Phylogenetic and Pathotypic Characterization of Newcastle Disease Viruses Circulating in West Africa and Efficacy of a Current Vaccine

Abstract

e Newcastle disease (ND) is a deadly avian disease worldwide. In Africa, ND is enzootic and causes large economic losses, but little is known about the Newcastle disease virus (NDV) strains circulating in African countries. In this study, 27 NDV isolates collected from apparently healthy chickens in live-bird markets of the West African countries Benin and Togo in 2009 were characterized. All isolates had polybasic fusion (F)-protein cleavage sites and were shown to be highly virulent in standard pathogenicity assays. Infection of 2-week-old chickens with two of the isolates resulted in 100% mortality within 4 days. Phylogenetic analysis of the 27 isolates based on a partial F-protein gene sequence identified three clusters: one containing all the isolates from Togo and one from Benin (cluster 2), one containing most isolates from Benin (cluster 3), and an outlier isolate from Benin (cluster 1). All the three clusters are related to genotype VII strains of NDV. In addition, the cluster of viruses from Togo contained a recently identified 6-nucleotide insert between the hemagglutinin-neuraminidase (HN) and large polymerase (L) genes in a complete genome of an NDV isolate from this geographical region. Multiple strains that include this novel element suggest local emergence of a new genome length class. These results reveal genetic diversity within and among local NDV populations in Africa. Sequence analysis showed that the F and HN proteins of six West African isolates share 83.2 to 86.6% and 86.5 to 87.9% identities, respectively, with vaccine strain LaSota, indicative of considerable diversity. A vaccine efficacy study showed that the LaSota vaccine protected birds from morbidity and mortality but did not prevent shedding of West African challenge viruses.

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

“…2A). Thirty-three strains from Nigeria (Sokoto, Yobe, and Benue States;, 2009 sequenced in this study clustered in subgenotype XIVb (previously named 5f [35], 7d [36], or cluster number 1 [29]; see Table S4) (Fig. 2B).…”

“…In addition, the phylogenetic grouping of recent strains from West Africa was not clear. Based on partial F sequences, they were either classified as three new sublineages of lineage 5 (19), three clusters in genotype VII (29), or as a new lineage, 7, with four sublineages (20). With the additional genetic information provided by 96 new complete F gene sequences from West and Central Africa generated in this study, we revisited all full-length F gene sequences and updated the recent classification based on objective criteria proposed by Diel and coworkers (9).…”

“…Based on the analysis of all complete F gene sequences, genotype XVII was divided into two subgenotypes, XVIIa and XVIIb. Subgenotype XVIIa (previously sublineage 5g [19], 7a [36], 7b [20], or cluster number 3 [29]; see Table S4 in the supplemental material) was geographically the most dispersed, as it was found in Nigeria, Côte d'Ivoire, Niger, Cameroon, and Burkina Faso in 2008, in Benin in 2009, and in Mali in 2008 (Fig. 2B).…”

Newcastle disease in Nigeria: epizootiology and current knowledge of circulating genotypes

“…The current vaccination program in Nigeria and the sub-region at large needs to be reviewed to accommodate the current circulating genotypes. Though, few studies have been carried out to assess the protection level of the currently circulating NDV genotypes (XIV and XVII) [94,104] with the exception of genotype XVIII against Lasota and V4 vaccine strains. The vaccination regimen in Nigeria includes the use of Komarov (Table 1) for the initially primed chicks at 7-10 weeks of age.…”

“…The none detection of this genotype could be as a result of poor surveillance system which exists in Nigeria as well as the sub-region as a whole. Initially, due to the genetic relatedness of the currently circulating genotypes indigenous to West Africa, earlier studies on NDV genotyping in West Africa, grouped the viruses to lineage 5 and 7 (genotype XIV and VII) [19,94,99]. The classification was later streamlined to genotypes XIV, XVII, and XVII with the existence of the unified nomenclature for the classification of NDV as proposed by Diel et al [25] and expanded by Snoeck et al [101].…”