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Table of Contents:
Taxonomy Information
  1. Species:
    1. Newcastle Disease Virus (Website 1):
      1. Common Name: Avian paramyxovirus, , pseudofowl pest, pseudovogel-pest, atypische Geflugelpest, pseudo-poultry plague, avian pest, avian distemper, Ranikhet disease, Tetelo disease, Korean fowl plague, and avian pneumoencephalitis. The nomenclature may also be confusing as sometimes infection of birds with any strain of the NDV may be termed ND. Strictly speaking, ND should be reserved for infections falling within the internationally accepted definition.
      2. GenBank Taxonomy No.: 11176
      3. Description: Paramyxoviruses contain nonsegmented, single-stranded RNA genomes of negative polarity, and they replicate entirely in the cytoplasm(Lamb et al., 2002). Newcastle disease (ND), caused by avian paramyxovirus serotype 1 (APMV-1) viruses, is included in the List A of the Office International des Epizooties. ND has been a devastating disease of poultry, and in many countries the disease remains one of the major problems affecting existing or developing poultry industries. Eight other serotypes of avian paramyxoviruses are recognised, namely APMV-2 to APMV-9. Most of these serotypes appear to be present in natural reservoirs of specific feral avian species, although other host species are usually susceptible. Only AMPV-2 and APMV-3 viruses have made a significant disease and economic impact on poultry production. Strains of NDV have been distinguished on the basis of the clinical signs produced in infected chickens. Beard and Hanson defined the following five groups or pathotypes: 1) Viscerotropic Velogenic: viruses responsible for disease characterised by acute lethal infections, usually with haemorrhagic lesions in the intestines of dead birds. 2) Neurotropic Velogenic: viruses causing disease characterised by high mortality, which follows respiratory and neurological disease, but in which gut lesions are usually absent. 3) Mesogenic: viruses causing clinical signs consisting of respiratory and neurological signs, with low mortality. 4) Lentogenic: viruses causing mild infections of the respiratory tract. 5) Asymptomatic enteric: viruses causing avirulent infections in which replication appears to occur primarily in the gut(Alexander et al., 2000). NDV and other avian paramyxoviruses have been included in the Rubulavirus genus, primarily because of their nonconserved intergenic junctions and lack of a C-protein open reading frame, hallmarks specific to the Rubulavirus genus. However, the organization of the NDV P gene and its mRNA editing profile resemble those found for the species of the genera Morbillivirus and Respirovirus, but not for other species in the genus Rubulavirus. Thus, further consideration of the appropriate taxonomy of NDV and avian paramyxoviruses is required(Lamb et al., 2002). The definition of ND adopted at the 67th General Session of the Office Internationale des Epizooties held in Paris in May 1999 was: Newcastle disease is defined as an infection of birds caused by a virus of avian paramyxovirus serotype 1 (APMV-1) that meets one of the following criteria for virulence: a) The virus has an intracerebral pathogenicity index (ICPI) in day-old chicks (Gallus gallus) of 07 or greater. or b) Multiple basic amino acids have been demonstrated in the virus (either directly or by deduction) at the C-terminus of the F2 protein and phenylalanine at residue 117, which is the N-terminus of the F1 protein. The term multiple basic amino acids refers to at least three arginine or lysine residues between residues 113 to 116. Failure to demonstrate the characteristic pattern of amino acid residues as described above would require characterisation of the isolated virus by an ICPI test'(Alexander et al., 2001).
      4. Variant(s):
Lifecycle Information
  1. Newcastle Disease Virus
    1. Stage Information:
      1. Virion:
        • Size: Paramyxoviridae are generally spherical and 150 to 350 nm in diameter.
        • Shape: Paramyxoviridae are generally spherical, but they can be pleiomorphic, and filamentous forms can be observed. Inserted in to the envelope are glycoprotein spikes that extend about 8 to 12 nm from the surface of the membrane and that can be readily visualized by electron microscopy.
Genome Summary
  1. Genome of Newcastle Disease Virus(Seal et al., 2000)
    1. Description: The enveloped virus has a negative sense single-stranded genome of approximately 15 kb which codes for six proteins including an RNA directed RNA polymerase (L), hemagglutininneuraminidase (HN) protein, fusion (F) protein, matrix (M) protein, phosphoprotein (P) and nucleoprotein (N). Transcription occurs in the 3' to 5' direction with decreasing amounts of protein resulting with each subsequent gene (Fig. 1). Replication of a positive-sense intermediate genome also is synthesized by the NDV polymerase. Cleavage of a precursor F0 to the F1 and F2 products is necessary for viral spread to other cells. The F and HN surface glycoproteins are the principal antigens that elicit a protective immune response(Seal et al., 2000).
    2. NCDV-B1(Website 34)
      1. GenBank Accession Number: NC_002617
      2. Size: 15186 bp(Website 34).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Complete sequence for the B1 strain of Newcastle disease virus(Website 34).
  2. Genome of Newcastle disease virus (STRAIN ULSTER/67)
    1. Newcastle disease virus Ulster/67(Website 38)
      1. GenBank Accession Number: AY562991
      2. Size: 15186 bp(Website 38).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate chicken/N. Ireland/Ulster/67, complete genome(Website 38).
  3. Genome of Newcastle disease virus strain U.S.-Largo-71
    1. Newcastle disease virus isolate mixed species/U.S./Largo/71(Website 39)
      1. GenBank Accession Number: AY562990
      2. Size: 15192 bp(Website 39).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate mixed species/U.S./Largo/71, complete genome(Website 39).
  4. Genome of Newcastle disease virus strain Italy-2736-00
    1. Newcastle disease virus isolate dove/Italy/2736/00(Website 40)
      1. GenBank Accession Number: AY562989
      2. Size: 15192 bp(Website 40).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate dove/Italy/2736/00, complete genome(Website 40).
  5. Genome of Newcastle disease virus strain U.S.(CA)-1083(Fontana)-72
    1. Newcastle disease virus isolate chicken/U.S.(CA)/1083(Fontana)/72(Website 41)
      1. GenBank Accession Number: AY562988
      2. Size: 15192 bp(Website 41).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate chicken/U.S.(CA)/1083(Fontana)/72, complete genome(Website 41).
  6. Genome of Newcastle disease virus strain U.S.(CA)-211472-02
    1. Newcastle disease virus isolate chicken/U.S.(CA)/1083(Fontana)/72(Website 42)
      1. GenBank Accession Number: AY562988
      2. Size: 15192 bp(Website 42).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate gamefowl/U.S.(CA)/211472/02, complete genome(Website 42).
  7. Genome of Newcastle disease virus strain NCDV-anhinga-U.S.(Fl)-44083-93
    1. Newcastle disease virus isolate anhinga/U.S.(Fl)/44083/93(Website 43)
      1. GenBank Accession Number: AY562986
      2. Size: 15192 bp(Website 43).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate anhinga/U.S.(Fl)/44083/93, complete genome(Website 43).
  8. Genome of Newcastle disease virus strain NCDV-Cockatoo-Indonesia-14698-90
    1. Newcastle disease virus isolate cockatoo/Indonesia/14698/90(Website 44)
      1. GenBank Accession Number: AY562985
      2. Size: 15192 bp(Website 44).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus isolate cockatoo/Indonesia/14698/90, complete genome(Website 44).
  9. Genome of Newcastle disease virus strain NCDV-ZJ1
    1. Newcastle Disease virus strain ZJ1(Website 45)
      1. GenBank Accession Number: AF431744
      2. Size: 15192 bp(Website 45).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle Disease virus strain ZJ1, complete genome(Website 45).
  10. Genome of Newcastle disease virus strain NCDV-HB92-isolate-V4
    1. Newcastle disease virus strain HB92 isolate V4(Website 46)
      1. GenBank Accession Number: AY225110
      2. Size: 15186 bp(Website 46).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus strain HB92 isolate V4, complete genome(Website 46).
  11. Genome of Newcastle disease virus strain NCDV-B1-isolate-Takaak
    1. Newcastle disease virus strain B1 isolate Takaak(Website 47)
      1. GenBank Accession Number: AF375823
      2. Size: 15186 bp(Website 47).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus strain B1 isolate Takaaki, complete genome(Website 47).
  12. Genome of Newcastle disease virus strain NCDV-virusB1
    1. Newcastle disease virus B1, Second Entry(Website 48)
      1. GenBank Accession Number: AF309418
      2. Size: 15186 bp(Website 48).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus B1, complete genome (second entry)(Website 48).
  13. Genome of Newcastle disease virus strain NCDV-LaSota
    1. Newcastle disease virus strain LaSota(Website 49)
      1. GenBank Accession Number: AF077761
      2. Size: 15186 bp(Website 49).
      3. Gene Count: The NDV genome comprises six genes which encode the six known viral structural proteins. Three of these are associated with the lipid envelope of the virion: the haemagglutin-neuraminidase and fusion glycoproteins are anchored in the membrane and appear as protruding spikes on the virion surface, the matrix protein is non-glycosylated and is peripherally attached to the inner surface of the envelope. The remaining three proteins are associated with genomic RNA to form the viral nucleocapsid, these are the nucleocapsid protein, the phosphoprotein and the large protein(Millar et al., 1988).
      4. Description: Newcastle disease virus strain LaSota, complete genome(Website 49).
Biosafety Information
Culturing Information
  1. Incubation of fertile eggs (Alexander et al., 2000):
    1. Description: Samples from dead birds should consist of oro-nasal swabs, as well as samples collected from lung, kidneys, intestine (including contents), spleen, brain, liver and heart tissues. These may be collected separately or as a pool, although intestinal samples are usually processed separately from other samples. Samples from live birds should include both tracheal and cloacal swabs, the latter should be visibly coated with faecal material. Small delicate birds may be harmed by swabbing. Collection of fresh faeces may serve as an adequate alternative. Where opportunities for obtaining samples are limited, it is important that cloacal swabs (or faeces) and tracheal swabs (or tracheal tissue) be examined as well as organs or tissues that are grossly affected or associated with the clinical disease. Samples should be taken in the early stages of the disease. Samples should be placed in isotonic phosphate buffered saline (PBS), pH 7.0-7.4, containing antibiotics. (penicillin (2000 units/ml), streptomycin (2 mg/ml), gentamycin (50 g/ml), and mycostatin (1000 units/ml) for tissues and tracheal swabs, but at five-fold higher concentrations for faeces and cloacal swabs) Readjust the solution to pH 7.0-7.4 following the addition of the antibiotics. Faeces and finely minced tissues should be prepared as 10-20% (w/v) suspensions in the antibiotic solution. Suspensions should be processed as soon as possible after leaving them for 1-2 hours at room temperature. When immediate processing is impracticable, samples may be stored at 4C for up to 4 days(Website 53). Virus isolation demands between 3 and 10 days for the result, especially with pigeon PMV-1 strains for which a second passage in embryonated eggs may be required to recover the virus (data not shown, observations in author's reference laboratory.)(Barbezange et al., 2002).
    2. Medium: Most virulent strains of NDV will grow in a wide range of cell culture systems and it is possible that in some instances, due to local conditions, inoculation of cell cultures may be the best method for attempting NDV isolation. However, the most widely recommended method is the treatment of samples with antibiotics and the inoculation of embryonated fowls' eggs. The choice of eggs is important, these should be obtained from a specific pathogen free flock or, at least, eggs from hens free of NDV antibodies, and used at 9 to 10 days old(Alexander et al., 1988B). The supernatant fluids of faeces or tissue suspensions obtained through clarification by centrifugation at 1000 g for about 10 minutes at a temperature not exceeding 25C are inoculated in 0.2 ml volumes into the allantoic cavity of each of at least five embryonated SPF fowl eggs of 9-11 days' incubation. After inoculation, these are incubated at 35-37C for 4-7 days. Eggs containing dead or dying embryos as they arise, and all eggs remaining at the end of the incubation period, should first be chilled to 4C and the allantoic fluids tested for haemagglutination (HA) activity. Fluids that give a negative reaction should be passaged into at least one further batch of eggs(Website 53).
    3. Optimal Temperature: incubated at 35-37C for 4-7 day(Website 53).
    4. Upper Temperature: 37C(Website 53).
    5. Lower Temperature: 35C(Website 53).
Epidemiology Information:
  1. Outbreak Locations:
    1. Outbreaks of Newcastle disease were first reported in poultry in Java, Indonesia and Newcastle-upon-Tyne in 1926. The disease currently has worldwide distribution(Seal et al., 2000).
    2. In Western Europe, reported outbreaks increased markedly during the early 1990s, peaking at 239 outbreaks in countries of the European Union in 1994. Between 1991 and 1995, the majority of outbreaks in the EU occurred in the Benelux countries and Germany, predominantly in backyard poultry. Most of the outbreaks since 1995 have also been in backyard poultry. One notable aspect of the outbreaks in Western Europe during the 1990s was the occurrence of outbreaks in countries, which had been free of the disease for many years. Since 1995, 18 outbreaks have been reported in Denmark, one in Sweden, two in Finland, one in Norway, one in the Republic of Ireland and twenty-six in Northern Ireland, all areas that had been declared free of ND and which were monitored regularly by serological testing with no evidence of ND virus infections. Although voluntary vaccination was permitted, Great Britain was also essentially free of ND, and the outbreak confirmed in pheasants in 1996 was the first in this country since 1984. The virus is still detected in racing pigeons. However in 1997, eleven outbreaks of ND were confirmed in Great Britain in commercial poultry, four in broiler chickens and seven in turkeys. Until 1998, Australia had been free of virulent NDV since the 1932 outbreak. Two outbreaks of virulent ND occurred in Australia in 1998 and further outbreaks were reported in 1999(Alexander et al., 2000).
    3. A sick chicken from a backyard flock appears to be the means of entry into California poultry flocks. When the bird exhibited signs of illness, it was taken, on September 25, 2002, to a private veterinary practitioner in Torrence, CA. The bird was found to have a very pathogenic strain (velogenic) of the exotic Newcastle disease (END). This bird or index case is considered to be the carrier of the very infectious and pathogenic virus that spread quickly into backyard poultry then moved from there into poultry production facilities in Southern California. This is the first time since the 1971-73 outbreak of END that the disease has been of epidemic proportions in California. The main methods of transmission of the disease from one location to another seem to have been via bird to bird contact, human activities, insects, rodents, cages, machinery equipment and infected eggs. It then spread to other areas of the state. Since this exotic strain of Newcastle disease was first identified, millions of birds have been sacrificed in California and as of May 2003, it has not been contained by depopulation and quarantine. At the time of publication, commercial flocks and back yard flocks in seven counties in California have been affected. Additional areas of the state are under quarantine. The disease had spread to adjacent states of Nevada, Arizona but the outbreak there seems to be under control through the use of depopulation and quarantine by government response teams. An outbreak of the virus had been detected in Texas, in May of 2003. DNA sequencing analysis confirmed that the Texas strain was caused by a separate introduction of the disease and not due by movement from affected areas in California, Nevada or Arizona. Intense surveillance, and early detection in El Paso County, seems to have contained and eliminated the disease in Texas(Website 50).
    4. Information received on 17 November 2003 from Dr Peter Fernandez, Associate Administrator, Animal and Plant Health Inspection Service, United States Department of Agriculture (USDA), Washington, DC: The exotic strain of Newcastle disease virus detected primarily in backyard flocks in the States of California, Nevada, Arizona, and Texas has been completely eradicated. The confirmation of this exotic strain of Newcastle disease virus triggered an emergency response resulting in the depopulation of almost 4.5 million birds. During the epizootic, 21 commercial operations and 911 backyard establishments were confirmed positive. The last infected commercial operation was found on 26 March 2003 and the last infected backyard establishment was found on 31 May 2003. During the peak of the eradication activities, over 19,000 establishments were quarantined and over 2,500 of these establishments were depopulated. With the successful eradication of the virus, effective 16 September 2003, all States and Federal quarantines in all areas were officially lifted. Enhanced surveillance in commercial flocks as well as targeted surveillance in backyard flocks has not detected any further evidence of the virus. Surveillance continues and efforts have now been shifted to prevention and mitigation through outreach and education programmes. The virus has been completely stamped out and, in accordance with Article 2.1.15.3 of the Terrestrial Animal Health Code, there are no further infected zones. All restrictive measures in relation to Newcastle disease in the United States of America have therefore been lifted(Website 35).
    5. The most recent outbreak reports as posted by the OIE include: Albania: 26 March 2004, Algeria: 14 February 2003, Australia: 27 June 2003, Austria: 14 November 2003, Bahrain: 30 January 2004, Belarus: 13 June 2003, Canada: 19 September 2003, Denmark: 7 March 2003, Italy: 6 February 2004, Kuwait: 31 January 2003, Namibia: 14 March 2003, Niger: 14 March 2003, Norway: 2 July 2004, Russia: 8 August 2003, Senegal: 16 July 2004, Serbia and Montenegro: 14 March 2003, Sudan: 18 April 2003, Sweden: 28 May 2004, Taipei China: 23 May 2003, Thailand: 16 July 2004, Turkey: 16 July 2004, and the United States of America: 21 November 2003 (see above)(Website 36).
  2. Transmission Information:
    1. From: Aves , To: Aves
      Mechanism: Although the administration of live vaccines by aerosol demonstrates clearly that infection may be established via the respiratory route, remarkably little experimental evidence exist to suggest that infected birds will pass on the virus to susceptible birds in this way, even over short distances. The success of this route of transmission will depend on many environmental factors, such as temperature, humidity, and stocking density(Alexander et al., 2000). Inhalation of infectious virus may occur as a result of the presence of either larger droplets or fine aerosols containing virus. The former may occur in the birds' environment due to the presence of infected hosts in which the virus is replicating in the respiratory tract or as a result of contaminated drinking water, e.g. as with vaccination by this medium. In addition, respiratory infection may produce fine aerosols containing virus, which may cover much greater distances before infecting susceptible hosts by inhalation. Faecal excretion may also result in the production of both large and small particles containing infectious virus, the latter most probably resulting from dried faeces(Alexander et al., 1988A).
    2. From: Aves , To: Aves
      Mechanism: Transmission of virus infection from one bird to another via contaminated faeces can be easily demonstrated. The pigeon variant virus, the asymptomatic enteric viruses, and other viruses which fail to induce significant respiratory signs in infected birds, are likely to be transmitted primarily this way(Alexander et al., 2000). Spread of the disease to chickens in Great Britain was shown to be due to food contaminated with faeces and carcasses of infected feral pigeons and Alexander et al., confirmed that virus presented in this way would result in infection in susceptible hens. A noticeable property of the disease seen in laying birds in Great Britain during the 1984 outbreaks was the extreme slowness of spread through a house. This was attributed by Alexander et al., to the barrier that battery cages would present to a virus dependent on fecal-oral route(Alexander et al., 1988A). It has been demonstrated that NDV will survive for period of six months or more in avian faeces under normal temperatures(Vindevogel et al., 1988).
    3. From: Aves , To: Aves
      Mechanism: The concept of vertical transmission in birds implies that the virus is passed directly from the parent to the progeny via the embryonated egg and excludes infection which may occur after the egg has been laid. The facts that virus may penetrate the shell of the egg after laying and that faecal contamination of eggs or the environment has frequently resulted in infection and disease early in the life of chicks hatched from infected parents have often confused the assessment of true vertical transmission. Experimental assessment has also been greatly hindered by the cessation of egg laying, which is usually associated with infection by pathogenic strains of NDV. There are many instances of infected embryos in eggs obtained from hens undergoing field infection but this generally results in death of the embryo long before hatching. In addition, the presence of infected eggs may further complicate assessment of vertical transmission in the field as cracked or broken infected eggs at the hatchery represents another source of virus that may result in early infection in chicks and apparent vertical spread. In contrast to infection of embryos with virulent viruses, lentogenic or vaccinal viruses may not cause death of the embryo and infected chicks may hatch from such eggs. Again it is not clear at what point such eggs become infected although La Sota vaccine has been shown to be present in the ovaries, oviduct and uterus after vaccination(Alexander et al., 1988A). The status of possible NDV egg transmission is similar to the situation for persistence, because both positive and negative results have been reported. Embryos that survived V4 strain infection in ovo hatched and the progeny were NDV positive. More recently virulent NDV was detected in uninfected cell cultures prepared from embryonated chicken eggs. However, chicks hatched from eggs collected from NDV infected flocks were virus negative even though dead embryos and infertile eggs in the same incubator contained NDV(Seal et al., 2000). Sporadic outbreaks of Newcastle disease (ND) occurred in Taiwan during 1998-2000. In some cases, the disease occurred in broilers less than 2 wk old that originated in a broiler breeder farm, so spread of the ND virus (NDV) from the infected breeder farm to broiler ranches was suspected. The purpose of the present study was to examine the possibility of the transmission of NDV through eggs. Both clinical and experimental evidence were used to prove that this is possible. From epidemiological investigation, the possibility of transmission through eggs was suggested in two separate ND cases from a breeder farm and its progeny because two identical NDVs were isolated from both cases. In order to clarify the possibility of the transmission through eggs, one mean egg lethal dose (ELD50) of NDV was inoculated into the allantoic cavity of 155 9-to-11-day-old specific-pathogen-free (SPF) chicken embryos. Seventy-one hatching chicks from the inoculated embryos were raised for 14 days. The cloacal swabs from those chicks at the ages of 1, 4, and 7 days and the tissues after necropsy at the ages of 14 days were taken for virus isolation. The same NDV was reisolated from three hatching chicks. This experiment confirms that a few chicken embryos infected in ovo with a low titer of NDV can hatch and contain NDV after hatching, which results in NDV spreading through eggs(Chen et al., 2002).
    4. From: Aves , To: Homo sapiens
      Mechanism: Many of the documented cases involved infections in laboratory workers who accidentally splashed high-titer NDV-infected egg fluids into their eyes, veterinary laboratory diagnosticians who performed postmortem examinations on infected birds or handled infectious tissues, workers in poultry processing plants, and poultry vaccination crews(Swayne et al., 2003).
    5. From: Homo sapiens , To: Aves
      Mechanism: Man may transfer NDV either mechanically on his person or equipment, or as a result of an infection, which is usually manifest as conjunctivitis(Alexander et al., 1988A). No evidence exists to support human-to-human transmission, but the potential for human-to-bird transmission exists(Swayne et al., 2003).
  3. Environmental Reservoir:
    1. Birds of various uses(Alexander et al., 2000):
      1. Description: FERAL BIRDS: Migratory feral birds may be responsible for the primary introduction of infection, but nearly all NDV isolates obtained from feral birds are of low virulence. A more significant role of such birds may be the transmission of virus within an area following NDV infection of poultry(Alexander et al., 2000). There appears to be two main reservoirs of NDV. The avirulent virus mainly associated with waterfowl and the highly virulent viruses associated with tropical birds, such as psitticines. Both are associated with growth in the intestine(McFerran et al., 1988). CAPTIVE CAGED BIRDS: World trade in captive caged birds is enormous, and in many countries virulent NDV has been isolated frequently from such birds held in quarantine. For example, 147 virulent NDV isolations were made from 2,274 lots of captive birds held in quarantine in the USA from 1974 to 1981. Some infected psittacines have been shown to excrete virulent virus intermittently for extremely long periods, in some cases for more than one year, which further emphasises the potential role these birds may have in the introduction of NDV to a country or area(Alexander et al., 2000). Smuggled pet birds, especially Amazon parrots from Latin America, pose a great risk of introducing exotic Newcastle into U.S. poultry flocks. Amazon parrots that are carriers of the disease but do not show symptoms are capable of shedding END virus for more than 400 days(Website 52). There appears to be a pool of highly virulent viruses maintained in exotic birds such as Psittacines. In the USA of 2.9 million quarantined birds examined, NDV was recovered from 173 lots. Of these isolates VVNDV was obtained from 141 lots, non-viscerotropic velogenic NDV was recognised in 6 lots, mesogenic in 3 lots and lentogenic NDV from 23 lots. The majority of velogenic isolates were from Psittaciformes, with Passeriformes next in importance. It appears some species can become carriers of infection. Thus whilst canaries appeared to eliminate the virus, nuns and conures excreted virus up to 84 days post exposure and parrots excreted the virus up to 84 days post exposure and parrots excreted for 376 days(McFerran et al., 1988). PRIVATELY OWNED GAME FOWL: Several premises in metropolitan Los Angeles were quarantined in early October after exotic Newcastle diseaseone of the most infectious poultry diseases knownwas detected in privately owned game fowl. The source of this outbreak isn't known, although it is speculated that infected birds were smuggled into California from Mexico. Birds carrying the virus have been confiscated at the border(Nolan et al., 2002). Game birds may also be implicated in the introduction of NDV to a country, since considerable trade occurs in these birds, which are often imported for immediate release(Alexander et al., 2000). RACING PIGEONS: The extremely rapid spread of the disease across Europe and the rest of the world probably resulted from contact associated with races, shows, trade and the gregarious nature of the sport. The practice of large transporters collecting birds in a wide area to take to the release point for races presents an excellent environment for the spread of NDV and was considered a prominent method of spread in Great Britain. In addition racing of disease birds offers opportunities for the wider dissemination of the disease as birds are expected to cover long distances and frequently fly widely off course (especially if sick). Such birds may be taken into other pigeon lofts to recuperate or mix with feral birds. In Great Britain, where there was no vaccination of domestic poultry at that time, the virus passed from racing pigeons to feral pigeons which resulted in the infection of domestic hens via food-stores infested with infected feral pigeons(Alexander et al., 1988A). Infected pigeons eliminate virus in the laryngeal secretions and faeces from the second day after infection for 10 to 15 days. Infection can thus be transmitted through direct and indirect contact with oro-nasal secretions and faeces even during the incubation period. It has been shown that in experimental infection of pigeons with velogenic NDV, virus persists for not more than 3 weeks in the intestine and 5 weeks in the brain. After they have been ill for 6 weeks, pigeons may be considered as no longer carriers of virus and thus are unlikely to transmit the infection(Vindevogel et al., 1988). POULTRY MARKETS: Modern methods of slaughter of commercial poultry, marketing of poultry meat and veterinary inspection, have reduced the movement of live commercial poultry (excluding day-old chicks) in many developed countries. However, in many countries, the normal method of trade is by live poultry markets. Such markets, where birds of many different species may be placed in close contact, represent ideal reservoirs of virus from which disease may be disseminated(Alexander et al., 2000). PERSONNEL AND EQUIPMENT: Secondary spread during most epizootics of ND in recent years has been the result of the movements of personnel or equipment. Humans may be infected with NDV, but the most likely role of personnel is in the transfer of infective faeces from one site to another on hair, clothing, footwear, crates, feed sacks, egg trays or vehicles(Alexander et al., 2000). Survives for long periods at ambient temperature, especially in faeces(Website 51). POULTRY WASTE: In the past, poultry meat has been incriminated as the main vehicle for the introduction and spread of NDV. For example, in 1947, one-third of the first 542 outbreaks in England and Wales were considered to be directly attributable to feeding poultry waste to chickens. Sampling of batches of frozen poultry imported into Great Britain in the same year produced an isolation rate of up to 66 percent. Modern methods of poultry carcass preparation and legislation on the feeding of untreated swill to poultry have greatly diminished the risk from poultry products, but the possibility of spread in this way nevertheless remains(Alexander et al., 2000). Poultry products contaminated with pathogenic strains of Newcastle disease virus are a source of virus transmission to susceptible poultry flocks. The probability of contamination varies according to the type of product. Research conducted by various laboratories in Europe has shown that pathogenic virus can be isolated from the carcasses of chickens, whether vaccinated or not, during a brief period after experimental infection. Eggs laid by hens infected with Newcastle disease virus present a very low risk. Furthermore, feathers, bones, blood and offal present potential risks if they are incorporated in poultry feed. Finally, poultry droppings used as a fertiliser can present a major risk of infection in certain circumstances(Guittet et al., 1997). FERAL PIGEONS: In countries of the British Isles, outbreaks of ND in commercial poultry have been associated with feed contaminated with infective faeces from feral pigeons infected with NDV. Similarly, water contaminated with infected faeces may introduce NDV to a flock(Alexander et al., 2000). AIR: Few studies have attempted to assess the survival of airborne virus, but Hugh-Jones were able to detect virus 64m but not 165 m downwind of an infected premises. These authors stressed the importance of environmental conditions, particularly relative humidity on the likelihood of airborne spread. When climatic conditions are favorable and poultry farms sufficiently concentrated, as in Northern Ireland in 1973, it is difficult not to conclude that airborne spread may play a significant role in epidemics of ND. However, in the majority of outbreaks there has been no evidence that airborne spread has played a major role and in recent years airborne spread has not been an issue in reported outbreaks and an alternative, more likely, cause has nearly always existed, particularly the movement of poultry and the agency of humans(Alexander et al., 2000). CONTAMINATED VACCINES: Good manufacturing practices should ensure that vaccines are highly unlikely to be carriers of virulent NDV. However, in the past, birds have become infected when vaccines against other disease have been contaminated with NDV, or as a result of failure to inactivate killed vaccines prepared from virulent NDV. In 1996 and 1997, a series of NDV isolates of low virulence were obtained from poultry flocks in Denmark, a country, which pursues a non-vaccinating policy for ND. These viruses were demonstrated to be the result of contamination of avian virus vaccines with vaccinal NDVs(Alexander et al., 2000). NON-AVIAN HOSTS: Non-avian hosts are likely to introduce NDV by mechanical transfer of infective faeces, e.g. by insects, rodents or scavenging animals. In hot countries, reptiles which may enter poultry houses should not be ignored as potential transmitters of NDV, as susceptibility to infection has been reported in reptiles(Alexander et al., 2000).
  4. Intentional Releases:
    1. Intentional Release Information:
      1. Description: Even before Newcastle disease was identified in the United States, its potential threat to the poultry industry was acknowledged by the War Department Commission during World War II. To be prepared for its possible use in biological warfare, a war research project was initiated to explore methods of protecting poultry by use of inactivated virus vaccines or by enhancing the immunity with a modified live virus vaccine(Hitchner et al., 2004). As of October 2001, the potential for use of infectious agents, such as anthrax, as weapons has been firmly established. It has been suggested that attacks on a nations' agriculture might be a preferred form of terrorism or economic disruption that would not have the attendant stigma of infecting and causing disease in humans. Highly pathogenic avian influenza virus is on every top ten list available for potential agricultural bioweapon agents, generally following foot and mouth disease virus and Newcastle disease virus at or near the top of the list(Perdue et al., 2003).
      2. Emergency Contact: Poultry or pet bird owners or veterinarians who suspect a bird may have END should immediately contact State or Federal animal health authorities or call 1-866-536-7593 (toll-free)(Website 52).
      3. Containment: To prevent END from being introduced into U.S. poultry flocks, USDA's Animal and Plant Health Inspection Service (APHIS) requires that all imported birds (poultry, pet birds, birds exhibited at zoos, and ratites) be tested and quarantined for diseases before entering the country. In addition to international import restrictions, APHIS has increased surveillance efforts to detect END if it is accidentally introduced into the United States. APHIS and State veterinarians trained to diagnose foreign animal diseases regularly conduct field investigations of suspicious disease conditions. This surveillance is enhanced by efforts from university personnel, State animal health officials, USDA-accredited veterinarians, and industry representatives. If END were detected in domestic poultry or pet birds, APHIS would work quickly with its State and industry counterparts to implement aggressive measures, including quarantine, control, and cleanup, to prevent opportunities for the disease to spread(Website 52). The infectivity of NDV and other avian paramyxoviruses may be destroyed by physical and chemical treatments such as heat, irradiation (including light and ultraviolet rays), oxidation processes, pH effects and various chemical compounds. The rate at which infectivity is destroyed depends on the strain of virus, the length of time of exposure, the quantity of virus, the nature of the suspending medium, and the interactions between treatments. No single treatment can guarantee destruction of all viruses but may result in low probability of infective virus remaining(Alexander et al., 1993).
Diagnostic Tests Information
  1. Immunoassay Test:
    1. Haemagglutination Inhibition (Website 53):
      1. Time to Perform: unknown
      2. Description: ND virus may be employed as an antigen in a wide variety of serological tests, enabling neutralisation or enzyme-linked immunosorbent assays (ELISA) to be used for diagnosis. At present, the HI test is most widely used. Chicken sera rarely give nonspecific positive reactions in this test and any pretreatment of the sera is unnecessary. Sera from species other than chickens may sometimes cause agglutination of chicken red blood cells (RBCs), so this property should first be determined and then removed by adsorption of the serum with chicken RBCs. This is done by adding 0.025 ml of packed chicken RBCs to each 0.5 ml of antisera, shaking gently and leaving for at least 30 minutes; the RBCs are then pelleted by centrifugation at 800 g for 2-5 minutes and the adsorbed sera are decanted. The value of serology in diagnosis is clearly related to the expected immune status of the affected birds. HI titres may be regarded as being positive if there is inhibition at a serum dilution of 1/16 (24 or log2 4 when expressed as the reciprocal) or more against 4 HAU of antigen. Some laboratories prefer to use 8 HAU in HI tests. While this is permissible, it affects the interpretation of results so that a positive titre is 1/8 (23 or log2 3) or more. Back titration of antigen should be included in all tests to verify the number of HAU used. HI titres may be used to assess the immune status of a flock. In vaccinated flocks that are being monitored serologically, it may be possible to identify anamnestic responses as the result of a challenge infection with field virus, but great care should be exercised as variations may occur from other causes. For example, it has been demonstrated that APMV-3 virus infections of ND-virus-vaccinated turkeys will result in substantially increased titres to ND virus(Website 53).
    2. Haemagglutination Assay (Website 53):
      1. Time to Perform: unknown
      2. Description: HA activity detected in bacteriologically sterile fluids harvested from inoculated eggs may be due to the presence of any of the 15 haemagglutinin subtypes of influenza A viruses or of the eight other paramyxovirus serotypes. (Nonsterile fluid could contain bacterial HA.)(Website 53).
      3. False Positive: The haemagglutination test is not specific for Newcastle disease virus and other viruses will agglutinate red blood cells. Therefore a sample of allantoic fluid testing positive for haemagglutinin will need further testing to confirm the presence of Newcastle disease virus. The presence of Newcastle disease virus in the sample is confirmed by using the haemagglutination inhibition (HI) test(Website 54).
    3. ELISA (Website 53):
      1. Time to Perform: unknown
      2. Description: Antibodies to NDV may be detected in poultry sera by a variety of tests including single radial immunodiffusion, single radial hemolysis, agar gel precipitin, VN in chick embryos, and plaque neutralization. ELISAs, which lend themselves to semiautomated techniques have become popular, especially as part of a flock screening procedures. Good correlation has been reported between ELISA and HI tests. Sera from other species (including turkeys) may cause low-titer, nonspecific agglutination of chicken RBCs, complicating the test. Such agglutination may be removed by adsorption with chicken RBCs before testing(Alexander et al., 1993). There are a variety of commercial ELISA kits available and these are based on several different strategies for the detection of ND virus antibodies, including indirect, sandwich and blocking or competitive ELISAs using MAbs. At least one kit uses a subunit antigen. Usually such tests have been evaluated and validated by the manufacturer, and it is therefore important that the instructions specified for their use be followed carefully(Website 53). ELISA procedures based on whole virus as coating antigen have also been developed. However, these ELISAs were of limited use, mainly because of non-specific reactions in the chicken sera(Kho et al., 2000).
  2. Nucleic Acid Detection Test: