Molecular Characterization of Velogenic Avian Avulavirus Type 1 Isolated from Apparently Healthy Emu Birds: Implications to Viral Maintenance and Spread

摘要

Background: Newcastle disease caused by Avian avulavirus type 1 (AAvV-1) is one of the dreadful diseases affecting poultry and other avian species. Wild birds and several domestic birds are recognized as reservoirs of AAvV-1 and probably contribute to the epidemiology of ND in the domesticated poultry. Hence, efforts have been made to understand the virulence and genetic nature of AAvV-1 isolates obtained from apparently healthy Emu birds. Methods: This study details characterization of a velogenic Emu/5 AAvV-1 isolate obtained from an asymptomatic emu flock. Full-length fusion gene was amplified and subsequent phylogenetic analysis was performed. Experimental inoculation of 3-week old chicken with the isolate resulted in virulent ND. Expression of cytokine mRNA levels in spleen of infected chicken at different time points correlated well with the clinical picture, gross and histopathological lesions. Result: To our knowledge this is the first evidence for the role of apparently healthy emu bird acting as a reservoir of velogenic AAvV-1 of subgenotype XIII 2.2 which proved to be highly virulent to chicken. This study further highlights the role of reservoir birds in AAvV-1 transmission and the need for adopting most realistic strategies in counteracting the disease.