Abstract
Newcastle disease virus (NDV) is an avian paramyxovirus that causes significant economic losses to the poultry industry in most parts of the world. The susceptibility of a wide variety of avian species coupled with synanthropic bird reservoirs has contributed to the vast genomic diversity of this virus as well as diagnostic failures. Since the first panzootic in 1926, Newcastle disease (ND) became enzootic in India with recurrent outbreaks in multiple avian species. The genetic characteristics of circulating strains in India, however, are largely unknown. To understand the nature of NDV genotypes in India, we characterized two representative strains isolated 13 years apart from a chicken and a pigeon by complete genome sequence analysis and pathotyping. The viruses were characterized as velogenic by pathogenicity indices devised to distinguish these strains. The genome length was 15,186 nucleotides (nt) and consisted of six non-overlapping genes, with conserved and complementary 3′ leader and 5′ trailer regions, conserved gene starts, gene stops, and intergenic sequences similar to those in avian paramyxovirus 1 (APMV-1) strains. Matrix gene sequence analysis grouped the pigeon isolate with APMV-1 strains. Phylogeny based on the fusion (F), and hemagglutinin (HN) genes and complete genome sequence grouped these viruses into genotype IV. Genotype IV strains are considered to have “died out” after the first panzootic (1926–1960) of ND. But, our results suggest that there is persistence of genotype IV strains in India.
Highlights
Newcastle disease (ND) is one of the most economically important and prevalent poultry diseases around the world
Residue substitution analysis indicated that the Indian strains exhibited a very low divergence (0 to 8.9%) with genotype IV viruses than genotype II vaccine strains across the coding regions of different proteins
The Indian strains clustered with genotype IV viruses (Herts’33 and Italien) when phylogenetic analysis was performed on 374 bp of the F gene or the full-length M gene or the complete genome, providing a strong evidence for the persistence of ‘genotype IV’ Newcastle disease virus (NDV) strains in India
Summary
Newcastle disease (ND) is one of the most economically important and prevalent poultry diseases around the world. Newcastle disease virus (NDV), the prototype avian paramyxovirus serotype 1 (APMV-1), belongs to the genus Avulavirus, in the family Paramyxoviridae and is the causative agent of ND [1]. NDV has a negative sense, single stranded RNA genome of approximately 15 kb that contains six genes in the order of 39-NP-P-MF.HN-L-59coding for the nucleocapsid protein (NP), phosphoprotein (P), matrix protein (M), fusion protein (F), an attachment protein, the haemagglutinin-neuraminidase (HN), and a large polymerase protein (L) [2]. APMV1 is considered to belong to single serotype, antigenic and genetic diversity have been recognized [6,7,9]. There are two different systems of classifying NDV genotypes based on the FPCS sequence with nominal discrepancies.
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