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

A Booster with a Genotype-Matched Inactivated Newcastle Disease Virus (NDV) Vaccine Candidate Provides Better Protection against a Virulent Genotype XIII.2 Virus

Newcastle disease (ND) is endemic in Bangladesh. Locally produced or imported live Newcastle disease virus (NDV) vaccines based on lentogenic virus strains, locally produced live vaccines of the mesogenic Mukteswar strain, as well as imported inactivated vaccines of lentogenic strains, are being used in Bangladesh under different vaccination regimens. Despite these vaccinations, frequent outbreaks of ND are being reported in Bangladesh. Here we compared the efficacy of booster immunization with three different vaccines in chickens that had been primed with two doses of live LaSota vaccine. A total of 30 birds (Group A) were primed with two doses of live LaSota virus (genotype II) vaccine at days 7 and 28, while 20 birds (Group B) remained unvaccinated. At day 60, birds of Group A were divided into three sub-groups, which received booster immunizations with three different vaccines; A1: live LaSota vaccine, A2: inactivated LaSota vaccine, and A3: inactivated genotype XIII.2 vaccine (BD-C161/2010 strain from Bangladesh). Two weeks after booster vaccination (at day 74), all vaccinated birds (A1-A3) and half of the unvaccinated birds (B1) were challenged with a genotype XIII.2 virulent NDV (BD-C161/2010). A moderate antibody response was observed after the primary vaccination, which substantially increased after the booster vaccination in all groups. The mean HI titers induced by the inactivated LaSota vaccine (8.0 log₂/5.0 log₂ with LaSota/BD-C161/2010 HI antigen) and the inactivated BD-C161/2010 vaccine (6.7 log₂/6.2 log₂ with LaSota/BD-C161/2010 HI antigen) were significantly higher than those induced by the LaSota live booster vaccine (3.6 log₂/2.6 log₂ with LaSota/BD-C161/2010 HI antigen). Despite the differences in the antibody titers, all chickens (A1-A3) survived the virulent NDV challenge, while all the unvaccinated challenged birds died. Among the vaccinated groups, however, 50% of the chickens in Group A1 (live LaSota booster immunization) shed virus at 5- and 7-days post challenge (dpc), while 20% and 10% of the chickens in Group A2 (inactivated LaSota booster immunization) shed virus at 3 and 5 dpc, respectively, and only one chicken (10%) in Group A3 shed virus at 5 dpc. In conclusion, the genotype-matched inactivated NDV booster vaccine offers complete clinical protection and a significant reduction in virus shedding.

The First Report of a Virulent Newcastle Disease Virus of Genotype VII.2 Causing Outbreaks in Chickens in Bangladesh

Newcastle disease (ND) is endemic in poultry in Bangladesh. We performed genotypic and pathotypic characterization of four ND virus (NDV) isolates from recent outbreaks in broiler chickens in Bangladesh during the period of 2020-2021. Phylogenetic analysis based on the complete fusion protein gene coding sequences classified the viruses into NDV class II genotype VII.2 together with viruses from Indonesia isolated between 2014 and 2021 and a single 2020 Indian isolate. Pathogenicity testing using the intracerebral pathogenicity index in day-old chickens and mean embryo death time in embryonating chicken eggs revealed that the Bangladeshi isolates are velogenic. Inoculation of 35-day-old chickens with two NDV isolates (LT67 and N5) resulted in 100% morbidity by 3 days post inoculation (DPI), and all birds succumbed to infection by 7 DPI. Massive hemorrhages, congestion and necrotic lesions were observed in different visceral organs, which were typical for infection with a velogenic viscerotropic pathotype of NDV. At microscopic examination, tracheitis, severe pneumonia, focal proventriculitis, transmural enteritis, focal myocarditis, severe congestion and necrosis in kidneys, and lymphoid depletion in lymphoid tissues were found. Our study reports the first outbreak of the panzootic genotype VII.2 NDV in poultry in Bangladesh and documents a possible recent re-introduction of this NDV genotype from Southeast or East Asia. This study further provides viral distribution and epidemiological data that can facilitate the effective control of NDV.

A Pigeon-Derived Sub-Genotype XXI.1.2 Newcastle Disease Virus from Bangladesh Induces High Mortality in Chickens

Newcastle disease virus (NDV) is a significant pathogen of poultry; however, variants also affect other species, including pigeons. While NDV is endemic in Bangladesh, and poultry isolates have been recently characterized, information about viruses infecting pigeons is limited. Worldwide, pigeon-derived isolates are commonly of low to moderate virulence for chickens. Here, we studied a pigeon-derived NDV isolated in Bangladesh in 2010. To molecularly characterize the isolate, we sequenced its complete fusion gene and performed a comprehensive phylogenetic analysis. We further studied the biological properties of the virus by estimating mean death time (MDT) and by experimentally infecting 5-week-old naïve Sonali chickens. The studied virus clustered in sub-genotype XXI.1.2 with NDV from pigeons from Pakistan isolated during 2014–2018. Deduced amino acid sequence analysis showed a polybasic fusion protein cleavage site motif, typical for virulent NDV. The performed in vivo pathogenicity testing showed a MDT of 40.8 h, and along with previously established intracerebral pathogenicity index of 1.51, these indicated a velogenic pathotype for chickens, which is not typical for pigeon-derived viruses. The experimental infection of chickens resulted in marked neurological signs and high mortality starting at 7 days post infection (dpi). Mild congestion in the thymus and necrosis in the spleen were observed at an advanced stage of infection. Microscopically, lymphoid depletion in the thymus, spleen, and bursa of Fabricius were found at 5 dpi, which progressed to severe in the following days. Mild to moderate proliferation of glial cells was noticed in the brain starting at 2 dpi, which gradually progressed with time, leading to focal nodular aggregation. This study reports the velogenic nature for domestic chickens of a pigeon-derived NDV isolate of sub-genotype XXI.1.2. Our findings show that not all pigeon-derived viruses are of low virulence for chickens and highlight the importance of biologically evaluating the pathogenicity of NDV isolated from pigeons.

Surveillance on respiratory diseases reveals enzootic circulation of both H5 and H9 avian influenza viruses in small-scale commercial layer farms of Bangladesh

Poultry production in Bangladesh has been experiencing H5N1 highly pathogenic avian influenza (HPAI) and H9N2 low pathogenic avian influenza (LPAI) for the last 14 years. Vaccination of chickens against H5 HPAI is in practice since the end of 2012. Subsequently, the official reporting of HPAI outbreaks gradually decreased. However, the true extent of circulation of avian influenza virus (AIV) in commercial poultry production is not clear. To explore this, we conducted active surveillance in 422 small-scale commercial layer farms in 20 villages of Mymensingh and Tangail districts of Bangladesh during 2017 and 2018 for the presence of diseases with respiratory signs. A total of 88 farms with respiratory disease problems were identified and investigated during the surveillance. In addition, 22 small-scale commercial layer farms in the neighbouring areas with respiratory disease problem were also investigated on request from the farmers. Pooled samples of oropharyngeal swabs from live birds or respiratory tissues from dead birds of the farm suffering from respiratory disease problem were tested for molecular detection of avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum and Avibacterium paragallinarum. A total of 110 farms (88 in the surveillance site and 22 in the neighbouring region) were investigated, and one or more respiratory pathogens were detected from 89 farms. AIV was detected in 57 farms often concurrently with other pathogens. Among these 57 farms, H5, H9, both H5 and H9 or non-H5 and non-H9 AIV were detected in 28, 9, 13 or 7 farms, respectively. Birds of most of the H5 AIV-positive farms did not present typical clinical signs or high mortality. Twenty such farms were observed longitudinally, which had only 1.05%-5.50% mortality but a marked drop in egg production. This widespread circulation of H5 AIV along with H9 AIV and other pathogens in small-scale commercial layer farms, often with low mortality, reaffirms the enzootic circulation of AIV in Bangladesh, which may escape syndromic surveillance focused on unusual mortality only. To reduce public health risks, strengthening of the control programme with comprehensive vaccination, enhanced biosecurity, improved surveillance and outbreak response is suggested.

Genetic and biological characterization of Newcastle disease viruses circulating in Bangladesh during 2010-2017: further genetic diversification of class II genotype XIII in Southcentral Asia

Newcastle disease virus (NDV) is endemic in Bangladesh and is a major threat to commercial poultry operations. While complete fusion (F) genes are recommended for molecular characterization and classification of NDV isolates, heretofore, only partial F gene data have been available for Bangladeshi NDVs. To this end, we obtained the full-length F gene coding sequences of 11 representative NDVs isolated in Bangladesh between 2010 and 2017. In addition, one of the viruses (MK934289/chicken/Bangladesh/C161/2010) was used in an experimental infection of chickens to establish the viral pathotype and study gross and microscopic lesions. Phylogenetic analysis provided evidence that all studied Bangladeshi isolates belong to genotype XIII.2 of class II NDVs. Six of the viruses were isolated between 2010 and 2017 and grouped together with isolates from neighbouring India during 2013-2016. Another four Bangladeshi isolates (2010-2016) formed a separate monophyletic branch within XIII.2 and showed high nucleotide distance from the isolates from India and the other six Bangladeshi viruses within the sub-genotype; however, none of these groups fulfils all classification criteria to be named as a separate sub-genotype. The eleventh Bangladeshi virus studied here (C162) was genetically more distant from the remaining isolates. It out-grouped the viruses from sub-genotypes XIII.2.1 and XIII.2.2 and showed more than 9.5 % nucleotide distance from all genotype XIII sub-genotypes. This isolate may represent an NDV variant that is evolving independently from the other viruses in the region. The experimental infection in chickens revealed that the tested isolate (C161) is a velogenic viscerotropic virus. Massive haemorrhages, congestion and necrosis in different visceral organs, and lymphoid depletion in lymphoid tissues, typical for infection with velogenic NDV, were observed. Our findings demonstrate the endemic circulation of sub-genotype XIII.2 in Southcentral Asia and further genetic diversification of these viruses in Bangladesh and neighbouring India. This constant evolution of the viruses may lead to the establishment of new genetic groups in the region. Additional historical and prospective virus and surveillance data from the region and neighbouring countries will allow a more detailed epidemiological inference.

Sequential Pathology of a Genotype XIII Newcastle Disease Virus from Bangladesh in Chickens on Experimental Infection

The sequential pathology of a genotype XIII Bangladeshi strain of Newcastle disease virus (NDV) was studied in 5-weeks old chickens. Layer chickens of ISA Brown breed were inoculated through the intranasal and intraocular routes with the BD-C161/2010 strain of NDV and examined at different times post-infection (pi). NDV-infected chickens showed depression at 3 days pi (dpi) followed by dropped wings, paralysis and death starting at 4 dpi. Lungs of infected chickens showed hemorrhagic lesions starting at 24 hours pi (hpi) that was followed by pallor and slight contraction by 2 to 3 dpi and subsequently developed into severe hemorrhagic pneumonia with mononuclear cell infiltration. Hemorrhagic and necrotizing lesions were found in different visceral organs including proventriculus, intestine, gut-associated lymphoid tissues, liver and kidneys starting at 3 dpi that progressed rapidly. Severe lymphoid depletion was observed in the thymus, spleen and bursa of Fabricius starting at 1–3 dpi followed by hemorrhages, necrosis, inflammation and atrophy at 4–5 dpi. In the brain, mild neuronal lesions such as focal to diffuse encephalitis with encephalomalacia was observed at 2–3 dpi and moderate and diffuse meningoencephalitis with encephalomalacia at advanced stages. In conclusion, the BD-C161/2010 strain of NDV produced lesions typical of velogenic viscerotropic pathotype of NDV.

Co-subsistence of avian influenza virus subtypes of low and high pathogenicity in Bangladesh: Challenges for diagnosis, risk assessment and control

Endemic co-circulation of potentially zoonotic avian influenza viruses (AIV) of subtypes H5N1 and H9N2 (G1 lineage) in poultry in Bangladesh accelerated diversifying evolution. Two clinical samples from poultry obtained in 2016 yielded five different subtypes (highly pathogenic [HP] H5N1, HP H5N2, HP H7N1, HP H7N2, H9N2) and eight genotypes of AIV by plaque purification. H5 sequences grouped with clade 2.3.2.1a viruses while N1 was related to an older, preceding clade, 2.2.2. The internal genome segments of the plaque-purified viruses originated from clade 2.2.2 of H5N1 or from G1/H9N2 viruses. H9 and N2 segments clustered with contemporary H9N2 strains. In addition, HP H7 sequences were detected for the first time in samples and linked to Pakistani HP H7N3 viruses of 2003. The unexpected findings of mixtures of reassorted HP H5N1 and G1-like H9N2 viruses, which carry genome segments of older clades in association with the detection of HP H7 HA segments calls for confirmation of these results by targeted surveillance in the area of origin of the investigated samples. Hidden niches and obscured transmission pathways may exist that retain or re-introduce genome segments of older viruses or reassortants thereof which causes additional challenges for diagnosis, risk assessment and disease control.

Chicken viperin inhibits Newcastle disease virus infection in vitro: A possible interaction with the viral matrix protein

Viperin is an interferon-inducible protein that helps in protecting mammals against various virus infections. Viperin is a highly conserved member of the interferon-stimulated genes (ISG) family in many species. Viperin has been shown to play a pivotal role in the innate immunity of chicken; however, its role has not been explored in its antiviral potential. Newcastle disease virus (NDV) is the causative agent of an infectious disease in poultry. In the present study, we have shown the anti-NDV effect of chicken viperin (cViperin). The impact of cViperin upon NDV infection was investigated in chicken embryo fibroblast. The modeling of the cViperin protein was done using I-TASSER and ZDOCK is used to predict the possible interaction with the matrix protein of NDV. The interaction was further confirmed by co-immunoprecipitation assay using recombinant matrix protein of NDV with the recombinant cViperin. The recombinant NDV expressing cViperin showed reduced replication of the virus upon its growth kinetics. Our results suggest downregulation of NDV replication in the presence of cViperin. The study will be critical to elaborate our understanding of the chicken innate immune system which could help develop antiviral strategies against NDV infection.

Adaptation of Newcastle Disease Virus (NDV) in Feral Birds and their Potential Role in Interspecies Transmission

Introduction:

Newcastle Disease (ND), caused by Avian avulavirus 1 (AAvV 1, avulaviruses), is a notifiable disease throughout the world due to the economic impact on trading restrictions and its embargoes placed in endemic regions. The feral birds including aquatic/migratory birds and other wild birds may act as natural reservoir hosts of ND Viruses (NDVs) and may play a remarkable role in the spread of the virus in environment. In addition, other 19 avulaviruses namely: AAvV 2 to 20, have been potentially recognized from feral avian species.

Expalantion:

Many previous studies have investigated the field prevailing NDVs to adapt a wide range of susceptible host. Still the available data is not enough to declare the potential role of feral birds in transmission of the virus to poultry and/or other avian birds. In view of the latest evidence related to incidences of AAvVs in susceptible avian species, it is increasingly important to understand the potential of viruses to transmit within the domestic poultry and other avian hosts. Genomic and phylogenomic analysis of several investigations has shown the same (RK/RQRR↓F) motif cleavage site among NDV isolates with same genotypes from domestic poultry and other wild hosts. So, the insight of this, various semi-captive/free-ranging wild avian species could play a vital role in the dissemination of the virus, which is an important consideration to control the disease outbreaks. Insufficient data on AAvV 1 transmission from wild birds to poultry and vice versa is the main constraint to understand about its molecular biology and genomic potential to cause infection in all susceptible hosts.

Conclusion:

The current review details the pertinent features of several historical and contemporary aspects of NDVs and the vital role of feral birds in its molecular epidemiology and ecology.

Emerging variant of genotype XIII Newcastle disease virus from Northeast India

Northeast India with its rich and diverse avifauna acts as a hotbed for emerging virulent Newcastle disease virus (NDV) strains. The present work describes the molecular and pathogenic characterization of NDV strain isolated from Pandu, Assam, India. Clinicopathological and genetic analysis showed the virulent nature of NDV strain Pandu. On molecular phylogenetic and evolutionary distance analysis, the NDV strain Pandu formed a distinct clade within the genotype XIII of class II NDV, suggesting a new sub-genotype XIIIc. The accumulation of mutations in the NDV strain Pandu makes it divergent enough to be considered as a new sub-genotype. The proposed NDV sub-genotype XIIIc consists of strains recently reported from eastern and northeastern India.

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.

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.