Simultaneous detection of velogenic Newcastle disease virus of genotype XIII 2.2 from spot-billed pelican and backyard chicken: implications to the viral maintenance and spread.

Despite the widespread occurence of Newcastle disease virus (NDV) in different avian species, there has been scanty reports on genetic characterization of NDV strains from wild birds in India. During 2017-18, a total of forty eight cloacal swab samples were collected from apparently healthy migratory birds (painted storks, n = 32 and spot-billed pelicans, n = 16) at the Telineelapuram bird sanctuary of Andhra Pradesh, India. NDV was isolated from a spot-billed pelican (NDV/Pelican/Telineelapuram/2018) which is genetically identical to that isolated from a naturally infected backyard chicken flock (NDV/Chicken/SKLM-1/2018). The isolates are found to be velogenic based on mean death time, intracerebral pathogenicity index and the putative fusion protein cleavage site (112R-R-R-K-R-F117). Phylogenetic analysis based on full-length fusion gene classified the isolates into genotype XIII, sub-genotype 2.2, however these isolates demonstrated multiple amino acid substitutions in the critical domains of F and HN proteins. The pelican strain (MIG-9) was tested for its pathogenic and transmission potential in three-weeks-old broiler chickens and the isolate proved to be highly virulent to chickens. To the best of our knowledge, this is the first evidence for the role of spot-billed pelicans in the maintenance of virulent NDV and its transmission to chickens in India. This study further highlights the role of wild birds in NDV transmission and the need for enhanced biosecurity in commercial poultry operations. Keywords: Newcastle disease virus; Pelecanus philippensis; chicken; transmission; pathogenicity; India.