High genetic diversity of Newcastle disease virus in poultry in West and Central Africa: cocirculation of genotype XIV and newly defined genotypes XVII and XVIII

Molecular characterization of chicken-derived genotype VIId Newcastle disease virus isolates in China during 2005-2012 reveals a new length in hemagglutinin-neuraminidase

Newcastle disease (ND) is one of the most important diseases of poultry, and causes severe economic losses in the global poultry industry. Although all Newcastle disease virus (NDV) isolates belong to a single serotype, significant genetic diversity has been described between different NDV isolates. Here, we report the molecular characterization of 23 virulent genotype VIId NDV isolates of class II circulating in China. Phylogenetic construction and analysis revealed the existence of distinctly genomic and amino acid differences that clearly distinguished these isolates from other typical NDV genotypes and vaccine strains. We also report a new 582-amino-acid hemagglutinin-neuraminidase in genotype VII NDV strains. This is believed to be the first study to investigate systematically the most predominant NDV strains, and provides more information on the genetic nature of genotype VIId NDV of class II circulating in China.

Molecular characterization of Newcastle disease viruses isolated from rural chicken in northwest Ethiopia reveals the circulation of three distinct genotypes in the country

Newcastle disease (ND) is a highly contagious disease that affects many species of birds and causes significant economic losses to the poultry industry worldwide. Fifteen Newcastle disease virus (NDV) isolates obtained from rural chickens in northwest Ethiopia in 2011 and 2012 were characterized genotypically. The main functional region of the F gene was amplified and sequenced (260 nucleotides). Among the Ethiopian NDV isolates, 2 isolates had the virulent motif (112)R-R-Q-K-R-F(117) at the cleavage site of the fusion protein while 13 isolates contained the lentogenic motif (112)G-G/R-Q-G-R-L(117). Phylogenetic analysis based on the variable region of the F gene indicated that the two isolates exhibiting the virulent motif belonged to lineage 5 (genotype VII) subgenotype d and the remaining 13 isolates were grouped into lineage 2 (genotype II). The nucleotide sequences of lineage 5 isolates were genetically related to the Sudanese NDV isolates, suggesting potential epidemiological link of ND outbreaks between neighbouring countries. The lentogenic strains shared similarities with La Sota vaccine strain and probably originated from the vaccine strain either through direct exposure of birds to the live vaccine or to infectious La Sota-like strains circulating in rural poultry. This study provides genetic evidence on the existence of different NDV genotypes circulating in the rural poultry in Ethiopia. The virulent NDV continues to be a problem in poultry sector in Ethiopia, and their continuous circulation in rural and commercial poultry calls for improved surveillance and intensified vaccination and other control measures.

Genetic diversity of newcastle disease virus in wild birds and pigeons in West Africa

In West and Central Africa, virulent Newcastle disease virus (NDV) strains of the recently identified genotypes XIV, XVII, and XVIII are enzootic in poultry, representing a considerable threat to the sector. The increasing number of reports of virulent strains in wild birds at least in other parts of the world raised the question of a potential role of wild birds in the spread of virulent NDV in sub-Saharan Africa as well. We investigated 1,723 asymptomatic birds sampled at live-bird markets and sites important for wild-bird conservation in Nigeria and 19 sick or dead wild birds in Côte d'Ivoire for NDV class I and II. Typical avirulent wild-type genotype I strains were found in wild waterfowl in wetlands in northeastern Nigeria. They were unrelated to vaccine strains, and the involvement of inter- or intracontinental migratory birds in their circulation in the region is suggested. Phylogenetic analyses also revealed that genotype VI strains found in pigeons, including some putative new subgenotype VIh and VIi strains, were introduced on multiple separate occasions in Nigeria. A single virulent genotype XVIII strain was found in a dead wild bird in Côte d'Ivoire, probably as a result of spillover from sick poultry. In conclusion, screening of wild birds and pigeons for NDV revealed the presence a variety of virulent and avirulent strains in West Africa but did not provide strong evidence that wild birds play an important role in the spread of virulent strains in the region.

Phylogenetic characterization and virulence of two Newcastle disease viruses isolated from wild birds in China

Wild birds are considered as a natural reservoir of Newcastle disease virus (NDV). However, there is no information about genotype IX NDV from wild birds, especially from Columbiformes. In this study, two genotype IX NDV viruses were isolated from wild birds. One was from Eurasian Blackbird, while the other was from Spotted-necked dove. After purification by plaque technique, complete genomes of both viruses were sequenced. Phylogenetic analysis of partial fusion (F) gene and complete genome indicated both strains belonged to genotype IX. Based on intracerebral pathogenicity index (ICPI), the virus from Eurasian Blackbird was velogenic virus, while the strain from Spotted-necked dove was lentogenic virus. However, both strains showed one of velogenic cleavage sites. In addition, the strain from Eurasian Blackbird showed greater replication ability and generated larger fusion foci in vitro than that of strain from Spotted-necked dove. Comparing all the corresponding protein sequences of both strains, there were only 9 different amino acid residues between them. Furthermore, after analysis of these differences, the information about lentogenic NDV with multi-basic cleavage site was presented.