the incidence of NDV in the vaccinatedEgyptian poultry flocks through histopathological and molecular investigation. Onehundred and nine broiler chicken flocks were examined during the period from January2021 to December 2022from seven different Egyptian governorates (El-Beheira, ElFayoum, El-Gizza, El-Gharbia, El-Menofia, El-Qalyubia, and El-Sharqia). History, clinicalsigns, 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 tissuesfor Real-time polymerase chain reaction (RT-PCR). The most observed gross lesion in theexamined 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 concludethat NDV circulates in the vaccinated broiler flocks in Egypt. Therefore, reconsidering theimmune status, vaccination programs, and surveillance of newly emerged strains areessential to reduce the incidence of ND in Egypt.