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.

Genetic characterization of pigeon- origin avian avulavirus-1 reveals unique substitutions in F and HN proteins.

Since decades, Newcastle disease (ND) has become endemic in the poultry population of the Indian subcontinent. ND is a highly contagious disease of poultry and other avian species. However, the genetic nature of ND viruses circulating in the rock pigeons is unraveled. The present investigation is a part of Newcastle disease virus (NDV) surveillance in wild birds. Two velogenic NDV strains could be isolated from apparently healthy rock pigeons, thus establishing the status of carrier/reservoir host. The fusion protein cleavage site in the fusion protein has multiple basic amino acid (RRRKRF) motifs similar to velogenic isolates. Phylogenetic analysis based on complete fusion gene sequences confirmed that the isolates belong to NDV sub genotype XIII 2.2. Further analysis revealed several amino acid substitutions in the hypervariable region, heptad repeat regions and neutralizing epitopes of the fusion protein and heptad repeat regions and antigenic sites of the hemagglutinin-neuraminidase (HN) protein that are critical for fusion. A unique D170A substitution in the neutralizing epitope is identified that is critical for structure and function of the fusion protein. Mutations within the virulence determinants including fusion (F) and HN, elucidate continuous evolution of the viruses among the rock pigeons. Accidental spillover of these mutated viruses into commercial poultry operations may result in disease outbreaks with economic breakdown.