Showing papers on "Newcastle disease published in 2019"

Epidemiology, control, and prevention of Newcastle disease in endemic regions: Latin America.

Abstract: Newcastle disease (ND) infects wild birds and poultry species worldwide, severely impacting the economics of the poultry industry. ND is especially problematic in Latin America (Mexico, Colombia, Venezuela, and Peru) where it is either endemic or re-emerging. The disease is caused by infections with one of the different strains of virulent avian Newcastle disease virus (NDV), recently renamed Avian avulavirus 1. Here, we describe the molecular epidemiology of Latin American NDVs, current control and prevention methods, including vaccines and vaccination protocols, as well as future strategies for control of ND. Because the productive, cultural, economic, social, and ecological conditions that facilitate poultry endemicity in South America are similar to those in the developing world, most of the problems and control strategies described here are applicable to other continents.

Innovation in Newcastle Disease Virus Vectored Avian Influenza Vaccines

Abstract: Highly pathogenic avian influenza (HPAI) and Newcastle disease are economically important avian diseases worldwide. Effective vaccination is critical to control these diseases in poultry. Live attenuated Newcastle disease virus (NDV) vectored vaccines have been developed for bivalent vaccination against HPAI viruses and NDV. These vaccines have been generated by inserting the hemagglutinin (HA) gene of avian influenza virus into NDV genomes. In laboratory settings, several experimental NDV-vectored vaccines have protected specific pathogen-free chickens from mortality, clinical signs, and virus shedding against H5 and H7 HPAI viruses and NDV challenges. NDV-vectored H5 vaccines have been licensed for poultry vaccination in China and Mexico. Recently, an antigenically chimeric NDV vector has been generated to overcome pre-existing immunity to NDV in poultry and to provide early protection of poultry in the field. Prime immunization of one-day-old poults with a chimeric NDV vector followed by boosting with a conventional NDV vector has shown to protect broiler chickens against H5 HPAI viruses and a highly virulent NDV. This novel vaccination approach can provide efficient control of HPAI viruses in the field and facilitate poultry vaccination.

Genomic comparison of Newcastle disease viruses isolated in Nigeria between 2002 and 2015 reveals circulation of highly diverse genotypes and spillover into wild birds.

Abstract: Newcastle disease virus (NDV) has a wide avian host range and a high degree of genetic variability, and virulent strains cause Newcastle disease (ND), a worldwide concern for poultry health. Although NDV has been studied in Nigeria, genetic information about the viruses involved in the endemicity of the disease and the transmission that likely occurs at the poultry-wildlife interface is still largely incomplete. Next-generation and Sanger sequencing was performed to provide complete (n = 73) and partial genomic sequence data (n = 38) for NDV isolates collected from domestic and wild birds in Nigeria during 2002-2015, including the first complete genome sequences of genotype IV and subgenotype VIh from the African continent. Phylogenetic analysis revealed that viruses of seven different genotypes circulated in that period, demonstrating high genetic diversity of NDV for a single country. In addition, a high degree of similarity between NDV isolates from domestic and wild birds was observed, suggesting that spillovers had occurred, including to three species that had not previously been shown to be susceptible to NDV infection. Furthermore, the first spillover of a mesogenic Komarov vaccine virus is documented, suggesting a previous spillover and evolution of this virus. The similarities between viruses from poultry and multiple bird species and the lack of evidence for host adaptation in codon usage suggest that transmission of NDV between poultry and non-poultry birds occurred recently. This is especially significant when considering that some viruses were isolated from species of conservation concern. The high diversity of NDV observed in both domestic and wild birds in Nigeria emphasizes the need for active surveillance and epidemiology of NDV in all bird species.

Development of a recombinant Newcastle disease virus-vectored vaccine for infectious bronchitis virus variant strains circulating in Egypt

Abstract: Infectious bronchitis virus (IBV) causes a major disease problem for the poultry industry worldwide. The currently used live-attenuated vaccines have the tendency to mutate and/or recombine with circulating field strains resulting in the emergence of vaccine-derived variant viruses. In order to circumvent these issues, and to develop a vaccine that is more relevant to Egypt and its neighboring countries, a recombinant avirulent Newcastle disease virus (rNDV) strain LaSota was constructed to express the codon-optimized S glycoprotein of the Egyptian IBV variant strain IBV/Ck/EG/CU/4/2014 belonging to GI-23 lineage, that is prevalent in Egypt and in the Middle East. A wild type and two modified versions of the IBV S protein were expressed individually by rNDV. A high level of S protein expression was detected in vitro by Western blot and immunofluorescence analyses. All rNDV-vectored IBV vaccine candidates were genetically stable, slightly attenuated and showed growth patterns comparable to that of parental rLaSota virus. Single-dose vaccination of 1-day-old SPF White Leghorn chicks with the rNDVs expressing IBV S protein provided significant protection against clinical disease after IBV challenge but did not show reduction in tracheal viral shedding. Single-dose vaccination also provided complete protection against virulent NDV challenge. However, prime-boost vaccination using rNDV expressing the wild type IBV S protein provided better protection, after IBV challenge, against clinical signs and significantly reduced tracheal viral shedding. These results indicate that the NDV-vectored IBV vaccines are promising bivalent vaccine candidates to control both infectious bronchitis and Newcastle disease in Egypt.

Impact of single and mixed infections with Escherichia coli and Mycoplasma gallisepticum on Newcastle disease virus vaccine performance in broiler chickens: an in vivo perspective.

Abstract: AIMS: This study was designed to investigate, in an in vivo setting, the effects of single and combined infections with either Mycoplasma gallisepticum (MG) and/or Escherichia coli on the chicken immune response induced by Newcastle disease virus (NDV) vaccine. METHODS AND RESULTS: Humoral immunity was measured through detection of NDV antibody and anti‐NDV IgG titres using haemagglutination‐inhibition test and enzyme‐linked immunosorbent assay, respectively. In addition, the expression levels of pro‐inflammatory cytokines' genes (interleukin (IL) 6, IL4 and interferon (IFN) γ) were analysed using quantitative reverse transcription PCR. Significant (P < 0·05) results in all immunological parameters were detected in the vaccinated noninfected chicken group in comparison with those in groups exposed to bacterial infections. Bacterial infection along with vaccination hampered the NDV antibodies production and reduced the vaccine upregulated cytokine genes. The vaccinated mixed infection group reported lower antibody titres and cytokines expression levels compared to those in the single infection groups. All the previously enhanced immunological parameters reflected the maximum protection post challenge with velogenic viscerotropic NDV in the vaccinated noninfected chicken group. CONCLUSIONS: These findings provide novel insights into the immunosuppression activities of MG and E. coli infection in chickens vaccinated against NDV. SIGNIFICANCE AND IMPACT OF THE STUDY: This study hopes to provide a better insight to the immunosuppressive action of bacterial pathogens in chickens. This will help to improve biosecurity strategies during NDV vaccination in the future.

Prevalence of avian influenza, Newcastle disease, and infectious bronchitis viruses in broiler flocks infected with multifactorial respiratory diseases in Iran, 2015-2016.

Abstract: In this study, the prevalence and spatial distribution of Newcastle disease, infectious bronchitis, and avian influenza have been evaluated in commercial broiler farms in 31 provinces in Iran. In this survey, a total of 233 affected broiler chicken farms were sampled. The infectious bronchitis virus (alone) was detected with highest frequency in 60 farms, and separately or combined with other agents, in 110 farms; Newcastle disease virus, separately, was detected in 28 farms, and in 63 farms separately or combined with other infectious agents; and avian influenza H9N2 was detected in 22 farms separately and in 51 farms separately or concomitant with other infectious agents. The sample tested negative for all H5 serotypes. The results of the present study show that the most prevalent avian viral infectious disease contributing to respiratory syndromes in broiler farms in Iran was infectious bronchitis due to infectious bronchitis virus serotypes variant 2 and 793/B. On the other hand, combined with the alternation of dominant viruses and circulating strains, flocks are exposed to unremitting anamorphic viral infections. Thus, the permanent monitoring of cases that have occurred and the review of vaccination plans of affected flocks every year are some of the necessary measures needed for strategic control of respiratory syndrome in broilers. It is noteworthy that execution of epidemiologic examinations on the cogent factors of prevalence of this syndrome and defeat of vaccination strategy in the flocks is urgent and has to be fulfilled on the definite causes of time.

Evaluation of Antiviral Activity of Allium Cepa and Allium Sativum Extracts Against Newcastle Disease Virus

Abstract: Newcastle Disease Virus (NDV) is the causative agent of the most devastating diseases affecting poultry especially in large scale production causing severe economic losses due to high mortality which may reach 100% in very virulent strains of NDV. In the present study, field samples of suspected to be infected by NDV were isolated in Embryonated chicken Eggs (ECEs) of 10 days-old via allantoic cavity for three passages, the isolated virus was identified to be NDV by Haemagglutination inhibition test (HI), electron microscope and reverse transcriptase polymerase chain reaction (RT- PCR). The antiviral effects of both onion and garlic extracts were studied on field isolates and reference strain of NDV. The antiviral effects involve the gross lesions changes of the embryo in inoculated ECEs, Haemagglutination test (HA) and Infectivity test (EID50%). The obtained results showed that most of the isolated viruses expressed subcutaneous Haemorrhage and death of the embryo at the fifth day post inoculation via allantoic cavity at the third passage of ECEs, while the field sample number (10) and the reference strain showed extensive haemorrhage and rapid death of embryos. The isolated viruses were identified to be NDV of the susceptible to be infected samples by HI using hyperimmune serum against NDV prepared in rabbit. The Mean Death Time (MDT) was calculated for the field sample number (10) and the reference strain which showed that the tested samples are velogenic strains. Electron microscopy investigation of some selected samples (of high HA titers) identified the virus as pleomorphic in shape. Some selected samples were analyzed by RT-PCR and gel electrophoresis expressing clear bands using primers against the F-gene of NDV. RT-PCR is considered as the most useful, reliable and accuret laboratory test for confirming field NDV. Brown leaves of onion (Allium Cepa) and bulbs of garlic (Allium sativum) were separately extracted and the extracts were tested for their antiviral activity against the previously isolated and identified NDV. Investigating the antiviral effects of both onion and garlic extracts on some field samples showed absence of virus activity after treatments by extracts, while samples number (10) and reference strain showed reduction of virus in HA test, subcutaneous hemorrhage and EID50%. The reduction of NDV infectivity may be due to the blocking of the attachment of the virus with the cell receptors.

Evaluation of a Recombinant Newcastle Disease Virus Expressing Human IL12 against Human Breast Cancer.

Abstract: The Newcastle disease virus (NDV) strain AF2240 is an avian avulavirus that has been demonstrated to possess oncolytic activity against cancer cells. However, to illicit a greater anti-cancer immune response, it is believed that the incorporation of immunostimulatory genes such as IL12 into a recombinant NDV backbone will enhance its oncolytic effect. In this study, a newly developed recombinant NDV that expresses IL12 (rAF-IL12) was tested for its safety, stability and cytotoxicity. The stability of rAF-IL12 was maintained when passaged in specific pathogen free (SPF) chicken eggs from passage 1 to passage 10; with an HA titer of 29. Based on the results obtained from the MTT cytotoxic assay, rAF-IL12 was determined to be safe as it only induced cytotoxic effects against normal chicken cell lines and human breast cancer cells while sparing normal cells. Significant tumor growth inhibition (52%) was observed in the rAF-IL12-treated mice. The in vivo safety profile of rAF-IL12 was confirmed through histological observation and viral load titer assay. The concentration and presence of the expressed IL12 was quantified and verified via ELISA assay. In summary, rAF-IL12 was proven to be safe, selectively replicating in chicken and cancer cells and was able to maintain its stability throughout several passages; thus enhancing its potential as an anti-breast cancer vaccine.

A double recombinant herpes virus of turkeys for the protection of chickens against Newcastle, infectious laryngotracheitis and Marek's diseases.

Abstract: A double recombinant strain of herpes virus of turkeys (HVT) was constructed that contains the fusion (F) gene from Newcastle disease virus (NDV) and the gD plus gI genes from infectious laryngotracheitis virus (ILTV) inserted into a non-essential region of the HVT genome. Expression of the F protein was controlled by a human cytomegalovirus promoter, whereas expression of gD plus gI was driven by an ILTV promoter. The double recombinant vaccine virus (HVT-NDV-ILT) was fully stable genetically and phenotypically following extended passage in cell culture and infection of chickens. Safety of the vaccine virus was confirmed by overdose and backpassage studies in specific-pathogen-free chickens. Chickens vaccinated with a single dose of HVT-NDV-ILT administered by the in ovo route were highly protected from challenge with the velogenic NDV (GB Texas), ILTV (LT 96-3) and Marek's disease virus (GA 5) strains (97%, 94% and 97%, respectively). Similarly, chickens vaccinated with a single dose by subcutaneous (SC) route at 1 day of age were highly protected from challenge with the same three viruses (100%, 100%, and 88%, respectively). The protection level of a single dose given by in ovo or SC route against challenge with a virulent Marek's disease virus strain demonstrates that insertion of multiple genes from two different pathogens within the HVT genome had no adverse effect on the capacity of HVT to protect against Marek's disease. These results demonstrate that HVT-NDV-ILT is a safe and efficacious vaccine for simultaneous control of NDV, ILTV and Marek's diseases.

Genetic Analyses of Tanzanian Local Chicken Ecotypes Challenged with Newcastle Disease Virus

Abstract: Newcastle Disease (ND) is a continuing global threat to domestic poultry, especially in developing countries, where severe outbreaks of velogenic ND virus (NDV) often cause major economic losses to households Local chickens are of great importance to rural family livelihoods through provision of high-quality protein To investigate the genetic basis of host response to NDV, three popular Tanzanian chicken ecotypes (regional populations) were challenged with a lentogenic (vaccine) strain of NDV at 28 days of age Various host response phenotypes, including anti-NDV antibody levels (pre-infection and 10 days post-infection, dpi), and viral load (2 and 6 dpi) were measured, in addition to growth rate We estimated genetic parameters and conducted genome-wide association study analyses by genotyping 1399 chickens using the Affymetrix 600K chicken SNP chip Estimates of heritability of the evaluated traits were moderate (018–035) Five quantitative trait loci (QTL) associated with growth and/or response to NDV were identified by single-SNP analyses, with some regions explaining ≥1% of genetic variance based on the Bayes-B method Immune related genes, such as ETS1, TIRAP, and KIRREL3, were located in regions associated with viral load at 6 dpi The moderate estimates of heritability and identified QTL indicate that NDV response traits may be improved through selective breeding of chickens to enhance increased NDV resistance and vaccine efficacy in Tanzanian local ecotypes

Investigation of suspected Newcastle disease (ND) outbreaks in Egypt uncovers a high virus velogenic ND virus burden in small-scale holdings and the presence of multiple pathogens.

Abstract: Highly contagious Newcastle disease (ND) is associated with devastating outbreaks with highly variable clinical signs among gallinaceous birds. In this study we aimed to verify clinical ND ...

Molecular epidemiology of respiratory viruses in commercial chicken flocks in Pakistan from 2014 through to 2016

Abstract: Viral diseases are a matter of great concern for poultry farmers in Pakistan. Multiple common viral respiratory diseases (CVRDs) cause huge economic losses in the poultry industry. The prevalence of CVRDs in many countries, including Pakistan, is not clearly understood. Incidences of 5 chicken respiratory viruses: avian influenza virus (AIV), Newcastle disease virus (NDV/AAVV-1), infectious bronchitis virus (IBV), avian metapneumovirus (aMPV) and infectious laryngotracheitis virus (ILTV) were assessed on commercial Pakistani farms with respiratory problems from 2014 through to 2016. While AIV and AAVV-1 were frequently detected (16 to 17% of farms), IBV and aMPV were rarely detected (in 3 to 5% of farms) and ILTV was not detected. We characterized H9 AIV of the G1 lineage, genotype VII AAVV-1, GI-13 IBV, and type B aMPV strains with very little genetic variability in the 2-year study period. Co-infections with AIV and AAVV-1 were common and wild type AAVV-1 was detected despite the use of vaccines. Control measures to limit the virus burden in chicken flocks are discussed. Our data shows that AIV (H9), AAVV-1, IBV and aMPV are prevalent in commercial poultry in Pakistan. Further studies are necessary to assess circulating strains, economic losses caused by infections and coinfections of these pathogens, and the costs and benefits of countermeasures. Furthermore, veterinarians and farmers should be informed of the pathogens circulating in the field and hence advised on the use of vaccines.

Construction and Immunogenicity of Novel Chimeric Virus-Like Particles Bearing Antigens of Infectious Bronchitis Virus and Newcastle Disease Virus

Abstract: Infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) are two poultry pathogens seriously affecting the poultry industry. Here, IBV S1 and the ectodomain of NDV F proteins were separately linked with the trans-membrane and carboxy-terminal domain of IBV S protein (STMCT), composing rS and rF; thus, a novel chimeric infectious bronchitis-Newcastle disease (IB-ND) virus-like particles (VLPs) vaccine containing the rS, rF, and IBV M protein was constructed. Under the transmission electron microscope (TEM), VLPs possessing similar morphology to natural IBV were observed. To evaluate the immunogenicity of chimeric IB-ND VLPs, specific pathogen-free (SPF) chickens were immunized with three increasing doses (50, 75, and 100 μg protein of VLPs). Results of ELISAs detecting IBV and NDV specific antibodies and IL-4 and IFN-γ T cell cytokines indicated that vaccination with chimeric IB-ND VLPs could efficiently induce humoral and cellular immune responses. In the challenge study, chimeric IB-ND VLPs (100 μg protein) provided 100% protection against IBV or NDV virulent challenge from death, and viral RNA levels in tissues and swabs were greatly reduced. Collectively, chimeric IB-ND VLPs are highly immunogenic and could provide complete protection from an IBV or NDV virulent challenge. Chimeric IB-ND VLPs are an appealing vaccine candidate and a promising vaccine platform bearing multivalent antigens.

Antigenicity, pathogenicity and immunosuppressive effect caused by a South American isolate of infectious bursal disease virus belonging to the “distinct” genetic lineage

Abstract: Infectious bursal disease virus (IBDV) is the causative agent of a highly contagious immunosuppressive disease affecting young chickens. The recently described "distinct IBDV" (dIBDV) genetic lineage encompasses a group of worldwide distributed strains that share conserved genetic characteristics in both genome segments making them unique within IBDV strains. Phenotypic characterization of these strains is scarce and limited to Asiatic and European strains collected more than 15 years ago. The present study aimed to assess the complete and comprehensive phenotypic characterization of a recently collected South American dIBDV strain (1/chicken/URY/1302/16). Genetic analyses of both partial genome segments confirmed that this strain belongs to the dIBDV genetic lineage and that it is not a reassortant. Antigenic analysis with monoclonal antibodies indicated that this strain has a particular antigenic profile, similar to that obtained in a dIBDV strain from Europe (80/GA), which differs from those previously found in the traditional classic, variant and very virulent strains. Chickens infected with the South American dIBDV strain showed subclinical infections but had a marked bursal atrophy. Further analysis using Newcastle disease virus-immunized chickens, previously infected with the South American and European dIBDV strains, demonstrated their severe immunosuppressive effect. These results indicate that dIBDV strains currently circulating in South America can severely impair the immune system of chickens, consequently affecting the local poultry industry. Our study provides new insights into the characteristics and variability of this global genetic lineage and is valuable to determine whether specific control measures are required for the dIBDV lineage. Research Highlights A South American strain of the dIBDV lineage was phenotypically characterized. The strain produced subclinical infections with a marked bursal atrophy. Infected chickens were severely immunosuppressed. The dIBDV strains are antigenically divergent from other IBDV lineages.

Isolation and Characterization of Newcastle Disease Virus from Live Bird Markets in Tanzania

Abstract: Chickens in live bird markets (LBMs) from six different regions of Tanzania were surveyed for Newcastle disease (ND) virus (NDV) and avian influenza virus in 2012. ELISA-based serology, virus isolation, and characterization, including pathotyping was conducted. Virulent NDV was isolated from almost 10% of the tested samples, with two distinct genotypes being detected. One genotype was similar to recent viruses circulating in Kenya and Uganda, which share a northern border with Tanzania. Several viruses of this genotype were also isolated from Tanzania in 1995, the last time surveillance for NDV was conducted in the country. The second genotype of virus from Tanzania was closely related to viruses from Mozambique, a southern neighbor, and more distantly to viruses from South Africa, Botswana, and several European countries. Partial fusion gene sequence from the isolated viruses showed identical fusion cleavage sites that were compatible with virulent viruses. Selected viruses were tested by the intracerebral pathogenicity index, and all viruses tested had scores of >1.78, indicating highly virulent viruses. Serology showed only a third of the chickens had detectable antibody to NDV, suggesting that vaccination is not being commonly used in the country, despite the availability of vaccines in agricultural-related markets. All samples were taken from clinically healthy birds, and it is believed that the birds were sold or slaughtered before showing ND clinical signs. LBMs remain a biosecurity risk for farmers through the return of live infected birds to the farm or village or the movement of virus on fomites, such as uncleaned wooden cages.

Genetics and Genomic Regions Affecting Response to Newcastle Disease Virus Infection under Heat Stress in Layer Chickens.

Abstract: Newcastle disease virus (NDV) is a highly contagious avian pathogen that poses a tremendous threat to poultry producers in endemic zones due to its epidemic potential. To investigate host genetic resistance to NDV while under the effects of heat stress, a genome-wide association study (GWAS) was performed on Hy-Line Brown layer chickens that were challenged with NDV while under high ambient temperature to identify regions associated with host viral titer, circulating anti-NDV antibody titer, and body weight change. A single nucleotide polymorphism (SNP) on chromosome 1 was associated with viral titer at two days post-infection (dpi), while 30 SNPs spanning a quantitative trait loci (QTL) on chromosome 24 were associated with viral titer at 6 dpi. Immune related genes, such as CAMK1d and CCDC3 on chromosome 1, associated with viral titer at 2 dpi, and TIRAP, ETS1, and KIRREL3, associated with viral titer at 6 dpi, were located in two QTL regions for viral titer that were identified in this study. This study identified genomic regions and candidate genes that are associated with response to NDV during heat stress in Hy-Line Brown layer chickens. Regions identified for viral titer on chromosome 1 and 24, at 2 and 6 dpi, respectively, included several genes that have key roles in regulating the immune response.

In Vitro and In Vivo Metabolomic Profiling after Infection with Virulent Newcastle Disease Virus.

Abstract: Newcastle disease (ND) is an acute, febrile, highly contagious disease caused by the virulent Newcastle disease virus (vNDV). The disease causes serious economic losses to the poultry industry. However, the metabolic changes caused by vNDV infection remain unclear. The objective of this study was to determine the metabolomic profiling after infection with vNDV. DF-1 cells infected with the vNDV strain Herts/33 and the lungs from Herts/33-infected specific pathogen-free (SPF) chickens were analyzed via ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS) in combination with multivariate statistical analysis. A total of 305 metabolites were found to have changed significantly after Herts/33 infection, and most of them belong to the amino acid and nucleotide metabolic pathway. It is suggested that the increased pools of amino acids and nucleotides may benefit viral protein synthesis and genome amplification to promote NDV infection. Similar results were also confirmed in vivo. Identification of these metabolites will provide information to further understand the mechanism of vNDV replication and pathogenesis.

Epidemiology, Diagnosis & Prevention of Newcastle Disease in Poultry

Abstract: Based on the number of animals, poultry represents the largest domestic animal stock in the world [1]. Poultry represents an important sector in animal production, with backyard flocks representing a huge majority, especially in the developing countries. In these countries, villagers raise poultry to meet household food demands and as additional sources of incomes. Backyard production methods imply low biosecurity measures and high risk of infectious diseases, such as Newcastle disease (ND) or zoonosis such as Highly Pathogenic Avian Influenza (HPAI) [2]. Newcastle disease is a contagious bird disease affecting many domestic and wild avian species; it is transmissible to humans. ND is an important infectious disease of the poultry that is caused by virulent strains of Avian Paramyxovirus-1, which is a single strand non-segmented negative sense RNA virus [3]. Newcastle disease is a viral disease caused by the avian Paramyxovirus serotype 1 (APMV1), is one of the most important poultry diseases worldwide [4]. The epizootics of ND in poultry continue to occur in Asia, Africa, Central and South America while in Europe, sporadic epizootics occur [5]. In developing countries, human diet is deficient in the animal proteins; approximately 66% population has protein deficient diet [6].

Molecular phylogenetics of Newcastle disease viruses isolated from vaccinated flocks during outbreaks in Southern India reveals circulation of a novel sub-genotype.

Abstract: Newcastle disease (ND) is an economically important, contagious poultry viral disease reported across the globe. In India, ND is endemic and episodes of ND outbreaks despite strict vaccinations are not uncommon. We isolated and characterized seven ND viruses from vaccinated commercial poultry farms during severe disease outbreaks in Tamil Nadu, in Southern India, between April 2015 and June 2016. All the seven isolates were categorized as virulent by mean death time (48-54 hr) in embryonated chicken eggs. Also, their sequences carried the virulence signature of multi-basic amino acid residues in their fusion protein cleavage site (RRQ/RR/KRF). Phylogenetic and evolutionary distance analyses revealed circulation of a novel sub-genotype of genotype XIII, class II ND viruses, herein proposed as sub-genotype XIIIe. The genetic divergence between the circulating virulent strains and the vaccine strains could possibly explain the disease outbreak in the vaccinated flocks. Further, our study signifies the need to implement routine epidemiological surveillance and to revisit the current vaccination program.