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 a Class I Newcastle disease virus strain isolated from a pigeon in China

Constant monitoring is performed to elucidate the role of natural hosts in the ecology of Newcastle disease virus (NDV). In this study, an NDV strain isolated from an asymptomatic pigeon was sequenced and analysed. Results showed that the full-length genomes of this isolate were 15,198 nucleotides with the gene order of 3'-NP-P-M-F-HN-L-5'. This NDV isolate was lentogenic, with an intracerebral pathogenicity index of 0.00 and a mean time of death more than 148 h. The isolate possessed a motif of -(112)E-R-Q-E-R-L(117)- at the F protein cleavage site. In addition, 7 and 13 amino acid substitutions were identified in the functional domains of fusion protein (F) and haemagglutinin-neuraminidase protein (HN) proteins, respectively. Analysis of the amino acids of neutralizing epitopes of F and HN proteins showed 3 and 10 amino acid substitutions, respectively, in the isolate. Phylogenetic analysis classified the isolate into genotype Ib in Class I. This isolate shared high homologies with the NDV strains isolated from wild birds and waterfowl in southern and eastern parts of China from 2005 to 2013. To our knowledge, this study is the first to report a NDV strain isolated from pigeon that belongs to genotype Ib in Class I, rather than to the traditional genotype VI or other sub-genotypes in Class II. This study provides information to elucidate the distribution and evolution of Class I viruses for further NDV prevention.

A robust and cost-effective approach to sequence and analyze complete genomes of small RNA viruses

Background

Next-generation sequencing (NGS) allows ultra-deep sequencing of nucleic acids. The use of sequence-independent amplification of viral nucleic acids without utilization of target-specific primers provides advantages over traditional sequencing methods and allows detection of unsuspected variants and co-infecting agents. However, NGS is not widely used for small RNA viruses because of incorrectly perceived cost estimates and inefficient utilization of freely available bioinformatics tools.

Methods

In this study, we have utilized NGS-based random sequencing of total RNA combined with barcode multiplexing of libraries to quickly, effectively and simultaneously characterize the genomic sequences of multiple avian paramyxoviruses. Thirty libraries were prepared from diagnostic samples amplified in allantoic fluids and their total RNAs were sequenced in a single flow cell on an Illumina MiSeq instrument. After digital normalization, data were assembled using the MIRA assembler within a customized workflow on the Galaxy platform.

Results

Twenty-eight avian paramyxovirus 1 (APMV-1), one APMV-13, four avian influenza and two infectious bronchitis virus complete or nearly complete genome sequences were obtained from the single run. The 29 avian paramyxovirus genomes displayed 99.6% mean coverage based on bases with Phred quality scores of 30 or more. The lower and upper quartiles of sample median depth per position for those 29 samples were 2984 and 6894, respectively, indicating coverage across samples sufficient for deep variant analysis. Sample processing and library preparation took approximately 25–30 h, the sequencing run took 39 h, and processing through the Galaxy workflow took approximately 2–3 h. The cost of all steps, excluding labor, was estimated to be 106 USD per sample.

Conclusions

This work describes an efficient multiplexing NGS approach, a detailed analysis workflow, and customized tools for the characterization of the genomes of RNA viruses. The combination of multiplexing NGS technology with the Galaxy workflow platform resulted in a fast, user-friendly, and cost-efficient protocol for the simultaneous characterization of multiple full-length viral genomes. Twenty-nine full-length or near-full-length APMV genomes with a high median depth were successfully sequenced out of 30 samples. The applied de novo assembly approach also allowed identification of mixed viral populations in some of the samples.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0741-5) contains supplementary material, which is available to authorized users.

Co-circulation of paramyxo- and influenza viruses in pigeons in Egypt

In recent years, avian influenza virus (AIV) and Newcastle disease virus (NDV) have caused large-scale outbreaks in many countries, including Egypt. The culling and vaccination strategies have failed to control both viruses in Egypt. In this study, we investigated the outbreaks of nervous manifestations and deaths in pigeons between 2013 and 2015. The H5N1 subtype of the highly pathogenic avian influenza virus and pigeon paramyxovirus-1, an antigenic variant of NDV, were found to be the cause; AIV and pigeon paramyxovirus-1 were isolated from 61.3% (19/31) and 67.8% (21/31) of tested pigeons, respectively. Co-infection with both viruses was detected in 51.6% of pigeons (16/31). The AIV sequences showed PQGEKRRKKR/GLF motif at the haemagglutinin gene cleavage site, which is typical of the highly pathogenic H5N1 subtype. The phylogenetic tree showed that the highly pathogenic avian influenza belonged to clade 2.2.1.2. The NDV sequences carried one of the three motifs, ¹¹²GKQGRL¹¹⁷, ¹¹²KRQKRF¹¹⁷ or ¹¹²RRQKRF¹¹⁷, at the fusion protein cleavage site and were classified as genotypes I, VI and II in NDV-class II, respectively. This indicated that different genotypes of NDV can circulate simultaneously among pigeons. Further analysis revealed the clustering of some sequences in sub-genotypes Ia and VIb.2. To the best of our knowledge, these sub-genotypes have not been previously reported from pigeons in Egypt. Our results should serve as a base for future studies on both viruses in Egypt.

Genotypic and pathogenic characterization of genotype VII Newcastle disease viruses isolated from commercial farms in Egypt and evaluation of heterologous antibody responses

Newcastle disease viruses (NDV) represent a major threat to poultry production worldwide. Recently in Egypt NDV circulated extensively, even in vaccinated farms. In the present study samples were collected from sixteen vaccinated broiler farms in animals exhibiting the typical gross lesions of NDV. Virus isolation and pathogenicity studies for positive samples were carried out in accordance to reference procedures and phylogenetic analysis was carried out based on partial sequences of the Fusion gene. Furthermore, in vivo investigation of the ability of heterologous antibody, induced by commercially available lentogenic strain-based vaccines, to efficiently reduce viral shedding was examined. Results revealed that all the sixteen farms were positive for the presence of NDV. Out of these fifteen were confirmed to due to velogenic viruses, based on a main death time (MDT) ≤ 48 hours and partial sequencing of the F gene that showed the presence of a polybasic amino acid motif. However, three patterns in the cleavage site of these velogenic viruses were identified in the present study. Phylogenetic analysis revealed that all fifteen isolates were clustered with class II genotype VIIb while the remaining isolate (B81) was class II genotype II. Results of the in vivo study revealed that adequate heterologous antibody levels, induced by the proposed vaccination program, sufficiently protected birds from morbidity and mortality. However, virus shedding was quantitatively affected in relation to the time of challenge after vaccination. Altogether, with an absence of vaccines able to induce homologous antibody to the presently circulating viruses, higher antibody levels, which depend on efficient and timely implementation of the vaccination program, are considered as highly important in relation to the reduction of virus shedding.

Genome-wide analysis reveals class and gene specific codon usage adaptation in avian paramyxoviruses 1

In order to characterize the evolutionary adaptations of avian paramyxovirus 1 (APMV-1) genomes, we have compared codon usage and codon adaptation indexes among groups of Newcastle disease viruses that differ in biological, ecological, and genetic characteristics. We have used available GenBank complete genome sequences, and compared codon usage of class I (CI-29 sequences containing 132,675 codons) and class II (CII-259 sequences containing 1,184,925 codons) APMV-1 genomes. We also compared available complete fusion protein gene sequences (CI-175 sequences containing 96,775 codons; CII-1166 sequences containing 644,798 codons). Adaptation to Gallus gallus was compared among the different classes of viruses, among different genomic regions based on transcriptional levels, or among the fusion gene. Interestingly, distinctive codon usage determined by differences in relative synonymous codon usage and by codon adaptation indexes was observed for the two APMV-1 classes and for different transcriptional regions within classes. Furthermore, differential use of the third codon position and preferential use of codon pairs were seen for the two different classes and for selected genotypes of class II despite the fact that there were no large differences in nucleotide composition. The data suggest that codon usage has changed significantly since the two APMV-1 classes diverged, however, these changes are not significantly pronounced among viruses of the same genotype, suggesting that codon adaptation in APMV-1 occurs through a slow evolutionary process.

Evidence of independent evolution of genotype XIII Newcastle disease viruses in India

Despite the prevalence of Newcastle disease virus (NDV) outbreaks in India through the decades, there has been little genetic characterisation of the virulent strains circulating in Northeast India. In 2014, a poultry farm in the Kamrup district of Assam reported an ND outbreak. In this study, genetic analysis and clinicopathological tests showed the virulent nature of the isolate Kamrup. Based on prudent classification criteria, the virulent strain Kamrup was found to be most closely related to members of genotype XIII of class II NDV. A phylogenetic analysis of NDV strains suggested three sub-genotypes: XIIIa, XIIIb and XIIIc. NDV strain Kamrup belonged to sub-genotype XIIIc. Sub-genotype XIIIc isolates were similar to the 1982 isolate from cockatoo and appeared to have evolved parallel to the preceding genotype XIII viruses circulating in India. The high genetic diversity and frequency of mutations observed in the envelope glycoproteins of strain Kamrup demonstrate the evolution of the pandemic genotype XIII NDV in India, which further undermines and complicates of NDV management in India.

Genome Sequence of a Virulent Genotype III Newcastle Disease Virus Isolated from Laying Ducks in China

Here, we report the complete genome sequence of a virulent Newcastle disease virus (NDV) strain HN1007, isolated from diseased duck flocks in Henan, China, in 2010. The isolate has a genome length of 15,186 nucleotides, and was classified as a member of genotype III of class II.

Genetic diversity of the genotype VII Newcastle disease virus: identification of a novel VIIj sub-genotype

Newcastle disease (ND) is a highly contagious disease of poultry caused by Newcastle disease virus (NDV). Multiple genotypes of NDV have been circulating worldwide and NDV is continuously evolving, resulting into more diversity. Of multiple viral genotypes, VII is particularly important given that it had been associated with most recent ND outbreaks worldwide. In this study, an epidemiological investigation performed in northeastern China during 2014-2015 showed that 11 genotype VII isolates amounted to 55 percent in a total number of NDV isolates. Therefore, to evaluate the genetic diversity worldwide and epidemiological distribution in China of genotype VII NDV, a phylogenetic analysis based on the 1255 complete F gene sequences showed that VII is the most predominant genotype worldwide. A further detailed characterization on genotype VII was conducted based on the 477 complete F gene sequences from 11 isolates and 466 reference viruses available in GenBank. The results demonstrated that VII can be further divided into 8 sub-genotypes (VIIb, VIId-VIIj), indicating its complex genetic diversity. It is worthy of note that the isolation rate of VIIj is increasing recently. It emphasizes the necessity to pay close attention to the epidemiological dynamic of genotype VII NDV and highlights the importance of vaccination program.

Detection of Inter-Lineage Natural Recombination in Avian Paramyxovirus Serotype 1 Using Simplified Deep Sequencing Platform

Newcastle disease virus (NDV) is a prototype member of avian paramyxovirus serotype 1 (APMV-1), which causes severe and contagious disease in the commercial poultry and wild birds. Despite extensive vaccination programs and other control measures, the disease remains endemic around the globe especially in Asia, Africa, and the Middle East. Being a single serotype, genotype II based vaccines remained most acceptable means of immunization. However, the evidence is emerging on failures of vaccines mainly due to evolving nature of the virus and higher genetic gaps between vaccine and field strains of APMV-1. Most of the epidemiological and genetic characterizations of APMVs are based on conventional methods, which are prone to mask the diverse population of viruses in complex samples. In this study, we report the application of a simple, robust, and less resource-demanding methodology for the whole genome sequencing of NDV, using next-generation sequencing (NGS) on the Illumina MiSeq platform. Using this platform, we sequenced full genomes of five virulent Malaysian NDV strains collected during 2004–2013. All isolates clustered within highly prevalent lineage 5 (specifically in lineage 5a); however, a significantly greater genetic divergence was observed in isolates collected from 2004 to 2011. Interestingly, genetic characterization of one isolate collected in 2013 (IBS025/13) shown natural recombination between lineage 2 and lineage 5. In the event of recombination, the isolate (IBS025/13) carried nucleocapsid protein consist of 55–1801 nucleotides (nts) and near-complete phosphoprotein (1804–3254 nts) genes of lineage 2 whereas surface glycoproteins (fusion, hemagglutinin-neuraminidase) and large polymerase of lineage 5. Additionally, the recombinant virus has a genome size of 15,186 nts which is characteristics for the old genotypes I–IV isolated from 1930 to 1960. Taken together, we report the occurrence of a natural recombination in circulating strains of NDV in commercial poultry using NGS methodology. These findings will not only highlight the potential of RNA viruses to evolve but also to consider the application of NGS in revealing the genetic diversity of these viruses in clinical materials. Factors that drive these evolutionary events and subsequent impact of these divergences on clinical outcome of the disease warrant future investigations.

Co-circulation of genetically distinct groups of avian paramyxovirus type 1 in pigeon Newcastle disease in Iran

Pigeons are considered as one of the major natural reservoirs in the epidemiology of Newcastle disease (ND). In this study, the partial sequence of fusion protein gene of 17 pigeon-origin ND viruses (NDVs) isolated during 2012-2013 in Iran was analysed. Since the studied isolates showed F0 protein cleavage sites compatible with velogenic NDVs, all were considered as virulent NDVs. Two isolates carried 112RRQKRF117 as the cleavage site motif, whereas the rest demonstrated 112KRQKRF117 motif which just recently has been reported among Iranian virulent NDVs. Phylogenetic analysis divided all these diverse isolates in two distinct clusters within class II genotype VI. Based on the partial fusion protein gene sequence, 15 out of 17 isolates showed the highest genetic identity to subgenotype VIb/2 and the other two isolates were placed in a distinct genetic group of genotype VI. Based on recent findings, at least two different sublineages of genotype VI are causing the ND outbreaks in the pigeon population and are circulating simultaneously along with virulent NDVs of genotype VII in various species in Iran. The continuing circulation of a diverse group of virulent NDVs as an enzootic in widespread species such as pigeon can cause outbreaks in commercial poultry flocks and also failure in controlling programmes. Therefore, the constant monitoring and awareness of the virus characteristics should be considered in controlling programmes against ND in Iran.

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

Over the years, Newcastle disease (ND) has defied all available control measures. The disease has remained at the forefront of infectious diseases afflicting poultry production after avian influenza. Despite the continuous global use of million doses of ND vaccine annually, the causative pathogen, avian paramyxovirus type 1 also known as Newcastle disease virus (NDV) has continued to evolve causing, even more, a threat not only to the unvaccinated but the vaccinated flocks inclusive. The disease has been well studied in the developed countries where the virus is found in circulation. However, limited information exists on the epizootiology and circulating genotypes of the virus in developing countries where the majority of the flocks are raised on the extensive management system. Identification of virulent NDV in apparently healthy free-range ducks in this system calls for concern and pragmatic approach to investigate factor(s) that favour the virus inhabiting the ducks without clinical manifestation of the disease. Recently, novel genotypes (XIV, XVII, and XVIII) with peculiarity to West and Central African countries have been discovered and due to lack or poor surveillance system possibility of hitherto unreported genotypes are likely. This review elucidates and discusses available literature on the diversity of the circulating NDV genotypes across the West Africa countries and the epizootiology (molecular) of the disease in Nigeria with the view of identifying gaps in knowledge that can assist in the development of effective vaccines and control strategies to combat the peril of the disease.

Genomic Characterizations of a Newcastle Disease Virus Isolated from Ducks in Live Bird Markets in China

One class I Newcastle disease virus (NDV), designated as duck/Guangxi/1261/2015 (GX1261), was isolated from asymptomatic ducks in live bird markets (LBM) from southern China during the national active surveillance for NDVs in 2015. The complete genome length of GX1261 isolate was 15,198 nucleotides with the gene order of 3'-NP-P-M-F-HN-L-5'. The motif at the cleavage site of F protein was 112ERQER/L117, which was typical of low virulence NDV. Several mutations were identified in the functional domains of F and HN proteins, including fusion peptide, heptad repeat region, transmembrane domains and neutralizing epitopes. Phylogenetic analysis based on the complete F gene revealed that the isolate was clustered into sub-genotype 1c in class I, and showed a high level of similarity with the strains isolated from waterfowl in the United States of America. This is the first report of this kind of virus in the mainland of China. These results demonstrated that GX1261-like viruses might exist in asymptomatic waterfowl, and remain undetected or unidentified. Thus, more investigation needs to be done in order to identify the source of the virus. This study revealed the genetic and phylogenetic characteristics of GX1261 isolate and could help us to better understand the epidemiological context of class I NDV in China.

COMPLETE GENOMIC SEQUENCE OF VIRULENT PIGEON PARAMYXOVIRUS IN LAUGHING DOVES (STREPTOPELIA SENEGALENSIS) IN KENYA

Following mass deaths of Laughing Doves (Streptopelia senegalensis) in different localities throughout Kenya, internal organs obtained during necropsy of two moribund birds were sampled and analyzed by next generation sequencing. We isolated the virulent strain of pigeon paramyxovirus type-1 (PPMV-1), PPMV1/Laughing Dove/Kenya/Isiolo/B2/2012, which had a characteristic fusion gene motif (110)GGRRQKRF(117). We obtained a partial full genome of 15,114 nucleotides. The phylogenetic relationship based on the fusion gene and genomic sequence grouped our isolate as class II genotype VI, a group of viruses commonly isolated from wild birds but potentially lethal to Chickens ( Gallus gallus domesticus ). The fusion gene isolate clustered with PPMV-I strains from pigeons (Columbidae) in Nigeria. The complete genome showed a basal and highly divergent lineage to American, European, and Asian strains, indicating a divergent evolutionary pathway. The isolated strain is highly virulent and apparently species-specific to Laughing Doves in Kenya. Risk of transmission of such a strain to poultry is potentially high whereas the cyclic epizootic in doves is a threat to conservation of wild Columbidae in Kenya.

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

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.

Newcastle Disease Viruses Causing Recent Outbreaks Worldwide Show Unexpectedly High Genetic Similarity to Historical Virulent Isolates from the 1940s

Virulent strains of Newcastle disease virus (NDV) cause Newcastle disease (ND), a devastating disease of poultry and wild birds. Phylogenetic analyses clearly distinguish historical isolates (obtained prior to 1960) from currently circulating viruses of class II genotypes V, VI, VII, and XII through XVIII. Here, partial and complete genomic sequences of recent virulent isolates of genotypes II and IX from China, Egypt, and India were found to be nearly identical to those of historical viruses isolated in the 1940s. Phylogenetic analysis, nucleotide distances, and rates of change demonstrate that these recent isolates have not evolved significantly from the most closely related ancestors from the 1940s. The low rates of change for these virulent viruses (7.05 × 10(-5) and 2.05 × 10(-5) per year, respectively) and the minimal genetic distances existing between these and historical viruses (0.3 to 1.2%) of the same genotypes indicate an unnatural origin. As with any other RNA virus, Newcastle disease virus is expected to evolve naturally; thus, these findings suggest that some recent field isolates should be excluded from evolutionary studies. Furthermore, phylogenetic analyses show that these recent virulent isolates are more closely related to virulent strains isolated during the 1940s, which have been and continue to be used in laboratory and experimental challenge studies. Since the preservation of viable viruses in the environment for over 6 decades is highly unlikely, it is possible that the source of some of the recent virulent viruses isolated from poultry and wild birds might be laboratory viruses.

Phylogenetic and Pathotypic Characterization of Newcastle Disease Viruses Circulating in South China and Transmission in Different Birds

Although Newcastle disease virus (NDV) with high pathogenicity has frequently been isolated in poultry in China since 1948, the mode of its transmission among avian species remains largely unknown. Given that various wild bird species have been implicated as sources of transmission, in this study we genotypically and pathotypically characterized 23 NDV isolates collected from chickens, ducks, and pigeons in live bird markets (LBMs) in South China as part of an H7N9 surveillance program during December 2013–February 2014. To simulate the natural transmission of different kinds of animals in LBMs, we selected three representative NDVs—namely, GM, YF18, and GZ289—isolated from different birds to evaluate the pathogenicity and transmission of the indicated viruses in chickens, ducks, and pigeons. Furthermore, to investigate the replication and shedding of NDV in poultry, we inoculated the chickens, ducks, and pigeons with 10⁶ EID₅₀ of each virus via intraocular and intranasal routes. Eight hour after infection, the naïve contact groups were housed with those inoculated with each of the viruses as a means to monitor contact transmission. Our results indicated that genetically diverse viruses circulate in LBMs in South China's Guangdong Province and that NDV from different birds have different tissue tropisms and host ranges when transmitted in different birds. We therefore propose the continuous epidemiological surveillance of LBMs to support the prevention of the spread of these viruses in different birds, especially chickens, and highlight the need for studies of the virus–host relationship.

Identification and Complete Genome Sequence Analysis of a Genotype XIV Newcastle Disease Virus from Nigeria

The first complete genome sequence of a strain of Newcastle disease virus (NDV) from genotype XIV is reported here. Strain duck/Nigeria/NG-695/KG.LOM.11-16/2009 was isolated from an apparently healthy domestic duck from a live bird market in Kogi State, Nigeria, in 2009. This strain is classified as a member of subgenotype XIVb of class II.

Molecular characterization and phylogenetic study of the fusion genes of Newcastle disease virus from the recent outbreaks in Ahvaz, Iran

Newcastle disease (ND) is an acute and highly contagious disease affecting many domestic and wild species of birds. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epizootic on the poultry industry. In this study, partial sequences of fusion genes of three Newcastle disease virus (NDV) isolates collected during 2013-14 outbreaks from the vaccinated commercial broiler chicken farms with high mortality around Ahvaz city (Southwest of Iran) were characterized. All three isolates showed the amino acid sequence 112RRQKRF117 at the C-terminus of the F2 protein and phenylalanine at the N-terminus of the F1 protein residue 117. These amino acid sequences were identical to a known virulent motif. The phylogenetic analysis revealed that the Iranian ND isolates in this study are closely related to the genotype VIId of class II NDV strains. Our results specified that there are velogenic NDV circulating in Ahvaz commercial broiler flocks and causing outbreaks in poultry industry.

Temporal, geographic, and host distribution of avian paramyxovirus 1 (Newcastle disease virus)

Newcastle disease is caused by virulent forms of avian paramyxovirus of serotype 1 (APMV-1) and has global economic importance. The disease reached panzootic proportions within two decades after first being identified in 1926 in the United Kingdom and Indonesia and still remains endemic in many countries across the world. Here we review information on the host, temporal, and geographic distribution of APMV-1 genetic diversity based on the evolutionary systematics of the complete coding region of the fusion gene. Strains of APMV-1 are phylogenetically separated into two classes (class I and class II) and further classified into genotypes based on genetic differences. Class I viruses are genetically less diverse, generally present in wild waterfowl, and are of low virulence. Class II viruses are genetically and phenotypically more diverse, frequently isolated from poultry with occasional spillovers into wild birds, and exhibit a wider range of virulence. Waterfowl, cormorants, and pigeons are natural reservoirs of all APMV-1 pathotypes, except viscerotropic velogenic viruses for which natural reservoirs have not been identified. Genotypes I and II within class II include isolates of high and low virulence, the latter often being used as vaccines. Viruses of genotypes III and IX that emerged decades ago are now isolated rarely, but may be found in domestic and wild birds in China. Containing only virulent viruses and responsible for the majority of recent outbreaks in poultry and wild birds, viruses from genotypes V, VI, and VII, are highly mobile and have been isolated on different continents. Conversely, virulent viruses of genotypes XI (Madagascar), XIII (mainly Southwest Asia), XVI (North America) and XIV, XVII and XVIII (Africa) appear to have a more limited geographic distribution and have been isolated predominantly from poultry.

High Genetic Diversity of Newcastle Disease Virus in Wild and Domestic Birds in Northeastern China from 2013 to 2015 Reveals Potential Epidemic Trends

Newcastle disease (ND), caused by the virulent Newcastle disease virus (NDV), is one of the most important viral diseases of birds globally, but little is currently known regarding enzootic trends of NDV in northeastern China, especially for class I viruses. Thus, we performed a surveillance study for NDV in northeastern China from 2013 to 2015. A total 755 samples from wild and domestic birds in wetlands and live bird markets (LBMs) were collected, and 10 isolates of NDV were identified. Genetic and phylogenetic analyses showed that five isolates from LBMs belong to class I subgenotype 1b, two (one from wild birds and one from LBMs) belong to the vaccine-like class II genotype II, and three (all from wild birds) belong to class II subgenotype Ib. Interestingly, the five class I isolates had epidemiological connections with viruses from southern, eastern, and southeastern China. Our findings, together with recent prevalence trends of class I and virulent class II NDV in China, suggest possible virus transmission between wild and domestic birds and the potential for an NDV epidemic in the future.

Isolation, Identification, and Sequencing of a Goose-Derived Newcastle Disease Virus and Determination of Its Pathogenicity

In August 2010, geese in the Meihekou area of Jilin province in China were found to be infected by a pathogen that caused a disease similar to Newcastle disease. To determine the causative agent of the infections, a virus was isolated from liver tissues of infected geese, followed by a pathogenicity determination. The isolated virus was named NDV/White Goose/China/Jilin(Meihekou)/MHK-1/2010. Specific primers were designed to amplify the whole genome of the MHK-1 virus, followed by sequencing and splicing of the entire genome. Sequencing and phylogenetic analysis of MHK-1 showed that the isolate was a virulent strain of Newcastle disease virus. The MHK-1 genome is 15,192 nucleotides long, and it belongs to the class II branch of Newcastle disease viruses, as evidenced by the amino acid sequence (112R-R-Q-K-R-F117) of the F protein. The hemagglutinin titer was 1:128 to 1:512. The chicken embryo mean death time, the intracerebral pathogenicity index, and the median lethal dose of chicken embryos of MHK-1 were 43 hr, 1.63, and 10(9)/ml, respectively, which revealed that the newly isolated MHK-1 strain is strongly pathogenic to geese.

An Epizootiological Report of the Re-emergence and Spread of a Lineage of Virulent Newcastle Disease Virus into Eastern Europe

A number of contemporary outbreaks of Newcastle disease (ND) in Israel, Turkey, Georgia and Bulgaria have all been caused by a very similar viruses related to lineage 5a (genotype VIIa). Comparison with published ND virus (NDV) sequences suggests that this virus strain originated in South-East Asia and on introduction has circulated widely in backyard poultry in the Middle East and into Eastern Europe. An intracerebral pathogenicity index of 1.9 was obtained for a representative isolate from Bulgaria. In addition, the International Reference Laboratory for ND has characterized a molecular epidemiologically linked virus that has been reported to have caused disease in well-vaccinated broiler chickens in Pakistan. In the 1990s, another strain from the 5a lineage NDV was introduced into Europe and spread across the continent causing numerous outbreaks up to 1999. Despite improved controls, including good diagnostic tests and widespread vaccination, in commercial poultry, the novel circulating NDV strains described here have been established widely in the region and represent an increased risk for similar disease outbreak events to reoccur within the EU.

Characterization and Sequencing of a Genotype VIId Newcastle Disease Virus Isolated from Laying Ducks in Jiangsu, China

We report here the complete genome sequence and biological characterization of a virulent Newcastle disease virus (NDV) strain, NDV/duck/Jiangsu/JSD0812/2008, isolated from laying ducks in Jiangsu Province, China. The genome is 15,192 nucleotides in length and is classified in subgenotype VIId of genotype VII, class II.

International Biological Engagement Programs Facilitate Newcastle Disease Epidemiological Studies

Infections of poultry species with virulent strains of Newcastle disease virus (NDV) cause Newcastle disease (ND), one of the most economically significant and devastating diseases for poultry producers worldwide. Biological engagement programs between the Southeast Poultry Research Laboratory (SEPRL) of the United States Department of Agriculture and laboratories from Russia, Pakistan, Ukraine, Kazakhstan, and Indonesia collectively have produced a better understanding of the genetic diversity and evolution of the viruses responsible for ND, which is crucial for the control of the disease. The data from Kazakhstan, Russia, and Ukraine identified possible migratory routes for birds that may carry both virulent NDV (vNDV) and NDV of low virulence into Europe. In addition, related NDV strains were isolated from wild birds in Ukraine and Nigeria, and from birds in continental USA, Alaska, Russia, and Japan, identifying wild birds as a possible mechanism of intercontinental spread of NDV of low virulence. More recently, the detection of new sub-genotypes of vNDV suggests that a new, fifth, panzootic of ND has already originated in Southeast Asia, extended to the Middle East, and is now entering into Eastern Europe. Despite expected challenges when multiple independent laboratories interact, many scientists from the collaborating countries have successfully been trained by SEPRL on molecular diagnostics, best laboratory practices, and critical biosecurity protocols, providing our partners the capacity to further train other employes and to identify locally the viruses that cause this OIE listed disease. These and other collaborations with partners in Mexico, Bulgaria, Israel, and Tanzania have allowed SEPRL scientists to engage in field studies, to elucidate more aspects of ND epidemiology in endemic countries, and to understand the challenges that the scientists and field veterinarians in these countries face on a daily basis. Finally, new viral characterization tools have been developed and are now available to the scientific community.

Characterization and Sequencing of a Genotype XII Newcastle Disease Virus Isolated from a Peacock (Pavo cristatus) in Peru

Here, we report the first complete sequence and biological characterization of a Newcastle disease virus (NDV) isolated from a peacock in South America (NDV/peacock/Peru/2011). This isolate, classified as genotype XII in class II, highlights the need for increased surveillance of noncommercial avian species.

Delayed Newcastle disease virus replication using RNA interference to target the nucleoprotein

Each year millions of chickens die from Newcastle disease virus (NDV) worldwide leading to severe economic and food losses. Current vaccination campaigns have limitations especially in developing countries, due to elevated costs, need of trained personnel for effective vaccine administration, and functional cold chain network to maintain vaccine viability. These problems have led to heightened interest in producing new antiviral strategies, such as RNA interference (RNAi). RNAi methodology is capable of substantially decreasing viral replication at a cellular level, both in vitro and in vivo. In this study, we utilize microRNA (miRNA)-expressing constructs (a type of RNA interference) in an attempt to target and knockdown five NDV structural RNAs for nucleoprotein (NP), phosphoprotein (P), matrix (M), fusion (F), and large (L) protein genes. Immortalized chicken embryo fibroblast cells (DF-1) that transiently expressed miRNA targeting NP mRNA, showed increased resistance to NDV-induced cytopathic effects, as determined by cell count, relative to the same cells expressing miRNA against alternative NDV proteins. Upon infection with NDV, DF-1 cells constitutively expressing the NP miRNA construct had improved cell survival up to 48 h post infection (h.p.i) and decreased viral yield up to 24 h.p.i. These results suggest that overexpression of the NP miRNA in cells and perhaps live animal may provide resistance to NDV.

An evolutionary insight into Newcastle disease viruses isolated in Antarctica

The disease caused by Newcastle disease virus (NDV) is a severe threat to the poultry industry worldwide. Recently, NDV has been isolated in the Antarctic region. Detailed studies on the mode of evolution of NDV strains isolated worldwide are relevant for our understanding of the evolutionary history of NDV. For this reason, we have performed Bayesian coalescent analysis of NDV strains isolated in Antarctica to study evolutionary rates, population dynamics, and patterns of evolution. Analysis of F protein cleavage-site sequences of NDV isolates from Antarctica suggested that these strains are lentogenic. Strains isolated in Antarctica and genotype I reference strain Ulster/67 diverged from ancestors that existed around 1958. The time of the most recent common ancestor (MRCA) was established to be around 1883 for all class II viruses. A mean rate of evolution of 1.78 × 10(-3) substitutions per site per year (s/s/y) was obtained for the F gene sequences of NDV strains examined in this study. A Bayesian skyline plot indicated a decline in NDV population size in the last 25 years. The results are discussed in terms of the possible role of Antarctica in emerging or re-emerging viruses and the evolution of NDV populations worldwide.

Genomic Characterizations of Six Pigeon Paramyxovirus Type 1 Viruses Isolated from Live Bird Markets in China during 2011 to 2013

The genomes of six pigeon paramyxovirus type 1 (PPMV-1) isolated from symptomless pigeons in live poultry markets during the national active surveillance from 2011 to 2013 were sequenced and analyzed in this study. The complete genome lengths of all isolates were 15,192 nucleotides with the gene order of 3’-NP-P-M-F-HN-L-5’. All isolates had the same motif of ¹¹²RRQKRF¹¹⁷ at the cleavage site of the fusion protein, which was typical of velogenic Newcastle disease virus (NDV). Several mutations were identified in the functional domains of F and HN proteins, including fusion peptide, heptad repeat region, transmembrane domains and neutralizing epitopes. Phylogenetic analysis based on sequences of complete genomes and six genes revealed that all isolates belonged to genotype VI in class II, but at least 2 sub-genotypes were identified. Most isolates were placed into sub-genotype VIb with the exception of pi/GX/1015/13, which was classified in sub-genotype VIa. The obvious antigenic difference between PPMV-1 isolates and La Sota strain was found based on the R-value calculated by cross hemagglutination inhibition (HI) assay. These results provided the evidence that PPMV-1 could be detected from healthy pigeons, and our study may be useful in designing vaccines used in pigeon, and developing molecular diagnostic tools to monitor and prevent future PPMV-1 outbreaks.

Molecular and antigenic characteristics of Newcastle disease virus isolates from domestic ducks in China

Newcastle disease (ND) is one of the most devastating diseases to the poultry industry. The causative agents of ND are virulent strains of Newcastle disease virus (NDV), which are members of the genus Avulavirus within the family Paramyxoviridae. Waterfowl, such as ducks and geese, are generally considered potential reservoirs of NDV and may show few or no clinical signs when infected with viruses that are obviously virulent in chickens. However, ND outbreaks in domestic waterfowl have been frequently reported in many countries in the past decade. In this study, 18 NDV strains isolated from domestic ducks in southern and eastern China, between 2005 and 2013, were genetically and phylogenetically characterized. The complete genomes of these strains were sequenced, and they exhibited genome sizes of 15,186 nucleotides (nt), 15,192 nt, and 15,198 nt, which follow the "rule of six" that is required for the replication of NDV strains. Based on the cleavage site of the F protein and pathogenicity tests in chickens, 17 of our NDV isolates were categorized as lentogenic viruses, and one was characterized as a velogenic virus. Phylogenetic analysis based on the partial sequences of the F gene and the complete genome sequences showed that there are at least four genotypes of NDV circulating in domestic ducks; GD1, AH224, and AH209 belong to genotypes VIId, Ib, and II of class II NDVs, respectively, and the remaining 15 isolates belong to genotype 1b of class I NDVs. Cross-reactive hemagglutination inhibition tests demonstrated that the antigenic relatedness between NDV strains may be associated with their genotypes, rather than their hosts. These results suggest that though those NDV isolates were from duck, they still don't form a phylogenetic group because they came from the same species; however, they may play an important role in promoting the evolution of NDVs.

Presence of virulent Newcastle disease virus in vaccinated chickens in farms in Pakistan

One year after a virulent Newcastle disease virus (vNDV) outbreak in Pakistan, the causative strain was present in vaccinated chickens of multiple farms despite the existence of high-average NDV-specific antibody titers (>4.75 log2). The data suggest a possible role of vaccinated birds as reservoirs of vNDV.

Identification of new sub-genotypes of virulent Newcastle disease virus with potential panzootic features

Virulent Newcastle disease virus (NDV) isolates from new sub-genotypes within genotype VII are rapidly spreading through Asia and the Middle East causing outbreaks of Newcastle disease (ND) characterized by significant illness and mortality in poultry, suggesting the existence of a fifth panzootic. These viruses, which belong to the new sub-genotypes VIIh and VIIi, have epizootic characteristics and do not appear to have originated directly from other genotype VII NDV isolates that are currently circulating elsewhere, but are related to the present and past Indonesian NDV viruses isolated from wild birds since the 80s. Viruses from sub-genotype VIIh were isolated in Indonesia (2009-2010), Malaysia (2011), China (2011), and Cambodia (2011-2012) and are closely related to the Indonesian NDV isolated in 2007, APMV1/Chicken/Karangasem, Indonesia (Bali-01)/2007. Since 2011 and during 2012 highly related NDV isolates from sub-genotype VIIi have been isolated from poultry production facilities and occasionally from pet birds, throughout Indonesia, Pakistan and Israel. In Pakistan, the viruses of sub-genotype VIIi have replaced NDV isolates of genotype XIII, which were commonly isolated in 2009-2011, and they have become the predominant sub-genotype causing ND outbreaks since 2012. In a similar fashion, the numbers of viruses of sub-genotype VIIi isolated in Israel increased in 2012, and isolates from this sub-genotype are now found more frequently than viruses from the previously predominant sub-genotypes VIId and VIIb, from 2009 to 2012. All NDV isolates of sub-genotype VIIi are approximately 99% identical to each other and are more closely related to Indonesian viruses isolated from 1983 through 1990 than to those of genotype VII, still circulating in the region. Similarly, in addition to the Pakistani NDV isolates of the original genotype XIII (now called sub-genotype XIIIa), there is an additional sub-genotype (XIIIb) that was initially detected in India and Iran. This sub-genotype also appears to have as an ancestor a NDV strain from an Indian cockatoo isolated in 1982. These data suggest the existence of a new panzootic composed of viruses of subgenotype VIIi and support our previous findings of co-evolution of multiple virulent NDV genotypes in unknown reservoirs, e.g. as recorded with the virulent NDV identified in Dominican Republic in 2008. The co-evolution of at least three different sub-genotypes reported here and the apparent close relationship of some of those genotypes from ND viruses isolated from wild birds, suggests that identifying wild life reservoirs may help predict new panzootics.

High pathogenicity and low genetic evolution of avian paramyxovirus type I (Newcastle disease virus) isolated from live bird markets in Uganda

Background

Newcastle disease is still a serious disease of poultry especially in backyard free-range production systems despite the availability of cross protective vaccines. Healthy-looking poultry from live bird markets have been suspected as a major source of disease spread although limited studies have been conducted to ascertain the presence of the virulent strains in the markets and to understand how they are related to outbreak strains.

Methods

This study evaluated the occurrence of Newcastle disease virus in samples collected from poultry in live bird markets across Uganda. The isolates were pathoyped using standard methods (mean death time (MDT), intracelebral pathogenicity index (ICPI), and sequencing of the fusion protein cleavage site motif) and also phylogenetically analysed after sequencing of the full fusion and hemagglutin-neuraminidase genes. The isolates were classified into genotypes and subgenotypes based on the full fusion protein gene classification system and compared with other strains in the region and world-wide.

Results

Virulent avian paramyxovirus type I (APMV-1) (Newcastle disease virus) was isolated in healthy-looking poultry in live bird markets. The viruses belonged to a new subgenotype, Vd, in genotype V, and clustered together with Tanzania and Kenya strains. They harbored low genetic diversity.

Conclusion

The occurrence of virulent AMPV-1 strains in live bird markets may serve as sources of Newcastle disease outbreaks in non-commercial farms.

Assessment of Preparation of Samples Under the Field Conditions and a Portable Real-Time RT-PCR Assay for the Rapid On-Site Detection of Newcastle Disease Virus

Newcastle disease virus (NDV), also known as virulent forms of avian paramyxovirus serotype 1 (AMPV-1), is the causative agent of Newcastle disease affecting many species of birds and causing heavy losses to the poultry industry worldwide. Early, rapid and sensitive detection of the viruses or the viral nucleic acids is very important for disease diagnosis and control. This study aimed to evaluate sample preparation under field conditions and the application of a real-time RT-PCR method in the portable T-COR4 platform for the rapid, on-site detection of NDV on a farm. In the laboratory setting, the portable real-time RT-PCR assay had a similar performance compared with that obtained with a larger, stationary Rotor Gene real-time thermocycler. In the field conditions, viral nucleic acids were manually extracted just outside of animal units with minimal equipment and real-time RT-PCR detection was performed with the portable thermocycler T-COR4 placed in a nearby room. The portable assay at the farm detected viral RNA in 15 samples and reached an agreement of 83% (39/47) when the same RNA preparations were tested in the Rotor Gene thermocycler under the laboratory setting. The results demonstrated the feasibility of performing field detection but also the need to improve and further simplify sample preparation procedures.

Effects of naturally occurring six- and twelve-nucleotide inserts on Newcastle disease virus replication and pathogenesis

Newcastle disease virus (NDV) isolates contain genomes of 15,186, 15,192 or 15,198 nucleotides (nt). The length differences reflect a 6-nt insert in the 5′ (downstream) non-translated region (NTR) of the N gene (15,192-nt genome) or a 12-nt insert in the ORF encoding the P and V proteins (causing a 4-amino acid insert; 15,198-nt genome). We evaluated the role of these inserts in the N and P genes on viral replication and pathogenicity by inserting them into genomes of two NDV strains that have natural genome lengths of 15,186 nt and represent two different pathotypes, namely the mesogenic strain Beaudette C (BC) and the velogenic strain GB Texas (GBT). Our results showed that the 6-nt and 12-nt inserts did not detectably affect N gene expression or P protein function. The inserts had no effect on the replication or virulence of the highly virulent GBT strain but showed modest degree of attenuation in mesogenic strain BC. We also deleted a naturally-occurring 6-nt insertion in the N gene from a highly virulent 15,192-nt genome-length virus, strain Banjarmasin. This resulted in reduced replication in vitro and reduced virulence in vivo. Thus, although these inserts had no evident effect on gene expression, protein function, or replication in vivo, they did affect virulence in two of the three tested strains.

Complete genome sequence of a velogenic newcastle disease virus isolated from an apparently healthy village chicken in South India

We report the complete genome sequence of a Newcastle disease virus (NDV) isolate, NDV-D1/1998, from an apparently healthy village chicken in South India. This class II, genotype II virus is 15,186 nucleotides in length with unique amino acid variations and was found to be a velogenic pathotype by standard pathogenicity tests.

Molecular and phylogenetic characterization based on the complete genome of a virulent pathotype of Newcastle disease virus isolated in the 1970s in Brazil

Newcastle disease (ND) is caused by the avian paramyxovirus type 1 (APMV-1) or Newcastle disease virus (NDV) that comprises a diverse group of viruses with a single-stranded, negative-sense RNA genome. ND is one of the most important diseases of chickens, because it severely affects poultry production worldwide. In the 1970s, outbreaks of virulent ND were recorded in Brazil, and the strain APMV-1/Chicken/Brazil/SJM/75 (SJM) of NDV was isolated. This strain was characterized as highly pathogenic for chickens but not pathogenic for other bird species. Here we present the complete genome of NDV strain SJM and investigate the phylogenetic relationships of this virus with other NDV strains in terms of genome and proteins composition, as well as characterizing its evolution process. The NDV strain SJM is categorized as a velogenic virus and the complete genome is 15,192 nucleotides in length, consisting of six genes in the order 3'-NP-P-M-F-HN-L-5'. The presence of the major pathogenic determinant of NDV strains ((112)R-R-Q-K-R↓F(117)) was identified in the Fusion protein of the NDV strain SJM. In addition, phylogenetic analysis classified the NDV strain SJM as a member of class II, genotype V, and indicates that this virus help us in the understanding of the evolutionary process of strains belonging to this genotype. This study contributes to the growing interest involving the characterization of NDV isolates to improve our current understanding about the epidemiology, surveillance and evolution of the pathogenic strains.

Characterization of complete genome sequence of genotype VI and VII velogenic Newcastle disease virus from Japan

The complete genome sequences of three strains of Newcastle disease virus (NDV) isolated from vaccinated commercial layer flocks in Japan in the span of three decades were characterized. All strains had genome lengths of 15,192 nucleotides consisting of six genes in the order of 3'-NP-P/V/W-M-F-HN-L-5'. The general genomic characteristics of the Japanese field strains were consistent with previously characterized class II NDV, except for those belonging to early genotypes (genotype I-IV), which lack the six nucleotide insertion at nucleotide positions 1,648-1,653 of the nucleoprotein (NP) gene. Phylogenetic analysis showed that the Japanese strains could be classified into genotypes VIc and VIIe using the complete genome sequence and the complete coding sequence of the fusion (F) gene according to the unified NDV classification system. Characterization of functional domains and neutralizing epitopes of the F and hemagglutinin-neuraminidase (HN) proteins of Japanese field strains revealed a total of 31 amino acid substitutions, as compared to vaccine strains Ishii and B1, which were widely used in Japan. Although virus neutralization (VN) test showed that poor flock immunity due to vaccination failure or partial and non-uniform immunization maybe the major factors involved in the mechanism of breakthrough infection of the Japanese field strains, approximately two to threefold decrease in the VN titers of the field NDV strains possessing a point mutation (E347K or E347G) at the linear epitope of the HN protein was observed, as compared to vaccine strain B1 and field strain 2440/69, which lack the point mutation. This study may be a useful reference in characterizing future ND outbreaks in vaccinated chickens and as a genetic map for future investigations regarding vaccine designs, reverse genetics systems, and development of molecular diagnostic tools to prevent future ND outbreaks in vaccinated poultry flocks.

Newcastle disease virus: current status and our understanding

Newcastle disease (ND) is one of the highly pathogenic viral diseases of avian species. ND is economically significant because of the huge mortality and morbidity associated with it. The disease is endemic in many third world countries where agriculture serves as the primary source of national income. Newcastle disease virus (NDV) belongs to the family Paramyxoviridae and is well characterized member among the avian paramyxovirus serotypes. In recent years, NDV has lured the virologists not only because of its pathogenic potential, but also for its oncolytic activity and its use as a vaccine vector for both humans and animals. The NDV based recombinant vaccine offers a pertinent choice for the construction of live attenuated vaccine due to its modular nature of transcription, minimum recombination frequency, and lack of DNA phase during replication. Our current understanding about the NDV biology is expanding rapidly because of the availability of modern molecular biology tools and high-throughput complete genome sequencing.

Separate evolution of virulent newcastle disease viruses from Mexico and Central America

An outbreak of Newcastle disease (ND) in poultry was reported in Belize in 2008. The characteristics of three virulent Newcastle disease virus (NDV) isolates from this outbreak (NDV-Belize-3/08, NDV-Belize-4/08, and NDV-Belize-12/08) were assessed by genomic analysis and by clinicopathological characterization in specific-pathogen-free (SPF) chickens. The results showed that all three strains belong to NDV genotype V and are virulent, as assessed by the intracerebral pathogenicity index and the polybasic amino acid sequence at the fusion protein cleavage site. In 4-week-old SPF chickens, NDV-Belize-3/08 behaved as a typical velogenic viscerotropic NDV strain, causing severe necrohemorrhagic lesions in the lymphoid organs, with systemic virus distribution. Phylogenetic analysis of multiple NDV genotype V representatives revealed that genotype V can be divided into three subgenotypes, namely, Va, Vb, and Vc, and that all tested Belizean isolates belong to subgenotype Vb. Furthermore, these isolates are nearly identical to a 2007 isolate from Honduras and appear to have evolved separately from other contemporary viruses circulating in Mexico, clustering into a new clade within NDV subgenotype Vb.

Pathologic characterization of genotypes XIV and XVII Newcastle disease viruses and efficacy of classical vaccination on specific pathogen-free birds

To characterize the clinicopathologic features of recently described genotypes of Newcastle disease virus (NDV), 1 representative strain of genotype XIV and 2 of genotype XVII, all isolated from West Africa, were used to infect groups of ten 4-week-old specific pathogen-free chickens. The pathobiology of these 3 strains was compared to a South African NDV strain classified within genotype VII. All chickens infected with the 4 viruses died or were euthanized by day 4 postinfection due to the severity of clinical signs. Gross and histologic lesions in all infected chickens included extensive necrosis of lymphoid tissues (thymus, spleen, bursa of Fabricius, cecal tonsils, gut-associated lymphoid tissue), gastrointestinal necrosis and hemorrhages, and severe hemorrhagic conjunctivitis. Immunohistochemical staining revealed systemic viral distribution, and the most intense staining was in the lymphoid organs. Results demonstrate that the 3 West African strains from the previously uncharacterized genotypes XIV and XVII are typical velogenic viscerotropic NDV strains with lesions similar to the South African strain. Under experimental conditions, QV4 and LaSota NDV vaccine strains successfully protected chickens from morbidity and mortality against the genotype VII and one genotype XVII NDV strain, with no significant differences in the amount of virus shed when 2 vaccine schemes were compared.