Molecular Characterization and Pathology of Virulent Newcastle Disease Virus Isolated from Broiler Chickens in District Lahore, Pakistan

Abstract

Background: This study elucidated the molecular detection and pathological alterations in broiler chickens naturally infected with field circulating NDV strains along with their phylogenomic dynamics. Methods: Morbid tissue samples of diseased/dead chickens were collected from 100 poultry flocks presented to poultry disease diagnostic laboratories from September 2018 to August 2019. Samples were subjected to molecular detection of NDV along with phylogenetic analysis and subsequent gross and histopathological examination. Result: Based on RT-PCR results, the positivity of NDV was 04/100 (4%). Genetic analysis of the NDV Fusion (F) gene revealed 98.92% and 98.74% similarity with Iranian and Pakistani isolates, respectively. The evolutionary tree showed that present study isolates were placed in a clade belongs to genotype Vll sub-genotype i and l. Necropsy examinations revealed the petechial haemorrhages associated with multifocal necrosis in gastrointestinal and respiratory organs. Besides these pathological findings, amino acid sequence of F gene revealed that study isolates are having pathogenic potential similar to the velogenic strains of NDV. Based on all essential analyses, the present study concluded that the evolution and distribution of the Newcastle disease virus of various genotypes VIIi and VIIl in Pakistan are having significant pathogenic potential. Therefore, it emphasizes developing ND vaccine from indigenous strains for better protection of commercial poultry in Pakistan.