Phylogenetic analysis of Newcastle disease viruses isolated from wild birds in the Poyang Lake region of China

The Genomic Evolution and the Transmission Dynamics of H6N2 Avian Influenza A Viruses in Southern China

In China, the broad prevalence of H6 subtype influenza viruses, increasingly detected in aquatic birds, promotes their exchange materials with other highly pathogenic human-infecting H5N1, H5N6, and H7N9 influenza viruses. Strikingly, some H6 subtype viruses can infect pigs, dogs, and humans, posing risks to public health. In this study, 9 H6N2 viruses recovered from waterfowl species in the Guangdong province of China in 2018 were isolated and sequenced. Phylogenetic analysis revealed that the genome sequences of these H6N2 viruses belonged to Group I, except for the NP gene in Group III. Coalescent analyses demonstrated that the reassortment of NA and NS genes have occurred in two independent clusters, suggesting H6 subtype viruses had been undergoing a complex reassortant. To examine the evolutionary dynamics and the dissemination of the H6 subtype viruses, a Bayesian stochastic search variable selection was performed for results showing higher viral migration rates between closer provinces, including Guangdong, Jiangxi, Guangxi, and Fujian. Notably, the transmission routes of the H6 subtype viruses were concentrated in Jiangxi Province, the most frequent location for input and output transmission and a region containing Poyang Lake, a well-known wintering site for migration birds. We also found that the aquatic birds, especially ducks, were the most common input source of the viral transmission. In addition, we also found that eight positively selected amino acid sites were identified in HA protein. Given their continuous dissemination and the broad prevalence of the H6 subtype influenza viruses, continued surveillance is warranted in the future.

Surveillance of Class I Newcastle Disease Virus at Live Bird Markets in China and Identification of Variants with Increased Virulence and Replication Capacity

In this study, 232 class I Newcastle disease viruses (NDVs) were identified from multiple bird species at nationwide live bird markets (LBMs) from 2017 to 2019 in China. Phylogenetic analysis indicated that all 232 isolates were clustered into genotype 1.1.2 of class I on the basis of the fusion (F) gene sequences, which were distinct from the genotypes identified in other countries. Most of the isolates (212/232) were shown to have the typical F gene molecular characteristics of class I NDVs, while a few (20/232) contained mutations at the site of the conventional start codon of the F gene, which resulted in open reading frames (ORFs) altered in length. The isolates with ACG, CTA, and ATA mutations showed different levels of increased virulence and replication capacity, suggesting that these viruses may be transitional types during the evolution of class I NDVs from avirulent to virulent. Further evaluation of biological characteristics with recombinant viruses obtained by reverse genetics demonstrated that the ATG located at genomic positions 4523 to 4525 was the authentic start codon in the F gene of class I NDV, and the specific ATA mutations which contributed to the expression of F protein on the surface of infected cells were the key determinants of increased replication capacity and virulence. Interestingly, the mutation at the corresponding site of genotype II LaSota of class II had no effects on the virulence and replication capacity in chickens. Our results suggest that the alteration of virulence and replication capacity caused by specific mutations in the F gene could be a specific characteristic of class I NDVs and indicate the possibility of the emergence of virulent NDVs due to the persistent circulation of class I NDVs. IMPORTANCE The available information on the distribution, genetic diversity, evolution, and biological characteristics of class I Newcastle disease viruses (NDVs) in domestic poultry is currently very limited. Here, identification of class I NDVs at nationwide live bird markets (LBMs) in China was performed and representative isolates were characterized. A widespread distribution of genotype 1.1.2 of class I NDVs was found in multiple bird species at LBMs in China. Though most isolates demonstrated typical molecular characteristics of class I NDVs, a few that contained specific mutations at the site of the conventional start codon of the fusion gene with increased virulence and replication capacity were identified for the first time. Our findings indicate that the virulence of class I NDVs could have evolved, and the widespread transmission and circulation of class I NDVs may represent a potential threat for disease outbreaks in poultry.

Comparison of the protective antigen variabilities of prevalent Newcastle disease viruses in response to homologous/heterologous genotype vaccines

The genotype VII Newcastle disease virus (NDV) vaccine has begun to replace the traditional genotype II NDV vaccine and is widely used in the commercial poultry of China. However, the effect of homologous and heterogeneous anti-NDV serum on the evolution of prevalent NDV is unknown. To understand the effect of genotype II and VII anti-NDV serum on the evolution of genotype VII NDV strains, ZJ1 (waterfowl origin) and CH/SD/2008/128 (ND128; chicken origin) were used for serial passage of 30 generations in DF-1 cells without anti-NDV serum or with genotype II and VII anti-NDV serum independently. The F and HN genes of the 2 viruses were amplified for the 10th, 20th, and 30th generations of each serial passage group and compared with their respective original viruses. We found that there was only one mutation at position 248 in the F gene of ZJ1 due to the serum pressure of genotype VII anti-NDV. Similarly, mutations at residue 527 of the F gene, and position 9 and 319 of the HN gene of ND128 were noted in both anti-NDV serum groups. The results show that the nonsynonymous (NS)-to-synonymous (S) ratio of the F gene of ZJ1 virus was 1.6, and for the HN gene, it was 2.5 in the anti-II serum group. In the anti-VII serum group, the NS/S ratio for the F gene was 2.1, and for the HN gene, it was 2.5. The NS/S ratio of the F gene of the ND128 virus was 0.8, and for the HN gene, it was 3 in the anti-II serum group. Furthermore, the NS/S ratio of the F gene was 0.8, and the HN gene was 2.3 in the anti-VII group. Taken together, our findings highlight that there was no significant difference in the variation of protective antigens in genotype VII NDV under the selection pressure of homologous and heterogeneous genotype NDV inactivated vaccines.

Phylogenetic relationship and genotype variation of six Newcastle disease viruses isolated from duck in Indonesia

Background and Aim:

Newcastle disease viruses (NDVs) are frequently acquired from all ages and types of bird species. In general, ducks are considered as potential reservoirs for different genotypes of NDV and are resistant even to velogenic NDV strains. This research was conducted to genotypically and phylogenetically characterize NDV isolates collected from unvaccinated ducks from Indonesia.

Materials and Methods:

A total of 200 samples were collected through cloacal swabs and were inoculated in the allantoic sacs of 8-day-old specific pathogen-free eggs. Hemagglutination (HA) activity was analyzed through a HA test, and isolated viruses were characterized by reverse transcription-polymerase chain reaction targeting the complete fusion (F)-gene of NDV using three primer sets. One primer set was specific for the F protein cleavage site sequences of velogenic, mesogenic, and lentogenic NDV strains.

Results:

The results demonstrated that three isolates (NDV/Duck/B104/19, NDV/Duck/B125/19, and NDV/Duck/BK43/19) belonged to genotype VII and one (NDV/Duck/TD19/19) to genotype VI. Other isolates (NDV/Duck/A74/19 and NDV/Duck/M147/19) belonged to genotype II Class II. Based on the F protein cleavage site and the pathogenicity tests, two isolates (NDV/Duck/B104/19 and NDV/Duck/B125/19) were categorized as velogenic viruses and four (NDV/Duck/BK43/19, NDV/Duck/TD19/19, NDV/Duck/A74/19, and NDV/Duck/M147/19) as lentogenic viruses.

Conclusion:

The results indicate that NDVs from unvaccinated ducks from Indonesia carry various genotypes and pathotypes of NDVs; therefore, these viruses are still circulating in the environment and might pose a risk of Newcastle disease outbreak.

Genomic and biological characteristics of Avian Orthoavulavirus-1 strains isolated from multiple wild birds and backyard chickens in Pakistan

Circulation of the dominant sub-genotype VII.2 of Avian Orthoavulavirus-1 (AOAV-1) is affecting multiple poultry and non-poultry avian species and causing significant economic losses to the poultry industry worldwide. In countries where ND is endemic, continuous monitoring and characterization of field strains are necessary. In this study, genetic characteristics of eleven AOAV-1 strains were analyzed isolated from wild birds including parakeets (n = 3), lovebird parrot (n = 1), pheasant (n = 1), peacock (n = 1), and backyard chickens (n = 5) during 2015-2016. Genetic characterization (genome size [15,192 nucleotides], the presence of typical cleavage site [^112-RRQKRF^-117]) and biological assessment (HA log 2⁷ to 2⁹ and intracerebral pathogenicity index [ICPI] value ranging from 1.50 to 1.86) showed virulent AOAV-1. Phylogenetic analysis showed that the studied isolates belonged to sub-genotype VII.2 and genetically very closely related (> 98.9%) to viruses repeatedly isolated (2011-2018) from commercial poultry. These findings provide evidence for the existence of epidemiological links between poultry and wild bird species in the region where the disease is prevalent. The deduced amino acid analysis revealed several substitutions in critical domains of fusion and hemagglutinin-neuraminidase genes. The pathogenesis and transmission potential of wild bird-origin AOAV-1 strain (AW-Pht/2015) was evaluated in 21-day-old chickens that showed the strain was highly virulent causing clinical signs and killed all chickens. High viral loads were detected in different organs of the infected chickens correlating with the severity of lesions developed. The continuous monitoring of AOAV-1 isolates in different species of birds will improve our knowledge of the evolution of these viruses, thereby preventing possible panzootic.

Molecular and virological characterization of the first poultry outbreaks of Genotype VII.2 velogenic avian orthoavulavirus type 1 (NDV) in North-West Europe, BeNeLux, 2018

After two decades free of Newcastle disease, Belgium encountered a velogenic avian orthoavulavirus type 1 epizootic in 2018. In Belgium, 20 cases were diagnosed, of which 15 occurred in hobby flocks, 2 in professional poultry flocks and 3 in poultry retailers. The disease also disseminated from Belgium towards the Grand Duchy of Luxembourg by trade. Independently, the virus was detected once in the Netherlands, almost simultaneously to the first Belgian detection. As such Newcastle disease emerged in the entire BeNeLux region. Both the polybasic sequence of the fusion gene cleavage site and the intracerebral pathotyping assay demonstrated the high pathogenicity of the strain. This paper represents the first notification of this specific VII.2 subgenotype in the North-West of Europe. Time-calibrated full genome phylogenetic analysis indicated the silent or unreported circulation of the virus prior to the emergence of three genetic clusters in the BeNeLux region without clear geographical or other epidemiological correlation. The Dutch strain appeared as an outgroup to the Belgian and Luxembourgian strains in the time-correlated genetic analysis and no epidemiological link could be identified between the Belgian and Dutch outbreaks. In contrast, both genetic and epidemiological outbreak investigation data linked the G.D. Luxembourg case to the Belgian outbreak. The genetic links between Belgian viruses from retailers and hobby flocks only partially correlated with epidemiological data. Two independent introductions into the professional poultry sector were identified, although their origin could not be determined. Animal experiments using 6-week- old specific pathogen-free chickens indicated a systemic infection and efficient transmission of the virus. The implementation of re-vaccination in the professional sector, affected hobby and retailers, as well as the restriction on assembly and increased biosecurity measures, possibly limited the epizootic and resulted in the disappearance of the virus. These findings emphasize the constant need for awareness and monitoring of notifiable viruses in the field.

Pathobiology of Avian avulavirus 1: special focus on waterfowl

Avian avulaviruses serotype 1 (abbreviated as APMV-1 for the historical name avian paramyxovirus 1) are capable of infecting a wide spectrum of avian species with variable clinical symptoms and outcomes. Ease of transmission has allowed the virus to spread worldwide with varying degrees of virulence depending upon the virus strain and host species. The emergence of new virulent genotypes from global epizootics, and the year-to-year genomic changes in low and high virulence APMV-1 imply that distinct genotypes of APMV-1 are simultaneously evolving at different geographic locations across the globe. This vast genomic diversity may be favoured by large variety of avian species susceptibility to APMV-1 infection, and by the availability of highly mobile wild birds. It has long been considered that waterfowls are not sensitive to APMV-1 and are unable to show any clinical signs, however, outbreaks from the 90's contradict these concepts. The APMV-1 isolates are increasingly reported from the waterfowl. Waterfowl have strong innate immune responses, which minimize the impact of virus infection, however, are unable to prevent the viral shedding. Numerous APMV-1 are carried by domestic waterfowl intermingling with terrestrial poultry. Therefore, commercial ducks and geese should be vaccinated against APMV-1 to minimize the virus shedding and for the prevention the transmission. Genetic diversity within APMV-1 demonstrates the need for continual monitoring of viral evolution and periodic updates of vaccine seed-strains to achieve efficient control and eradication of APMV-1 in waterfowls.

Molecular Characterization of Newcastle Disease Virus from Backyard Poultry Farms and Live Bird Markets in Kenya

Newcastle disease (ND) is a serious disease of poultry that causes significant economic losses. Despite rampant ND outbreaks that occur annually in Kenya, the information about the NDV circulating in Kenya is still scarce. We report the first countrywide study of NDV in Kenya. Our study is aimed at evaluating the genetic characteristics of Newcastle disease viruses obtained from backyard poultry in farms and live bird markets in different regions of Kenya. We sequenced and analyzed fusion (F) protein gene, including the cleavage site, of the obtained viruses. We aligned and compared study sequences with representative NDV of different genotypes from GenBank. The fusion protein cleavage site of all the study sequences had the motif 112RRQKRFV118 indicating their velogenic nature. Phylogenetic analysis revealed that the NDV from various sites in Kenya was highly similar genetically and that it clustered together with NDV of genotype V. The study samples were 96% similar to previous Ugandan and Kenyan viruses grouped in subgenotype Vd This study points to possible circulation of NDV of similar genetic characteristics between backyard poultry farms and live bird markets in Kenya. The study also suggests the possible spread of velogenic NDV between Kenya and Uganda possibly through cross-border live bird trade. Our study provides baseline information on the genetic characteristics of NDV circulating in the Kenyan poultry population. This highlights the need for the ND control programmes to place more stringent measures on cross-border trade of live bird markets and poultry products to prevent the introduction of new strains of NDV that would otherwise be more difficult to control.

Potential of genotype VII Newcastle disease viruses to cause differential infections in chickens and ducks

Newcastle disease (ND), caused by ND virus (NDV), is one of the most infectious and economically important diseases of the poultry industry worldwide. While infections are reported in a wide range of avian species, the pathogenicity of chicken-origin virulent NDV isolates in ducks remains elusive. In this study, two NDV strains were isolated and biologically and genetically characterized from an outbreak in chickens and apparently healthy ducks. Pathogenicity assessment indices, including the mean death time (MDT), intracerebral pathogenicity index (ICPI) and cleavage motifs in the fusion (F) protein, indicated that both isolates were velogenic in nature. While these isolates carried pathogenic characteristics, interestingly they showed differential pathogenicity in ducks. The chicken-origin isolate caused high (70%) mortality, whereas the duck-origin virus resulted in low (20%) mortality in 4-week-old ducks. Intriguingly, both isolates showed comparable disease pathologies in chickens. Full-genome sequence analysis showed that the virus genome contains 15 192 nucleotides and carried features that are characteristic of velogenic strains of NDV. A phylogenetic analysis revealed that both isolates clustered in class II and genotype VII. However, there were several mutations in the functionally important regions of the fusion (F) and haemagglutinin-neuraminidase (HN) proteins, which may be responsible for the differential pathogenicity of these viruses in ducks. In summary, these results suggest that NDV strains with the same genotype show differential pathogenicity in chickens and ducks. Furthermore, chicken-origin virulent NDVs are more pathogenic for ducks than duck-origin viruses. These findings propose a role for chickens in the evolution of viral pathogenicity and the potential genetic resistance of ducks to poultry viruses.

Molecular characterization of two novel sub-sublineages of pigeon paramyxovirus type 1 in China

Pigeon paramyxovirus type 1 (PPMV-1) infection is enzootic in pigeon flocks and poses a potential risk to the poultry industry in China. To gain insight into the biological characteristics and transmission routes of circulating PPMV-1 in pigeons, 13 PPMV-1 isolates from domestic pigeons isolated during 2011-2015 in Guangxi province, China, were characterized using a pathogenicity assessment and phylogenetic analysis. All PPMV-1 isolates were mesogenic or lentogenic strains and had a mean death time (MDT) in 9-day-old SPF chicken embryos and a intracerebral pathogenicity index (ICPI) values of 54-154 h and 0.00-0.90, respectively. Analysis of the F and HN gene sequences of the PPMV-1 isolates and the Newcastle Disease (ND) vaccine strain La Sota, revealed that the nucleotide sequence similarity of the F and HN genes were all < 85% between the PPMV-1 isolates and La Sota, significantly lower than those > 98% among the PPMV-1 isolates. The amino acids sequence of the F protein at the cleavage site of the 13 PPMV-1 isolates was ¹¹²RRQKR↓F¹¹⁷, characteristic of virulent Newcastle disease virus (NDV). All 13 isolates were classified as sublineage 4b by phylogenetic analysis and evolutionary distances, based on the F gene sequences. It was also found that the 13 isolates were divided into two novel sub-groups of sublineage 4b, sub-sublineages 4biig and 4biih. Since these two novel sub-sublineages had two different geographic sources, we speculated that they represent two different transmission routes of PPMV-1 in China. Phylogenetic analysis of these isolates will help to elucidate the sources of the transmission and evolution of PPMV-1 and may help to control PPMV-1 infection in the pigeon industry in China.

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.

Assessment of contemporary genetic diversity and inter-taxa/inter-region exchange of avian paramyxovirus serotype 1 in wild birds sampled in North America

BACKGROUND

Avian paramyxovirus serotype 1 (APMV-1) viruses are globally distributed, infect wild, peridomestic, and domestic birds, and sometimes lead to outbreaks of disease. Thus, the maintenance, evolution, and spread of APMV-1 viruses are relevant to avian health.

METHODS

In this study we sequenced the fusion gene from 58 APMV-1 isolates recovered from thirteen species of wild birds sampled throughout the USA during 2007-2014. We analyzed sequence information with previously reported data in order to assess contemporary genetic diversity and inter-taxa/inter-region exchange of APMV-1 in wild birds sampled in North America.

RESULTS

Our results suggest that wild birds maintain previously undescribed genetic diversity of APMV-1; however, such diversity is unlikely to be pathogenic to domestic poultry. Phylogenetic analyses revealed that APMV-1 diversity detected in wild birds of North America has been found in birds belonging to numerous taxonomic host orders and within hosts inhabiting multiple geographic regions suggesting some level of viral exchange. However, our results also provide statistical support for associations between phylogenetic tree topology and host taxonomic order/region of sample origin which supports restricted exchange among taxa and geographical regions of North America for some APMV-1 sub-genotypes.

CONCLUSIONS

We identify previously unrecognized genetic diversity of APMV-1 in wild birds in North America which is likely a function of continued viral evolution in reservoir hosts. We did not, however, find support for the emergence or maintenance of APMV-1 strains predicted to be pathogenic to poultry in wild birds of North America outside of the order Suliformes (i.e., cormorants). Furthermore, genetic evidence suggests that ecological drivers or other mechanisms may restrict viral exchange among taxa and regions of North America. Additional and more systematic sampling for APMV-1 in North America would likely provide further inference on viral dynamics for this infectious agent in wild bird populations.

Complete Genome Sequences of Two Subgenotype 1b Newcastle Disease Viruses Isolated from Sansui Sheldrake Ducks in Guizhou, China

Here, we report the complete genome sequences of two Newcastle disease viruses, Sheldrake duck/China/Guizhou/01/2016 and Sheldrake duck/China/Guizhou/02/2016, isolated from Sansui Sheldrake ducks in Guizhou Province, China. The genome of the isolates is 15,198 nucleotides in length. Phylogenetic analysis revealed that the isolates are clustered into subgenotype 1b in class I.

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.

Genetic characterization and evolutionary analysis of Newcastle disease virus isolated from domestic duck in South Korea

Domestic ducks are considered a potential reservoir of Newcastle disease virus. In the study, a Newcastle disease virus (NDV) isolated from a domestic duck during surveillance in South Korea was characterized. The complete genome of the NDV isolate was sequenced, and the phylogenetic relationship to reference strains was studied. Phylogenetic analysis revealed that the strain clustered in genotype I of Class II ND viruses, has highly phylogenetic similarity to NDV strains isolated from waterfowl in China, but was distant from the viruses isolated in chickens and vaccine strains used in South Korea. Pathogenicity experiment in chickens revealed it to be a lentogenic virus. The deduced amino acid sequence of the cleavage site of the fusion (F) protein confirmed that the isolate contained the avirulent motif (112)GKQGRL(117) at the cleavage site and caused no apparent disease in chickens and ducks. With phylogeographic analysis based on fusion gene, we estimate the origin of an ancestral virus of the isolate and its sister strain located in China around 1998. It highlights the need of continuous surveillance to enhance current understanding of the molecular epidemiology and evolution of the pathogenic strains.