Intracerebral Pathogenicity Index Research Articles

Biological Pathotyping of Newcastle Disease Viruses in Sudan 2008-2013.

The biological properties and pathogenicity of seven Newcastle disease virus field isolates were studied. These isolates were recovered from different outbreaks in Sudan (5 from chickens and 2 from pigeons) during 2008–2013. Based on intracerebral pathogenicity index, four NDV isolates were characterized as velogenic (their ICPI ranged 2.0–1.6) and three isolates were characterized as mesogenic (ICPI ranged 1.2–1.3). The mean death time for all isolates ranged from 54 to 76.8 hours. The elution time of the viruses from chicken erythrocytes and the ability to haemagglutinate mammalian red blood cells differed considerably in their reactions.

Pathotypic and Sequence Characterization of Newcastle Disease Viruses from Vaccinated Chickens Reveals Circulation of Genotype II, IV and XIII and in India.

Newcastle disease virus (NDV) causes a highly contagious disease which continuously haunts the global poultry industry. The nature and molecular epidemiology of NDVs prevalent in recent outbreaks in India is poorly understood. This study aimed to characterize NDVs prevalent in vaccinated flocks in India using whole-genome sequencing and biological pathotyping. Twelve field isolates were collected from outbreaks which occurred in different parts of India and characterized as velogenic based on their intracerebral pathogenicity index (ICPI) and amino acid sequence at the F protein cleavage site. All 12 of the field isolates and five commonly used vaccine strains were selected for whole-genome sequencing using Ion Torrent PGM technology, yielding complete genome sequences for ten field isolates and all vaccine strains. The genome of all isolates was found to be 15192 nt long with a high level of conservation across multiple genomic features with APMV-I viruses. Phylogenetic analysis and evolutionary distance calculations placed the isolates in genotypes II, IV and XIII. Revisiting other recently reported strains provided preliminary evidence of genotypes VI, VII and XVIII circulating in India. Comparison between the field and vaccine virus sequences revealed unique genomic and amino acid differences in important antigenic regions of the F and hemagglutinin-neuraminidase (HN) genes which can be targeted for site directed mutagenesis to evaluate the impact of these substitutions on virus pathogenicity. This study highlights the requirement to evaluate current vaccines through systematic protection assays to determine protection efficacy against field isolates.

Genetic characterization and pathogenicity assessment of Newcastle disease virus isolated from wild peacock

The continued spread and occurrence of Newcastle disease virus (NDV) has posed potential threat to domestic poultry industry around the globe. Mainly, wild avian species has always been implicated for the natural reservoir for virus and spread of the disease. In the present study, we report the isolation of Newcastle disease virus (NDV/Peacock/India/2012) in necropsy brain tissue sample of wild peacock from North India. Complete genome of the virus was found to be 15,186 nucleotides (nts) with six genes in order of 3'-N-P-M-F-HN-L-5', which was limited by 55-nts leader region at the 3' end and a 114-nts trailer sequence at 5' end. Sequence analysis of fusion protein revealed the dibasic amino acid cleavage site (112)R-R-Q-K-R-F(117), a characteristic motif of virulent virus. Phylogenetic analysis placed the isolate in genotype II of Newcastle disease virus showing the lowest mean percent divergence (6 %) with other genotype II counterparts. The isolate was characterized as mesogenic (intermediate pathotype) based on the mean death time (63 h) in embryonated chicken eggs and the intra-cerebral pathogenicity index (1.40) in day-old chicks. The report emphasizes the dynamic ecology of NDV strains circulating in a wild avian host during the outbreak of 2012 in North India. Further the genotypic and pathotypical characterizations of the isolate could help in development of homologous vaccine against NDV strain circulating in avian population.

Pigeon paramyxovirus type 1 variants with polybasic F protein cleavage site but strikingly different pathogenicity.

Newcastle disease viruses (NDV) isolated from pigeons (pigeon paramyxovirus type 1; PPMV-1) are mostly of mesogenic pathotype and characterized by a polybasic amino acid sequence motif at the fusion protein (F) cleavage site. This feature also applies to isolate R75/98 from Germany. Its genome consists of 15,192 nucleotides and it specifies an intracerebral pathogenicity index (ICPI) of 1.1, as is typical for mesogenic NDV. Recombinant R75/98 (rR75/98) derived by reverse genetics also possesses a polybasic F protein cleavage site but exhibits ICPI of 0.28, indicating a lentogenic virus. While ten virus passages of rR75/98 on embryonated chicken eggs did not result in any alteration of virus characteristics, virus which had been re-isolated from the brain of an intracerebrally inoculated chicken showed an increase in virulence, characterized by an ICPI of 0.93. Comparison of whole genome sequences of rR75/98 and re-isolated rR75/98 (RrR75/98) demonstrated only two amino acid differences, one in the F protein (N472K) and one in the polymerase protein (K2168R). This result indicates that only very few amino acid alterations are sufficient to modulate virus virulence in the presence of a polybasic amino acid sequence at the proteolytic F protein cleavage site.

Biological and genotypic characterization of the Newcastle disease virus isolated from disease outbreaks in commercial poultry farms in northern Punjab, Pakistan

Newcastle disease (ND) is a highly contagious disease of many avian species and is particularly responsible for devastating disease outbreaks in commercial poultry flocks in Pakistan that incur huge economic losses to the national poultry industry annually. Despite implementation of an extensive vaccination program for poultry birds, the disease appears in an endemic form in commercial broiler and layer poultry farms. This study was conducted to identify the prevalent velogenic NDV strain responsible for disease outbreaks in commercial poultry farms in Punjab, Pakistan. The NDV strains isolated from pathological specimens through inoculation in embryonated chicken eggs were characterized biologically through the intracerebral pathogenicity index (ICPI), and genetically on the basis of the fusion (F) protein cleavage site. Among these, six NDV isolates showed an F protein cleavage site motif (112RRQKRF117) and an ICPI value ranging between 1.5 and 1.88, both are characteristics for velogenic strains of NDV. In addition, phylogenetic analysis based on a partial sequence of the F protein gene clustered these isolates within class II, genotype VII and specifically within genotype VII-e. This is the first report that demonstrated the presence of such NDV strains in commercial poultry farms in northern Punjab of Pakistan.

English

This study was designed to characterize a field isolate of Newcastle disease virus (NDV) to check its suitability as an inactivated vaccine and to determine the comparative efficacy of this inactivated NDV vaccine with conventional live vaccines, Baby Chick Ranikhet Disease Vaccine (BCRDV, F strain) and Ranikhet Disease Vaccine (RDV, Mukteswar strain). The field isolate of NDV was identified as velogenic strain based on the pathogenicity indices {mean death time (MDT), intracerebral pathogenicity index (ICPI) and intravenous pathogenicity index (IVPI)}. Formalin precipitated inactivated NDV vaccine was prepared from the field isolate and adjuvanted with aluminium hydroxide. The comparative efficacy of three distinct vaccination schedules (Group A, inactivated vaccine three times only; group B, BCRDV followed by inactivated and group C, BCRDV followed by RDV) was then evaluated on the basis of haemagglutination inhibition (HI) antibody titre of sera samples collected at day 4, 27, 55 and 72 of post vaccinated chicks. The prepared inactivated vaccine with the field isolate induced satisfactory level of antibody following vaccination in chicken. Combined vaccination in chickens with live BCRDV followed by inactivated NDV vaccine induced better immune response than the live or inactivated NDV vaccine alone. The antibody titre though differed significantly (P <0.05, group B versus group C at 55- and 72-days and group B versus group A at 72 days) in the chickens among the vaccinated groups, the protection rate was 100% in all groups following virulent challenge infection. Key words:  Newcastle disease virus, vaccine, velogenic, haemagglutination inhibition (HI), antibody.

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.

Comparison of Use of Agglutination of Mammalian Erythrocytes Plus Heat Stability Test and Use of Agglutination of Mammalian Erythrocytes Plus Erythrocyte Elution Time to Characterize Isolates of Newcastle Disease Virus

Aim: For a simpler, more rapid and more accurate method of characterizing new isolates of Newcastle disease virus (NDV), agglutination of mammalian erythrocytes (HA) plus heat stability test and agglutination of mammalian erythrocytes plus erythrocytes elution time (EET) were compared with use of Intra-cerebral pathogenicity index (ICPI) to characterize the isolates. Materials and Methods : NDV isolates characterized by their ICPI were re-characterized by HA of mammalian erythrocytes plus heat stability test and by HA of mammalian erythrocytes plus EET. Rate of agreement of each of the two combinations with ICPI was calculated. Results: HA of mammalian erythrocytes plus heat stability agreed with ICPI in

A Case of Newcastle Disease Virus in Red-Headed Lovebird in Sudan

Two diseased red-headed lovebirds were presented for diagnosis to the Department of Avian Diseases and Diagnosis,Veterinary Research Institute, aged 37 days and 4 years. The symptoms were dyspnea, cyanosis of the comb, diarrhea, and fever. Postmortem lesions included pale liver and bloody enteritis. Newcastle disease virus was isolated from lungs, trachea, and intestines following inoculation in the allantoic cavity of 10-day-old fertile eggs; the NDV was identified by the means of HA&HI tests using specific NDV antisera (Lasota strain). The isolate agglutinated equine RBCs but failed to agglutinate sheep and bovine RBCs. The pathogenicity of the NDV isolate was studied, the mean death time was 96 hours, and the intracerebral pathogenicity index (ICPI) value was 0.9, indicating the isolate of lentogenic type.

Molecular epidemiology of Newcastle disease virus isolates from vaccinated commercial poultry farms in non-epidemic areas of Japan

BackgroundNewcastle Disease (ND) is a highly contagious and economically devastating disease of poultry. At present, limited molecular epidemiological data are available regarding the causes of ND outbreaks in vaccinated commercial poultry farms. Knowing the genomic characteristics of Newcastle disease virus (NDV) infecting commercial poultry operations in spite of vaccination might give important insights on the infection dynamics of these viruses. In addition, molecular analyses at the subgenotype level and studies on the relationship of Japanese NDVs with other isolates from around the world are lacking. Therefore, in the present study, a molecular epidemiological investigation was conducted to characterize nine NDVs isolated from vaccinated commercial poultry flocks in five different Prefectures in non-epidemic areas of Japan between 1969 and 2002.MethodsNucleotide sequencing and phylogenetic studies were performed to characterize the complete fusion (F)-protein gene, 3-prime end of the nucleoprotein (NP)-gene and 5-prime end of the RNA dependent RNA polymerase (L)-gene. Sequence data were compared with 180 NDV strains from GenBank representing different NDV genotypes and subgenotypes from different regions of the world at different time periods. Deduced amino acids were analyzed for homologies, recombination and mutation. Recombination events were estimated using Recombination Detection Program (RDP) version 3.44. Phylogenetic trees were constructed to determine evolutionary relationships among strains.ResultsMean death time (MDT: 48-56 hr), Intracerebral Pathogenicity Index (ICPI: 1.7-1.9) and deduced amino acid sequences of the F0 proteolytic cleavage site (112RRQKR116) revealed that all nine field isolates were velogenic. Phylogenetic analysis showed that these isolates could be classified into two genetic lineages and three sublineages namely genotypes VIa (lineage 4a), VId (lineage 4d) and VIId (lineage 5d). No recombination events were observed but a point mutation in one of the neutralizing epitope of the F-protein was identified in the field isolates from Japan.ConclusionsAll field isolates from vaccinated commercial poultry in non-epidemic areas of Japan were part of much bigger outbreaks in provinces and regions and, in some cases, continents. In general, four ND panzootics occurred in Japan and that these outbreaks were mostly characterized by co-circulation of genetically distinct virus lineages due to involvements of infected wild birds. The point mutation identified in the field isolates from Japan may be due to escape from vaccine pressure. The identification of such mutation may be useful for future site-directed mutagenesis to understand the dynamics of NDV infection in vaccinated chickens.

Characterization of genotype IX Newcastle disease virus strains isolated from wild birds in the northern Qinling Mountains, China

This study was conducted to evaluate the virulence and evolution of genotype IX Newcastle disease virus (NDV) isolates obtained from wild birds in the northern Qinling Mountains of China. Five isolates were obtained from 374 larynx and cloacae swabs, which were collected from multiple asymptomatic wild bird species from August 2008 to July 2011, and were subsequently characterized by pathotype and genotype. Deduced amino acid sequences revealed that all five NDV isolates exhibited velogenic fusion protein cleavage sites motif (112)R-R-Q-R-R-F(117), shared as high as 99.8-99.9 % homology with each other, and varied in pathotype by intracerebral pathogenicity indices (ICPI) of 0.425-1.638. Phylogenetic analysis showed that all five isolates were clustered to genotype IX NDV. This is the first study to confirm multiple asymptomatic wild bird species as natural carriers of virulent genotype IX NDV. A novel NDV isolate from the Spotted-necked Dove (family Columbidae) exhibited discordance between its lentogenic ICPI and its virulent proteolytic cleavage site motif (112)R-R-Q-R-R-F(117). Although the five isolates underwent several amino acid mutations in the fusion protein, evidence of continuous evolutionary divergence did exist in the genotype IX NDV, which was always regarded as a conservative genotype.

Effects of the HN gene C-terminal extensions on the Newcastle disease virus virulence

The hemagglutinin-neuraminidase (HN) of Newcastle disease virus (NDV) is a multifunctional protein that has receptor recognition, neuraminidase, and fusion promotion activities. Sequence analysis revealed that the HN gene of many extremely low virulence NDV strains encodes a larger open-reading frame (616 amino acids, aa) with additional 45 aa at its C-terminus when compared with that (571 aa) of virulent NDV strains. Therefore, it has been suspected that the 45 aa extension at the C-terminus of the HN may affect the NDV virulence. In this study, we generated an NDV mesogenic strain Anhinga-based recombinant virus with an HN C-terminal extension of 45 aa (rAnh-HN-ex virus) using reverse genetics technology. The biological characterization of the recombinant virus showed that the rAnh-HN-ex virus had similar growth ability to its parental virus rAnh-wt both in embryonating chicken eggs and DF-1 cells. However, the pathogenicity of this recombinant virus in embryonating chicken eggs and day-old chickens decreased, as evidenced by a longer mean death time and lower intracerebral pathogenicity index when compared with the parental virus. This is consistent with our previous finding that the recombinant LaSota virus with a 45-aa extension at its HN C-terminal was attenuated in chickens and embryonating eggs. These results suggest that the HN protein C-terminal extension may contribute to the reduced virulence in some low virulence NDV strains.

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.

Pathogenesis of Newcastle Disease in Vaccinated Chickens: Pathogenicity of Isolated Virus and Vaccine Effect on Challenge of Its Virus

ABSTRACTThe pathogenicity of Newcastle disease (ND) virus, isolated from ND outbreak in vaccinated chickens, was evaluated through experiments. The pathogenicity indexes (mean death time (MDT); 58 hr, intracerebral pathogenicity index (ICPI); 1.7 and intravenous pathogenicity index (IVPI); 2.51) indicated that the ND virus was velogenic. The ND virus caused lymphocytic necrosis in the spleen with fibrinous exudation and proliferation of macrophages, sinusoidal fibrin exudation in the liver, proliferation of macrophages in the lung, lymphocytic necrosis and depletion in the bursa of Fabricius, cecal tonsils and thymus, necrosis of bone marrow, tracheitis, conjunctivitis and necrosis of feather epithelial cells in specific-pathogen-free chickens. Immunohistochemically, ND virus antigens were seen in the lesions mentioned above. The ND virus could not induce the encephalitis and pancreatitis that were observed in the natural case of ND in vaccinated chickens. There was no clinical disease in vaccinated chickens after the challenge of the ND virus. In diluted ND vaccine experiments, chickens vaccinated with a high dilution of vaccine and then challenged with the ND virus showed clinical sign and mortality with pancreatic focal necrosis. Vaccine diluted with fresh tap water had no effect on protection against the challenge of the ND virus. This study suggests that improper vaccination may be involved in outbreaks of ND in vaccinated chickens.

Isolation of a Virulent Newcastle Disease Virus from Confiscated LaSota Vaccine

Vials of Newcastle disease vaccine labeled as LaSota were confiscated by the Arizona Division of Customs and Border Protection officials. Two different avian type 1 paramyxoviruses were isolated from all three vials of vaccine submitted to the National Veterinary Services Laboratories. The LaSota strain of avian paramyxovirus type 1 virus was isolated from all three vials and analyzed by nucleotide sequence analysis. A virulent Newcastle disease virus was also present in all three vials, but in low concentration. The virulence of the Newcastle disease virus was characterized by the intracerebral chicken pathogenicity index chicken inoculation assay but could not be determined by nucleotide sequence analysis from the virus isolated from embryonating chicken eggs. The intracerebral chicken pathogenicity index value for the isolated Newcastle disease virus was 1.55. Strains of Newcastle disease virus with intracerebral pathogenicity indexes significantly above 1.0 have been found to selectively kill many types of cancer cells while not affecting normal nonneoplastic cells and are considered to be a viable option for cancer treatment in humans by alternative medical researchers; however, the treatment is not approved for use in the United States by the Food and Drug Administration. Customs and Border Protection officials have been notified of an increased risk of Newcastle disease virus entering the United States for use as a nonapproved cancer treatment. Illegal importation of Newcastle disease vaccine for vaccination of backyard poultry is also a threat. This case report emphasizes the importance of conducting chicken inoculation for complete virus pathotyping and demonstrates the need for stringent security procedures at U.S. borders to detect known livestock pathogens that may be smuggled in for use in animal agriculture and reasons unrelated to animal agriculture.

Pathotypic and Genotypic Characterization of Two Bangladeshi Isolates of Newcastle Disease Virus of Chicken and Pigeon Origin

Two Bangladeshi isolates of Newcastle disease virus (NDV), one from a chicken and one from a pigeon, were characterized in this study. Pathogenicity of the isolates was evaluated on the basis of intracerebral pathogenicity index (ICPI). Both the isolates were found to be of velogenic pathotype having ICPI of 1.83 and 1.51 for the chicken and pigeon isolate, respectively. Genotype of the isolates was determined by phylogenetic analysis based on partial F gene sequences. A 766-bp genome fragment spanning partial M and F gene was amplified by RT-PCR and sequenced. The first 354bp of the coding region of F gene and corresponding deduced amino acid sequences (residues 1-118) of these two NDV isolates were aligned with that of other NDV strains retrieved from GenBank. A phylogenetic tree constructed from the alignment showed that the chicken isolate (BD-C162) belonged to the newly described genotype XIII and the pigeon isolate (BD-P01) to genotype VI. Both the chicken and pigeon isolates possessed a virulent-like fusion protein cleavage site (112) RRQKRF(117) .

Characteristics of Pigeon Paramyxovirus Serotype-1 Isolates (PPMV-1) from the Russian Federation from 2001 to 2009

Monitoring programs for highly dangerous avian diseases in the Russian Federation from 2001 to 2009 detected 77 samples that were PCR positive for avian paramyxovirus serotype-1 (APMV-1) from sick or dead feral and domestic pigeons. Nucleotide sequences of the fusion (F) gene, including a nucleotide sequence encoding the F protein cleavage site, were determined for these isolates. All of the studied isolates possessed virulent F0 protein cleavage sites (112KRKKRF117, 112RRQKRF117, or 112KRQKRF117). Intracerebral pathogenicity index (ICPI) values determined for seven of the isolates exceeded the value of 0.7 (the range from 0.8 to 1.41). Based on partial genome sequencing and phylogenetic analysis, the isolates were assigned to two individual sublineages within class II genotype VIb. It was determined that most of these Newcastle disease virus isolates (70/77) recovered from the pigeons belonged to a relatively poorly studied sublineage VIb/2. The complete nucleotide sequence of the genome for the Pigeon/Russia/Vladimir/687/05 isolate of sublineage VIb/2 was determined.

Newcastle Disease Virus in Little Owls (Athene noctua) and African Penguins (Spheniscus demersus) in an Israeli Zoo

Newcastle disease is a contagious and often fatal disease, capable of affecting all species of birds. A velogenic Newcastle disease virus (vNDV) outbreak occurred in an Israeli zoo, in which Little owls (Athene noctua) and African penguins (Spheniscus demersus) were found positive for presence of NDV. Some of them have died. The diagnostic process included: post-mortem examination, histopathology, real-time RT-PCR assay, virus isolation, serology, intracerebral pathogenicity index and phylogenetic analysis. A vNDV was diagnosed and found to be closely related to isolates from vNDV outbreaks that occurred in commercial poultry flocks during 2011. All isolates were classified as lineage 5d.

Phylogenetic and pathogenic analyses of two virulent Newcastle disease viruses isolated from Crested Ibis (Nipponia nippon) in China

The crested ibis is one of the most endangered birds in the world, found only in Shaanxi Province in Central China, and it has been reintroduced in Sadogashima in Japan. Two Newcastle disease virus (NDV) isolates were collected from sick crested ibises, and their pathogenic and phylogenetic characteristics were investigated. The results showed that they are virulent, with intracerebral pathogenicity indices of 1.46-1.83 and a mean time of death of 54.4-84.4 h. They shared the same virulent motif (112)-R-R-Q-K-R-F-(117) at the F protein cleavage site. The phylogenetic analysis revealed that both isolates were clustered with class II NDVs, with one in genotype VIId and another in a novel genotype (provisionally designated as VIi). The two isolates shared high homology with the strains isolated from poultry flocks in the same region from 2006 to 2010. We first isolated and characterised the NDV isolates from crested ibises, one of which showed new genetic characteristics and formed a new subgenotype with isolates from pigeons and ostriches in the same area. These data are useful for further epidemiological studies on NDV and the protection of crested ibises.

Surveillance and molecular characterization of Newcastle disease virus in seafowl from coastal areas of China in 2011

Four Newcastle disease virus (NDV) isolates were obtained from 997 fecal and tissue samples were collected in 2011 from seafowl that included seagull, sea duck, and swan from the coastal areas of Guangdong, Jiangsu, and Shandong in China. These isolates (SD1, SD2, GD1, and JS1) were characterized for their pathogenicity according to their mean death time, intracerebral pathogenicity index and intravenous pathogenicity index. Full-length fusion protein genes containing the cleavage site were sequenced, and amino-acid sequences around the cleavage site were deduced. One isolate (SD2) was virulent to poultry as indicated by its mean death time, intracerebral pathogenicity index, and fusion gene cleavage site sequence, which was specific for virulent NDV ((112)R-R-Q-K-R-F(117)). The phylogenic analysis indicated that three of the isolates (SD1, GD1, and JS1) belonged to genotype II and the virulent isolate (SD2) belonged to genotype VIId. These findings suggest that some seafowl NDVs in the coastal areas of China have different virulences and molecular characterizations, and these NDVs have some similarity with vaccine- or poultry-adapted isolates.