Antigenic and genetic characterisation of Newcastle disease viruses isolated from outbreaks in domestic fowl and turkeys in Great Britain during 1997

Molecular Characterization of Velogenic Newcastle Disease Virus (Sub-Genotype VII.1.1) from Wild Birds, with Assessment of Its Pathogenicity in Susceptible Chickens

Simple Summary

Newcastle disease virus (NDV) is a highly contagious viral disease affecting a wide range of avian species. The disease can be particularly virulent in chickens, resulting in high mortality and morbidity. In this study, we characterized velogenic NDV sub-genotype VII.1.1 from wild birds and assessed its pathogenicity in susceptible chickens. One hundred wild birds from the vicinity of poultry farms with a history of NDV infection were examined clinically. Pooled samples from the spleen, lung, and brain were screened using real-time reverse transcriptase polymerase chain reaction (RRT-PCR) and reverse transcriptase polymerase chain reaction (RT-PCR) to detect the NDV F gene fragment, and phylogenetic analysis was carried out for identification of the genetic relatedness of the virus. Chickens were infected with the strains identified, and the major histopathological changes were assessed. Interestingly, NDV was detected in 44% of cattle egret samples and 26% of house sparrow samples by RRT-PCR, while RT-PCR detected NDV in 36% of cattle egrets examined and 20% of house sparrow samples. Phylogenetic analysis revealed close identity, of 99.7–98.5% (0.3–1.5% pairwise distance), between the isolates used in our study and other Egyptian class II, sub-genotype VII.1.1 NDV strains. Histopathological examination identified marked histopathological changes that are consistent with NDV. These findings provide interesting data in relation to the detection of NDV sub-genotype VII.1.1 in wild birds and reveal the major advantages of the combined use of molecular and histopathological methods in the detection and characterization of the virus. More research is needed to determine the characteristics of this contagious disease in the Egyptian environment.

Abstract

Newcastle disease (ND) is considered to be one of the most economically significant avian viral diseases. It has a worldwide distribution and a continuous diversity of genotypes. Despite its limited zoonotic potential, Newcastle disease virus (NDV) outbreaks in Egypt occur frequently and result in serious economic losses in the poultry industry. In this study, we investigated and characterized NDV in wild cattle egrets and house sparrows. Fifty cattle egrets and fifty house sparrows were collected from the vicinity of chicken farms in Kafrelsheikh Governorate, Egypt, which has a history of NDV infection. Lung, spleen, and brain tissue samples were pooled from each bird and screened for NDV by real-time reverse transcriptase polymerase chain reaction (RRT-PCR) and reverse transcriptase polymerase chain reaction (RT-PCR) to amplify the 370 bp NDV F gene fragment. NDV was detected by RRT-PCR in 22 of 50 (44%) cattle egrets and 13 of 50 (26%) house sparrows, while the conventional RT-PCR detected NDV in 18 of 50 (36%) cattle egrets and 10 of 50 (20%) of house sparrows. Phylogenic analysis revealed that the NDV strains identified in the present study are closely related to other Egyptian class II, sub-genotype VII.1.1 NDV strains from GenBank, having 99.7–98.5% identity. The pathogenicity of the wild-bird-origin NDV sub-genotype VII.1.1 NDV strains were assessed by experimental inoculation of identified strains (KFS-Motobas-2, KFS-Elhamoul-1, and KFS-Elhamoul-3) in 28-day-old specific-pathogen-free (SPF) Cobb chickens. The clinical signs and post-mortem changes of velogenic NDV genotype VII (GVII) were observed in inoculated chickens 3 to 7 days post-inoculation, with 67.5–70% mortality rates. NDV was detected in all NDV-inoculated chickens by RRT-PCR and RT-PCR at 3, 7, and 10 days post-inoculation. The histopathological findings of the experimentally infected chickens showed marked pulmonary congestion and pneumonia associated with complete bronchial stenosis. The spleen showed histocytic cell proliferation with marked lymphoid depletion, while the brain had malacia and diffuse gliosis. These findings provide interesting data about the characterization of NDV in wild birds from Egypt and add to our understanding of their possible role in the transmission dynamics of the disease in Egypt. Further research is needed to explore the role of other species of wild birds in the epidemiology of this disease and to compare the strains circulating in wild birds with those found in poultry.

Complete genome sequence of a subgenotype XXI.1.1 pigeon paramyxovirus type 1 virus (PPMV‑1) isolated from Iran in 2018 and phylogenetic analysis of a possible novel, but unassigned, PPMV-1 group isolated in 2014

Newcastle disease (ND) is one of the most serious infectious and contagious viral diseases in avian species. Recently, several ND outbreaks in pigeon caused by pigeon paramyxovirus serotype-1 (PPMV-1) have been reported from Iran, but unfortunately, phylogenetic studies have been mostly conducted on partial sequence of NDV fusion (F) gene. In addition, a complete genome data of Iranian PPMV-1 strains are not available. In the present study, a PPMV-1, named Avian avulavirus 1/pigeon/Iran/UT-EGV/2018, isolated from an infected pigeon, was subjected to whole-genome sequencing. The isolate showed an MDT of 74 h, thus categorizing it as mesogenic. The phylogenetic analysis based on the F gene sequence revealed the isolate belongs to XXI.1.1 subgenotype (min 0.9 % and max 3 %). To our knowledge, our study is the first study to publish the complete genome of a PPMV-1 from Iran. According to BLAST results, the whole genome of UT-EGV had high homology with some Russian, Egyptian and Ukrainian strains (the highest was 96.55 %). Additionally, we conducted a phylogenetic analysis on five PPMV-1 that we isolated in 2014 to find that they may belong to a completely unreported subgenotype (6 % distance when compared as a group). The information obtained from this study can be useful in preventive measures, including constructing an effective vaccine against PPMV-1 in Iran.

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

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.

Of Ducks and Men: Ecology and Evolution of a Zoonotic Pathogen in a Wild Reservoir Host

A hallmark of disease is that most pathogens are able to infect more than one host species. However, for most pathogens, we still have a limited understanding of how this affects epidemiology, persistence and virulence of infections—including several zoonotic pathogens that reside in wild animal reservoirs and spillover into humans. In this chapter, we review the current knowledge of mallard (Anas platyrhynchos) as host for pathogens. This species is widely distributed, often occupying habitats close to humans and livestock, and is an important game bird species and the ancestor to domestic ducks—thereby being an excellent model species to highlight aspects of the wildlife, domestic animal interface and the relevance for human health. We discuss mallard as host for a range of pathogens but focus more in depth of it as a reservoir host for influenza A virus (IAV). Over the last decades, IAV research has surged, prompted in part to the genesis and spread of highly pathogenic virus variants that have been devastating to domestic poultry and caused a number of human spillover infections. The aim of this chapter is to synthesise and review the intricate interactions of virus, host and environmental factors governing IAV epidemiology and evolution.

Temporal, geographic, and host distribution of avian paramyxovirus 1 (Newcastle disease virus)

Newcastle disease is caused by virulent forms of avian paramyxovirus of serotype 1 (APMV-1) and has global economic importance. The disease reached panzootic proportions within two decades after first being identified in 1926 in the United Kingdom and Indonesia and still remains endemic in many countries across the world. Here we review information on the host, temporal, and geographic distribution of APMV-1 genetic diversity based on the evolutionary systematics of the complete coding region of the fusion gene. Strains of APMV-1 are phylogenetically separated into two classes (class I and class II) and further classified into genotypes based on genetic differences. Class I viruses are genetically less diverse, generally present in wild waterfowl, and are of low virulence. Class II viruses are genetically and phenotypically more diverse, frequently isolated from poultry with occasional spillovers into wild birds, and exhibit a wider range of virulence. Waterfowl, cormorants, and pigeons are natural reservoirs of all APMV-1 pathotypes, except viscerotropic velogenic viruses for which natural reservoirs have not been identified. Genotypes I and II within class II include isolates of high and low virulence, the latter often being used as vaccines. Viruses of genotypes III and IX that emerged decades ago are now isolated rarely, but may be found in domestic and wild birds in China. Containing only virulent viruses and responsible for the majority of recent outbreaks in poultry and wild birds, viruses from genotypes V, VI, and VII, are highly mobile and have been isolated on different continents. Conversely, virulent viruses of genotypes XI (Madagascar), XIII (mainly Southwest Asia), XVI (North America) and XIV, XVII and XVIII (Africa) appear to have a more limited geographic distribution and have been isolated predominantly from poultry.

High genetic diversity of Newcastle disease virus in poultry in West and Central Africa: cocirculation of genotype XIV and newly defined genotypes XVII and XVIII

Despite rampant Newcastle disease virus (NDV) outbreaks in Africa for decades, the information about the genetic characteristics of the virulent strains circulating in West and Central Africa is still scarce. In this study, 96 complete NDV fusion gene sequences were obtained from poultry sampled in Cameroon, Central African Republic, Côte d'Ivoire, and Nigeria between 2006 and 2011. Based on rational criteria recently proposed for the classification of NDV strains into classes, genotypes, and subgenotypes, we revisited the classification of virulent strains, in particular those from West and Central Africa, leading to their grouping into genotype XIV and newly defined genotypes XVII and XVIII, each with two subgenotypes. Phylogenetic analyses revealed that several (sub)genotypes are found in almost every country. In Cameroon, most strains were related to vaccine strains, but a single genotype XVII strain was also found. Only three highly similar genotype XVII strains were detected in Central African Republic. Subgenotypes XVIIa, XVIIIa, and XVIIIb cocirculated in Côte d'Ivoire, while subgenotypes XIVa, XIVb, XVIIa, XVIIb, and XVIIIb were found in Nigeria. While these genotypes are so far geographically restricted, local and international trade of domestic and exotic birds may lead to their spread beyond West and Central Africa. A high genetic diversity, mutations in important neutralizing epitopes paired with suboptimal vaccination, various levels of clinical responses of poultry and wild birds to virulent strains, strains with new cleavage sites, and other genetic modifications found in these genotypes tend to undermine and complicate NDV management in Africa.

A survey of avian paramyxovirus type 1 infections among backyard poultry in New Zealand

AIMS

To determine the presence and the pathotype of avian paramyxovirus type 1 (APMV-1), as well as the prevalence of APMV-1 antibodies, among backyard flocks of poultry in selected New Zealand locations.

METHODS

Archival pooled (n = 162) tracheal and cloacal swabs collected from backyard poultry were tested for the presence of APMV-1 RNA by real-time and conventional reverse transcription (RT)-PCR assays. Archival blood samples (n = 240) from a subpopulation of the same birds were tested for the presence of the APMV-1 antibody using a commercial ELISA assay. The archival samples were collected from geographical areas close to bodies of water, in the Bay of Plenty or Wairarapa regions of the North Island of New Zealand, with the high likelihood of interactions between wild waterfowl and domestic poultry.

RESULTS

Avian paramyxovirus type 1 RNA was not detected in any of the swabs tested. Antibodies to APMV-1 were detected on 18/19 farms, in 71/240 (29.5%) blood samples tested. The percentage of seropositive birds varied between seropositive farms and ranged from 8.3 to 100%. The percentage of seropositive birds on each farm was not statistically correlated with the flock size, the number of birds sampled, the number of farmed waterfowl, or with the distance to the closest lake/river. However, all chickens from the farm with the highest number of farmed ducks were seropositive for APMV-1.

CONCLUSIONS

Lack of detection of APMV-1 in any of the samples indicates that APMV-1 was not circulating among the poultry at the time of sampling. However, detection of APMV-1 antibodies in a proportion of birds on each farm indicates that infection with APMV-1, or antigenically related APMV, is common among backyard poultry.

CLINICAL RELEVANCE

On-going proactive surveillance and characterisation of circulating APMV-1 is important for monitoring changes in circulating genotypes of APMV-1 and for understanding the regional ecology of these viruses for the purpose of planning appropriate disease control and prevention strategies. Our data suggest that backyard flocks should be considered as potential reservoirs of APMV. Chickens from backyard farms with multiple bird species may provide good targets for surveillance purposes.

Characterization of newcastle disease viruses in wild and domestic birds in Luxembourg from 2006 to 2008

Newcastle disease virus (NDV) is one of the most important viral diseases of birds. Wild birds constitute a natural reservoir of low-virulence viruses, while poultry are the main reservoir of virulent strains. Exchange of virus between these reservoirs represents a risk for both bird populations. Samples from wild and domestic birds collected between 2006 and 2010 in Luxembourg were analyzed for NDV. Three similar avirulent genotype I strains were found in ducks during consecutive years, suggesting that the virus may have survived and spread locally. However, separate introductions cannot be excluded, because no recent complete F gene sequences of genotype I from other European countries are available. Detection of vaccine-like strains in wild waterbirds suggested the spread of vaccine strains, despite the nonvaccination policy in Luxembourg. Among domestic birds, only one chicken was positive for a genotype II strain differing from the LaSota vaccine and exhibiting a so-far-unrecognized fusion protein cleavage site of predicted low virulence. Three genotype VI strains from pigeons were the only virulent strains found. The circulation of NDV in wild and free-ranging domestic birds warrants continuous surveillance because of increased concern that low-virulence wild-bird viruses could become more virulent in domestic populations.

Molecular epidemiology of outbreak-associated and wild-waterfowl-derived newcastle disease virus strains in Finland, including a novel class I genotype

Newcastle disease (ND) is a highly contagious, severe disease of poultry caused by pathogenic strains of Newcastle disease virus (NDV; or avian paramyxovirus-1). NDV is endemic in wild birds worldwide and one of the economically most important poultry pathogens. Most of the published strains are outbreak-associated strains, while the apathogenic NDV strains that occur in wild birds, posing a constant threat to poultry with their capability to convert into more virulent forms, have remained less studied. We screened for NDV RNA in cloacal and oropharyngeal samples from wild waterfowl in Finland during the years 2006 to 2010: 39 of 715 birds were positive (prevalence, 5.5%). The partial or full-length F genes of 37 strains were sequenced for phylogenetic purposes. We also characterized viruses derived from three NDV outbreaks in Finland and discuss the relationships between these outbreak-associated and the wild-bird-associated strains. We found that all waterfowl NDV isolates were lentogenic strains of class I or class II genotype I. We also isolated a genetically distinct class I strain (teal/Finland/13111/2008) grouping phylogenetically together with only strain HIECK87191, isolated in Northern Ireland in 1987. Together they seem to form a novel class I genotype genetically differing from other known NDVs by at least 12%.

The nucleoprotein is responsible for intracerebral pathogenicity of A/duck/Mongolia/47/2001 (H7N1) in chicks

Avian influenza viruses A/duck/Mongolia/47/2001 (H7N1) (47/01) and A/duck/Mongolia/867/2002 (H7N1) (867/02) were defined as low-pathogenic avian influenza viruses (LPAIVs) using an intravenous pathogenicity test in chickens. On the other hand, the intracerebral pathogenicity indices of 47/01 and 867/02 were 1.30 and 0.00, respectively. A series of reassortant viruses were generated between 47/01 and 867/02, and their intracerebral pathogenicity was compared in one-day-old chicks to identify the protein(s) responsible for the intracerebral pathogenicity of 47/01. The results indicate that the amino acids at positions 50 and 98 of the nucleoprotein are related to the pathogenicity of 47/01 in chicks by intracerebral inoculation. A significant association was found between mortality of the chicks inoculated intracerebrally with 47/01 and virus replication in the lungs and/or brain. These results indicate that the NP of avian influenza viruses may be responsible for intracerebral pathogenicity in the host.

Newcastle disease in the European Union 2000 to 2009

Newcastle disease (ND) is a devastating disease of poultry that has to some extent been neglected by those working in the field in the past 10 to 15 years while attention has been focused on the emergence and spread of highly pathogenic avian influenza caused by a H5N1 subtype virus. During 2000 to 2009 in the European Union (EU) member states, ND viruses virulent for chickens have been detected in wild birds, domesticated pigeons and poultry. Based on these isolations it appears that the epizootic in racing pigeons caused by the variant viruses termed pigeon avian paramyxovirus type 1, which form the genetic group 4b(VIb) first seen in Europe in 1981, continued during 2000 to 2009, and the virus is probably enzootic in racing pigeons in some EU countries. This virus appears to have spread regularly to wild birds, especially those of the Columbidae family, and has been the cause of significant outbreaks in poultry. Other avian paramyxovirus type 1 viruses responsible for ND outbreaks in the EU during 2000 to 2009 have been those from genetic groups 5b(VIIb) and 5d(VIId). There is evidence that the former may well represent spread from a wild bird source and these viruses have also been isolated from wild birds, while the latter represents continuing spread from the East. Future legislation or recommendations aimed at the control and eradication of ND will need to encompass these three sources of virulent ND viruses.

Genetic data from avian influenza and avian paramyxoviruses generated by the European network of excellence (EPIZONE) between 2006 and 2011--review and recommendations for surveillance

Since 2006, the members of the molecular epidemiological working group of the European "EPIZONE" network of excellence have been generating sequence data on avian influenza and avian paramyxoviruses from both European and African sources in an attempt to more fully understand the circulation and impact of these viruses. This review presents a timely update on the epidemiological situation of these viruses based on sequence data generated during the lifetime of this project in addition to data produced by other groups during the same period. Based on this information and putting it all into a European context, recommendations for continued surveillance of these important viruses within Europe are presented.

Infection dynamics of highly pathogenic avian influenza and virulent avian paramyxovirus type 1 viruses in chickens, turkeys and ducks

A range of virus doses were used to infect 3-week-old chickens, turkeys and ducks intranasally/intraocularly, and infection was confirmed by the detection of virus shedding from the buccal or cloacal route by analysis of swabs collected using real-time reverse transcriptase-polymerase chain reaction assays. The median infectious dose (ID(50)) and the median lethal dose (LD(50)) values for two highly pathogenic avian influenza (HPAI) viruses of H5N1 and H7N1 subtypes and one virulent Newcastle disease virus (NDV) were determined for each virus and host combination. For both HPAI viruses, turkeys were >100-fold more susceptible to infection than chickens, while both these hosts were >10-fold more susceptible to H5N1 virus than the H7N1 virus. All infected chickens and turkeys died. Ducks were also much more readily infected with the H5N1 virus (ID(50)< or =10(1) median embryo infective dose [EID(50)]) than the H7N1 virus (ID(50)=10(4.2) EID(50)). However, the most notable difference between the two viruses was their virulence for ducks, with a LD(50) of 10(3) EID(50) for the H5N1 virus, but no deaths in ducks being attributed to infection with H7N1 virus even at the highest dose (10(6) EID(50)). For both HPAI virus infections of ducks, the ID(50) was lower than the LD(50), indicating that infected birds were able to survive and thus excrete virus over a longer period than chickens and turkeys. The NDV strain used did not appear to establish infection in ducks even at the highest dose used (10(6) EID(50)). Some turkeys challenged with 10(6) EID(50), but not other doses, of NDV excreted virus for a number of days (ID(50)=10(4.6) EID(50)), but none died. In marked contrast, chickens were shown to be extremely susceptible to infection and all infected chickens died (ID(50)/LD(50)=10(1.9) EID(50)).

Molecular characterization of avian paramyxovirus type 1 (Newcastle disease) viruses isolated from pigeons between 2000 and 2008 in Slovenia

Fourteen avian paramyxovirus type 1 (APMV-1; Newcastle disease) viruses isolated from dead free-living and domestic pigeons in Slovenia between 2000 and 2008 were analyzed by a molecular characterization of a part of the fusion protein gene, which included the region encoding the fusion protein cleavage site. Phylogenetic analysis indicated that the Slovene pigeon paramyxovirus type 1 (PPMV-1) viruses do not cluster together but instead are divided into two groups--4bi and 4bii--of sublineage 4b. Nine Slovenian strains were placed in group 4bii. Five other strains clustered together with PPMV-1 from group 4bi. The sequence of the fusion protein cleavage site of all Slovenian strains was typical for pathogenic APMV-1. The 112RRQKRF117 motif was present in the strains from group 4bii, whereas strains from group 4bi displayed the 112GRQKRF117 motif.

Clinicopathological Characterization in Poultry of Three Strains of Newcastle Disease Virus Isolated From Recent Outbreaks

Newcastle disease is a severe threat to the poultry industry and is caused by Newcastle disease virus, a member of the genus Avulavirus, family Paramyxoviridae. The virus is rapidly evolving, and several new genotypes have been discovered in the past few years. Characterization of these strains is important to evaluate field changes, anticipate new outbreaks, and develop adequate control measures. Three Newcastle disease isolates (APMV-1/duck/Vietnam, Long Bien/78/2002, APMV-1/chicken/Australia/9809-19-1107/1998, and APMV-1/double-crested cormorant/USA, Nevada/19529-04/2005) from recent outbreaks were investigated via clinicopathological assessment, immunohistochemistry (IHC), in situ hybridization, virus isolation, and serology in experimentally infected 4-week-old chickens. Phylogenetic studies showed that Australia isolate belongs to class II genotype I, Long Bien to class II genotype VIId, and Nevada cormorant to class II genotype V. Even though all 3 viruses had a virulent fusion protein cleavage site and ICPI values greater than 1.5, they all differed in their ability to cause clinical signs, in their lesions, and in their viral distribution in body tissues. The Long Bien isolate showed the most severe clinicopathological picture and the most widespread viral distribution. The Australia and Nevada cormorant isolates had a milder pathological phenotype, with viral replication restricted to only a few organs. The variability in clinicopathological characteristics despite the similarity in ICPI suggests that full clinicopathological assessment is necessary to fully characterize new isolates and that there are differences in pathogenesis among viruses of different genotypes.

Complete genome characterisation of a Newcastle disease virus isolated during an outbreak in Sweden in 1997

The complete genome sequence of a Newcastle disease virus (NDV) isolated from a chicken in Sweden was determined and compared with other NDV sequences. The isolate was shown to belong to genotype VIIb, which arose in the Far East and spread around the world during the 1990s. It had a length of 15,192 bases and consisted of six genes in the order 3'-NP-P-M-F-HN-L-5'. The F protein cleavage site was 112-RRQRRF-117, corresponding to that of a virulent pathotype.

Development of an L gene real-time reverse-transcription PCR assay for the detection of avian paramyxovirus type 1 RNA in clinical samples

A real-time reverse-transcription PCR (rRT-PCR) that targets a region of the polymerase (L) gene was developed to detect all known lineages of avian paramyxovirus type 1 (APMV-1), also known as Newcastle disease virus (NDV). A panel of 23 viruses representing the current known phylogenetic diversity of the APMV-1 population with a bias towards the more recent European strains, which had been grown in embryonated fowls' eggs, were tested. A range of positive and negative clinical samples (n = 350) provided by the National Reference Laboratory and International Reference Laboratory at VLA Weybridge were also tested. Positive clinical material included samples considered representative of lineages 3, 4 and 5 obtained from chickens, ducks, pigeons and partridges. The negative sample population was obtained from chickens, turkeys and ducks. The APMV-1 L gene rRT-PCR gave high relative sensitivity (96.05%) and specificity (98.18%) when compared with virus isolation in embryonated fowls' eggs. It is proposed that this assay could provide a first-line screening tool for the detection of APMV-1 in clinical samples.

Characterization of newly emerging Newcastle disease viruses isolated during 2002-2008 in Taiwan

To elucidate the epidemiological relationships between ND outbreaks and genetic lineages, a portion of the F gene (535 bp) and the full-length HN gene (1922 bp) of recent Taiwanese NDVs isolated in 2002-2008 was amplified by reverse transcription (RT)-polymerase chain reaction (PCR) and sequenced. Only a portion of above amplified PCR products of the F and HN genes (374 and 1713 bp) and their deduced amino acid residues were compared with the other 60 NDVs retrieved from GenBank. Most (29/30) of the recent Taiwanese isolates were clustered in subgenotype VIIe while only one isolate was classified as subgenotype VIIc. All the 29 isolates of subgenotype VIIe were further subclassified and termed provisionally as sub-subgenotypes VIIe2 (13 isolates), VIIe3 (5 isolates), and VIIe4 (11 isolates). The sub-subgenotype VIIe2 isolates possessing the motif (112)R-R-Q-K-R-F(117) and amino acid residue substitutions at positions 23 (L to F) and 90 (T to A) were collected during 2002-2005. The sub-subgenotype VIIe3 isolates possessing the motif (112)R-R-K-K-R-F(117) and amino acid residue substitutions at positions 74 (E to G) and 75 (A to G) within epitopes and 114 (Q to K) within cleavage site of F protein were collected during 2003-2006. The sub-subgenotype VIIe4 isolates possessing the motif (112)R-R-Q-K-R-F(117) and amino acid residue substitutions at positions 23 (L to F), 26 (I to T), and 90 (T to A) were collected during 2007-2008. All the NDV isolates in this study exhibited a high intra-cerebral pathogenicity index (ICPI), they were all classified as velogenic type of NDVs. The sub-subgenotype VIIe2 and VIIe4 viruses are now dominant and have been implicated in most of the recent ND outbreaks in Taiwan. Phylogenetic analysis of these isolates revealed that they may have evolved from previously reported local strains (VIIe1). This finding is essential for improving the disease control strategies and development of vaccines for ND.

Rapid discrimination of H5 and H9 subtypes of avian influenza viruses and Newcastle disease virus by multiplex RT-PCR

Avian influenza and Newcastle disease are the highly contagious and most economically important diseases in poultry industry throughout the world. A multiplex reverse transcription polymerase chain reaction (mRT-PCR) assay was developed for the rapid and specific discrimination of H5 and H9 subtypes of avian influenza viruses (AIV) and Newcastle disease virus (NDV). Three sets of specific primers were applied in the assay based on the sequences of the hemagglutinin gene of H5-AIV, H9-AIV and fusion protein gene of NDV. 59 clinical samples including the throat washes, oral swabs, and cloacal scrapings were detected by mRT-PCR and single RT-PCR (sRT-PCR), respectively. The results indicated that the sensitivity and specificity of mRT-PCR were in accordance with sRT-PCR. The mRT-PCR developed in this study may therefore provide a new avenue to rapid detection of these important pathogens in one reaction.

Orthomyxo-, paramyxo- and flavivirus infections in wild waterfowl in Finland

Background

Screening wild birds for viral pathogens has become increasingly important. We tested a screening approach based on blood and cloacal and tracheal swabs collected by hunters to study the prevalence of influenza A, paramyxo-, flavi-, and alphaviruses in Finnish wild waterfowl, which has been previously unknown. We studied 310 blood samples and 115 mixed tracheal and cloacal swabs collected from hunted waterfowl in 2006. Samples were screened by RT-PCR and serologically by hemagglutination inhibition (HI) test or enzyme-linked immunosorbent assay (ELISA) for influenza A (FLUAV), type 1 avian paramyxo-(APMV-1), Sindbis (SINV), West Nile (WNV) and tick-borne encephalitis (TBEV) virus infections.

Results

FLUAV RNA was found in 13 tracheal/cloacal swabs and seven strains were isolated. Five blood samples were antibody positive. Six APMV-1 RNA-positive samples were found from which four strains were isolated, while two blood samples were antibody positive. None of the birds were positive for flavivirus RNA but three birds had flavivirus antibodies by HI test. No antibodies to SINV were detected.

Conclusion

We conclude that circulation of both influenza A virus and avian paramyxovirus-1 in Finnish wild waterfowl was documented. The FLUAV and APMV-1 prevalences in wild waterfowl were 11.3% and 5.2% respectively, by this study. The subtype H3N8 was the only detected FLUAV subtype while APMV-1 strains clustered into two distinct lineages. Notably, antibodies to a likely mosquito-borne flavivirus were detected in three samples. The screening approach based on hunted waterfowl seemed reliable for monitoring FLUAV and APMV by RT-PCR from cloacal or tracheal samples, but antibody testing in this format seemed to be of low sensitivity.

Newcastle disease in pheasants (Phasianus colchicus): a review

Newcastle disease (ND) is regarded throughout the world as one of the most important diseases of poultry, not only due to the serious disease and high flock mortality that may result from some ND virus (NDV) infections, but also through the economic impact that may ensue due to trading restrictions and embargoes placed on areas and countries where outbreaks have occurred. All ages of pheasants are purported to be highly susceptible to infection with NDV, but clinical signs and mortality levels in infected birds vary considerably. This article reviews the available literature relating to infections in pheasants, describing the clinical presentation of the disease and the epidemiological role these hosts may have in the spread of ND.

Molecular Characterization of Virulent Newcastle Disease Virus Isolates from Chickens during the 1998 NDV Outbreak in Kazakhstan

Newcastle disease virus (NDV) infects domesticated and wild birds throughout the world and has the possibility to cause outbreaks in chicken flocks in future. To assess the evolutionary characteristics of 10 NDV strains isolated from chickens in Kazakhstan during 1998 we investigated the phylogenetic relationships among these viruses and viruses described previously. For genotyping, fusion (F) gene phylogenetic analysis (nucleotide number 47-421) was performed using sequences of Kazakhstanian isolates as compared to sequences of selected NDV strains from GenBank. Phylogenetic analysis showed that all newly characterized strains belonged to the genetic group designated as VIIb. All strains possessed a virulent fusion cleavage site (RRQRR/F) belonging to velogenic or mesogenic pathotypes with intracerebral pathogenicity indexes (ICPI) varying from 1.05 to 1.87.

Detection and differentiation of pathogenicity of avian paramyxovirus serotype 1 from field cases using one-step reverse transcriptase-polymerase chain reaction

Amplification of avian paramyxovirus serotype 1 (APMV-1)-specific nucleic acid fragments, followed by restriction endonuclease analysis (REA) using BglI, was carried out to type strains according to their virulence. Primer sequences were used to amplify a 202 base pair fragment, encompassing the fusion protein cleavage site, in a one-step reverse transcriptase-polymerase chain reaction (RT-PCR) test for detection of a range of field cases and reference strains of APMV-1. Subsequent REA of the amplified fragments enabled differentiation of low virulent lentogenic field and vaccine strains from more virulent mesogenic and velogenic field strains of APMV-1, including pigeon PMV-1. In the present paper, we report the development and application of a one-step RT-PCR test coupled with REA as a fast, specific method for both the detection and typing of APMV-1 from field samples.

Phylogenetic analysis of Newcastle disease virus genotypes isolated in Japan

We genetically analyzed field isolates of the Newcastle disease (ND) virus isolated in Japan from 1930 to 2001. The coding region of the fusion protein was amplified by reverse transcriptase PCR and directly sequenced. Phylogenetic analysis revealed the presence of viruses belonging to six of the eight known genotypes. It can be concluded from this study that ND outbreaks in Japan have been of multiple etiologies. [All sequences used in this study were sent to DDBJ and assigned accession numbers AB 070382 to AB 074042.]

Newcastle disease outbreaks in Italy during 2000

Among the consequences of the epidemic of highly pathogenic avian influenza which affected Italy between 1999 and 2000 was an epidemic of Newcastle disease in northern and central Italy. It affected industrially reared poultry, dealer flocks and backyard flocks, with a total of 254 outbreaks notified up to December 31, 2000. Virological investigations yielded virulent isolates of Newcastle disease virus, which produced intracerebral pathogenicity indices ranging from 1.6 to 2.0 and which, on the basis of their monoclonal antibody binding patterns, could be classified as belonging to group C1. The clinical, gross and microscopical findings were typical of Newcastle disease, and different avian species were susceptible to different degrees. Chickens and guinea fowl appeared to be the most susceptible, followed by pheasants, turkeys and ostriches. The epidemiological inquiry highlighted the crucial role of a broiler hatchery in initiating the epidemic, and of dealers in perpetuating it. The control measures imposed by Directive 92/66/EEC are discussed with reference to the outbreaks in backyard flocks.

Characterization of newly emerging Newcastle disease virus isolates from the People's Republic of China and Taiwan

Seven Newcastle disease (ND) virus (NDV) isolates which were recovered from ND outbreaks in chicken and pigeon flocks in China and Taiwan between 1996 and 2000 were genotypically and pathotypically characterized. By phylogenetic analysis of the fusion protein genes, isolates Ch-A7/96, Ch/98-3, Ch/99, Ch/2000, and TW/2000 were placed into two novel subgenotypes, VIIc and VIId. Isolate Ch/98-1 was grouped into subgenotype VIb, while Ch-W6/96 was proven to be a mixture of isolates Ch-A7/96 and Ch/98-1. These isolates were pathotyped as viscerotropic velogenic for Ch/98-3, Ch/99, Ch/2000, and TW/2000; neurotropic velogenic for Ch-A7/96; and mesogenic for Ch/98-1. Three separate, comparative, genetic analyses of the F genes, including genetic distance measurement, phylogenetic tree analysis, and residue substitution analysis, were performed with our isolates and selected NDV strains from GenBank. Results showed that the close genetic similarity provided evidence for the epidemiological linkage between the outbreaks in China and Taiwan and that the 1990s outbreaks in Asia, the Middle East, Africa, and Europe constituted the fourth panzootic of ND. In combination with epidemiological analysis, an evolutionary model of the NDV strains, representative of the direction of transmission within the NDV strains, was proposed, and epidemiology of NDV transmission was evaluated with emphasis on molecular aspects. Finally, a cross-protective experiment indicated that at least one strain (Ch-A7/96) among our NDV isolates was an antigenic variant, responsible for recent outbreaks of ND in vaccinated chicken flocks.

Virulent Newcastle disease in Australia: molecular epidemiological analysis of viruses isolated prior to and during the outbreaks of 1998-2000

Gene sequence analysis of fusion (F) gene cleavage motifs and haemagglutinin-neuraminidase (HN) carboxyl-terminal extension sequences was used to analyse Newcastle disease viruses (NDV) associated with virulent outbreaks of the disease which occurred in New South Wales, Australia in 1998-2000. PCR fragments were amplified directly from diseased tissue or allantoic fluids and sequence analyses used for phylogenetic comparisons between these viruses and Australian reference NDV. F and HN gene sequence comparison showed a strong relationship to sequences derived from endemic Australian NDV rather than those of overseas viruses or wild bird isolates. Prior to notification of the 1998 outbreak, an NDV was isolated from chickens suffering respiratory disease that appeared to be the progenitor virus from which the virulent virus originated. In turn, these viruses are closely related to two previously isolated 'ancestor' viruses that have the same unique HN extension sequence.

Rapid pathotyping of Newcastle disease virus (NDV) using fluorogenic probes in a PCR assay

Hybridisation of PCR fragments with fluorogenic probes specific for pathotype allowed an estimation of pathogenicity of Newcastle disease virus (NDV) isolates using a modified TaqMan procedure. Six probes were used, designed to recognise nucleotide sequences in the fusion protein gene sequence corresponding to the precursor protein F0 cleavage site of both virulent and avirulent viruses. Forty-three of the 45 isolates tested, including 18 examined in a blind study were pathotyped successfully and rapidly, with close correlation between cleavage site nucleotide sequences, TaqMan results and intracerebral pathogenicity index (ICPI) values. One isolate, which could not be pathotyped by nucleotide sequencing, was shown using the TaqMan system to be a mixture of virulent and avirulent NDV. The results of this study suggest that using this modified TaqMan protocol, the likely virulence of most ND isolates can be determined rapidly and reproducibly.

Gordon Memorial Lecture. Newcastle disease

1. In this paper several historical and contemporary aspects of Newcastle disease (ND) are reviewed, with particular reference to the greater understanding which modern techniques have allowed. 2. Virulent ND viruses were generally thought to have emerged in 1926 as a result of transfer from a wild bird host reservoir but there is evidence that the virulent virus may have existed in poultry before 1926. Recent findings suggest that the virulent virus may emerge in poultry as a result of mutations in viruses of low virulence. 3. The history of ND in Great Britain reflects the four known panzootics that have occurred and serves as a model for the impact this disease may have on poultry populations. 4. Attempts to control and eradicate ND are not as straightforward as it may appear; in particular vaccination, while preventing deaths and disease, on challenge may not prevent virus replication and could therefore lead to the virulent virus becoming endemic. 5. Village chickens are extremely important assets in most developing countries, representing a significant source of protein in the form of eggs and meat but endemic ND can cause mortality of up to 60% in village chickens.