Newcastle disease outbreak in pheasants in Great Britain in May 1996

Isolation, full sequence analysis, and in situ hybridization of pigeon paramyxovirus-1 genotype VI.2.1.1.2.2 from oriental turtle doves (Streptopelia orientalis)

Pigeon paramyxovirus-1 (PPMV-1), a genetic variant of avian paramyxovirus-1 (APMV-1), has been identified in Columbiformes and is the primary cause of diseases in captive and free-ranging pigeons. However, it has also been reported that PPMV-1 can infect chickens naturally and experimentally, thus posing a potential threat to the poultry industry. This study investigated a lethal outbreak of paramyxovirus infection that occurred among 16 oriental turtle doves (Streptopelia orientalis) in a walk-in aviary at a zoo from March to April 2021. Necropsies were performed, and histopathological findings revealed mild to moderate lymphoplasmacytic infiltration in several organs, such as the pancreas, liver, kidneys, and lungs. Reverse transcription polymerase chain reaction (RT-PCR) using formalin-fixed paraffin-embedded tissue blocks, virus isolation from fresh tissue, and in situ hybridization against the fusion (F) protein confirmed the diagnosis for PPMV-1 infection. The isolated strain NTU/C239/21 was fully sequenced by next-generation sequencing, and the results of phylogenetic analyses revealed that the F protein of NTU/C239/21 shared 98.8% nucleotide sequence identity with Pigeon/Taiwan/AHRI121/2017, which was isolated from a feral pigeon in Taiwan. The present study is the first to identify PPMV-1 infection in Streptopelia orientalis and suggests that Streptopelia orientalis may also play an important role in spreading the infection, similar to pigeons in APMV-1 spreading.

Identification of a Virulent Newcastle Disease Virus Strain Isolated from Pigeons (Columbia livia) in Northeastern Brazil Using Next-Generation Genome Sequencing

Newcastle disease virus (NDV), also known as avian paramyxoviruses 1 (APMV-1) is among the most important viruses infecting avian species. Given its widespread circulation, there is a high risk for the reintroduction of virulent strains into the domestic poultry industry, making the surveillance of wild and domestic birds a crucial process to appropriately respond to novel outbreaks. In the present study, we investigated an outbreak characterized by the identification of sick pigeons in a large municipality in Northeastern Brazil in 2018. The affected pigeons presented neurological signs, including motor incoordination, torticollis, and lethargy. Moribund birds were collected, and through a detailed histopathological analysis we identified severe lymphoplasmacytic meningoencephalitis with perivascular cuffs and gliosis in the central nervous system, and lymphoplasmacytic inflammation in the liver, kidney, and intestine. A total of five pigeons tested positive for NDV, as assessed by rRT-PCR targeted to the M gene. Laboratory virus isolation on Vero E6 cells confirmed infection, after the recovery of infectious NVD from brain and kidney tissues. We next characterized the isolated NDV/pigeon/PE-Brazil/MP003/2018 by next-generation sequencing (NGS). Phylogenetic analysis grouped the virus with other NDV class II isolates from subgenotype VI.2.1.2, including two previous NDV isolates from Brazil in 2014 and 2019. The diversity of aminoacid residues at the fusion F protein cleavage site was analyzed identifying the motif RRQKR↓F, typical of virulent strains. Our results all highlight the importance of virus surveillance in wild and domestic birds, especially given the risk of zoonotic NDV.

Avian Paramyxovirus Type 1 in Egypt: Epidemiology, Evolutionary Perspective, and Vaccine Approach

Avian orthoavulavirus 1, formerly known as avian paramyxovirus type-1 (APMV-1), infects more than 250 different species of birds. It causes a broad range of clinical diseases and results in devastating economic impact due to high morbidity and mortality in addition to trade restrictions. The ease of spread has allowed the virus to disseminate worldwide with subjective virulence, which depends on the virus strain and host species. The emergence of new virulent genotypes among global epizootics, including those from Egypt, illustrates the time-to-time genomic alterations that lead to simultaneous evolution of distinct APMV-1 genotypes at different geographic locations across the world. In Egypt, the Newcastle disease was firstly reported in 1947 and continued to occur, despite rigorous prophylactic vaccination, and remained a potential threat to commercial and backyard poultry production. Since 2005, many researchers have investigated the nature of APMV-1 in different outbreaks, as they found several APMV-1 genotypes circulating among various species. The unique intermingling of migratory, free-living, and domesticated birds besides the availability of frequently mobile wild birds in Egypt may facilitate the evolution power of APMV-1 in Egypt. Pigeons and waterfowls are of interest due to their inclusion in Egyptian poultry industry and their ability to spread the infection to other birds either by presence of different genotypes (as in pigeons) or by harboring a clinically silent disease (as in waterfowl). This review details (i) the genetic and pathobiologic features of APMV-1 infections in Egypt, (ii) the epidemiologic and evolutionary events in different avian species, and (iii) the vaccine applications and challenges in Egypt.

Health surveillance of a potential bridge host: Pathogen exposure risks posed to avian populations augmented with captive-bred pheasants

Augmentation of wild populations with captive‐bred individuals presents an inherent risk of co‐introducing novel pathogens to naïve species, but it can be an important tool for supplementing small or declining populations. Game species used for human enterprise and recreation such as the ring‐necked pheasant (Phasianus colchicus) are commonly raised in captivity and released onto public and private wildlands as a method of augmenting naturalized pheasant populations. This study presents findings on pathogen exposure from three sources of serological data collected in California during 2014–2017 including (a) 71 pen‐reared pheasants sampled across seven game bird breeding farms, (b) six previously released pen‐reared pheasants captured at two study sites where wild pheasants occurred and (c) 79 wild pheasants captured across six study sites. In both pen‐reared and wild pheasants, antibodies were detected against haemorrhagic enteritis virus (HEV), infectious laryngotracheitis (ILT), infectious bursal disease virus (IBDV), paramyxovirus type 1 (PMV‐1) and Pasteurella multocida (PM). Previously released pen‐reared pheasants were seropositive for HEV, ILT, and PM. Generalized linear mixed models accounting for intraclass correlation within groups indicated that pen‐reared pheasants were more than twice as likely to test positive for HEV antibodies. Necropsy and ancillary diagnostics were performed in addition to serological testing on 40 pen‐reared pheasants sampled from five of the seven farms. Pheasants from three of these farms tested positive by PCR for Siadenovirus, the causative agent of both haemorrhagic enteritis in turkeys and marble spleen disease of pheasants, which are serologically indistinguishable. Following necropsy, owners from the five farms were surveyed regarding husbandry and biosecurity practices. Farms ranged in size from 10,000 to more than 100,000 birds, two farms raised other game bird species on premises, and two farms used some form of vaccination. Biosecurity practices varied by farm, but the largest farm implemented the strictest practices.

Pathological and molecular findings of avian avulavirus type 1 outbreak in pigeons (Columba livia) of southern Brazil

ABSTRACT: The Newcastle disease, caused by avian avulavirus type 1 strains (APMV-1) is an important avian disease involved into high rates of mortality and economic losses. Several outbreaks have been reported over the last 30 years in Columbiformes in different parts of the world, caused by a adapted variant strain of AAvV-1, called pigeon paramyxovirus type 1 (PPMV-1). A high mortality associated with an outbreak was analyzed in free-living pigeons (Columba livia) in a public square in Porto Alegre in Southern Brazil. A total of 24 pigeons moribund or freshly dead, within five weeks interval were submitted to necropsy, histopathological, immunohistochemical (anti-Newcastle), and RT-PCR followed by sequencing of the amplification products analysis. They presented neurological signs, non-suppurative encephalitis and encephalomyelitis, and mononuclear inflammatory infiltrate in different organs. Immunohistochemical analysis in nine pigeons tissue showed that anti-Newcastle was expressed in brain, kidney, liver and pancreas. The RT-PCR test for the M protein of Newcastle disease virus was positive in six pigeons. The differential diagnosis of Influenza, West Nile, Mycoplasma gallisepticum and Mycoplasma synoviae in all pigeons presented negative results. The sequence of amino acids in the cleavage site region of the F protein was 112RRQKRF117 classifying the strain as virulent. The phylogenetic analysis classified this virus strain into Class II and VI genotype.

Functions of innate and acquired immune system are reduced in domestic pigeons (Columba livia domestica) given a low protein diet

Racing pigeons are exposed to and act as carriers of diseases. Dietary protein requirement for their maintenance has not been determined experimentally despite their being domesticated for over 7000 years. A maintenance nitrogen (protein) requirement (MNR) for pigeons was determined in a balance study using diets containing 6, 10 and 14% crude protein (CP). Then, the effects of feeding the diets were investigated to determine whether they were adequate to sustain innate and acquired immune functions. Nitrogen intake from the 6% CP diet was sufficient to maintain nitrogen balance and body weight in pigeons. However, the immune functions of phagocytosis, oxidative burst and lymphocyte proliferation in pigeons fed this diet were reduced compared with those fed 10 and 14% CP diets. Pigeons given the 6 and 10% CP diets had lower antibody titres following inoculation against Newcastle disease (ND) than those on the 14% CP diet. A confounding factor found on autopsy was the presence of intestinal parasites in some of the pigeons given the 6 and 10% CP diets; however, none of the pigeons used to measure MNR or acquired immunity to ND were infested with parasites. In conclusion, neither the 6 nor 10% CP diets adequately sustained acquired immune function of pigeons.

Experimental assessment of the pathogenicity of the Newcastle disease viruses from outbreaks in Great Britain in 1997 for chickens and turkeys, and the protection afforded by vaccination

The Newcastle disease virus isolated from healthy turkeys in outbreak GB 97/6 was used to challenge 4-week-old turkeys and chickens, which were either not vaccinated or had received a single dose of Hitchner B1 live vaccine 14 days earlier, by one of the intramuscular, intranasal or contact routes. Similar experiments were done in 38-day-old turkeys and chickens using virus isolated from severely sick chickens in outbreak GB 97/1. All vaccinated chickens showed low but measurable immune responses 14 days after vaccination, but only three of the turkeys had detectable antibodies. No vaccinated turkey or chicken showed any clinical sign after challenge with either virus. The virus from healthy turkeys in outbreak GB 97/6 induced clinical signs in 12/30 unvaccinated turkeys after challenge and 7/30 died. In unvaccinated chickens, challenge with this virus produced clinical signs in 25/30 birds and 21/30 died. In challenge experiments with the virus from outbreak GB 97/1 in chickens, 3/30 unvaccinated turkeys showed clinical signs and all three subsequently died. In contrast, 30/30 unvaccinated chickens challenged with this virus showed clinical signs and died. Vaccination did not prevent infection and excretion of either challenge virus. However, when compared with unvaccinated birds, vaccination reduced significantly the length of time virus was excreted and the overall proportion of swabs that were positive.

The evolution of pigeon paramyxovirus type 1 (PPMV-1) in Great Britain: a molecular epidemiological study

Newcastle disease (ND), caused by virulent strains of avian paramyxovirus type 1 (APMV-1), is considered throughout the world as one of the most important animal diseases. For over three decades now, there has been a continuing panzootic caused by a variant virulent APMV-1 strain, so-called pigeon paramyxovirus type 1 (PPMV-1), primarily in racing pigeons, which has also spread to wild birds and poultry. PPMV-1 isolations have been made in Great Britain every year since 1983. In this study, we have completed a comparative phylogenetic analysis based on a 374 nucleotide section of the fusion protein gene of 63 isolates of PPMV-1 that were isolated over a 26-year period; 43 of these were sequenced for this study. Phylogenetic analysis of these sequences revealed that all were closely related and placed in the genetic sublineage 4b (VIb), subdivision 4biif.

Genetic characterization of a pigeon paramyxovirus type 1 isolated from Columba livia in Uruguay

SUMMARY. The isolation and molecular characterization of pigeon paramyxovirus type 1 (PPMV-1) from a sick racing pigeon in Uruguay is reported for the first time. Hemagglutination inhibition (HI) tests were performed to detect antibodies against avian paramyxovirus serotype 1 (APMV-1), and a HI titer of 1/32 was obtained. Tracheal and cloacal swabs were processed by real-time reverse transcription-polymerase chain reaction (rRT-PCR) with the use of the National Veterinary Services Laboratory-U.S. Department of Agriculture validated matrix (M) gene assay and were positive for APMV-1. Viral isolation in embryonated chicken eggs confirmed the molecular detection of the isolate. A fragment corresponding to the 3' region of the fusion (F) protein gene was amplified by RT-PCR, and subsequently sequenced. The deduced amino acid sequence at the F protein cleavage site displayed the motif 112RRQKR/F117. Phylogenetic analysis of this part of the genome allowed the isolated virus to be grouped in the lineage VIb/ 4b, which suggests that it shares the same ecologic niche with other PPMV-1 that were found in the region, and it is not imported as other European or North American viruses.

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.

A comparative infection study of pigeon and avian paramyxovirus type 1 viruses in pigeons: evaluation of clinical signs, virus shedding and seroconversion

The pathogenesis of pigeon paramyxovirus type 1 (PPMV-1) isolate AV324/96 and of its recombinant derivative, rgAV324, was studied in pigeons. For comparison, the virulent chicken virus FL-Herts, which is a recombinant derivative of strain Herts/33, was also included. After inoculation by the combined intraocular, intranasal and intratracheal route, clinical signs, virus shedding and serological responses were examined. Clinical signs were observed only in the FL-Herts-infected group. All virus-inoculated pigeons had positive tracheal swabs until 5 days post infection. However, only the AV324/96-infected and rgAV324-infected birds, and not the FL-Herts-infected birds, shed virus in the cloaca. The AV324/96-infected pigeons showed higher mean antibody titres than the rgAV324-infected birds, whereas the antibody titres of the FL-Herts-infected group were rather low. The results show that the pigeon strain AV324 is not virulent for pigeons, but underlines the potential risk of poultry becoming infected by PPMV-1 shed by non-symptomatic pigeons.

A molecular epidemiological investigation of avian paramyxovirus type 1 viruses isolated from game birds of the order Galliformes

The partial (370 nucleotides) fusion gene sequences of 55 avian paramyxovirus type 1 (APMV-1) isolates were obtained. Included were 41 published sequences, of which 16 were from strains of APMV-1 of previously determined lineages included as markers for the data analysed and 25 were from APMV-1 viruses isolated from game birds of the order Galliformes. In addition, we sequenced a further 14 game bird isolates obtained from the repository at the Veterinary Laboratories Agency. The game bird isolates had been obtained from 17 countries, and spanned four decades. Earlier studies have shown that class II APMV-1 viruses can be divided into at least 15 lineages and sub-lineages. Phylogenetic analysis revealed that the 39 game bird isolates were distributed across 12 of these sub-lineages. We conclude that no single lineage of Newcastle disease viruses appears to be prevalent in game birds, and the isolates obtained from these hosts reflected the prevailing, both geographically and temporally, viruses in poultry, pigeons or wild birds.

Experimental infection of mice with avian paramyxovirus serotypes 1 to 9

The nine serotypes of avian paramyxoviruses (APMVs) are frequently isolated from domestic and wild birds worldwide. APMV-1, also called Newcastle disease virus, was shown to be attenuated in non-avian species and is being developed as a potential vector for human vaccines. In the present study, we extended this evaluation to the other eight serotypes by evaluating infection in BALB/c mice. Mice were inoculated intranasally with a prototype strain of each of the nine serotypes and monitored for clinical disease, gross pathology, histopathology, virus replication and viral antigen distribution, and seroconversion. On the basis of multiple criteria, each of the APMV serotypes except serotype 5 was found to replicate in mice. Five of the serotypes produced clinical disease and significant weight loss in the following order of severity: 1, 2>6, 9>7. However, disease was short-lived. The other serotypes produced no evident clinical disease. Replication of all of the APMVs except APMV-5 in the nasal turbinates and lungs was confirmed by the recovery of infectious virus and by substantial expression of viral antigen in the epithelial lining detected by immunohistochemistry. Trace levels of infectious APMV-4 and -9 were detected in the brain of some animals; otherwise, no virus was detected in the brain, small intestine, kidney, or spleen. Histologically, infection with the APMVs resulted in lung lesions consistent with broncho-interstitial pneumonia of varying severity that were completely resolved at 14 days post infection. All of the mice infected with the APMVs except APMV-5 produced serotype-specific HI serum antibodies, confirming a lack of replication of APMV-5. Taken together, these results demonstrate that all APMV serotypes except APMV-5 are capable of replicating in mice with minimal disease and pathology.

Passaging of a Newcastle disease virus pigeon variant in chickens results in selection of viruses with mutations in the polymerase complex enhancing virus replication and virulence

Some Newcastle disease virus (NDV) variants isolated from pigeons (pigeon paramyxovirus type 1; PPMV-1) do not show their full virulence potential for domestic chickens but may become virulent upon spread in these animals. In this study we examined the molecular changes responsible for this gain of virulence by passaging a low-pathogenic PPMV-1 isolate in chickens. Complete genome sequencing of virus obtained after 1, 3 and 5 passages showed the increase in virulence was not accompanied by changes in the fusion protein--a well known virulence determinant of NDV--but by mutations in the L and P replication proteins. The effect of these mutations on virulence was confirmed by means of reverse genetics using an infectious cDNA clone. Acquisition of three amino acid mutations, two in the L protein and one in the P protein, significantly increased virulence as determined by intracerebral pathogenicity index tests in day-old chickens. The mutations enhanced virus replication in vitro and in vivo and increased the plaque size in infected cell culture monolayers. Furthermore, they increased the activity of the viral replication complex as determined by an in vitro minigenome replication assay. Our data demonstrate that PPMV-1 replication in chickens results in mutations in the polymerase complex rather than the viral fusion protein, and that the virulence level of pigeon paramyxoviruses is directly related to the activity of the viral replication complex.

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.

Genotyping of Newcastle Disease Viruses Isolated from 2002 to 2004 in China

The main function region of the fusion (F) protein gene of 124 strains of Newcastle disease virus isolated from 2002 to 2004 in China was amplified and sequenced for further phylogenetic and residue substitutive analysis. Most of the isolates were classified into genotype VIIc, VIId, VIf, and VIb, while others into genotype IX, III, or II. The genotype IX, a unique genotype which includes strain F48, the first Chinese virulent NDV strain isolated in 1948, were still found inducing sporadic infections in certain areas. Subgenotype VIIc, VIId, and VIIe viruses, which were distributed in clusters in the phylogenetic tree distinct from members of subgenotypes VIIa and VIIb, were responsible for most outbreaks in China and circulated predominantly in China in recent years. Strain NDV03-026, an isolate of the genotype II which was normally lentogenic, was found carrying (112)RRQKRF(117) motif at the cleavage site of F protein as the virulent strain.

A molecular epidemiological investigation of isolates of the variant avian paramyxovirus type 1 virus (PPMV-1) responsible for the 1978 to present panzootic in pigeons

A sequence of 375 nucleotides, which included the region encoding the cleavage activation site and signal peptide of the fusion protein gene, was determined for 178 isolates of the pigeon variant strain of Newcastle disease virus (PPMV-1). These were compared with the sequences of 47 similar isolates published by GenBank, which included 30 isolates from pigeons and 17 representatives from each sublineage of avian paramyxovirus type 1. The resulting alignment was analysed phylogenetically using maximum likelihood and the results are presented as unrooted phylogenetic trees. By phylogenetic analysis all the PPMV-1 isolates except one were placed in lineage 4b (VIb). Within this lineage there was considerable genetic heterogeneity, which appears to be predominantly influenced by the date of isolation and, to a lesser extent, geographical origins of the isolates. There were two large distinguishable groups, 4bi and 4bii. The earliest isolate available, PIQPI78442, isolated in 1978 in Iraq, was situated at the node from which the two groups diverge.

Quasispecies nature of an unusual avian paramyxovirus type-1 isolated from pigeons

An avian paramyxovirus type-1 (APMV-1) was classified as virulent according to its Intra Cerebral Pathogenicity Index (ICPI), but as avirulent according to the motif of its F protein cleavage site. Although this atypical APMV-1 was isolated from sick, unvaccinated pigeons, it was not grouped with pigeon variants regarding its antigenic and genetic characterisation. We analysed its quasispecies nature by cloning and sequencing parts of the genome in three different genes to evaluate if heterogeneity might explain the difference observed between the ICPI and the F protein cleavage site motif. Two distinct sub-populations were detected in the phosphoprotein gene. In the fusion protein gene, two clones were found to be related to typical pigeon variants in the hypervariable domain.

Molecular study of the quasispecies evolution of a typical pigeon paramyxovirus type 1 after serial passages in pigeons by contact

The quasispecies nature of a typical pigeon paramyxovirus type 1 (pPMV-1) was, for the first time, studied under conditions close to the natural infectious environment. The virus was serially passaged in pigeons by successive contacts. Viral heterogeneity was analysed in the kidneys and brain of five pigeons from the last contact, by reverse transcriptase-polymerase chain reactions performed on RNA directly extracted from the organ and targeting the P and HN genes of the virus. The viral diversity following in vivo passage was found to be different from that in the inoculum, but demonstrated the reality of the quasispecies concept for pPMV-1 strains. Moreover, some aberrant genomic RNAs comprising insertions in the P gene editing site or deletions in the HN gene were also detected, with possible consequences for the pathogenicity and infectivity of the virus.

Characterization of a Newcastle disease virus isolated from apparently normal guinea fowl (Numida melagridis)

This report describes the isolation and molecular characterization of Newcastle disease virus isolated from an apparently normal guinea fowl (Numida melagridis). With a mean death time of 54 h and intracerebral pathogenicity index of 1.80, the isolate has been identified as velogenic by biological methods. Fusion protein cleavage site amino acid sequence analysis of the isolate indicated the presence of two pairs of basic amino acids at the C-terminus of the F2 region and phenylalanine at the N-terminus of the F1 region, confirming the velogenic nature of the isolate. Phylogenetic analysis of the isolate revealed that this isolate is genotypically related to other neurotropic velogenic isolates like Iowa/Salsbury, Texas GB, Kansas/Manhattan and mesogenic Michigan.

Molecular characterisation of three avian paramyxovirus type 1 isolated from pigeons in France

Three avian Paramyxovirus type 1 (aPMV-1) isolated from pigeons duringpigeon paramyxovirosis outbreaks were molecularly characterised by sequencing parts of the six genes (NP, P, M, F, HN and L) of each strain. Virulent 99143 isolate was found to be very closely related to non-pathogenic vaccine strains of aPMV-1, even for its F protein cleavage site motif. Strains 99299 and 99106, typical pigeon paramyxovirus type 1 (pPMV-1) variants, exhibited between 10% and 20% difference with aPMV-1 at the nucleotide level. The aPMV-1 specific pattern of eight amino acids in the intracellular domain of HN protein was found different by one residue for these two isolates, and might represent a specific pattern for pPMV-1. The unique sequence of the polycistronic P gene editing site of 99299 and 99106 was characterised by four instead of three cytosine residues, and might so have an influence on the expression level of the three proteins encoded by P. This work is also the first to provide molecular data on NP, P and L genes of typical pPMV-1.

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.

Pheasant ataxia: a new condition in pheasant poults

Between 1995 and 1997 a neurological condition in pheasant poults from 24 sites in England and Scotland was investigated. Affected birds showed varying degrees of ataxia and incoordinated movements and, in severe cases, recumbency, but generally remained alert with their heads held upright. The condition characteristically affected poults from seven weeks of age and the incidence on any one site was low. No significant bacteria were isolated consistently from brain tissue. The condition was characterised histologically by a non-suppurative meningoencephalitis, in which lesions were found predominantly in the cerebellum in 61 of 81 samples examined (75.3 per cent). A non-suppurative myelitis was recorded in 16 of 20 spinal cords examined. No lesions were recorded in peripheral neural tissue and lesions were rare in other tissues. The condition appeared not to have been recorded previously in pheasants. A viral aetiology was suspected but Newcastle disease virus was not involved.

Newcastle disease outbreaks in domestic fowl and turkeys in Great Britain during 1997

Between January 6 and April 23, 1997, 11 outbreaks of Newcastle disease were confirmed in Great Britain, four in broiler chickens and seven in turkeys. Although the viruses isolated gave intracerebral pathogenicity indices in day-old chicks between 1.65 and 1.95, the clinical signs of disease in field infections were variable and not always associated with high mortality, especially in turkeys. Epidemiological investigations indicated that the majority of the outbreaks occurred as a result of secondary spread by human agency from two or more primary infected flocks. The presence of similar outbreaks in Scandinavian countries in 1996 and the unusual patterns of movement of migratory birds at the end of 1996 and beginning of 1997 suggest they may have been responsible for the primary introduction of the causative virus into Great Britain.