Characterization of Newcastle disease virus isolates obtained from outbreak cases in commercial chickens and wild pigeons in Ethiopia.

Delesa Damena,Hassen Chaka,Alireza Heidari,Abera Kebede,Menbere Kidane,Redeat Belaineh,Alice Fusaro,Melaku Sombo

doi:10.1186/s40064-016-2114-8

Delesa Damena, Hassen Chaka + Show 6 more

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https://doi.org/10.1186/s40064-016-2114-8

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Newcastle disease (ND), caused by virulent avian paramyxovirus type 1, is one of the most important diseases responsible for devastating outbreaks in poultry flocks in Ethiopia. However, the information about genetic characteristics of the Newcastle disease viruses (NDVs) circulating in commercial chickens and wild birds is scarce. In this study, we characterized isolates obtained from ND suspected outbreaks during 2012–2014 from poultry farms (n = 8) and wild pigeons (n = 4). The NDVs isolated from pathological specimens, through inoculation in embryonated chicken eggs, were characterized biologically by conventional intracerebral pathogenicity indices (ICPI), and genetically on the basis of Phylogenic analysis of partial F-gene sequences (260 bp) encompassing the cleavage site. The ICPI values of isolates from chickens ranged from 0.9 to 1.8; whereas, the ICPI of pigeon isolates was 1.4. All isolates contained multiple basic amino acids at the deduced cleavage site of fusion protein, which is a typical feature of virulent viruses. Phylogenic analysis of the partial cleavage site of F-gene (260 bp) indicated that all the sequences of viruses obtained from pigeons were identical and clustered within the genotype VIh while the sequences of viruses obtained from chickens were clustered together within the genotype VIf. The similarity between the viruses obtained from chickens and those obtained from pigeons ranged from 82.5 to 85.6 %. This suggests that different sub genotypes of genotype VI are circulating in chicken and wild pigeon population in Ethiopia. This warrants further study to understand the role of wild birds in the epidemiology of NDV in Ethiopia and as well highlights the importance of continuous surveillances both in wild birds and domestic poultry.

Highlights

Newcastle disease (ND) is a highly contagious and devastating disease of poultry caused by the Newcastle disease virus (NDV) known as avian paramyxovirus type 1, (APMV-1)
All eight haemagglutinating isolates obtained from poultry farm outbreaks were identified as Newcastle disease virus that reacted with monospesific antiserum specific for avian paramyxovirus 1
The pathotype prediction according to the deduced amino acid sequence of the cleavage site of the fusion protein showed that, the pigeon isolates have sequence motifs SVGRRRKR*F and chicken isolates have sequence motifs SGGRRQKR*F and SGGRRRKR*F suggestive of virulent strains (Table 1)

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Introduction

Newcastle disease (ND) is a highly contagious and devastating disease of poultry caused by the Newcastle disease virus (NDV) known as avian paramyxovirus type 1, (APMV-1). It is classified under the genus Avulavirus of family Paramyxoviridae (Mayo 2002). NDV is an enveloped nonsegmented, single-stranded, negativesense RNA virus. Based on genomic size and the nucleotide sequences of F and L genes, NDVs can be categorized as class I or class II viruses. Class I NDVs are occasionally isolated from wild aquatic birds and domestic poultry and are mostly avirulent to chickens.

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