Advances in Animal and Veterinary Sciences

Research Article
Adv. Anim. Vet. Sci. 9(12): 2054-2061
Http://dx.doi.org/10.17582/journal.aavs/2021/9.12.2054.2061
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Mahmoud Fawzy, Manal Afify*, Youssef, I. Youssef

Department of Poultry Diseases, Faculty of Veterinary Medicine, Cairo University, 12211; Giza, Egypt

Abstract | Newcastle disease (ND) still threatening the poultry industry in Egypt despite stringent vaccination programs. This study was performed to evaluate the pathological lesions of Newcastle disease virus (NDV) genotype VIId in different organs of commercial layer chickens (ND antibodies-free). Therefore, forty, 1-day-old chicks were divided into 2 equal groups with 20 birds each. Group 1 served as the non-infected (negative control) group, while group 2 was infected at 28 days old by intranasal inoculation of 0.2 ml containing 106 EID50 of NDV genotype VII. Tissue samples from trachea, lung, spleen and liver were collected from dead infected chickens at 4 days post-infection (dpi) and 6 dpi for detection of NDV RNA by real time Polymerase chain reaction (rRT-PCR). Tissue sections from lung, trachea, spleen, liver and proventriculus from the infected group and non-infected group were collected for histopathology at 5 dpi. The clinical signs in infected group appeared at 3 dpi and lasted for the 6th dpi represented by obvious greenish droppings at 5th dpi, leg paralysis and torticollis at the 4th and 5th dpi. Mortality was 10, 6 and 3 birds at 4 dpi, 5 dpi and 6 dpi respectively in infected group with total mortality rate 95%. Grossly, enlarged mottled spleen, severe hemorrhages on the tips of periventricular glands, severe muscle congestion, hemorrhagic ulcers on cecal tonsils and severe congestion with hemorrhages on the thymus gland at 4th and 5th dpi. Detection of NDV nucleic acid by rRT-PCR revealed highest detection rate (80% and 100%) in respiratory tissues (pooled trachea and lung), moderate detection rate (60% and 66.7%) in spleen and lowest detection rate (30% and 33.3%) in liver at 4 dpi and 6 dpi respectively. Histopathological investigation of different organs revealed pneumonia, tracheitis, spleenitis with lymphoid depletion, hepatitis and moderate proventriculitis. We conclude that our velogenic Newcastle disease virus (vNDV) strain is viscerotropic neurotropic pathotype exhibited high morbidity and mortality rates (95%) associated with immunosuppression in infected layer chickens. Detection of NDV RNA by rRT-PCR in our infected chicken organs emphasizing tissue tropism and distribution of vNDV in different organs, also suggesting the use of rRT-PCR in detection of NDV infected organs. further periodical investigations are needed to evaluate vNDV pathogenesis in chickens with considering the virus distribution pattern in different tissues.
 
Keywords | Experimental infection, Genotype VII, Histopathology, NDV, rRT-PCR