Restriction fragment length polymorphism analysis of the F gene of Newcastle disease viruses isolated from chickens and an owl in Taiwan

Pathotyping of Newcastle Disease Virus: a Novel Single BsaHI Digestion Method of Detection and Differentiation of Avirulent Strains (Lentogenic and Mesogenic Vaccine Strains) from Virulent Virus

We provide a novel single restriction enzyme (RE; BsaHI) digestion approach for detecting distinct pathotypes of Newcastle disease virus (NDV). After scanning 4,000 F gene nucleotide sequences in the NCBI database, we discovered a single RE (BsaHI) digestion site in the cleavage site. APMV-I “F gene” class II-specific primer-based reverse transcriptase PCR was utilized to amplify a 535-bp fragment, which was then digested with the RE (BsaHI) for pathotyping avian NDV field isolates and pigeon paramyxovirus-1 isolates. The avirulent (lentogenic and mesogenic strains) produced 189- and 346-bp fragments, respectively, but the result in velogenic strains remained undigested with 535-bp fragments. In addition, 45 field NDV isolates and 8 vaccine strains were used to confirm the approach. The sequence-based analysis also agrees with the data obtained utilizing the single RE (BsaHI) digestion approach. The proposed technique has the potential to distinguish between avirulent and virulent strains in a short time span, making it valuable in NDV surveillance and monitoring research.

IMPORTANCE The extensive use of the NDV vaccine strain and the existence of avirulent NDV strains in wild birds makes it difficult to diagnose Newcastle Disease virus (NDV). The intracerebral pathogenicity index (ICPI) and/or sequencing-based identification, which are required to determine virulent NDV, are time-consuming, costly, difficult, and cruel techniques. We evaluated 4,000 F gene nucleotide sequences and discovered a restriction enzyme (RE; BsaHI) digestion technique for detecting NDV and vaccine pathotypes in a short time span, which is cost-effective and useful for field cases as well as for large-scale NDV monitoring and surveillance. The data acquired using the single RE BsaHI digestion technique agree with the sequence-based analysis.

Insights into Genomic Epidemiology, Evolution, and Transmission Dynamics of Genotype VII of Class II Newcastle Disease Virus in China

Newcastle disease virus (NDV) is distributed worldwide and has caused significant losses to the poultry industry. Almost all virulent NDV strains belong to class II, among which genotype VII is the predominant genotype in China. However, the molecular evolution and phylodynamics of class II genotype VII NDV strains in China remained largely unknown. In this study, we identified 13 virulent NDV including 11 genotype VII strains and 2 genotype IX strains, from clinical samples during 1997 to 2019. Combined NDV sequences submitted to GenBank, we investigate evolution, and transmission dynamics of class II NDVs in China, especially genotype VII strains. Our results revealed that East and South China have the most genotypic diversity of class II NDV, and East China might be the origin of genotype VII NDVs in China. In addition, genotype VII NDVs in China are presumably transmitted by chickens, as the virus was most prevalent in chickens. Furthermore, codon usage analysis revealed that the F genes of genotype VII NDVs have stronger adaptation in chickens, and six amino acids in this gene are found under positive selection via selection model analysis. Collectively, our results revealed the genetic diversity and evolutionary dynamics of genotype VII NDVs in China, providing important insights into the epidemiology of these viruses in China.

Newcastle disease virus: macromolecules and opportunities

Over the past two decades, enormous advances have occurred in the structural and biological characterization of Newcastle disease virus (NDV). As a result, not only the complete sequence of the viral genome has been fully determined, but also a clearer understanding of the viral proteins and their respective roles in the life cycle has been achieved. This article reviews the progress in the molecular biology of NDV with emphasis on the new technologies. It also identifies the fundamental problems that need to be addressed and attempts to predict some research opportunities in NDV that can be realized in the near future for the diagnosis, prevention and treatment of disease(s).

Exchange of Newcastle disease viruses in Korea: the relatedness of isolates between wild birds, live bird markets, poultry farms and neighboring countries

Newcastle disease virus (NDV) has a worldwide distribution and is often carried by wild ducks, which may represent one of the natural reservoirs. However, the epidemiological relatedness of NDV between wild ducks and domestic poultry is unclear. A total of 14 isolates were obtained from 8439 samples from live bird markets (LBMs) and wild bird populations in Korea during from 2007 to 2010. These isolates were characterized genetically and phylogenetic analysis was conducted to investigate the relatedness between isolates from wild birds, LBM and poultry farms. In phylogenetic analysis, all 14 isolates belonged to genotype I virus within class II. Of these, nine isolates from wild birds were most closely related to the Aomori-like cluster. The five LBM isolates were most closely related to the V4-like cluster. All isolates in this study were closely related to isolates from domestic duck farms in Korea and Chinese LBM isolates. The results indicate that NDV exchange occurs between wild birds, poultry farms, LBMs and neighboring countries. Enhanced NDV surveillance is required to monitor the introduction of variant NDV in consequence of evolution in LBMs and to investigate NDV epidemiology in various species of putative hosts.

A review of RT-PCR technologies used in veterinary virology and disease control: sensitive and specific diagnosis of five livestock diseases notifiable to the World Organisation for Animal Health

Real-time, reverse transcription polymerase chain reaction (rRT-PCR) has become one of the most widely used methods in the field of molecular diagnostics and research. The potential of this format to provide sensitive, specific and swift detection and quantification of viral RNAs has made it an indispensable tool for state-of-the-art diagnostics of important human and animal viral pathogens. Integration of these assays into automated liquid handling platforms for nucleic acid extraction increases the rate and standardisation of sample throughput and decreases the potential for cross-contamination. The reliability of these assays can be further enhanced by using internal controls to validate test results. Based on these advantageous characteristics, numerous robust rRT-PCRs systems have been developed and validated for important epizootic diseases of livestock. Here, we review the rRT-PCR assays that have been developed for the detection of five RNA viruses that cause diseases that are notifiable to the World Organisation for Animal Health (OIE), namely: foot-and-mouth disease, classical swine fever, bluetongue disease, avian influenza and Newcastle disease. The performance of these tests for viral diagnostics and disease control and prospects for improved strategies in the future are discussed.

Clinical epidemiologic and experimental evidence for the transmission of Newcastle disease virus through eggs

Sporadic outbreaks of Newcastle disease (ND) occurred in Taiwan during 1998-2000. In some cases, the disease occurred in broilers less than 2 wk old that originated in a broiler breeder farm, so spread of the ND virus (NDV) from the infected breeder farm to broiler ranches was suspected. The purpose of the present study was to examine the possibility of the transmission of NDV through eggs. Both clinical and experimental evidence were used to prove that this is possible. From epidemiological investigation, the possibility of transmission through eggs was suggested in two separate ND cases from a breeder farm and its progeny because two identical NDVs were isolated from both cases. In order to clarify the possibility of the transmission through eggs, one mean egg lethal dose (ELD50) of NDV was inoculated into the allantoic cavity of 155 9-to-11-day-old specific-pathogen-free (SPF) chicken embryos. Seventy-one hatching chicks from the inoculated embryos were raised for 14 days. The cloacal swabs from those chicks at the ages of 1, 4, and 7 days and the tissues after necropsy at the ages of 14 days were taken for virus isolation. The same NDV was reisolated from three hatching chicks. This experiment confirms that a few chicken embryos infected in ovo with a low titer of NDV can hatch and contain NDV after hatching, which results in NDV spreading through eggs.

Pathogenicity and gene analysis of adenovirus from pigeons with inclusion body hepatitis

The pathogenicity of an adenovirus isolated from pigeons (Pigeon adenovirus, PA) with inclusion body hepatitis in Taiwan was investigated in specific-pathogen-free (SPF) chicks and in racing pigeons. One-day-old SPF chicks were inoculated subcutaneously with 10(4) 50% tissue culture infective dose (TCID50, low dose) and 10(8) TCID50 (high dose) of the virus, respectively. The chicks began to die three days post inoculation (DPI) with high dose of the virus and the mortality reached 100%; the chicks began to die 6 DPI and the mortality reached 90% at 14 DPI with low dose. The adult pigeons seemed to be resistant to the PA. However, this virus decreased the production of antibody against Newcastle disease virus in pigeons. It is found that this PA belongs to genetic group D from the restriction patterns produced by BamH I and Hind III.