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[Trails with levamisole to stimulate immunity against Newcastle disease in poultry].

Attempts to stimulate the immunity against Newcastle disease in birds aged 2 months, of the Leghorn breed, were carried out. It was found that levamisol at the rate of 3 mg/kg body weight given once, parenterally, 24 hours prior to or after the immunization of the birds with a live La Sota vaccine or given three times, parenterally or orally, did not stimulate the humoral immune response. No differences were found in the level of the total protein, protein fractions, and the titer of the hemagglutinating antibodies between the test and the control birds. There was, however, prolongation of the time of effective immunity in the levamisol-treated and vaccinated birds as against the birds that were vaccinated against Newcastle disease only. Discussed in the possible mechanism of stimulating the immunity with levamisol.

Animals↗

Newcastle disease virus antigens and strain variations.

Study of antigenic differences among strains of Newcastle disease virus is complicated by the presence in most field isolates and strains of several genetically distinct plaque populations, and by differences in avidity (reactions to antibody) among Newcastle disease viruses. Kinetic neutralization tests were used to demonstrate antigenic differences among 3 plaque clones of velogenic viscerotropic Newcastle disease viruses recently isolated from 3 avian species. The 3 viruses could be distinguished on the basis of plaque structure and hemagglutinin and neuraminidase activity. Antigenic differences among these viruses distinguished them from older, well characterized Newcastle disease viruses.

Animals↗

Newcastle disease vaccination in Malaysia: application of oil emulsion vaccine.

An experimental oil emulsion Newcastle disease vaccine was evaluated for its efficacy in broiler chickens. A group of chickens vaccinated at one day old with a live lentogenic Newcastle disease vaccine and subsequently revaccinated at three and eight weeks old with the experimental oil emulsion vaccine showed satisfactory haemagglutination inhibition antibody response which persisted for 18 weeks. Between 90 and 100 per cent of the vaccinated chickens were protected when challenged with the velogenic viscerotropic Newcastle disease virus. Although the vaccinated chickens were protected against clinical disease, virus could be isolated from a number of birds. By day 10 to 12 after challenge all the chickens were free from Newcastle disease infection.

Animals↗

Protective effect of antibodies to two viral envelope glycoproteins on lethal infection with Newcastle disease virus.

The protective effect of humoral immunity against lethal infection of chickens with Newcastle disease virus was studied. Chickens hatched from eggs laid by hens vaccinated with live attenuated Newcastle disease virus vaccine possessed antibody to various components of the virus, and were resistant to a challenge with a virulent strain of Newcastle disease virus which was 100 per cent fatal for the offspring of nonvaccinated hens. Passive administration of antiserum raised against whole virions provided susceptible chickens protection comparable to that seen in the birds with maternal antibody. When administered passively, both anti-HN serum with virus neutralizing activity, and anti-F serum with only marginal virus neutralizing activity significantly prolonged the survival of infected birds but failed to achieve the level of protection as afforded by the anti-whole NDV serum. The protection provided by the simultaneous presence of anti-HN and anti-F serum was significantly greater than that afforded by either alone and comparable to that of anti-whole NDV serum, indicating the complementary effect of anti-HN and anti-F antibodies not only in cell cultures as reported previously (19), but also in a natural host.

Animals↗

Immune response to oil-emulsion vaccines with single or mixed antigens of Newcastle disease, avian influenza, and infectious bronchitis.

Inactivated Newcastle disease virus (NDV), avian influenza virus (AIV), and infectious bronchitis virus (IBV) antigens were evaluated for immunological efficacy in monovalent and polyvalent vaccines. Vaccinated broilers were bled for hemagglutination-inhibition (HI) tests at 1- or 2-week intervals. Half of the chickens were challenged with the Largo isolate of velogenic viscerotropic (VV) NDV at 8 weeks post-vaccination, and the remainder were challenged with the Massachusetts 41 strain IBV at 9 weeks post-vaccination. Newcastle disease HI titers were reduced significantly (P less than 0.05) from those of monovalent control vaccine groups when IBV antigen was emulsified in mixtures with low (1-3x) concentrated NDV or NDV and AIV antigens. Avian influenza HI titers were significantly (P less than 0.05) lower than those of the control monovalent groups when highly concentrated NDV was part of the polyvalent vaccine. Infectious bronchitis HI titers were higher than those of control monovalent groups in 13 of 15 vaccine groups when IBV antigen was in polyvalent formulations. VV NDV challenge killed all non-NDV vaccinates and induced increased HI titers in NDV vaccinates but no morbidity or mortality. Sixty of 80 IBV vaccinates experienced a fourfold or greater HI titer increase following challenge. All non-IBV vaccinates seroconverted at 1 week post-challenge.

Animals↗

Velogenic viscerotropic Newcastle disease virus strains in Morocco.

Isolates of Newcastle disease virus (NDV) in Morocco were characterized as velogenic. Two isolates were from tracheal swabs taken at a Moroccan live poultry market, and four isolates were from field cases. Infection of 8-week-old chickens showed that these isolates and previously characterized Moroccan isolates were of the viscerotropic pathotype. Based on hemagglutinin thermostability and the capacity to agglutinate equine erythrocytes, the Moroccan velogenic viscerotropic NDV isolates were classified as belonging to at least three distinct strains.

Animals↗

Comparison of various diagnostic methods in characterizing Newcastle disease virus isolates from Desi chickens.

Eleven Newcastle disease viruses (NDV), isolated from apparently healthy and ailing Desi chickens were subjected to both conventional and modern characterization techniques. The virulence and strain differentiating experiments placed 10 isolates in the velogenic group and one in the mesogenic group. In MDBK cells, 9 isolates produced characteristic cytopathogenic effects up to 5 and 2 up to 3 passages. Molecular characterization with a 21-mer oligonucleotide probe placed all the isolates in the velogenic/mesogenic group. The results of this study clearly indicated that the isolates obtained are either velogenic or mesogenic but not lentogenic.

Animals↗

Influence of chicken breed on pathogenicity evaluation of velogenic neurotropic Newcastle disease virus isolates from cormorants and turkeys.

Three isolates of Newcastle disease virus (NDV) from cormorants and turkeys were classified as velogenic neurotropic NDV (VNNDV) by standard pathotyping procedures in specific-pathogen-free white leghorn and white rock chickens. White leghorns inoculated by eye drop, cloaca, intravenous, or intracerebral routes had a higher frequency of nervous signs and mortality than was observed in similarly inoculated white rocks. Two backpassages in white rocks increased the intravenous pathogenicity index of all three isolates, but none had a value after backpassage that was as high as the classical VNNDV strain Texas GB. The breed of chicken used in standard procedures did influence the numerical values of pathotyping determinations, but the differences between breeds were not large enough to change the pathotype assigned to these isolates.

Animals↗

Thermostable Newcastle disease vaccines in Tanzania.

The V4 thermostable Newcastle disease vaccine was tested under village conditions in Central Tanzania. The vaccination regimes were four vaccinations by eye drop (eye drop group), one vaccination by eye drop followed by three vaccinations by drinking water (drinking water group), one vaccination by eye drop followed by three vaccinations with vaccine supplied on boiled sorghum (food vaccine group) and no vaccine (control group). Antibody responses in the eye drop and drinking water groups suggested that at least 70% of the chickens would be protected against challenge with virulent virus. In both groups, eight of the 11 chickens survived laboratory challenge. Only three of the 11 chickens in the food vaccine group resisted challenge, and none of the 10 control chickens.

Administration, Oral↗

Aerosol administration of Newcastle disease vaccines at one day of age.

Newcastle disease vaccines were administered at one day of age by 3 general procedures: 1) discharge of a vaccine aerosol over chicks confined in an enclosed space, 2) aerosol adminstration in a poultry house, 3) a commercial device which emits a fine spray into the nasopharynx while the chick is being debeaked. From this work the following conclusions have been drawn: 1) All 3 methods are of some value with respect to the development of antibody titers and resistance to challenge. 2) The efficacy is universely proportional to the maternal antibody titer. 3) Aerosol vaccination into an enclosed air space is superior to the other methods tested. 4) Day-old vaccination is useful primarily in conferring some early resistance until a subsequent aerosol vaccination at 9-14 days of age confers additional protection. Other important factors include strain of vaccine, vaccine titer, the nature of the diluent, and site of the aerolized particles.

Administration, Oral↗

Correlation of haemagglutinin-neuraminidase and fusion protein content with protective antibody response after immunisation with inactivated Newcastle disease vaccines.

The correlation between the antigen content of inactivated Newcastle disease (ND) oil emulsion-vaccines and the serological response after immunisation was studied. The haemagglutinin-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV) were quantified in 33 inactivated oil-adjuvanted ND vaccines using isopropylmyristate (IPM)-extraction and antigen ELISAs. These commercial vaccines differed in NDV-vaccine strain, the method applied to inactivate the vaccine virus, the vaccine valence and the composition of the oil emulsions. Large differences, up to 100-fold, in the antigen quantities present in different vaccines were found. The NDV-HN content and the NDV-F content of the vaccines both highly correlated with the haemagglutination-inhibiting (HI) antibody titres after immunisation. These correlation's were found over a 10,000-fold range of applied antigen. The antigen content of the oil emulsion-vaccines also highly correlated with virus neutralising antibody titres. The presence of serum HI antibody titres in individual specific pathogens free (SPF)-chickens after immunisation with inactivated ND vaccines was highly indicative for clinical protection against challenge with the virulent NDV-Herts strain. Our results are the first to demonstrate that the protective serological response after immunisation highly correlates with the antigen content of oil-adjuvanted vaccines.

Adjuvants, Immunologic↗

Occurrence of velogenic viscerotropic Newcastle disease in pet and exotic birds in 1991.

In 1991, velogenic viscerotropic Newcastle disease (VVND) was diagnosed in domestic psittacine birds in six states: Illinois, Indiana, Michigan, Texas, California, and Nevada. In the first four states, the disease assumed outbreak proportions. The affected psittacine birds--yellow-headed Amazon parrots (Amazona ochrocephala oratrix), yellow-naped Amazon parrots (Amazona ochrocephala auropalliata), cockatiels (Nymphicus hollandicus), and conures (unknown species)--exhibited respiratory and/or central nervous system signs. The velogenic viscerotropic Newcastle disease virus (VVNDV) was isolated from cloacal and tracheal swabs and various tissues, such as the lung, trachea, distal intestine, and spleen. The origin of the birds could not be established. The disease in the six states was promptly controlled, with no evidence that domestic poultry had been exposed. Also, VVNDV was isolated from quarantined birds intended for importation into the United States. Included were 53 moustached parakeets (Psittacula alexandri fasciata), a mynah (Gracula religiosa), a drongo (Dicrurus sp.), and three partridges (family Phasianidae). Groups of birds that yielded VVNDV were denied entry into the United States. Birds that are illegally imported and therefore not tested for the presence of foreign animal pathogens are a potential source of VVNDV and a threat to domestic poultry and caged birds.

Animals↗

Pathology of Newcastle disease in double-crested cormorants from Saskatchewan, with comparison of diagnostic methods.

Newcastle disease (ND) in juvenile double-crested cormorants (Phalacrocorax auritus) occurred several times since 1975, but there are relatively few studies on its pathology and diagnosis. In order to describe the distribution of Newcastle disease virus (NDV) and associated lesions in cormorants with ND and to compare diagnostic methods, 25 cormorants with nervous signs from a ND epizootic in Saskatchewan in 1995 (NDE cormorants) were compared with 18 negative control cormorants. Tissues of these birds were examined by necropsy, histology, virus isolation, immunohistochemistry, serology, and reverse transcriptase-polymerase chain reaction (RT-PCR) methods. The NDE cormorants had a characteristic non-suppurative encephalomyelitis, with a significantly higher prevalence of neuronal necrosis, gliosis, perivascular infiltration with mononuclear cells, and endothelial hypertrophy than control cormorants. These lesions were found more frequently in the cerebellum and brain stem than in other parts of the central nervous system. Immunohistochemically, NDV antigen was limited to neurons, glial and endothelial cells in the central nervous system, and to tubular epithelial cells in the kidney. Newcastle disease virus was isolated with the highest prevalence (4/5) and the highest concentration (10(4.8) ELD50/g) from the kidney. The virus isolates often did not agglutinate erythrocytes in the standard hemagglutination test; the presence of NDV was confirmed by use of an indirect immunoperoxidase assay. By RT-PCR, NDV was detected in kidney and jejunum of a NDE cormorant. There was no significant difference between sensitivity of histology, virus isolation, and serology for detecting ND in NDE cormorants.

Animals↗