Vol. 10, Special Issue 11 (2021)

Author(s):
Dr. Sangeeta Das, Dr. Pubaleem Deka, Dr. Pankaj Deka, Dr. Anu Malik, Dr. Taufique Ansari, Dr. Lewa Rapthap and Dr. Ritam Hazarika

Abstract:
Poultry sector is the sustainable means of livelihood in developing countries like India. The major obstacle for the poultry producers comes from infectious diseases. Newcastle Disease (ND) caused by a virulent strain of Avian orthoavulavirus 1 is the most economically important viral disease of poultry worldwide due to the substantial morbidity and mortality associated with it. This report describes an outbreak of an acute, highly lethal, ND in 3 weeks old age, vaccinated broiler chickens in a private broiler farm in Kamrup district, Assam. The farmer presented the infected and dead birds for diagnostic investigation. Ante mortem evaluation revealed severe neurologic signs, including tremors, ataxia, torticollis, and paralysis of wings and legs. Gross lesions included haemorrhagic intestinal lesions and characteristic haemorrhages at the proventriculus and in the caecal tonsils. The study aimed to isolate and identify Newcastle disease virus (NDV) by haemagglutination inhibition (HI) assay using NDV-specific hyperimmune serum and reverse transcription-polymerase chain reaction (RT-PCR) targeting Fusion (F) gene of NDV. Virus was isolated from samples of intestinal tissues, lungs, trachea and spleen in embryonated specific-pathogen-free (SPF) chicken eggs by allaontoic cavity route. The pathogenic evaluation of the isolated samples was determined on the basis of mean death time (MDT) in eggs and intracerebral pathogenicity test (ICPI) in day-old chicks. The suspected samples isolated in SPF chicken eggs were NDV positive in the haemagglutination assay. The virus was identified as NDV by the HI assay and RT-PCR of the isolate resulted in the amplification of 363 bp partial length F gene. Pathogenicity indices classified the NDV isolate as mesogenic strain. This study indicates that traditional NDV vaccines may not be sufficient to protect the birds against newly emerging virulent viruses, implying the requirement for a more efficient vaccine against virulent NDV infection.