Direct evidence of H7N7 avian influenza virus mutation from low to high virulence on a single poultry premises during an outbreak in free range chickens in the UK, 2008

H5 and H7 subtypes of low pathogenicity avian influenza viruses (LPAIVs) have the potential to evolve into highly pathogenic avian influenza viruses (HPAIVs), causing high mortality in galliforme poultry with substantial economic losses for the poultry industry. This study provides direct evidence of H7N7 LPAIV mutation to HPAIV on a single poultry premises during an outbreak that occurred in June 2008 in free range laying hens in Oxfordshire, UK. We report the first detection of a rare di-basic cleavage site (CS) motif (PEIPKKRGLF), unique to galliformes, that has previously been associated with a LPAIV phenotype. Three distinct HPAIV CS sequences (PEIPKRKKRGLF, PEIPKKKKRGLF and PEIPKKKKKKRGLF) were identified in the infected sheds suggesting molecular evolution at the outbreak premises. Further evidence for H7N7 LPAIV preceding mutation to HPAIV was derived by examining clinical signs, epidemiological descriptions and analysing laboratory results on the timing and proportions of seroconversion and virus shedding at each infected shed on the premises. In addition to describing how the outbreak was diagnosed and managed via statutory laboratory testing, phylogenetic analysis revealed reassortant events during 2006-2008 that suggested likely incursion of a wild bird origin LPAIV precursor to the H7N7 HPAIV outbreak. Identifying a precursor LPAIV is important for understanding the molecular changes and mechanisms involved in the emergence of HPAIV. This information can lead to understanding how and why only some H7 LPAIVs appear to readily mutate to HPAIV.

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.

Demonstration of Ornithobacterium rhinotracheale in pheasants (Phasianus colchicus) with pneumonia and airsacculitis

Outbreaks of respiratory disease were investigated in reared pheasants (Phasianus colchicus) aged approximately 18 to 32 weeks, released into the semi-wild on four shooting estates in southern England. The clinical signs in the affected birds included swelling of the face and eyes, loss of condition, gasping respirations and coughing. The gross pathology findings included sinusitis, airsacculitis, pleural oedema and lung lesions. The histopathological findings in the affected lungs were characterized by a granulomatous pneumonia. Ornithobacterium rhinotracheale (ORT) was isolated from respiratory tract tissues, and 16S rRNA gene sequencing on three isolates revealed two distinct genotypes, one previously associated with some electrophoretic type (ET) 1 strains and the other a novel genotype that clustered among sequences previously associated with ET 3, ET 4, ET 5 and ET 6 isolates. The localization of ORT within the lung tissue was demonstrated by fluorescent in-situ hybridization in the bronchial exudate of three cases, although not within the granulomatous lesions themselves. In each case, ORT was identified as part of a complex of other respiratory agents including avian paramyxovirus type 2, avian coronavirus, Mycoplasma gallisepticum, Mycoplasma synoviae and other Mycoplasma species, Escherichia coli, Pasteurella multocida, other Pasteurellaceae and Syngamus trachea, suggesting synergism with other agents. Exposure to other intercurrent factors, including adverse weather conditions and internal parasitism, may also have exacerbated the severity of disease.

Antigenic and genetic analyses of isolate APMV/wigeon/Italy/3920-1/2005 indicate that it represents a new avian paramyxovirus (APMV-12)

Isolate wigeon/Italy/3920-1/2005 (3920-1) was obtained during surveillance of wild birds in November 2005 in the Rovigo province of Northern Italy and shown to be a paramyxovirus. Analysis of cross-haemagglutination-inhibition tests between 3920-1 and representative avian paramyxoviruses showed only a low-level relationship to APMV-1. Phylogenetic analysis of the whole genome and each of the six genes indicated that while 3920-1 grouped with APMV-1 and APMV-9 viruses, it was quite distinct from these two. In the whole-genome analysis, 3920-1 had 52.1 % nucleotide sequence identity to the closest APMV-1 virus, 50.1 % identity to the APMV-9 genome, and less than 42 % identity to representatives of the other avian paramyxovirus groups. We propose isolate wigeon/Italy/3920-1/2005 as the prototype strain of a further APMV group, APMV-12.

Phylogenetic and molecular characteristics of Eurasian H9 avian influenza viruses and their detection by two different H9-specific RealTime reverse transcriptase polymerase chain reaction tests

Avian influenza viruses (AIVs) of the H9 haemagglutinin subtype are endemic in many Asian and Middle-East countries, causing mortality and morbidity in poultry. Consequently there is a need for accurate and sensitive detection of Eurasian H9 subtype viruses. Two H9 RealTime reverse transcriptase polymerase chain reaction (RRT-PCR) tests, developed by Monne et al. (2008) and Ben Shabat et al. (2010), were originally validated with a limited number of H9 specimens. In the present study, the two tests have been assessed using 66 diverse H9 isolates and 139 clinical specimens from six H9 poultry outbreaks in four geographically disparate Eurasian countries. The Monne et al. (2008) test was modified and successfully detected all H9 viruses from all three Eurasian H9 lineages. Bayesian analysis of the clinical specimens' results revealed this test to be more sensitive (97%) than the Ben Shabat et al. (2010) test (31%). The latter test detected most H9 isolates of the G1 lineage, but no isolates from other H9 lineages. Mismatches in the primer/probe binding sequences accounted for sensitivity differences between the two H9 RRT-PCRs. Genetic analysis of 34 sequenced H9 haemagglutinin genes showed the South Asian and Middle-East H9 isolates to belong to the H9 G1 lineage, and possessed residues that appear to preferably bind alpha 2,6-linked sialic acid receptors which indicate a potential for human infection. European H9s clustered phylogenetically in a broader geographical group that includes recent North American H9 wild bird isolates and contemporary Asian viruses in the Y439 H9 lineage.

Isolation of a highly pathogenic influenza A virus of subtype H7N3 from a peregrine falcon ( Falco peregrinus )

A peregrine falcon ( Falco peregrinus ) was presented to the Al Safa Falcon Clinic in Dubai, UnitedArab Emirates unable to stand. Four hours after hospitalization, the bird died despite supportive care and calcium disodiumedetate treatment. The falcon had been on a hunting trip to Syria with its owner of 2 years, prior to its death. The carcass was submitted to the Central Veterinary Research Laboratory in Dubai where it was subjected to postmortem examination. Investigations resulted in the isolation of an influenza A virus subtype H7N3, which proved to be highly pathogenic for chickens.

Isolation of influenza a virus, subtype H5N2, and avian paramyxovirus type 1 from a flock of ostriches in Europe

A total of 146 of 506 ostriches (Struthio camelus) introduced into a quarantine in Denmark died within the first 23 days. The majority of deaths were in young birds up to 10 kg body weight. Avian influenza A viruses (AIVs) were isolated from 14 pools of organ tissues representing seven groups each of three or four ostriches, which died over the first 3 weeks. The AIVs were detected in respiratory tissues, kidneys and intestines. All were subtype H5N2. The intravenous pathogenicity index of each isolate for chickens was 0.0 and the four isolates examined each had the amino acid sequence -P-Q-R-E-T-R*G-L-F- at the cleavage site of the haemagglutinin protein, typical of non-pathogenic AIVs. In addition, an avirulent avian paramyxovirus type 1 virus was isolated from one pool of kidney tissues.

Bacteriological examination gave no significant results. The most characteristic pathological findings were impaction of the proventriculus and gizzard, enteritis with stasis and multi-focal necrotic hepatitis.

Use of monoclonal antibodies in the characterisation of avian paramyxovirus type 1 (Newcastle disease virus) isolates submitted to an international reference laboratory

A total of 106 Newcastle disease viruses submitted to the International Reference Laboratory at the Central Veterinary Laboratory, Weybridge from field investigations in 15 different countries was characterised using pathogenicity index tests in chickens and mouse monoclonal antibodies raised against NDV-Ulster 2C (Russell and Alexander, Archives of Virology, 75: 243, 1983) and pigeon isolate 617/83. These isolates could be placed into six distinct groups on the basis of their reaction with the monoclonal antibodies although four isolates gave ambiguous results and remained untyped. Forty isolates, obtained from chickens (21), pigeons (16), a duck (1), a sparrow (1) and a kestrel (1), were indistinguishable from isolates which were responsible for the recent panzootic in pigeons. Twenty-one isolates from domestic poultry, one isolate from a pheasant and one from a chicken in quarantine were identified as vaccinal virus of Bi or La Sota type. Thirty-five isolates placed in the same monoclonal antibody group were velogenic viruses. These had been obtained from domestic poultry in Italy, Austria, Mauritius and Saudi Arabia during 1983-1985, commercial pigeons in Hong Kong in 1986 and exotic birds in Italy, Great Britain and the Federal Republic of Germany during 1981-1985. This group was distinguishable from velogenic viruses responsible for disease outbreaks in poultry during the 1970s. Two lentogenic isolates from commercial ducks in England showed different monoclonal antibody binding patterns both of which have been associated with feral ducks. An isolate from chickens in Italy was also placed in one of these groups. A single isolate from a loon (Gavia sp) in the USA showed a monoclonal antibody binding pattern which had not been seen previously. In addition, 11 vaccinal or laboratory viruses were received for confirmatory characterisation which was greatly aided by the use of the monoclonal antibodies.

Experimental assessment of the pathogenicity of eight avian influenza A viruses of H5 subtype for chickens, turkeys, ducks and quail

Clinical signs, death, virus excretion and immune response were measured in 2-week-old chickens, turkeys, quail and ducks infected by intramuscular, intranasal and contact routes with eight influenza viruses of H5 subtype. Six of the viruses: A/chicken/Scotland/59 (H5N1), ck/Scot; A/tern/South Africa/61 (H5N3), tern/SA; A/turkey/Ontario/ 7732/66 (H5N9); ty/Ont; A/chicken/Pennsylvania/1370/83 (H5N2); Pa/1370; A/turkey/Ireland/83 (H5N8); ty/Ireland, and A/duck/Ireland/ 113/84 (HSN8); dk/Ireland, were highly pathogenic for chickens and turkeys. Two viruses, A/chicken/Pennsylvania/1/83 (H5N2), Pa/1 and A/turkey/Italy/ZA/80 (H5N2), ty/Italy, were of low pathogenicity. Ck/Scot was more pathogenic for chickens than turkeys while ty/Ont was more pathogenic for turkeys than chickens. Other viruses showed little difference in their pathogenicity for these two hosts. No clinical signs or deaths were seen in any of the infected ducks. Only two viruses, dk/Ireland and ty/Ireland, produced consistent serological responses in ducks, although intramuscular infection with tern/SA and ty/Italy resulted in some ducks with positive HI titres. These four were the only viruses reisolated from ducks. Quail showed some resistance to viruses which were highly pathogenic for chickens and turkeys, most notably to ck/Scot and ty/Ont and to a lesser extent tern/SA and Pa/1370. Transmission of virus from intranasally infected birds to birds placed in contact varied considerably with both host and infecting virus and the various combinations of these.

Recent epidemiology and ecology of influenza A viruses in avian species in Europe and the Middle East

There have been at least ten distinct outbreaks of LPAI or HPAI in poultry caused by H5 or H7 viruses in the last eight years in Europe and the Middle East. There appears to be an increased occurrence of such episodes consistent with global trends. As a result, surveillance systems have been enhanced to facilitate early detection of infection in poultry, together with active surveillance of wild bird populations. These complementary activities have resulted in the detection of a number of viruses in wild bird populations, including some with high genetic similarity to newly detected viruses in poultry, for example, H7N3 in Italy and H7N7 in the Netherlands. Furthermore, there is evidence for continued circulation of H5 and H7 viruses in wild Anseriformes, thereby presenting a real and current threat for the introduction of viruses to domestic poultry, especially those reared in outdoor production systems. Viruses of H9N2 subtype continue to circulate widely in the Middle East and are associated with significant disease problems in poultry. The epidemiology has the potential to be complicated further by introduction of novel viruses through illegal importation of captive birds, such as was detected with H5N1 in Belgium in 2004. Continual genetic exchange in the avian virus gene pool and independent evolution of all gene segments either within an individual host species or among wild bird hosts suggests that these viruses are not in evolutionary stasis in the natural reservoir.

Characterization of avian paramyxovirus type 1 strains isolated in Germany during 1992 to 1996

In Germany all avian paramyxoviruses (APMV) isolated in regional laboratories are collected and characterized by the National Reference Laboratory. From 1992 until 1996, 635 APMV-1 virus isolates were submitted from almost all regions. Of these viruses, 371 were isolated from chickens, 39 from other poultry, 171 from pigeons and 54 from exotic birds. All isolates were examined for virulence in intracerebral pathogenicity index (ICPI) tests, for their ability to react with a panel of monoclonal antibodies (mAb) and their thermostability. In addition, the nucleotide sequences of the cleavage site of the fusion protein of a few virus isolates were determined. Most isolates from chickens and other poultry were of the velogenic pathotype. This virus was responsible for the epizootic in 1993 to 1995 in many small flocks. The same virus was obtained from some pigeons and some exotic birds. The pathogenicity of the velogenic/epizootic virus was high with most viruses giving ICPI values of 1.8 to 1.9, and the sequences of the cleavage site of all velogenic isolates tested were closely related. However, viruses isolated at the beginning of the epizootic period differed from viruses isolated towards the end in their reaction with some mAbs. 149 virus isolates were identified as pigeon variant PMV-1 (PPMV-1). Most of these were obtained from pigeons but a few were isolated from chickens and other birds. Most lentogenic isolates proved to be vaccine virus strains.

Strains of avian paramyxovirus type 1 of low pathogenicity for chickens isolated from poultry and wild birds in Denmark

Twenty-one strains of avian paramyxovirus type 1 of low virulence for chickens were isolated in Denmark between 1996 and the beginning of 2003. The low virulence of the strains was demonstrated by sequencing the fusion (F) gene at the cleavage site motif and in some cases by determining the intracerebral pathogenicity index in day-old chicks. By using a panel of monoclonal antibodies it was shown that the isolates belonged to four different antigenic groups (five C2 isolates, six E isolates, six H isolates and four G/Q isolates). They were placed in three distinguishable genetic groups by phylogenetic analysis of a partial sequence of the F gene. The origin of the six E isolates was probably contaminated vaccines; the other viruses were isolated from wild birds and from poultry which probably came into contact with wild birds.

Pathogenesis of H7 Influenza A Viruses Isolated from Ostriches in the Homologous Host Infected Experimentally

Infections of ostriches with avian influenza A viruses are generally associated with clinical disease, but the occasional high mortality in young birds does not appear to be related directly to virus pathotype. In this study we investigated the pathogenesis of two H7 viruses for 11-wk-old ostriches inoculated intranasally, and clinical symptoms, virus excretion, and immune response were studied. One of the viruses (A/Ostrich/Italy/1038/00) was highly pathogenic for chickens, whereas the other (A/Ostrich/South Africa/1609/91) was of low pathogenicity for chickens. Clinical signs in ostriches receiving virulent virus were slight depression and hemorrhagic diarrhea, while the group receiving avirulent virus was clinically normal except for green diarrhea. Both viruses were transmitted to in-contact sentinel birds housed with the infected groups 3 days postinfection. Postmortem examination of the birds infected (including the sentinel bird) with virus highly pathogenic for chickens were grossly normal except for localized pneumonic lesions. The results of the study are presented and discussed.

Avian paramyxoviruses and influenza viruses isolated from mallard ducks (Anas platyrhynchos) in New Zealand

A comprehensive study using virological and serological approaches was carried out to determine the status of live healthy mallard ducks (Anas platyrhynchos) in New Zealand for infections with avian paramyxoviruses (APMV) and influenza viruses (AIV). Thirty-three viruses isolated from 321 tracheal and cloacal swabs were characterized as: 6 AIV (two H5N2 and four H4N6), 10 APMV-1 and 17 APMV-4. Of 335 sera samples tested for AIV antibodies, 109 (32.5%) sera were positive by nucleoprotein-blocking ELISA (NP-B-ELISA). Serum samples (315) were examined for antibody to APMV-1, -2, -3, -4, -6, -7, -8, -9 by the haemagglutination inhibition test. The largest number of reactions, with titres up to > or =1/64, was to APMV-1 (93.1%), followed by APMV-6 (85.1%), APMV-8 (56%), APMV-4 (51.7%), APMV-7 (47%), APMV-9 (15.9%), APMV-2 (13.3%) and APMV-3 (6.0%). All of the H5N2 isolates of AIV and the APMV-1 isolates from this and earlier New Zealand studies had low pathogenicity indices assessed by the Intravenous Pathogenicity Index (IVPI) with the result 0.00 and Intracerebral Pathogenicity Index (ICPI) with results 0.00-0.16. Partial genomic and antigenic analyses were also consistent with the isolates being non-pathogenic. Phylogenetic analysis of the 10 APMV-1 isolates showed 9 to be most similar to the reference APMV-1 strain D26/76 originally isolated in Japan and also to the Que/66 strain, which was isolated in Australia. The other isolate was very similar to a virus (MC 110/77) obtained from a shelduck in France.

Newcastle disease and avian influenza A virus in wild waterfowl in South Africa

In an intensive ostrich farming area in South Africa with a history of ostrich influenza outbreaks, we conducted a survey of avian influenza virus (AIV) and Newcastle disease virus (NDV) in wild aquatic birds. During late autumn and winter 1998, the time of year when outbreaks in ostriches typically start to occur, 262 aquatic birds comprising 14 species were sampled and tested for both virus infections. From eight samples, AIV, serotype H10N9, could be isolated. All isolates were apathogenic as determined by the intravenous pathogenicity index (0.00). Conversely, none of 33 sera of these wild birds showed antibodies against H10. However, one bird was found serologically positive for H6 AIV. This AIV serotype was later isolated from ostriches during an avian influenza outbreak in this area. No NDV was isolated although 34 of 46 serum samples contained NDV-specific antibodies. This is the first H10N9 isolate to be reported from Africa. In addition, our data support the notion that wild aquatic birds may function as a reservoir for AIV and NDV in South Africa.

Similarity of avian paramyxovirus serotype 1 isolates of low virulence for chickens obtained from contaminated poultry vaccines and from poultry flocks

At present Denmark has the status of a 'non-vaccinating' country for Newcastle disease and its poultry population should therefore be free of antibodies to avian paramyxovirus 1 (APMV-1). Three live avian vaccines against infectious bronchitis, avian encephalomyelitis, and chick anaemia which had been found to be contaminated with APMV-1 viruses of low virulence for chickens were examined. The vaccines were produced by the same company and the affected batches had been used in Denmark in 1996/97. Furthermore, APMV-1 isolates of low virulence were obtained from three commercial broiler breeder flocks, one of which had been vaccinated with two of the contaminated vaccines. The flocks belonged to the same hatchery organisation. A comparison of viral F0 gene sequences and typing of virus isolates with a panel of monoclonal antibodies showed that the vaccine and field isolates were identical.

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

Antigenic and genetic analyses of viruses from the 11 outbreaks of Newcastle disease in Great Britain, 12 of the outbreaks in Northern Ireland and the single outbreak in the Republic of Ireland which occurred in 1997, indicated that they were all essentially similar. In addition, the viruses from the British Isles were very similar to viruses isolated from three outbreaks in pheasants in Denmark between August and November 1996, from a goosander in Finland in September 1996, from an outbreak in chickens in Norway in February 1997, and from an outbreak in chickens in Sweden in November 1997. Viruses from outbreaks in other countries during 1995 to 1997 could be distinguished antigenically and/or genetically from the 1996 to 1997 Scandinavian/British Isles isolates, as could viruses responsible for two separate outbreaks in caged birds in quarantine premises in Great Britain in March 1997. Minor nucleotide differences in the 413-base region of the fusion gene and the 187-base region of the haemagglutinin-neuraminidase gene sequenced in this study allowed the 1996 to 1997 Scandinavian/British Isles isolates to be divided into groups. These groups broadly corresponded to the clusters of disease outbreaks, but suggested that the discrete outbreak in Scotland was probably the result of virus spread from Northern Ireland. Overall, the antigenic and genetic analyses of these viruses were consistent with the theory that the virus was introduced into the British Isles by migratory birds moving from north-east Europe. However, it was not possible to rule out other sources, such as the movement of pheasants from Denmark.

An outbreak of Newcastle disease in free-living pheasants (Phasianus colchicus)

The epidemiology of an outbreak of Newcastle disease in a population of approximately 12,000 free-living pheasants (Phasianus colchicus) on the island of Faenø in Denmark in 1996 is described. The mortality during the epizootic was 56%. The spread of the disease between 7 groups of pheasants could be demonstrated over an observation period of 3 weeks. A total of 70 avian paramyxovirus serotype 1 (APMV-1) isolates was made from the flock. The intra cerebral pathogenicity indices of the 4 isolates tested were in the range 1.78-1.88. By means of immunoperoxidase monolayer assay with murine monoclonal antibodies and sequence analysis of an RT-PCR amplified segment of the F0 viral protein it was found, that the virus belonged to the highly virulent C1 antigenic group and that the amino acid sequence at the F0 cleavage site corresponded with the sequences of virulent APMV-1 strains. Based on the epidemiological circumstances it is believed that the virus was transmitted to the pheasants by feral birds.

Pathotyping isolates of Newcastle disease virus using antipeptide antibodies to pathotype-specific regions of their fusion and hemagglutinin-neuraminidase proteins

Antipeptide antibodies have been evaluated for their abilities to predict the characteristics of the cleavage motifs of the fusion protein precursors (F0) of 25 isolates of Newcastle disease virus (NDV) with a range of virulences, grouped into 12 sets according to their monoclonal antibody reactivities. A Western blot format was used to show that antisera to synthetic peptides representing sequences at the C-termini of the F2-polypeptides of defined pathotypes of NDV usually distinguish between pathotypes on the basis of their Fo cleavage sequences. However, exceptions were found with three groups of virulent isolates. Protein sequencing and mass spectral analysis of the F2-polypeptide of isolate Texas GB from one of these groups, identified an anomalous cleavage/activation process which removed the amino acids required for recognition by the antisera. This probably also explained the lack of reactivity of the Roakin isolate and low reactivity of the Komarov isolate from this group. The other exceptions involved isolates in groups with cleavage region variations from the usual motif of virulent isolates or isolates with undefined cleavage motifs. Antipeptide antisera were also raised to sections of the 45 residue C-terminal extension the hemagglutinin-neuraminidase precursor (HN0) encoded by the genes of some avirulent isolates. Western blot analysis showed that positive reactions with antibodies to peptides based on sequences between residues 577 and 613 of the HN0 was evidence for the presence of an avirulent isolate but did not exclude the presence of other pathotypes. Antisera designed to target residues 569-577 detected HN0 extensions of 6 residues on isolates known to encode such extensions. These antisera also enabled differentiation of isolates with HN0 extensions of 6 residues from those with no extension, however, it was not possible to determine the virulence of isolates based on reaction with these antisera.

Comparison of Newcastle disease viruses isolated from cormorants in Canada and the USA in 1975, 1990 and 1992

Seventeen Newcastle disease virus (NDV) isolates obtained from cormorants, turkeys, a pelican, and a gull in Canada and the USA collected in 1975, 1990 and 1992 were analyzed for relatedness by monoclonal antibody profiling. In addition, nucleotide sequence analysis was performed in two areas of the fusion (F) gene for 5 of the isolates. No difference in the antigenicity of these 17 viruses, as determined by monoclonal antibody binding patterns, was seen. The amino acid sequences obtained via nucleotide sequencing at the cleavage site of the F protein showed that all the isolates tested had two pairs of basic amino acids immediately upstream of the cleavage site, and a phenylalanine residue at the N-terminus of the F1 protein, which is consistent with velogenic NDV. The deduced amino acid sequence obtained at the cleavage site of the F protein from 6 of the isolates was virtually identical regardless of the species, year of isolation, or location. However, the 1975 cormorant isolate showed marked differences from the 1990-1992 isolates in the nucleotide and deduced amino acid sequence of the F gene signal region. These data indicate that the 1990 and 1992 outbreaks were caused by the same epizootic virus and further suggest that the population of NDV in these wild birds may be very stable. The belief that the velogenic NDV circulating in cormorants in 1992 was transmitted into the free-ranging turkey flocks located near the cormorants in North Dakota is supported by the present study in which no distinction could be made between the viruses isolated from turkeys or wild birds.

Isolation of the pigeon PMV-1 variant of Newcastle disease virus from imported pheasants (Phasianus colchicus)

Isolation of a virulent pigeon paramyxovirus 1 (PPMV-1) strain of Newcastle disease virus (NDV) from pheasants imported for release is reported. Although no clinical signs or postmortem lesions suggesting NDV infection were detected, the intestine was processed for attempted virus isolation as part of a surveillance programme on wild-bird populations. The potential role of pheasants as carriers of the disease, and the importance of developing surveillance programmes for wild bird populations is discussed.

Isolation of an influenza A virus of unusual subtype (H1N7) from pigs in England, and the subsequent experimental transmission from pig to pig

A novel H1N7 influenza virus (A/swine/Eng/191973/92) was isolated from nasal swabs collected from two pigs on a farm where there had been recent clinical disease due to infection with an H1N1 virus (A/swine/Eng/195852/92). Antigenically, the haemagglutinin (HA) of the H1N7 virus was related most closely to the HA of A/USSR/90/77, whilst the neuraminidase (NA) appeared to be related most closely to the NA of A/equine/Prague/1/56 (H7N7). Pigs infected experimentally with A/swine/Eng/191973/92 developed mild clinical signs, excreted virus into the nasal passages for up to nine days after infection, appeared normal at necropsy, transmitted the virus to sentinel pigs, but seven out of eight pigs failed to seroconvert. These findings suggest that the H1N7 virus has a low pathogenicity for pigs, resulting in limited virus multiplication which is insufficient to stimulate a detectable primary humoral immune response.

Characterisation of Newcastle disease viruses isolated in India

Eleven Newcastle disease virus (NDV) isolates obtained from outbreaks of disease in chickens (9) and Japanese quail (2) in Tamil Nadu, India were characterised in pathogenicity tests, antigenically, using mouse monoclonal antibodies (MAbs), and other established tests devised to distinguish between different strains. All 11 isolates were shown to be highly virulent for chickens. In indirect immunoperoxidase tests used to assess the ability of a panel of 28 MAbs to bind to infected cell cultures, 10 of the isolates showed an identical reaction pattern, the other isolate (No. 4) failed to react with one MAb which bound to cells infected with the other isolates. Isolates 9 was unstable at pH 3 while the other 10 were stable. All other properties were shared by the 11 isolates.

Avian paramyxovirus serotype 1 (Newcastle disease virus)--infections in falcons

From eight falcons and one pigeon which died from NDV over a period of 15 months in Dubai, United Arab Emirates, PMV-1 viruses were isolated on quail embryo cell cultures. The identification of all 9 strains were achieved with the haemagglutination inhibition test against polyclonal chicken PMV-1 antiserum, against mouse monoclonal antibodies as well as with the immunoperoxidase test. Intracerebral pathogenicity index and intravenous pathogenicity index tests were also carried out. Although the virus isolates in this study fell into two distinct groups, the overall clinical symptoms displayed by the falcons tailed to demonstrate any trends or specificity unique to a group. The isolate obtained from a pigeon was similar to the isolates from one group of the falcons and showed no identity with the pigeon variant virus.

Characterisation of an antigenically unusual virus responsible for two outbreaks of Newcastle disease in the Republic of Ireland in 1990

Antigenic characterisation of two highly virulent virus isolates from outbreaks of Newcastle disease on two closely connected farms in County Monaghan, Republic of Ireland, in 1990 showed the viruses to be indistinguishable but unlike other Newcastle disease viruses so far tested. However, they appeared to be antigenically closest to avirulent viruses isolated from waterfowl from several countries and from chickens in Northern Ireland in 1986. Despite the antigenic differences, chickens vaccinated with a live commercial Hitchner B1 vaccine were protected against intramuscular challenge with one of the virulent isolates.

Evaluation of relationships between avian paramyxoviruses isolated from birds of the family Columbidae

The prototype virus for the PMV-7 serotype of avian paramyxoviruses, PMV-7 dove Tennessee/4/75 (Tn 4) and five other isolates obtained from birds of the Columbidae family, which had been shown to be distinct from PMV-1 serotype, were tested for antigenic relationships between themselves and to other avian paramyxoviruses. By serological tests and analysis of structural polypeptides the viruses appeared to be distinct from other avian paramyxoviruses. One isolate appeared to be very closely related to Tn/4. Three other isolates showed only minor relationships to these two but were very closely related to each other. However, the sixth virus, pigeon Japan/Otaru/76, showed high levels of homology in haemagglutination inhibition tests and at least one line of identity in immunodoublediffusion tests with all five of the other isolates.

Evaluation of mouse monoclonal antibodies raised against an isolate of the variant avian paramyxovirus type 1 responsible for the current panzootic in pigeons

Nine monoclonal antibodies raised against "pigeon variant" avian paramyxovirus type 1 isolate pigeon/England/617/83 were tested for their ability to react with "classical" and other "pigeon variant" isolates. Two of the monoclonal antibodies appeared to be specific for 617/83 reacting with no other virus. The remaining seven monoclonal antibodies bound to cells infected with all other "pigeon" isolates in indirect immunoperoxidase (IIP) tests but four distinct groups of other PMV-1 viruses were formed on the basis of the binding patterns. One of the monoclonal antibodies 161/617 caused haemagglutination inhibition (HI) of all the "pigeon" isolates tested but none of the other PMV-1 viruses and these results reflected the IIP results with this monoclonal antibody. 161/617 was also shown to inhibit viruses of the avian paramyxovirus type 3 serogroup in HI tests. This reaction and the ability to bind to infected cells in IIP tests appeared to be restricted to PMV-3 viruses isolated from exotic birds and did not occur with viruses of ostensively the same serotype from turkeys.

Characterization of paramyxoviruses isolated from penguins in Antarctica and sub-Antarctica during 1976-1979

Nine paramyxovirus isolates obtained from penguins were tested for antigenic relationships amongst themselves and to other avian paramyxoviruses. One of the isolates was shown to be a lentogenic Newcastle disease virus (NDV), i.e., of PMV-1 serotype. By serological tests and analysis of structural polypeptides the other penguin isolates could be placed into three groups. No relationship with other avian paramyxoviruses could be determined except that six of the penguin viruses, representing two of the groups, showed reaction with a monoclonal antibody raised against NDV Ulster 2C and three of the isolates, representing one of the penguin groups, also reacted with another PMV-1 directed monoclonal antibody.