Immune Response of Salmonella Challenged Broiler Chickens Fed Diets Containing Gallipro®, a Bacillus subtilis Probiotic

This study was conducted to investigate the effect of feeding a probiotic, Bacillus subtilis, on antibody titers against Newcastle and infectious bursal viruses in broiler chickens challenged with Salmonella enterica serotype Enteritidis. One hundred and sixty 1-day-old broiler chicks were randomly assigned to four treatments in a completely randomized design. The treatments were negative control, probiotic-treated group, challenged group, and challenged probiotic treated group. Salmonella challenging decreased (P < 0.05) the relative weights of spleen and bursa. Inclusion of probiotic to diet of challenged chickens increased the relative weight of spleen, but had no effect on the relative weight of bursa. There were no differences for the antibody titers of chickens between negative control and probiotic-treated group. Salmonella challenging decreased (P < 0.05) antibody titers against Newcastle and infectious bursal viruses. Improvements in the antibody titers were observed by the addition of probiotic to diet of these chickens. The results showed that dietary inclusion of probiotic had no significant effect on immune parameters of chickens at non-contaminated environment, display a greater efficacy at environment contaminated with pathogen and can improve immune responses of infected chickens.

[Effect difference between two segments in invariant chain CLIP on humoral immune]

OBJECTIVE

To compare the effect between two segments (PBS and GBS) of Class II -associated invariant chain peptide (CLIP) of invariant chain (Ii) on humoral immune by immune carrier.

METHODS

First six hybrids containing Newcastle disease virus (NDV) epitope F2 and Ii segments (Cyt/TM/F2, Cyt/TM/F2/GBS, Cyt/TM/PBS/F2, Cyt/TM/F2/TRIM, Cyt/TM/F2/GBS/TRIM, Cyt/TM/PBS/F2/TRIM) were reconstructed respectively. Then they were inserted into the prokaryotic expression vector pET-32a and transformed into E. coli Rosetta (DE3) to induce the expression of the recombinant proteins. Finally mice were immunized with these purified fusion proteins, the specific antibody titers were detected with ELISA, to compare and analyze the effect among different groups on the immune response.

RESULTS

All the six groups immunized with these hybrids increased antibody titers (from 1.5-fold to 4.9-fold, respectively) compared with the group immunized with F2 alone. Within the above six groups, the hybrids containing either PBS or GBS had higher antibody titers from 1.6-fold to 2.4-fold than the hybrids without the both segments. However, the group of the hybrid containing PBS had a 1.5-fold antibody titer higher than the group of GBS hybrid.

CONCLUSION

Ii cytosolic and transmembrane domains could increase the immune response, while the segment PBS behaved better than GBS in an immune vector based on Ii.

Combined exposure to cyanobacterial biomass, lead and the Newcastle virus enhances avian toxicity

Under environmental conditions, wild birds can be exposed to multiple stressors including natural toxins, anthropogenic pollutants and infectious agents at the same time. This experimental study was successful in testing the hypothesis that adverse effects of cyanotoxins, heavy metals and a non-pathogenic immunological challenge combine to enhance avian toxicity. Mortality occurred in combined exposures to naturally occurring cyanobacterial biomass and lead shots, lead shots and Newcastle vaccination as well as in single lead shot exposure. Mostly acute effects around day 10 were observed. On day 30 of exposure, there were no differences in the liver accumulation of lead in single and combined exposure groups. Interestingly, liver microcystin levels were elevated in birds co-exposed to cyanobacterial biomass together with lead or lead and the Newcastle virus. Significant differences in body weights between all Pb-exposed and Pb-non-exposed birds were found on days 10 and 20. Single exposure to cyanobacterial biomass resulted in hepatic vacuolar dystrophy, whereas co-exposure with lead led to more severe granular dystrophy. Haematological changes were associated with lead exposure, in particular. Biochemical analysis revealed a decrease in glucose and an increase in lactate dehydrogenase in single and combined cyanobacterial and lead exposures, which also showed a decreased antibody response to vaccination. The combined exposure of experimental birds to sub-lethal doses of individual stressors is ecologically realistic. It brings together new pieces of knowledge on avian health. In light of this study, investigators of wild bird die-offs should be circumspect when evaluating findings of low concentrations of contaminants that would not result in mortality on a separate basis. As such it has implications for wildlife biologists, veterinarians and conservationists of avian biodiversity.

Neurochemical and neuroendocrine responses to Newcastle disease virus administration in mice

Mice injected intraperitoneally with Newcastle disease virus (NDV) responded with increased plasma concentrations of ACTH and corticosterone and increased hypothalamic concentrations of the tryptophan and of the norepinephrine catabolite, 3-methoxy,4-hydroxyphenylethyleneglycol (MHPG) and the serotonin catabolite, 5-hydroxyindoleacetic acid (5-HIAA). Two different strains of NDV, a lentogenic and a mesogenic one, elicited dose-dependent effects in these responses. Both strains elicited near maximal responses at doses around 1000 hemagglutination units. The maximal effects on ACTH, corticosterone and MHPG occurred around 2 h, but the effects on tryptophan and 5-HIAA were greatest at 8 h. Similar responses in plasma corticosterone, and cerebral tryptophan and 5-HIAA were observed following i.p. injection of polyinosinic-polycytidylic acid, but MHPG was not altered. The cyclo-oxygenase inhibitor, indomethacin, had little effect on the NDV-induced increases in plasma corticosterone and ACTH, and hypothalamic indolamines, but essentially ablated the MHPG response. The effect of NDV on plasma corticosterone, like that of endotoxin (LPS), was prevented by hypophysectomy, suggesting that the pituitary was required for these responses. These endocrine and neurochemical responses to NDV resemble those to interleukin-1 (IL-1) and LPS. Therefore we tested mice pretreated with the IL-1-receptor antagonist. This treatment prevented the neurochemical and plasma ACTH and corticosterone responses to IL-1, but did not alter those to LPS, and prevented the endocrine and neurochemical responses to NDV in approximately half of the animals. Thus IL-1 may be a mediator of the responses to NDV, but additional factors may also be involved.

An oligonucleotide probe that distinguishes isolates of low virulence from the more pathogenic strains of Newcastle disease virus

A synthesized oligonucleotide, termed cleavage probe (NDV-CL), has been designed to complement the cleavage-activation site of the fusion gene of the Texas GB isolate of Newcastle disease virus (NDV). This oligonucleotide probe, 21 bases in length, bound with RNA from velogenic strains of NDV tested in a slot-blot hybridization assay. The probe also recognized RNA from the mesogenic strains used in this assay, although no signal was observed with RNA isolated from lentogenic NDVs or with that from other common avian viruses used as controls. This probe did not recognize RNA from isolates of other paramyxovirus serotypes (PMV-2 or PMV-3) included in this study. The ability of this probe to distinguish lentogenic NDVs, which cause little or no clinical disease, from those strains that may produce severe morbidity and/or mortality suggests a potential use for the probe in a molecular diagnostic assay.

Immunohistochemical detection of Newcastle disease virus in chickens

An immunoperoxidase histochemical technique utilizing a monoclonal primary antibody was developed for detection of Newcastle disease virus (NDV) antigen in tissues from chickens. The technique was applied to trachea, lung, spleen, Harderian gland, and cecal tonsil harvested from specific-pathogen-free (SPF) chickens at 2, 5, 7, 10, and 14 days postinoculation (PI) with NDV, and to corresponding tissues from commercial broiler chickens representing 30 cases of spontaneous respiratory disease. Positive staining occurred in the cytoplasm of respiratory epithelial cells in the trachea or bronchi of NDV-inoculated SPF chickens at 5 and 7 days PI. Staining also occurred in the respiratory epithelium of the trachea and bronchi of commercial broilers from seven of 30 cases of spontaneous respiratory disease. These results indicate that the immunoperoxidase technique has value as a rapid diagnostic test for Newcastle disease.

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.

[The tenacity of Newcastle disease virus (LaSota) in the excrement of laying hens in different housing systems]

The survival time of NDV (LaSota) in the excrement of layers was in summer (winter) 22 and 18 days (26 and 36 days) in two cage houses, 14 and 18 days (36 and 33 days) in two floor-pen houses, as well as 8 days (54 and 68 days) in two dropping store places. By one week staying in battery cages and following the storage in dropping store place after 47 or 50 days NDV (LaSota) could not be reisolated. Besides environment factors, temperature, pH and dry matter was the thermic effect very significant. The comparison of the tenacity of NDV (LaSota) in different housing systems was besides of the quantitative determination of survival time supported through the application of a life time distribution test.

Isolation and characterisation of Newcastle disease virus strain in a feral dove (Stigmatopelia senegalensis) in Nigeria

An isolate of Newcastle disease virus (NDV) was obtained from a feral dove, (Stigmatopelia senegalensis). The isolate was shown to have a mean-death-time of 96 h and an intracerebral pathogenicity index of 0.10. It was immunogenic but not pathogenic for 6-week old chicks on experimental infection. Based on these observations the isolate was classified as a lentogenic strain. The role of such isolates of NDV from wild birds on the Nigerian poultry industry is discussed.

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.

Pathogenicity of two strains of Newcastle disease virus in the grey-breasted helmet guinea fowl

Thirty-five 6-week-old guinea fowl keets, seronegative for maternal antibodies to Newcastle disease virus, were infected with Herts strain (33/56) and Kumarov strain of Newcastle disease virus intramucularly (IM) or intranasally (IN). Clinical signs were first noticed four days post infection (PI) in the group infected IM but five days PI in the group infected IN with Herts strain of Newcastle disease virus. These clinical signs were similar in both groups and included anorexia, droopiness, huddling together, greenish diarrhoea and marked cachexia. Prominent nervous signs, including spasms of the head and neck, were observed in groups infected with Herts strain. The major gross lesions observed were emaciation with prominent keel bone, empty intestinal tract and distended gall bladder in most keets. The histological lesions were characterised by meningoencephalitis, necrosis and loss of lymphocytes from splenic and lymphoid aggregates. There was muscular degeneration and necrosis in the gizzard and mild pulmonary congestion and oedema in some keets. Neither gross or microscopic lesions were observed in keets that had received the Kumarov strain.

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.

Characterization of Newcastle disease viruses isolated from pigeons in Italy

The authors report the results of characterization studies of three strains of Newcastle disease virus (NDV) (two isolated from pigeons and one from chickens). The plaque cloning of the viruses, showed that each NDV strain consists of different clones of genetically mixed viral populations. The pigeon NDV isolates were classified as lentogenic using mean death time (MDT) determination; while the intracerebral pathogenicity index (ICPI) was the same as the velogenic NDV strain.

The pathogenesis of velogenic Newcastle disease virus infection of chickens of different ages and different levels of immunity

Chickens of 7 weeks or 20 weeks of age were divided into three groups according to their antibody status (high, low, absent) and were infected with a velogenic viscerotropic Newcastle disease virus. To follow patterns of viral replication, birds were necropsied at regular intervals up to 22 days and organs were sampled from each bird. In non-immune birds, virus could be isolated from all organs examined. In birds with antibody, virus was most frequently isolated from the proventriculus, cecal tonsil, bursa, and brain. However, because no one organ could be recommended for all situations, all four should be sampled for field diagnosis. In immune birds, although clinical signs were either mild or absent, widespread virus replication occurred up to 19 days post-challenge.

Protective effect of monoclonal antibodies to Newcastle disease virus in passive immunization

A series of monoclonal antibodies (MAbs) against the haemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins and the matrix (M) protein of Newcastle disease virus (NDV) were tested for protective effects in passive immunization of newborn chickens against challenge with a virulent heterologous strain of NDV (Italien). MAbs with high virus-neutralizing activity directed to one antigenic site of the HN protein delayed virus growth and significantly prolonged survival time, but all chickens eventually succumbed to infection. MAbs directed to two antigenic sites of the F protein completely suppressed virus growth and prevented death of chickens, although the neutralizing activities of these anti-F MAbs were lower than those of the above anti-HN MAbs. Combined administration of the anti-HN and anti-F MAbs had a synergistic protective effect, but no protective effects were shown by MAbs against the M protein.

Elevated virulence of Newcastle disease virus strains following serial passages in kidney cells in vitro

Serial passage of two lentogenic Newcastle disease virus (NDV) strains in kidney cell lines increased virulence and changed viral biological properties. In two cell lines (BHK and MDBK), elevation in virulence was demonstrated by plaque formation under an overlay with no additives, decrease in mean death times, elevated intracerebral pathogenicity index, and cytopathic effect in chicken embryo fibroblasts. Some other markers not directly correlated to virulence, such as heat inactivation of hemagglutinin and neuraminidase, were not influenced by passage in kidney cells. In addition, all strains were slow eluters. This observation emphasizes the importance of preventing the virus from reaching the viscera.

Effect of Newcastle disease virus on ocular and paraocular tissues in experimentally inoculated chickens

The effects of a mesogenic strain of Newcastle disease virus on ocular and paraocular structures were studied in 10-to-12-week-old chickens inoculated conjunctivally, intraocularly, intracerebrally, or intravenously. Paraffin-embedded tissues were examined by light and fluorescent microscopy using conventional staining and immunohistochemistry. Lesions were most severe in intraocularly inoculated chickens, where a marked iridocyclochoroiditis was evident from 8-12 hours up to 21 days postinfection. Viral antigens were detected in the iris, ciliary body, Schlemm's canal, and occasionally the lens, choroid, and base of the pecten. Although optic neuritis and iridocyclochoroiditis were found in intracerebrally inoculated birds, no viral antigens were detected in the optic nerve.

Virus distribution and histopathologic changes in organs of chickens inoculated with Newcastle disease virus (avian paramyxovirus-1) isolated from racing pigeons

The virus distribution and histopathologic changes in organs of 1-week-old chickens inoculated with three representative isolates of Newcastle disease virus isolated from racing pigeons in Japan were examined. All three isolates were recovered from various organs, including brain, for several days, but not from the blood. Results were highly correlated with their high intracerebral pathogenicity indices (ICPI), in spite of their long mean death time of minimum lethal dose (MDT/MLD).

Antigenic variation of Newcastle disease viruses isolated from wild ducks in Japan

Nineteen strains of Newcastle disease virus (NDV) isolated from wild ducks in Japan were placed into 4 distinct antigenic groups on the basis of their reactivities to 8 monoclonal antibodies against the HN molecule of NDV in hemagglutination inhibition tests. The NDV strains of duck origin were antigenically distinct from NDV-B1 and NDV-Miyadera originated from chickens, and varied in their virulence to chicken embryos. No apparent correlation was found between the antigenicity of the HN molecule and virulence.

Serological and pathological studies of Newcastle disease viruses isolated from caged birds from Southeast Asia

Eleven isolates of Newcastle disease virus (NDV), from caged birds imported from or captured in Southeast Asia in 1979-80, were antigenically divided into five distinct groups. Most of them were distinguishable from more classical NDVs (vaccine B1 strain and Miyadera strain) on the basis of their reactivity to eight monoclonal antibodies against the HN molecule of NDV in hemagglutination-inhibition tests. However, when three representative isolates were evaluated for their biological properties and pathogenicity against 1-day-old chickens, all three were found to be velogenic types that could induce serious symptoms of Newcastle disease and which eventually killed all of the chickens, regardless of the route of infection. There was not any significant correlation between their reactivity patterns with the monoclonal antibodies and their virulence.

Tracheal mucus transport rate and bacterial clearance in turkeys exposed by aerosol to La Sota strain of Newcastle disease virus

Tracheal mucus transport rate (TMTR) and quantitative clearance of aerosolized Escherichia coli from the trachea, lung, and air sac were measured in healthy unanesthetized turkeys and in turkeys exposed by aerosol to a La Sota vaccine strain of Newcastle disease virus (NDV). The TMTR of uninfected turkeys was 42.4 +/- 14.7 cm/min. The TMTR of NDV-infected turkeys was depressed on days 3 through 7 postexposure (PE); depression was significant (P less than or equal to 0.05) on day 7 PE. Tracheal E. coli clearance in NDV-infected turkeys was reduced on days 4 through 9 PE, significantly so on day 5 PE (P less than or equal to 0.01). Depression of TMTR and tracheal E. coli clearance were associated histologically with replacement of normal pseudostratified columnar epithelium by 3 to 8 layers of immature nonciliated cells. E. coli clearance by the lung and air sac of NDV-infected turkeys was depressed on days 5 through 9 PE.

Characterization of Newcastle disease virus (avian paramyxovirus-1) isolated from pigeons

Newcastle disease virus (avian paramyxovirus-1) was isolated from pigeons in 12 states between May 1984 and December 1985. One of the isolates was from a feral pigeon; the remainder were from privately owned pigeon lofts. Use of monoclonal antibodies showed seven of the eight isolates tested to be indistinguishable from the 1982 and 1983 Great Britain and European isolates. Clinical signs were paralysis, torticollis, tremors, incoordination, and death. Pigeons inoculated with the paramyxovirus-1 isolates intravenously or intramuscularly developed clinical disease identical to that described for natural infection; however, only one pigeon inoculated intranasally developed clinical signs. The mean death time for inoculated pigeons was 9.5 days, with a range of 4 to 25. Virus was shed for up to 20 days. Primary lesions observed on necropsy were gastroenterocolitis and pancreatic necrosis. Chickens experimentally infected by the cloacal, intranasal, or caudal thoracic air-sac route remained healthy. However, the intracerebral pathogenicity index (ICPI) in day-old chickens was similar to that observed with velogenic Newcastle disease virus isolates. Four of six isolates inoculated intravenously into 6-week-old chickens induced neurotropic disease.

Two types of Newcastle disease viruses isolated from feral birds in western Australia detected by monoclonal antibodies

Thirteen viruses isolated from feral birds and one isolated from a domestic duck, obtained in 1979-1980 during a survey of birds in Western Australia, were shown to be Newcastle disease viruses of low virulence for chickens. The binding of mouse monoclonal antibodies, raised against NDV-Ulster 2C to MDBK cells infected with the isolates was assessed using an indirect immunoperoxidase test. Five viruses caused binding of all 9 monoclonal antibodies tested, whereas the other 9 isolates induced binding of only 4 monoclonal antibodies.

Experimental infection of rosellas (Platycercus eximius) with velogenic viscerotropic Newcastle disease virus (VVNDV)

Plaque-purified and non-plaque-purified velogenic viscerotropic Newcastle disease viruses (VVNDVs) were inoculated into golden-mantled rosellas (Platycercus eximius). VVNDV produced acute clinical disease in this species: all birds died within 6 days postexposure. There was no difference between the two inoculation groups in clinical signs. Seven tissues and five tissue swabs were collected from each of 15 birds. The VVNDV concentration in each specimen was titrated, and the concentrations were compared. The lung and trachea had the highest concentrations of virus in both the tissue suspensions and the swab suspensions. The average virus concentrations of the lung were 10(5.9) 50% embryo lethal doses (ELD50) per 0.1 ml for the tissue suspension and 10(4.9) for the swab. The average virus concentrations of the trachea were 10(5.6) ELD50 per 0.1 ml of tissue suspension and 10(4.6) for the swab.

In ovo interference of embryo non-lethal avian infectious bronchitis viruses (IBV) with velogenic Newcastle disease virus and embryo adapted IBV

Avian infectious bronchitis virus (IBV) interfered with the lethal effects of velogenic Newcastle disease virus (NDV) and embryo adapted IBV in eggs previously inoculated with non-lethal IBV. Greater interference was noted in eggs superinfected with embryo adapted IBV than velogenic NDV. The interference could be eliminated by treating the initial IBV with homologous anti-IBV serum.

Characterization of Nigerian strains of Newcastle disease virus

Newcastle disease virus was isolated from outbreaks of the disease in vaccinated and unvaccinated poultry flocks representing commercial and backyard farms in different parts of Nigeria. On characterization, all 12 isolates were found to be velogenic.

Paramyxovirus type 1 infections of racing pigeons: 1 characterisation of isolated viruses

Viruses isolated from field outbreaks of disease in racing pigeons in continental Europe and Great Britain were shown to be identical by serological tests using conventional chicken antisera and mouse monoclonal antibodies. The pigeon viruses showed high levels of cross-reaction to Newcastle disease virus (NDV) in haemagglutination inhibition tests and Madin-Darby bovine kidney cells infected with pigeon virus isolates bound three out of nine mouse monoclonal antibodies prepared against NDV Ulster 2C. These results confirm their classification in the paramyxovirus type 1 serotype of avian paramyxoviruses. However, the pigeon viruses could be distinguished from more classical paramyxovirus type 1 viruses by the significantly different titres obtained in haemagglutination inhibition tests, the failure of mouse monoclonal antibodies directed against the HN1 epitope of NDV Ulster 2C to inhibit their haemagglutinating activity and a unique binding pattern seen with the nine mouse monoclonal antibodies.

Isolation and biological properties of some Moroccan strains of Newcastle disease virus

Newcastle disease virus was isolated from six field cases in Morocco. On the basis of the mean death time of chicken embryos, the intracerebral pathogenicity index, and plaque formation on chicken embryo fibroblast monolayers, five isolates were determined to be of the velogenic pathotype. One of these differed from the others in that it agglutinated equine erythrocytes. The sixth isolate was found to be of low virulence but differed from the vaccinal strain tested.

Atypical disease produced in chickens by Newcastle disease virus isolated from exotic birds

Chickens were infected with a Newcastle disease virus (NDV) recovered from exotic birds with severe clinical disease and with lesions characteristic of viscerotropic velogenic Newcastle disease (VVND). The infection in chickens was inconsistently lethal, some infected chickens were not clinically affected, and gastrointestinal involvement was only marginally evident. Pathogenicity of the virus for chickens was not detectably altered by laboratory passage in chickens or by limit dilution passage in chicken embryos. The results suggest that the difference between velogenic NDV pathotypes may not always be distinct and that clinical manifestations of VVND in chickens may not always be predictable based on signs and lesions observed in exotic birds.

Duration of excretion of virulent Newcastle disease virus following challenge of chickens with different titres of serum antibody to the virus

Virulent Newcastle disease virus (NDV) was isolated from susceptible and immune chickens following intra-ocular challenge with the Essex '70 strain. Challenge virus was isolated from the trachea and cloaca of susceptible birds until they died 7 to 9 days after challenge. This virus was isolated from immunised chickens for up to 14 days after challenge. The duration of excretion was influenced by the prechallenge serum antibody titre to NDV. It persisted longest in chickens with titres of 2(3) to 2(7) and decreased in length and frequency from chickens with titres in the range 2(8) to 2(12). Chickens with pre-challenge titres of 2(3) to 2(5) developed 2- to 3- fold increases in post-challenge titres, whereas those with higher pre-challenge titres had smaller proportional increases in titre. Excretion of virulent virus from immunised birds should be considered in the development of Newcastle disease control programs.

Comparison of the immunogenicity of Newcastle disease virus strains V4, B1 and La Sota in chickens. 1. Tests in susceptible chickens

The immunogenicity of the Australian Newcastle disease virus (NDV) strain V4 was compared with that of the International reference preparation of Hitchner B1 and a commercial La Sota strain. Immunity was assessed serologically using the log mean HI titres 21 days after immunisation, the percentage of birds in each group which developed titres greater than 2(3) and their resistance to graded challenge doses of the virulent Herts 33/56 strain of NDV. These tests showed that the V4 strain was significantly less immunogenic (P less than 0.01) than the B1 or La Sota strains when administered intraocularly (eye drop) or by aerosol methods. When given in the drinking water V4 induced a better immunity (P less than 0.01) than the B1 strain in one of 2 experiments.

Comparison of the immunogenicity of Newcastle disease virus strains V4, Hitchner B1 and La Sota in chickens. 2. Tests in chickens with maternal antibody to the virus

The immunogenicity of three Newcastle disease virus (NDV) strains--V4, Hitchner B1 and La Sota, was assessed in chickens that had varying levels of maternal antibody to the virus. Chickens were immunised at different ages by the eye drop and aerosol methods. The immune response of chickens to similar doses of the strains was affected by the presence of maternal antibody. Both the level of maternal antibody and the strain of virus used affected the result. Strain La Sota was least affected as it took higher levels of maternal antibody to depress response to it than were required to have a similar effect on Hitchner B1 and V4. Strain V4 was the strain most affected by circulating maternal antibody. The results demonstrated that strain V4 was less immunogenic than Hitchner B1 and La Sota when used in chickens with maternal antibody to NDV.

Pathology of the trachea in turkeys exposed by aerosol to lentogenic strains of Newcastle disease virus

Five groups of 4-week-old turkey poults were each infected by aerosol with a different lentogenic strain of Newcastle disease virus. Four days postinfection, sections of tracheas were collected for histopathologic characterization and virus titration. The most prominent lesions were fibrinopurulent exudate in tracheal lumens, hyperplasia of epithelial cells, and infiltration by lymphocytes. All strains multiplied to high titers and produced similar microscopic lesions, but the number of poults with severe microscopic lesions varied among groups.

Progression of tracheal lesions in turkeys exposed by aerosol to LaSota strain of Newcastle disease virus

Five-week-old turkeys were exposed by aerosol to the LaSota strain of Newcastle disease virus. Poults were killed on days 2, 4, 6, 8, 10, 12, and 14 postexposure, and tracheas were processed for virus quantitation and histologic examination. Newcastle disease virus was recovered at a high titer from all tracheas collected 2, 4, and 6 days postexposure. The initial tracheal lesion observed on day 2 was swelling of ciliated columnar and mucous gland cells. Some of the affected cells contained intracytoplasmic inclusions. Cell swelling and degeneration were followed by epithelial cell proliferation, fibrinopurulent exudation, and lymphocytic infiltration. Epithelial cell proliferation was most severe on days 4 and 6, when tracheas were lined with several layers of immature cells. Lymphoid nodules appeared on day 6 and persisted up to day 14. From day 8 on, there was regression of the proliferative lesion accompanied by differentiation of the immature epithelium. By day 14, the tracheal mucosa regained its normal histologic appearance.

An occurrence of Newcastle disease in pigeons: virological and serological studies on the isolates

The antigenic and pathogenetic relationship between pigeon Newcastle disease virus (NDV) isolates during outbreaks of 1982 in Italy and reference pathogen and non-pathogen NDV-strains were investigated. The pigeon-isolates were slow-eluters and showed a thermostability at 56 degrees C of over 30 min. They proved to be lentogenic as measured by the mean-death-time in chicken-embryos, and between lentogenic and mesogenic as measured by the Hanson test. They failed to produce plaques in chicken-embryo-fibroblasts and showed high pathogenicity for experimentally infected pigeons, low-pathogenicity for quails and were not pathogenic for chickens. They were antigenically different from the LaSota strain as measured by the cross-HI-test and induced considerable seroconversion in inoculated animals. The existence of a lentogenic neurotropic pigeon-pathogenic strain was considered.

Newcastle disease virus in waterfowl in wisconsin

Newcastle disease virus was isolated from the cloaca of 1-5% of live-trapped waterfowl in Wisconsin in the fall from 1978-1980. Antibody to NDV was detected in 8% of the birds tested, with no apparent difference between sex and age classes. Experimental infection resulted in persistence of virus shedding for months after exposure. Lack of detectable antibody in some of the experimentally infected birds suggests that reported antibody prevalence may not be indicative of the true prevalence of the infection. Isolation of NDV for the last 9 years as well as the detection of antibody in waterfowl over 25 years ago, suggests a well-adapted host-parasite relationship. Experimental evidence of virus persistence in individual mallards (Anas platyrhynchos) provides a mechanism for maintenance of the virus in the wild population.

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.

The in vitro effects of Newcastle disease virus on the metabolic and antibacterial functions of human neutrophils

Live Newcastle disease virus (NDV) was used to investigate the in vitro effects of a viral infection on phagocytosis, chemiluminescence generation, superoxide production, oxygen consumption, NADPH-oxidase activity, and intracellular killing of bacteria by Ficoll-Hypaque separated human neutrophils. Phagocytosis of oil red O particles by NDV-treated PMN was inhibited by 50%. Chemiluminescence by PMN was inhibited 79% after zymosan stimulation and 86% after tetradeconyl phorbol acetate stimulation. Superoxide generation was inhibited by 68%. Oxygen consumption was inhibited in the presence of NDV by 37% after stimulation with phorbol myristate acetate, while membrane-associated NADPH-enzyme activity was decreased by 19%. The percent of surviving intracellular S. aureus was significantly elevated in NDV-treated PMN after 60 and 120 min of incubation. Purified bacterial neuraminidase markedly suppressed chemiluminescence, while neuraminic acid blocked the effects of the virus. These observations suggest that infections with myxoviruses may suppress a number of vital neutrophil functions. It appears that the effects may be partly mediated by the interaction of viral neuraminidase with the external neutrophil membrane.

Characterization of a Newcastle disease virus isolated from a parrot (Psittacus erythracus) in Nigeria

The characteristics of a Newcastle disease virus isolated from a parrot (Psittacus erythracus) in Nigeria were examined using standard laboratory tests. Minimum lethal dose in embryos was 10(-10), mean death time 44.8 h. The intracerebral and intravenous pathologic indices were 1.65 and 2.42, respectively. The virus was resistant at pH 3 and pH 7.2 and the hemagglutinin was thermostable at 56 C for 120 min. Of 10 mammalian species of erythrocytes examined, those of equine and rat were not agglutinated. The isolate was typed as a velogenic viscerotropic Newcastle disease virus.

Embryonated eggs compared with fragments of chorioallantois attached to egg shell for isolation of Newcastle disease virus

The feasibility of using fragments of chorioallantois attached to egg shell (C-S) as an alternative to embryonated eggs for isolating Newcastle disease virus (NDV) was assessed. In paired titrations of 6 strains of virus, embryonated eggs detected an average of 6-to-7-fold greater amounts of virus than did C-S fragments. The efficiency of isolation of viscerotropic velogenic NDV from 240 swab samples was 97% in embryonated eggs and 84% in C-S fragments. Sensitivity differences between the 2 host systems were revealed only in tests of samples expected to contain small amounts of virus. These results suggest that C-S fragments can be reliably used in some but not all instances, thereby relieving logistic constraints sometimes associated with the use of embryonated eggs.

Transmissibility of Australian strains of Newcastle disease virus

The transmission of Newcastle disease virus strains from infected to direct-, indirect-, and aerosol-contact groups of chickens was studied. Chickens 7, 21, and 63 days old were used in separate trials. Chicken age and virus strain were found to be important in spread of the virus. Strain V4 spread quickly to all contact groups and was classed as highly transmissible, whereas strain JA failed to infect all contact chickens of each age group, thus spreading less efficiently than strain V4. The viruses spread more readily among the 2 older groups. The significance of the transmissibility of Newcastle disease virus vaccine is briefly discussed.