Newcastle disease in Nigeria: epizootiology and current knowledge of circulating genotypes

Genomic Diversity and Geographic Distribution of Newcastle Disease Virus Genotypes in Africa: Implications for Diagnosis, Vaccination, and Regional Collaboration

The emergence of new virulent genotypes and the continued genetic drift of Newcastle disease virus (NDV) implies that distinct genotypes of NDV are simultaneously evolving in different geographic locations across the globe, including throughout Africa, where NDV is an important veterinary pathogen. Expanding the genomic diversity of NDV increases the possibility of diagnostic and vaccine failures. In this review, we systematically analyzed the genetic diversity of NDV genotypes in Africa using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Information published between 1999 and 2022 were used to obtain the genetic background of different genotypes of NDV and their geographic distributions in Africa. The following genotypes were reported in Africa: I, II, III, IV, V, VI, VII, VIII, XI, XIII, XIV, XVII, XVIII, XX, and XXI. A new putative genotype has been detected in the Democratic Republic of the Congo. However, of 54 African countries, only 26 countries regularly report information on NDV outbreaks, suggesting that this number may be vastly underestimated. With eight different genotypes, Nigeria is the country with the greatest genotypic diversity of NDV among African countries. Genotype VII is the most prevalent group of NDV in Africa, which was reported in 15 countries. A phylogeographic analysis of NDV sequences revealed transboundary transmission of the virus in Eastern Africa, Western and Central Africa, and in Southern Africa. A regional and continental collaboration is recommended for improved NDV risk management in Africa.

Seroprevalence and risk factors associated with Newcastle disease in backyard chickens in West Kordofan State, Sudan

Background and Aim

Newcastle disease (ND), a major constraint to poultry production worldwide, is a highly contagious disease of many species of domestic, exotic, and wild birds caused by ND virus (NDV). Epidemiological studies are lacking regarding ND in village chickens, including the traditional and intensive production systems used in Sudan. However, it is necessary to develop appropriate strategies to control the disease. Therefore, this study aimed to estimate the flock- and bird-level seroprevalence of NDV in backyard chickens in West Kordofan State, Sudan, and to identify the risk factors associated with ND in the study area.

Materials and Methods

The seroprevalence of the circulating NDV and bird-level risk factors associated with ND was determined in backyard chickens from March to October 2017, in six villages (Alnowara, Alleait, Geibaish, Baiad, Sougoh, and Alnuhoud) in the Geibaish and Elnuhoud localities of West Kordofan State.

Results

Using the hemagglutination-inhibition test, the bird- and flock-level seroprevalences of antibodies to NDV were estimated as 20.6% (78/378) and 45% (18/40), respectively. Bird-level NDV seropositivity in backyard chickens was significantly associated with the reason for raising chickens, type of housing, contact with neighboring poultry, contact with wild birds, and chicken mortality caused by infectious diseases (p ≤ 0.05).

Conclusion

This study indicated that NDV is circulating in backyard chickens and may act as a potential source of infection for other birds and thus persistence of ND among local traditionally managed chickens in the areas of West Kordofan State. Risk factors contributing to ND occurrence are important for designing appropriate prevention and control strategies.

Evaluating Disease Threats to Sustainable Poultry Production in Africa: Newcastle Disease, Infectious Bursal Disease, and Avian Infectious Bronchitis in Commercial Poultry Flocks in Kano and Oyo States, Nigeria

The growth of the poultry industry in Nigeria is constrained by major poultry diseases, despite the implementation of vaccination programs. This study aimed to assess the level of protection against Newcastle disease (ND), infectious bursal disease (IBD), and avian infectious bronchitis (IB) afforded by current vaccination schedules and characterize the circulating virus strains in commercial poultry flocks in Nigeria. A cross-sectional study was conducted on 44 commercial poultry farms in Oyo and Kano states of Nigeria. Serum and tissue samples and data on flock, clinical and vaccination records were collected on each farm. Farms were classified as being protected or not protected against ND, IBD and IB based on a defined criterion. Real-time reverse transcription polymerase chain reaction (rRT-PCR) testing was performed for each target virus on tissue samples and positive samples were sequenced. A total of 15/44 (34.1%), 35/44 (79.5%), and 1/44 (2.3%) farms were considered to be protected against ND, IBD, and IB, respectively, at the time of sampling. NDV RNA was detected on 7/44 (15.9%) farms and sequences obtained from 3/7 farms were characterized as the lentogenic strain. Infectious bursal disease virus (IBDV) RNA was detected on 16/44 (36.4%) farms tested; very virulent (vv) IBDV and non-virulent (nv) IBDV strains were both detected in 3/16 (18.8%) positive samples. Sequences of IBDV isolates were either clustered with a group of genotype 3 virulent IBDV strains or were related to vaccine strains MB and D78 strains. IBV RNA was detected on 36/44 (81.8%) farms, with variant02, Massachusetts, 4/91, and Q1 variants detected. Sequences of IBV isolates were either clustered with the vaccines strains Massachusetts M41 and H120 or were most closely related to the D274-like strains or a clade of sequences reported in Nigeria and Niger in 2006 and 2007. This study revealed that most study farms in Oyo and Kano states did not have adequate protective antibody titers against IBV and NDV and were therefore at risk of field challenge. Infectious bursal disease virus and IBV RNA were detected on farms with a history of vaccination suggesting potential vaccination failure, or that the vaccine strains used mismatch with the circulating strains and are therefore not protective.

Discriminant analysis of response to Newcastle disease and heat tolerance among chicken genotypes in hot humid tropical environment

Newcastle disease and heat stress reduce the productivity of local chickens of Nigeria (LCN). This study compared the antibody response to Newcastle disease and heat tolerance among different LCN genotypes in hot humid tropics using multivariate discriminant analysis. A total of 299 birds were used for the study. Geometric mean titre against Newcastle disease before vaccination (GMTB), geometric mean titre against Newcastle disease after vaccination (GMTA), rectal temperature at week 4 (RT4), pulse rate at week 4 (PR4), respiratory rate at week 4 (RR4), heat stress index at week 4 (H4), rectal temperature at week 13 (RT13), pulse rate at week 13 (PR13), respiratory rate at week 13 (RR13) and heat stress index at week 13 (H13) were measured. All the traits were significantly (p < 0.05) affected by the genotype while sex differences were only observed in GMTB, GMTA and RR13. The stepwise discriminant analysis revealed RR4, PR13, RT13, H4, GMTA, GMTB, H13 and RT4 to be effective in differentiating the three chicken genotypes. Two canonical variables that accounted for 60.21% and 39.79% of the total variation were revealed. Linear discriminant functions for differentiation of the three chicken genotypes were also developed. 87.39% of normal feather, 76.58% of naked neck and 100% of frizzle feather chickens were correctly assigned into their genotypes. The longest Mahalanobis distance was observed between normal feather and frizzle feather chickens. The discriminant functions developed in this study could be used to differentiate the three genotypes of LCN using antibody response to Newcastle disease and heat tolerance.

Vaccine Quality Is a Key Factor to Determine Thermal Stability of Commercial Newcastle Disease (ND)Vaccines

Vaccination against Newcastle disease (ND), a devastating viral disease of chickens, is often hampered by thermal inactivation of the live vaccines, in particular in tropical and hot climate conditions. In the past, “thermostable” vaccine strains (I-2) were proposed to overcome this problem but previous comparative studies did not include formulation-specific factors of commercial vaccines. In the current study, we aimed to verify the superior thermal stability of commercially formulated I-2 strains by comparing six commercially available ND vaccines. Subjected to 37 °C as lyophilized preparations, two vaccines containing I-2 strains were more sensitive to inactivation than a third I-2 vaccine or compared to three other vaccines based on different ND strains. However, reconstitution strains proved to have a comparable tenacity. Interestingly, all vaccines still retained a sufficient virus dose for protection (10⁶ EID₅₀) after 1 day at 37 °C. These results suggest that there are specific factors that influence thermal stability beyond the strain-specific characteristics. Exposing ND vaccines to elevated temperatures of 51 and 61 °C demonstrated that inactivation of all dissolved vaccines including I-2 vaccine strains occurred within 2 to 4 h. The results revealed important differences among the vaccines and emphasize the importance of the quality of a certain vaccine preparation rather than the strain it contains. These data highlight that regardless of the ND strain used for vaccine preparation, the appropriate cold chain is mandatory for keeping live ND vaccines efficiency in hot climates.

Spatial Distribution and Seroprevalence of Newcastle Disease in Kaduna State, Nigeria

Newcastle disease is one of the greatest constraints to the development of poultry production in Nigeria. In this study, the spatial distribution of Newcastle disease antibodies was determined using the Geographic Information System. A total of 400 serum samples were collected from chickens in districts around Kaduna Metropolis and screened for Newcastle disease virus antibodies using the haemagglutination inhibition test done according to the procedure of OIE (2002). The spatial distribution demonstrated that the highest antibody titre level for Newcastle disease was closely associated with communities that were at entry points (Zaria— Kaduna road; Nnamdi Azikiwe bypass road; Television garage; Abuja—Kaduna expressway and Kachia road) to the metropolis and houses that are closely situated near live bird markets signifying the importance of bird movements in the spread of the disease. About 31 % (124 of 400) of chickens had antibodies to Newcastle disease virus, with exotics breeds (32.0 %) with more Newcastle disease virus antibodies than local breeds (29.8 %). The Newcastle disease prevalence was 33.9 % (39 out of 115), 31.8 % (41 out of 129) and 28.2 % (44 out of 156) for Kaduna North, Kaduna South and Chikun Local Government Areas (LGA), respectively. A Newcastle disease prevalence of 29.8 % (54 out of 181) was recorded in the local chickens, while 32.0 % (70 out of 219) was obtained from the exotic chickens.

Prevalence of Newcastle disease virus in feces of free-range turkeys in Enugu, Nigeria

Background and Aim:

Newcastle disease (ND) virus of free-range turkeys may be linked to outbreaks of ND in backyard chickens seen during Harmattan in Enugu State in Southeast Nigeria. This study aimed to determine the prevalence of ND virus and (NDV) detect NDV in the feces of free-range, domestic turkeys in Enugu, Nigeria.

Materials and Methods:

A total of 569 serum and 569 cloacal swab samples were collected from adult turkeys in selected households that keep turkeys and chickens together in the study area. The serum samples were assayed for antibodies against NDV using the hemagglutination inhibition (HI) test, whereas the cloacal samples were subjected to virus detection using a hemagglutination (HA) test.

Results:

A total of 186 serum samples (32.7%) were positive for NDV and 383 (67.3%) were negative. Of the 186 NDV-positive serum samples, 138 (74.2%) had HI titers ≥ 8. The remaining 48 (25.8%) serum samples had HI titers <8. NDV was detected from the cloacal swabs of turkeys with NDV -positive serum samples.

Conclusion:

The turkeys in this study were not previously vaccinated with the NDV vaccine; thus, those with NDV -positive serum samples and virus shedding in their feces may be potential risks to chickens reared in the same households as well as on commercial farms in the area. Those turkeys with sera negative for NDV are regarded to be at risk if they encounter a virulent strain of NDV. Regular vaccination of turkeys against the NDV is advised, especially in backyard farms, where turkeys are reared together with chickens and other species of poultry.

Molecular and pathological investigation of a natural outbreak of Newcastle disease caused by genotype XVII in White Leghorn chickens

ABSTRACT Newcastle disease (ND) is an infectious viral poultry disease with great economic consequences. In developing countries, outbreaks of ND caused by virulent Newcastle disease virus (NDV) have been identified as a limiting factor to the growth of the poultry industry. Limited reports exist on the pathology of natural field infection caused by NDV genotype XVII in chickens. Here, we present clinical, pathological and molecular investigation of confirmed ND in a 24-week-old layer-type, semi-intensive poultry flock with recorded mortality of over 50%. During PM examination, tissues were harvested for virus isolation, histopathology and immunohistochemistry. Virus isolation was performed in 10-day-old embryonated chicken eggs, and a haemagglutinating agent thereof identified by one-step reverse transcription-polymerase chain reaction (RT-PCR). For the genotyping of the isolate, the full fusion gene was sequenced. Clinical signs observed included general body lethargy, inappetence and greenish diarrhoeic faeces from the cloaca before death with daily mortality exceeding 100 chickens. The pathology was characteristic of a viral haemorrhagic infection, with serosal haemorrhages, mucosal surface erosion and ulceration. In most of the carcasses, the main lesions seen included airsacculitis, meningeal congestion, haemorrhagic oophoritis, pancreatic necrosis, enteritis and faecal matting of the vent. Virus isolation and RT-PCR made a confirmatory diagnosis of ND. Based on the cleavage site motif sequence (¹¹²RRQKR/F¹¹⁷), the isolate was identified as a virulent strain with phylogenetic analysis showing clustering in genotype XVII viruses. To the best of the authors' knowledge, this is the first report describing the pathological findings of a natural outbreak caused by NDV involving viruses of genotype XVII. RESEARCH HIGHLIGHTS First report of a natural outbreak of Newcastle disease in White Yarkon Leghorns. The outbreak was caused by virulent NDV belonging to genotype XVII. Pathology differed slightly from those in experimental studies using SPF and other unvaccinated chickens.

Protective efficacy of the Newcastle disease virus genotype VII-matched vaccine in commercial layers

Newcastle disease virus (NDV) is a major threat to the poultry industry worldwide, with a diversity of genotypes associated with severe economic losses in all poultry sectors. Class II genotype VII NDV are predominant in the Middle East and Asia, despite intensive vaccination programs using conventional live and inactivated NDV vaccines. In Egypt, the disease is continuously spreading, causing severe economical losses in the poultry industry. In this study; the protective efficacy of a commercial, inactivated recombinant genotype VII NDV–matched vaccine (KBNP-C4152R2L strain) against challenge with the velogenic NDV strain (Chicken/USC/Egypt/2015) was evaluated in commercial layers. Two vaccination regimes were used; live NDV genotype II (LaSota) vaccine on days 10, 18, and 120, with either the inactivated NDV genotype II regime or inactivated NDV genotype VII–matched vaccine regime on days 14, 42, and 120. The 2 regimes were challenged at the peak of egg production on week 26. Protection by the 2 regimes was evaluated after experimental infection, based on mortality rate, clinical signs, gross lesions, virus shedding, seroconversion, and egg production schedule. The results show that these 2 vaccination regimes protected commercial layer chickens against mortality, but some birds showed mild clinical signs and reduced egg production temporarily. However, the combination of live NDV genotype II and recombinant inactivated genotype VII vaccines provided better protection against virus shedding (20% and 0% vs. 60% and 40%) as assessed in tracheal swabs and (20% and 0% vs. 20% and 20%) in cloacal swabs collected at 3 and 5 D post challenge (dpc), respectively. In addition, egg production levels in birds receiving the inactivated NDV genotype VII–matched vaccine regime and in those given inactivated genotype II vaccines were 76.6, 79, 82, and 87.4% and 77.7, 72.5, 69, and 82.5% at 7, 14, 21, and 28 dpc, respectively. The results of this study indicate that recombinant genotype-matched inactivated vaccine along with a live attenuated vaccine can reduce virus shedding and improve egg production in commercial layers challenged with a velogenic genotype VII virus under field conditions. This regime may ensure a proper control strategy in layers.

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

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.

Genotype Diversity of Newcastle Disease Virus in Nigeria: Disease Control Challenges and Future Outlook

Newcastle disease (ND) is one of the most important avian diseases with considerable threat to the productivity of poultry all over the world. The disease is associated with severe respiratory, gastrointestinal, and neurological lesions in chicken leading to high mortality and several other production related losses. The aetiology of the disease is an avian paramyxovirus type-1 or Newcastle disease virus (NDV), whose isolates are serologically grouped into a single serotype but genetically classified into a total of 19 genotypes, owing to the continuous emergence and evolution of the virus. In Nigeria, molecular characterization of NDV is generally very scanty and majorly focuses on the amplification of the partial F gene for genotype assignment. However, with the introduction of the most objective NDV genotyping criteria which utilize complete fusion protein coding sequences in phylogenetic taxonomy, the enormous genetic diversity of the virus in Nigeria became very conspicuous. In this review, we examine the current ecological distribution of various NDV genotypes in Nigeria based on the available complete fusion protein nucleotide sequences (1662 bp) in the NCBI database. We then discuss the challenges of ND control as a result of the wide genetic distance between the currently circulating NDV isolates and the commonest vaccines used to combat the disease in the country. Finally, we suggest future directions in the war against the economically devastating ND in Nigeria.

Biological and phylogenetic characterization of a novel hemagglutination-negative avian avulavirus 6 isolated from wild waterfowl in China

Up to now only nine whole genome sequences of avian avulavirus 6 (AAvV‐6) had been documented in the world since the first discovery of AAvV‐6 (AAvV‐6/duck/HongKong/18/199/77) at a domestic duck in 1977 from Hong Kong of China. Very limited information is known about the regularities of transmission, genetic and biological characteristics of AAvV‐6 because of the lower isolation rate and mild losses for poultry industry. To better further explore the relationships among above factors, an AAvV‐6 epidemiological surveillance of domestic poultry and wild birds in six provinces of China suspected of sites of inter‐species transmission and being intercontinental flyways during the year 2013–2017 was conducted. Therefore, 9,872 faecal samples from wild birds and 1,642 cloacal and tracheal swab samples from clinically healthy poultry of live bird market (LBM) were collected respectively. However, only one novel hemagglutination‐negative AAvV‐6 isolate (AAvV‐6/mallard/Hubei/2015) was isolated from a fresh faecal sample obtained from mallard at a wetland of Hubei province. Sequencing and phylogenetic analyses of this AAvV‐6 isolate (AAvV‐6/mallard/Hubei/2015) indicated that this isolate grouping to genotype I were epidemiological intercontinentally linked with viruses from the wild birds in Europe and America. Meanwhile, at least two genotypes (I and II) are existed within serotype AAvV‐6. In additional, this novel hemagglutination‐negative AAvV‐6 isolate in chicken embryos restored its hemagglutination when pre‐treated with trypsin. These findings, together with data from other AAvV‐6, suggest potential epidemiological intercontinental spreads among AAvV‐6 transmission by wild migratory birds, and reveal potential threats to wild birds and domestic poultry worldwide.