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Ultrastructural changes in the cardiac muscle of chickens infected with the GB strain of Newcastle disease virus.

The changes in chicken cardiomyocytes resulting from infection with the GB strain of Newcastle disease virus were studied by electron microscopy. The virus infection caused shortening of the sarcomeres and generalized oedema in the perivascular region of the heart muscle, containing debris from degenerated mitochondria and myofilaments. Some of the cardiomyocytes had condensed chromatin, resembling that of apoptotic cells.

Animals↗

Oral vaccination of chickens against Newcastle disease with V4 vaccine delivered on processed rice grains.

An international effort (sponsored by the Australian Centre for International Agricultural Research) is being made to develop oral vaccines that will protect village chickens against Newcastle disease. The vaccines being used are derivatives of the avirulent Australian V4 strain that have been selected for enhanced heat resistance. The present study, undertaken in Sri Lanka, used local processed (parboiled) rice as a vehicle for the vaccine. Chickens receiving two doses of vaccine on cooked, parboiled rice were completely protected against contact challenge with the virulent SL 88/1 Sri Lankan strain of Newcastle disease virus Chickens kept in contact with these vaccinated chickens were similarly protected. Lower levels of protection were achieved with vaccine given on uncooked parboiled rice. V4 vaccine administered intranasally also gave complete protection. Serums from vaccinated chickens that survived challenge were tested for haemagglutination-inhibition antibodies, using both vaccine virus and challenge virus as antigens. Titres were higher against vaccine virus.

Administration, Oral↗

Laboratory evaluation of the immune response of young broiler chickens vaccinated against Newcastle disease under field conditions.

Four experiments were conducted to examine the efficiency of 4 different Newcastle disease (ND) field vaccination programs. For all experiments young broiler chickens were obtained from breeder flocks regularly vaccinated against ND. The following vaccination programs were tested: 1) vaccination at 1 day of age; 2) vaccination at 1 and 20 days of age; 3) vaccination at 7 days, and 4) vaccination at 12 days of age. In all experiments, 10 randomly chosen birds from each of 6 farms that were commercially vaccinated plus 10 nonvaccinated control birds were bled just prior to vaccination and the farms separated into 2 groups based on the birds' mean NDV hemagglutination-inhibition (HI) titers. At various times after vaccination, sera from 10 different birds from each of the 6 farms and 10 nonvaccinated birds were assayed for HI titers and then challenged with virulent NDV to establish disease resistance. Serologic and challenge data indicated that the majority of chickens from any one of the 4 vaccination programs produced measurable HI titers and were refractory to challenge. However, the greatest serologic response and best resistance to clinical ND were found in birds with relatively low levels of maternal immunity at the time of initial vaccination and in birds receiving a booster vaccination at 20 days of age.

Age Factors↗

Multivalent inactivated virus oil emulsion vaccines in broiler breeder chickens. III. Trivalent Newcastle disease, infectious bursal disease, and arthritis/tenosynovitis viruses vaccine in primed breeders.

Inactivated Newcastle disease (NDV), infectious bursal disease (IBDV), and viral arthritis/tenosynovitis (VA) viruses were incorporated into water-in-oil emulsion vaccines, either alone, in bivalent combinations, or in a trivalent vaccine. Twenty-week-old broiler breeder chickens that had received previous live virus vaccination with NDV, IBDV, and VA were injected intramuscularly with the monovalent, bivalent, or trivalent vaccines. The antibody titers to the antigens contained in the monovalent, bivalent, or trivalent vaccines increased rapidly and peaked 4 to 8 weeks postvaccination. The titers declined during the next 3 months and increased to levels equal to or higher than the initial peak values. The titers remained high through 10 months postvaccination. Progeny hatched at intervals throughout the 40-week trial possessed detectable antibody titers to the appropriate antigens incorporated into the breeder vaccine through 21 days of age.

Animals↗

Immunization of chickens with live Newcastle disease vaccine adjuvanted with oil.

Chickens of various ages and breeds were vaccinated subcutaneously with Newcastle disease live-in-oil vaccines. These vaccines were prepared immediately prior to the vaccination by mixing the lyophilized live vaccine with the oil adjuvant, which was kept at room temperature. The live-in-oil vaccines were shown to be 30-50 times more effective in efficacy tests than either the same vaccines reconstituted in water or killed-in-oil vaccines. In addition to its biological advantage, the method of preparation of live-in-oil vaccine saves the expensive space of cold storage and shipment necessary for conventional killed-in-oil vaccines.

Adjuvants, Immunologic↗

Virulence of pigeon-origin Newcastle disease virus isolates for domestic chickens.

The virulence of six pigeon-origin isolates of Newcastle disease virus (NDV) was evaluated before and after passage in white leghorn chickens. Four isolates were defined as pigeon paramyxovirus-1 (PPMV-1) and two isolates were classified as avian paramyxovirus-1 (APMV-1) with NDV monoclonal antibodies. The four PPMV-1 isolates were passaged four times in chickens, and the APMV-1 isolates were passaged only once. Infected birds were monitored clinically and euthanatized. Tissues were collected for histopathology, in situ hybridization with a NDV matrix gene digoxigenin-labeled riboprobe, and immunohistochemistry with an anti-peptide antibody to the nucleoprotein. Mean death time, intracerebral pathogenicity index, and intravenous pathogenicity index tests performed before and after passage in chickens demonstrated increased virulence of the passaged PPMV-1 isolates and high virulence of the original isolates of APMV-1. Sequence analysis of the fusion protein cleavage site of all six isolates demonstrated a sequence typical of the virulent pathotype. Although the pathotyping results indicated a virulence increase of all passaged PPMV-1 isolates, clinical disease was limited to depression and some nervous signs in only some of the 4-wk-old specific-pathogen-free white leghorns inoculated intraconjunctivally. However, an increased frequency of clinical signs and some mortality occurred in 2 wk olds inoculated intraconjunctivally with passaged virus. Histologically, prominent lesions in heart and brain were observed in birds among all four groups inoculated with the PPMV-1 isolates. The behavior of the two pigeon-origin APMV-1 isolates when inoculated into chickens was characteristic of velogenic viscerotropic NDVs and included necro-hemorrhagic lesions in the gastrointestinal tract.

Amino Acid Sequence↗

Comparison of the effect of live Newcastle disease vaccine Clone 30 in broilers administered at day 1 or at day 7 and the effect of H120 vaccination at 17 days of age: a field experiment.

To analyse the results of a vaccination on the first day of age against Newcastle disease (ND) and on the 17th day of age against Infectious Bronchitis (IB) resp. with spray vaccines with Clone 30 and H120 vaccine. These vaccinations are compared in field circumstances with other vaccination methods. A serological examination and challenge test were used to be informed about the response and protection. From the present study the following conclusions can be drawn: Clear indications are obtained that following a spray vaccination against ND with Clone 30 vaccine of one-day-old broilers which possessed maternal antibodies, birds received a moderately good protection against ND, in spite of very low levels of HI antibodies. A spray vaccination against IB with H120 vaccine of broilers at 17 days of age gave some protection from two weeks after vaccination, however making a good conclusion about the protection is impossible and further investigation is required.

Animals↗

Evidence of genetic heterogeneity of some lentogenic Newcastle disease virus strains.

Two distinguishable subpopulations were recovered from chickens infected with lentogenic strains of Newcastle disease virus originally ioslated from chickens in Australia and Ireland. In both instances, a subpopulation that rapidly eluted from chicken erythrocytes was recovered predominantly from tracheal swabs, and a slow-eluting subpopulation from cloacal swabs. The two subpopulations differed in thermostability of the hemagglutinatin and mean survival time of infected chicken embryos, as well as in elution pattern. The heterogeneity characteristic of the Aust-V4 strain and NI-Ulster strain could not be demonstrated in B1, NJ-LaSota, and ENG-F, lentogenic strains commonly used in vaccines. The question is discussed of whether standard vaccine strains are also hetrogeneous if a technique for separating stock populations is found, and the significance of possible heterogeneity to the effectivenss of the vaccines.

Agglutination Tests↗

Use of sentinel chickens to evaluate the effectiveness of cleaning and disinfection procedures in noncommercial poultry operations infected with exotic Newcastle disease virus.

The use of sentinel chickens in establishing the negative status of commercial poultry flocks depopulated due to exotic Newcastle disease (END) is considered to be an economically beneficial process. However, the costs and benefits of using sentinel chickens in noncommercial operations are in question. The objective of this study was to use sentinel chickens to evaluate whether adequate cleaning and disinfection coupled with an appropriate time period without susceptible poultry species on the premises would eliminate END virus from a noncommercial poultry operation and preclude the need for placement of sentinels in previously infected operations before declaring them free of virus. Noncommercial poultry operations were selected from the 2002 to 2003 END outbreak database. Operations included in the study had one or more isolations of END virus (ENDV) from cloacal or oropharyngeal swabs of birds on the premises. A total of 546 birds were placed on 53 premises. All sentinel birds sampled after placements were negative by virus detection methods and serologic tests. Results of this study indicate that time and the application of appropriate cleaning and disinfection procedures will adequately mitigate the risk of viable virus persisting in noncommercial poultry operations. In the future, this information may eliminate the need for sentinel bird placement to ensure virus free status of premises before repopulation, thereby decreasing the costs of END eradication.

Animals↗

Protective immune response of chickens against Newcastle disease, induced by the intranasal vaccination with inactivated virus.

Intranasal vaccination of chickens with inactivated Newcastle disease virus (NDV) induced both local and systemic antibody responses, resulting in protection against intranasal challenge with a lethal dose of a virulent NDV strain. The immune response was enhanced by the use of cholera toxin B subunit (CTB) as an adjuvant and only small amounts of the challenge virus were recovered from the birds vaccinated together with CTB. On the other hand, subcutaneous vaccination with the same antigen induced only a serum antibody response in chickens, allowing the challenge virus to replicate in the sinus. The present results indicate that secretory antibodies induced on the respiratory mucosal surface by intranasal vaccination with inactivated NDV protected chickens from lethal infection by inhibiting virus replication at the portal of entry for the virus.

Adjuvants, Immunologic↗

[Experimental vaccination of broiler chickens against Newcastle disease in Burkina Faso using thermotolerant LaSota/A300 and V4/276 coated-millet vaccines].

Vaccination against Newcastle disease with the thermotolerant LaSota/A300 and V4/276 coated-millet vaccines was tried in Ouagadougou, Burkina Faso, by feeding 298 European broiler chickens exhibiting maternal antibodies. Opportunistic infections, such as colibacteriosis, decimated 70-81% of the three vaccinated groups and 24% of control, before being eradicated by antibiotic therapy. The surviving chickens were challenged two months after vaccination with the Hertz 33/56 virus strain. This resulted in 100% deaths in the control group, 78% in birds vaccinated with the V4/276, 7% in birds fed with LaSota/A300, and in no death in the group given both vaccines at one week interval. These last two groups also exhibited high titres of 1HA antibodies before the challenge. The lyophilized LaSota/A300 and V4/276 vaccines kept high viral titres after 8-34 days' ambient temperature exposure during the cool season in Ouagadougou.

Animals↗

Molecular evolution of the Newcastle disease virus matrix protein gene and phylogenetic relationships among the paramyxoviridae.

Matrix (M) gene sequences for recent field isolates and older reference Newcastle disease viruses (NDV) were examined to determine phylogenetic relationships and population trends among these viruses. Overall, the M gene has a majority of synonymous nucleotide sequence substitutions occurring among NDV isolates. However, several predicted amino acid changes in the M protein of specific NDV isolates have occurred that correlate to phylogenetic relationships. Nucleotide substitutions in these codons have a greater number of nonsynonymous base changes. The NDV isolates arising since the 1970s belong to a population of viruses that expanded worldwide at an exponential rate. These viruses may have their origins in free-living birds, are present worldwide, and continue to circulate causing disease in poultry. A specific NDV lineage composed of virulent isolates obtained in the US prior to 1970 appears to no longer exists among free-living birds or commercial poultry. However, "vaccine-like" viruses are common in the US and continue to circulate among commercial poultry. Based on M protein amino acid sequences, NDV separates as a clade most closely related to morbilliviruses and not with their current designated category, the rubulaviruses among the Paramyxoviridae. Consequently, avian paramyxoviruses should have their own taxonomic subfamily among the Paramyxovirinae.

Animals↗

Selection of thermostable Newcastle disease virus progeny from reference and vaccine strains.

In a study of low-virulence Newcastle disease virus (NDV) isolates from poultry, 38% of the isolates had a more thermostable hemagglutinin than the lentogenic reference strains B1 and La Sota or live vaccines derived from those strains. Whether those strains with a more thermostable hemagglutinin are truly indigenous or whether they could have originated from vaccines used in the flocks was unknown. Seven monovalent NDV vaccines of B1 or La Sota type and reference B1 and La Sota strains were heat treated at 56 C to select variants more thermostable than the parent virus. Four thermal treatment cycles were completed, and virus propagated from the second and fourth heat treatments was assayed for changes in thermostability and antigenicity. The hemagglutinin thermostability of all vaccine and reference strain variants increased from the initial < or =10 min to > or =120 min after four treatments. Antigenic changes evaluated by hemagglutination inhibition against NDV monoclonal antibodies identified changes in only the heat-treated La Sota strains. The results demonstrate that the field isolates with a more thermostable hemagglutinin could have been derived by selection from the heterogenous NDV populations in vaccine strains and that minor antigenic changes may be a result of that selection.

Animals↗

Characterization of isolates of Newcastle disease virus from migratory birds and turkeys.

The susceptibility of wild birds to infection with Newcastle disease virus (NDV) has resulted in speculation about the role of these free-flying birds in the origin and transmission of the virus infection. Since several NDV isolates from free-flying waterfowl and turkey flocks in the Midwest were avirulent for chickens and had thermostable hemagglutinins, isolates were collected from both waterfowl and turkeys over a seven-year period, 1974-1980, for comparison. Strains from both waterfowl and turkeys were avirulent, based on mean death times in chicken embryos, and could be differentiated from licensed vaccine strains with similar mean death times by in vitro markers. Waterfowl strains were generally thermostable, were slow to elute from chicken red blood cells, and produced plaques in chicken embryo fibroblasts. Some of the turkey isolates were similar to the waterfowl strains in thermostability, elution, and production of plaques in chick embryo fibroblasts. However, in the latter years of the study, there was a tendency toward isolation from turkey flocks of vaccine-like strains that did not produce plaques without additives and whose hemagglutinin was thermolabile. The appearance of these strains reflects either a selection for this virus type by the host or replacement of field strains by vaccine strains as the result of an increased usage of vaccines by producers.

Animals↗

Adaptation of a velogenic Newcastle disease virus to vero cells: assessing the molecular changes before and after adaptation.

A velogenic Newcastle disease virus isolate was passaged 50 times in Vero cell culture and the virus was assessed for the molecular changes associated with the passaging. At every 10th passage, the virus was characterized conventionally by mean death time (MDT) analysis, intracerebral pathogenicity index (ICPI) and virus titration. At increasing passage levels, a gradual reduction in the virulence of the virus was observed. Molecular characterization of the virus included cloning and sequencing of a portion of the fusion gene (1349 bp) encompassing the fusion protein cleavage site (FPCS), which was previously amplified by reverse transcription-polymerase chain reaction. Sequence analysis revealed a total of 135 nucleotide substitutions which resulted in the change of 42 amino acids between the velogenic virus and the 50th passage virus. The predicted amino acid motif present at the cleavage site of the virulent virus was (109)SRRRRQRRFVG(119) and the corresponding region of the adapted adapted virus was (109)SGGRRQKRFIG(119). Pathogenicity studies conducted in 20-week-old seronegative birds revealed gross lesions such as petechial haemorrhages in the trachea, proventricular junction and intestines, and histopathological changes such as depletion and necrosis of the lymphocytes in thymus, spleen, bursa and caecal tonsils in the birds injected with the velogenic virus and absence of the lesions in birds injected with the adapted virus. The 50th-passage cell culture virus was back-passaged five times in susceptible chickens and subjected to virulence attribute analysis and sequence analysis of the FPCS region, with minor difference found between them.

Amino Acid Sequence↗

Experimentally induced changes in nasalucous secretory systems and their effect on virus infection in chickens. II. Effects on adsorption of Newcastle disease virus.

Chickens 3 wk old, inoculated intranasally with a mesogenic (moderately virulent) strain of Newcastle disease virus, developed necrotic lesions of the mucous acini, predominantly of the middle turbinates. The infection subsequently spread to involve much of the rest of the mucosa, including mucous and ciliated epithelial cells, and other acini. The early phase of adsorption of a virulent strain of the virus to the middle turbinates of chicks 5-21 days of age was studied by giving a standard inoculum intranasally to unanesthetized animals. Variation in amounts adsorbed by individual chickens was large, but was minimized by making measurements on pools of turbinates from three chicks at intervals of 1, 3, and 5 hr after exposure of the excised turbinates to antibody, by washing, and by trypsinization. The virus released from the cells into the trypsin was designated as adherent virus, and the infectious virus in the cells after destruction of the cells by water grinding, as cell virus. Paralysis of ciliary action by cocaine increased the number of infected cells in the turbinates about 10-fold at all three time intervals. Pilocarpine injection before virus inoculation caused a large increase in the amount of infected cells 1 hr after virus administration, but was followed by a sharp drop in infected cells by 3 or 5 hr. Pilocarpine given after the virus decreased the number of infected cells and changed the relationship of infected cells to adherent virus. Exposure of chicks to sustained or severe cold caused a similar but less marked effect. The drop in infected cells was restored to control values if chicks were returned to brooder temperatures. The marked drop of infected cells produced by pilocarpine and cold in living chicks, and in cultures of chicken trachea (previous study), is consonant with the idea that virus has been adsorbed on mucus granules in the mucous cells of the turbinates and then has been reexcreted, as unincorporated virus, into the moving mucous sheet. A series of accessory data support this interpretation.

Adsorption↗

Changes in lymphoid organs and blood lymphocytes induced by vitamin A deficiency and Newcastle disease virus infection in chickens.

The effect of vitamin A deficiency in the presence or absence of Newcastle disease virus infection (NDV, La Sota strain) on weight of lymphoid organs and on the number and type of circulating white blood cells (WBC) was investigated in chickens. Day-old chickens with limited vitamin A reserves were fed purified diets containing either marginal (ad libitum) or adequate (pair-fed) levels of vitamin A and at 21-28 days of age; half the chickens in each group were infected with NDV. Vitamin A deficiency resulted only in significantly lower absolute and relative weights of bursa of Fabricius and after infection both weights of bursa and thymus were significantly lower. Relative weight of spleen was significantly higher after infection irrespective of vitamin A status. Liver weights were not affected by vitamin A status and/or NDV infection. Both vitamin A deficiency and NDV infection resulted in lymphopenia, while the lowest number of WBC were observed in vitamin A-deficient chickens during the acute phase of NDV (5 days after infection). Subsequent to lymphopenia due to NDV infection, a marked lymphocytosis was observed in controls and to a lesser extent in vitamin A-deficient birds. These results indicate that vitamin A deficiency, which is aggravated by concomitant NDV infection, affects lymphoid cell systems.

Animals↗