Comparative clinico-pathological assessment of velogenic (sub-genotype VIIi) and mesogenic (sub-genotype VIm) Avian avulavirus 1 in chickens and pigeons

Geographic distribution and genetic diversity of Newcastle disease virus in pigeons from Pakistan

RESEARCH HIGHLIGHTS

Virulent NDV genotypes were repeatedly isolated from pigeons.Evidence of epidemiological links among viruses isolated from various locations.Distinct phylogenetic branches suggest separate, simultaneous evolution of NDVs.Study information could be helpful in the development of an effective vaccine.

Detection of Avian Orthoavulavirus-1 genotypes VI.2.1 and VII.1.1 with neuro-viscerotropic tropism in some backyard pigeons (Columbidae) in Eastern Saudi Arabia

Introduction

Avian orthoavulavirus-1 (AOAV1) has a wide host range, including domestic and wild birds. The present study aimed to identify the currently circulating AOAV1 strains from some outbreaks in some backyard pigeons in the eastern region of Saudi Arabia (ERSA).

Methods

Tracheal/cloacal swabs and tissue specimens were collected from eight backyards in Al-Ahsa, ERSA, between January 2021 and March 2023. Samples were tested for the presence of AOAV1 using commercial real-time RT-PCR. Part of the fusion gene was also amplified by gel-based RT-PCR, and the obtained amplicons were sequenced.

Results and discussion

AOAV1 was detected in samples from the eight flocks. The retrieved sequences from samples of 6/8 pigeon backyards are reported. Phylogenetic analysis based on the obtained sequences from these backyard pigeons showed the segregation of the obtained sequences in AOAV1 genotypes VI.2.1 and VII.1.1. Clinically, nervous manifestations were dominant in pigeons infected with both genotypes. Respiratory manifestations and significantly higher overall mortality rate were induced by genotype VI.2.1. The deduced amino acid sequences of the fusion protein cleavage site (FPCS) showed that all the detected isolates belong to velogenic strains. Differences in clinical profiles induced by the natural infection of pigeons with AOAV1 genotypes VI.2.1 and VII.1.1 were reported. The present findings highlight the potential roles of some backyard pigeons in the long-distance spread and cross-species transmission of the reported AOAVI genotypes. Further research is required to perform biotyping and pathotyping of the reported strains.

Comparative pathogenicity of a genotype XXI.1.2 pigeon Newcastle disease virus isolate in pigeons and chickens

Here, we performed molecular and pathogenic characterization of a Newcastle disease virus (NDV) isolate from pigeons in Bangladesh. Molecular phylogenetic analysis based on the complete fusion gene sequences classified the three study isolates into genotype XXI (sub-genotype XXI.1.2) together with recent NDV isolates obtained from pigeons in Pakistan (2014-2018). The Bayesian Markov Chain Monte Carlo analysis revealed that the ancestor of Bangladeshi pigeon NDVs and the viruses from sub-genotype XXI.1.2 existed in the late 1990s. Pathogenicity testing using mean embryo death time pathotyped the viruses as mesogenic, while all isolates carried multiple basic amino acid residues at the fusion protein cleavage site. Experimental infection of chickens and pigeons revealed no or minimum clinical signs in chickens, while a relatively high morbidity (70%) and mortality (60%) were observed in pigeons. The infected pigeons showed extensive and systemic lesions including hemorrhagic and/or vascular changes in the conjunctiva, respiratory and digestive system and brain, and atrophy in the spleen, while only mild congestion in the lungs was noticed in the inoculated chickens. Histologically, consolidation in the lungs with collapsed alveoli and edema around the blood vessels, hemorrhages in the trachea, severe hemorrhages and congestion, focal aggregation of mononuclear cells, and single hepatocellular necrosis in the liver, severe congestion, multifocal tubular degeneration, and necrosis, as well as mononuclear cell infiltration in the renal parenchyma, encephalomalacia with severe neuronal necrosis with neuronophagia were noticed in the brain in infected pigeons. In contrast, only slight congestion was found in lungs of the infected chickens. qRT-PCR revealed the replication of the virus in both pigeons and chickens; however, higher viral RNA loads were observed in oropharyngeal and cloacal swabs, respiratory tissues, and spleen of infected pigeons than the chickens. In conclusion, genotype XXI.1.2 NDVs are circulating in the pigeon population of Bangladesh since 1990s, produce high mortality in pigeons with pneumonia, hepatocellular necrosis, renal tubular degeneration, and neuronal necrosis in pigeons, and may infect chickens without overt signs of clinical disease and are likely to shed viruses via the oral or cloacal routes.

A comparative evaluation of transcriptome changes in lung and spleen tissues of chickens infected with velogenic and mesogenic Avian Orthoavulavirus 1

Newcastle disease is an acute, highly contagious disease responsible for severe economic losses to the poultry industry worldwide. Clinical assessment of different pathotypes of AOaV-1 strains is well-elucidated in chickens. However, a paucity of data exists for a comparative assessment of avian innate immune responses in birds after infection with two different pathotypes of AOaV-1. We compared early immune responses in chickens infected with a duck-originated velogenic strain (high virulent: genotype VII) and a pigeon-originated mesogenic stain (moderate virulent; genotype VI). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) identified 4737 differentially expressed genes (DEGs) in the transcriptional profiles of lung and spleen tissues of chickens infected with both pathotypes. More DEGs were expressed in spleen tissue infected with velogenic strain compared to spleen or lung exposed to mesogenic strain. An enriched expression was observed for genes involved in metabolic processes and cellular components, including innate immune-associated signaling pathways. Most DEGs were involved in RIG-I, Toll-like, NF-Kappa B, and MAPK signaling pathways to activate interferon-stimulated genes (ISGs). This study provided a comparative insight into complicated molecular mechanisms and associated DEGs involved in early immune responses of birds to two different AOaV-1 strains.

Surveillance and Assessment of Risk Factors for Newcastle Disease Virus from Live Bird Retail Stalls in Lahore District of Pakistan

Live bird markets (LBMs) in Asian countries are considered hubs for the spread of several poultry viruses. In Pakistan, there is a lack of uniformity in practices used in LBMs, which leads to the spread of poultry diseases. A cross-sectional survey was conducted in June-October 2017 to determine the circulation of Newcastle disease virus (NDV) in chickens being sold in live bird retail stalls (LBRSs) and to identify potential risk factors associated with estimated prevalence. A total of 189 stalls (n = 1134 birds) distributed in eight administrative towns of Lahore were visited. A pool of six oropharyngeal swabs was collected from each stall and tested by real-time reverse transcriptase PCR for the presence of NDV. Forty-two out of 189 swabs were found positive with an overall prevalence of 22.22% (95% confidence interval [Cl]: 16.88%-28.67%). Data for 11 potential risk factors acquired through questionnaires were analyzed by survey-weighted logistic regression and prevalence odds ratios (ORs) for associated risk factors were calculated. A final multivariable model identified three risk factors for NDV prevalence in LBRSs, including trading other poultry breeds alongside broilers (OR = 2.41; 95% confidence interval [CI] = 1.5-6.1), purchasing birds from mixed sources (OR = 3.12; 95% CI = 1.4-11.9), and number of birds sold per day (OR = 6.32; 95% CI = 1.9-23.5). Additionally, 24 selected samples were sequenced and phylogenetic analysis of the complete fusion gene (1662 bp) revealed that all isolates belonged to Subgenotype VII.2. This study provides important information on the epidemiology of NDV in Pakistan and highlights the importance of implementing surveillance and biosecurity practices in LBRSs.

Pathology of Komarov vaccine in Hitchner B1 vaccinated and unvaccinated broilers

Newcastle disease (ND) is a major problem of poultry production worldwide. Control is by biosecurity and vaccination. In this project, we studied the pathology of Komarov vaccine which is commonly used in many countries of Africa on the Hitchner B1 (HBI) vaccinated and unvaccinated broilers. Seventy-five Arbor Acres broilers were obtained at 1 day old. Twenty-five of the broilers were given HB1 vaccine at the hatchery and Komarov vaccine at 5 weeks of age (group HK). A second group of 25 broilers were given only Komarov vaccine at 5 weeks of age (group K). The third group remained as unvaccinated (UU). All the groups were observed for clinical signs and lesions. Depression, sneezing, coughing and noisy respiration were observed in group K broilers from day 2 post Komarov vaccination (PKV). Leg paralysis occurred in 6 broilers on day 8 PKV. The clinical signs were milder in the HK broilers. Only one broiler showed leg paralysis in this group on day 18 PKV. No mortality occurred in the three groups. The bursa, spleen and thymus showed mild to moderate enlargement, atrophy and depletion of lymphocytes on days 3, 5, 8 and 14 PKV in HK and K groups. The trachea and lungs were congested. The haemagglutination inhibition (HI) antibody titres in the K group were higher than those of HK and UU groups on days 7, 24 and 21 PKV. The above observations show that Komarov vaccine may cause no mortality in vaccinated and unvaccinated broilers and higher HI antibodies are produced in broilers that have not been vaccinated earlier.

Zoonotic potential of Newcastle disease virus: Old and novel perspectives related to public health

Newcastle disease virus (NDV) has a worldwide distribution, causing lethal infection in a wide range of avian species. Affected birds develop respiratory, digestive and neurologic symptoms with profound immunosuppression. Mild systemic Newcastle disease (ND) infection restricted to the respiratory and neurological systems can be observed in humans and other non-avian hosts. Evidence of ND infection and its genome-based detection have been reported in Bovidae (cattle and sheep), Mustelidae (mink), Cercetidae (hamster), Muridae (mice), Leporidae (rabbit), Camelidae (camel), Suidae (pig), Cercophithecidae (monkeys) and Hominidae (humans). Owing to frequent ND outbreaks in poultry workers, individuals engaged in the veterinary field, including poultry production or evisceration and vaccine production units have constantly been at a much higher risk than the general population. A lethal form of infection has been described in immunocompromised humans and non-avian species including mink, pig and cattle demonstrating the capability of NDV to cross species barriers. Therefore, contact with infectious material and/or affected birds can pose a risk of zoonosis and raise public health concerns. The broad and expanding host range of NDV and its maintenance within non-avian species hampers disease control, particularly in disease-endemic settings.

Comparative pathogenicity of two closely related Newcastle disease virus isolates from chicken and pigeon respectively

Newcastle disease (ND), caused by virulent Newcastle disease virus (NDV), is a highly contagious disease that has led to tremendous economic losses worldwide. Pigeon paramyxovirus type 1 (PPMV-1) is an antigenic and host variant of NDV. However, limited in-depth studies are available concerning side-by-side comparison of pathogenicity of PPMV-1 and its phylogenetically close NDV both in chickens and pigeons. To this end, two phylogenetically closely related NDV isolates, Kuwait 256 and JS/07/04/Pi from chicken and pigeon respectively were pathotypically and genotypically characterized in this study. The results indicated that Kuwait 256 was a velogenic strain, while JS/07/04/Pi was a mesogenic strain based on the mean death time of chick embryos (MDT) and intracerebral pathogenicity index in 1-day-old chicks (ICPI). Pathogenicity tests showed that Kuwait 256 caused severe clinical signs and 100 % mortality, while JS/07/04/Pi caused no apparent disease in chickens. Interestingly, both Kuwait 256 and JS/07/04/Pi caused morbidity and mortality in pigeons. Notably, pigeons infected with JS/07/04/Pi exhibited viral shedding for longer time compared to Kuwait 256-infected pigeons. Collectively, the findings of this study suggested that PPMV-1 decreased the pathogenicity in chickens but gained a survival advantage over NDV of chicken origin after its adaptive variation in pigeons based on the previous evidence that PPMV-1 originated from chicken-origin viruses. This study laid the foundation for the elucidation of the molecularmechanism underlying difference in pathogenicity of PPMV-1 and chicken-origin NDV in chickens.

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.

A comparative evaluation of serum biochemistry profile and antigenic relatedness among velogenic and mesogenic Avian avulavirus 1 infection in chickens and pigeons

Newcastle disease (ND), caused by virulent Avian avulavirus 1 (AAvV 1), affects variety of avian species around the globe. Several AAvV 1 viruses of different genotypes have recently emerged with varying clinical impacts on their susceptible hosts. Although experimental infection with velogenic and mesogenic strains in chickens and pigeons is well-studied, nevertheless, there exists a paucity of data for comparative variations in serum biochemistry profile of susceptible hosts upon challenge with isolates of varying pathogenicities. With this background, a comparative assessment of a range of serum biochemical parameters was made following challenge with duck-originated velogenic strain (sub-genotype VIIi; MF437287) and pigeon-originated mesogenic strain (sub-genotype VIm; KU885949) in chickens and pigeons. For each of the isolate, commercial broiler chickens and wild pigeons were challenged (10^-6.51 EID₅₀/0.1 mL for sub-genotype VIIi and 10^-6.87 EID₅₀/0.1 mL sub-genotype Vim) separately via intranasal and intraocular route. Sera were collected on 0, 3rd, 5th, 7th, and 9th day post-infection (dpi), and processed for quantitative analysis of different biochemical parameters. By day 3 post-infection (pi), a substantial decrease (p < 0.0001) in serum alkaline phosphatase (ALP) was observed in chickens and pigeons challenged with velogenic isolate. On the other hand, from day 5 pi and onward, a significant increase (p < 0.001) in serum ALP and total protein concentration was observed exclusively in pigeons challenged with mesogenic isolate. For serum aspartate aminotransferase (AST), a significant increase (p < 0.05) in concentration was observed on day 3 pi which decreased from day 5 pi and onward in pigeons and chickens challenged with mesogenic isolate. Also, to reveal antigenic differences among homologous and heterologous vaccine and field-prevalent strains, cross-hemagglutination inhibition assay demonstrated antigenically diverse nature (R-value < 0.5) of both strains from vaccine strain (LaSota, genotype II). The study concludes antigenic differences among prevalent genotypes than vaccine strain and, although requires further studies to ascertain study outcomes, the serum biochemical profile may facilitate presumptive diagnosis of disease in their susceptible hosts.