Tolerance and safety evaluation of N,N-dimethylglycine, a naturally occurring organic compound, as a feed additive in broiler diets.

N,N-Dimethylglycine (DMG) is a tertiary amino acid that naturally occurs as an intermediate metabolite in choline-to-glycine metabolism. The objective of the present trial was to evaluate tolerance, safety and bioaccumulation of dietary DMG in broilers when supplemented at 1 g and 10 g Na-DMG/kg. A feeding trial was conducted using 480 1-d-old broiler chicks that were randomly allocated to twenty-four pens and fed one of three test diets added with 0, 1 or 10 g Na-DMG/kg during a 39 d growth period.

Antigenic and phylogenetic studies on a variant Newcastle disease virus using anti-fusion protein monoclonal antibodies and partial sequencing of the fusion protein gene.

A virulent Newcastle disease virus (NDV) isolate, 34/90, reported to show considerable antigenic diversity from more classical strains of NDV, including vaccine strains, was evaluated phylogenetically and for the presence of neutralizing epitopes on the fusion protein. Comparison of a 309 nucleotide sequence of the fusion protein gene of 34/90 with other viruses confirmed the diversity of this virus, placing it in a discrete fifth genetic lineage with an avirulent virus isolated from waterfowl and genetically quite distant from other strains and isolates. The virus-neutralizing mAbs used in the present study were directed against at least seven distinct epitopes on the fusion protein.

Development of an M2e-specific enzyme-linked immunosorbent assay for differentiating infected from vaccinated animals.

Vaccination programs for the control of avian influenza (AI) in birds have restrictions because of some limited efficacy and the difficulty of discriminating between vaccinated and virus-infected poultry. We studied M2e, the highly conserved external domain of the influenza A M2 protein, as a potential differential diagnostic marker for influenza virus infection. The M2 protein is an integral membrane protein, scarcely present on virus particles, but abundantly expressed on virus-infected cells.

Inclusion body disease in snakes: a review and description of three cases in boa constrictors in Belgium.

Inclusion body disease, a fatal disorder in Boidae, is reviewed, and three cases in boa constrictors, the first reported cases in Belgium, are described. The snakes showed nervous signs, and numerous eosinophilic intracytoplasmic inclusions, which are considered to be characteristic of the disease, were found in the liver and pancreas. The disease is suspected to be caused by a retrovirus, but transmission electron microscopic examinations of several tissues from one of the snakes did not reveal particles with a typical retroviral morphology.

Vaccination of chicken embryos with escape mutants of La Sota Newcastle disease virus induces a protective immune response.

To reduce the embryonic pathogenicity of Newcastle disease virus (NDV), escape mutants of the La Sota strain were produced with selected monoclonal antibodies. Immunoselection resulted in the elimination of an epitope by single amino acid substitution (F and HN molecule) or in a conformational change (HN molecule). The embryonic pathogenicity of these escape mutants was reduced and their dose was optimised for in ovo vaccination.

Ultrastructural changes of the tracheal epithelium after vaccination of day-old chickens with the La Sota strain of Newcastle disease virus.

The progression of tracheal lesions induced by vaccination of day-old specific pathogen-free chicks with the La Sota strain of Newcastle disease virus (NDV) was examined by relating surface changes as observed by scanning electron microscopy with subcellular changes seen by transmission electron microscopy. NDV infection resulted in hypertrophy of goblet cells, their rupture, and the formation of excess mucus. Activation of goblet cells peaked within 4 days postvaccination.

Phylogenetic analysis of fowl adenoviruses.

The sequences of the L1 loop of the hexon protein from representative fowl adenovirus (FAdV) strains of the different European and American collections were determined and compared. This study highlighted the lack of consensus in the numbering of the individual serotypes between the American and the European classifications. An identification system is proposed based on restriction fragment length polymorphism of the hexonA/hexonB polymerase chain reaction product.

Assessment of the cell-mediated immune response in chickens by detection of chicken interferon-gamma in response to mitogen and recall Newcastle disease viral antigen stimulation.

The potential of a capture enzyme-linked immunosorbent assay (ELISA) specific for chicken interferon-gamma (ChIFN-gamma) has been evaluated as a tool to assess cell-mediated immunity (CMI) in the chicken. In a first step, ChIFN-gamma production and cell proliferation of mitogen-activated chicken splenocytes have been compared. In general, for each of the stimulation conditions where significant proliferation was observed, production of ChIFN-gamma could be measured by ELISA.

Significance of interactions between Escherichia coli and respiratory pathogens in layer hen flocks suffering from colibacillosis-associated mortality.

This study aimed to examine the significance of interactions between Escherichia coli and various respiratory pathogens during outbreaks of colibacillosis-associated mortality in layer hen flocks under field conditions. For this purpose, a case-control study involving 20 control flocks with baseline mortality and 20 flocks with increased mortality due to E. coli septicaemia and polyserositis, was conducted.

Adhesion of Salmonella enterica serotype Enteritidis isolates to chicken isthmal glandular secretions.

The ability of Salmonella enterica serotype Enteritidis isolates to adhere to immobilized secretions of the isthmus of the laying hen was determined in an ELISA-type assay. One-third of the 56 isolates tested in the logarithmic growth phase, adhered to the isthmal secretions. Using a binding assay of the isolates to thin paraffin sections of the oviduct, we demonstrated that the receptor of the adhesion was localized inside the tubular gland cells of the isthmus.

Evolution of pigeon Newcastle disease virus strains.

Twenty-seven Newcastle disease virus isolates obtained during the years 1998 and 1999 from racing pigeons were shown to be antigenically indistinguishable from the pigeon paramyxovirus type 1 (PPMV-1) viruses isolated in the years 1983 and 1984. Partial sequencing of 240 base pairs of the F gene demonstrated at least 94.7% identity at the nucleotide level between isolates from 1983 and 1984, and more recent viruses isolated in 1998 and 1999.

Polymerase chain reaction combined with restriction enzyme analysis for detection and differentiation of fowl adenoviruses.

A polymerase chain reaction combined with restriction enzyme analysis was developed for detection and differentiation of all 12 fowl adenovirus (FAdV) serotypes representing the five fowl adenovirus (A to E) species. For primer design, the published sequences of the hexon proteins of FAdV1, FAdV8 and FAdV9 were aligned and conserved regions in the two pedestal regions adjacent to the L1 loop region were determined. A primer pair (hexon A/hexon B) was constructed and was shown to amplify approximately 900 bp of the hexon gene including the L1 loop region.

Epidemiology of infectious bronchitis virus in Belgian broilers: a retrospective study, 1986 to 1995.

Infectious bronchitis virus (IBV) was isolated from each of 236 broiler flocks that had respiratory infection (86%), impaired growth, enteritis and/or nephritis (14%), over a 10-year period from 1986 to 1995 in Belgium. Among them, 65% of the investigated flocks had not been vaccinated against infectious bronchitis. Type-specific reverse transcriptase polymerase chain reactions (RT-PCRs) were used after propagation of the isolates in embryonated eggs in order to detect and differentiate Massachusetts, D274, B1648 and 793/B types.

[Significance of paramyxovirinae protein F in physiopathology and immunity].

The Paramyxovirinae sub-family contains viruses of major importance for humans (measles and mumps viruses) and animals (Newcastle disease virus, canine distemper virus, rinderpest virus) but also zoonotic viruses (Hendra and Nipah viruses). Newcastle disease virus, a Rubulavirus, which is specific of birds, can be used as a model for understanding the pathogenicity mechanisms of Paramyxovirinae and for the study of vaccination against the diseases they cause. The F protein of pathogenic strains of Newcastle disease virus have a polybasic cleavage site (K/R-Q-K/R-R) which is specific of furine, a cellular enzyme present in all cellular types, what allows viral multiplication in all cells of the host.

Infectious bursal disease (Gumboro disease).

Infectious bursal disease (IBD) (Gumboro disease) has been described throughout the world, and the socio-economic significance of the disease is considerable world-wide. Various forms of the disease have been described, but typing remains unclear, since antigenic and pathotypic criteria are used indiscriminately, and the true incidence of different types is difficult to determine. Moreover, the infection, when not fatal, leads to a degree of immunosuppression which is often difficult to measure.

Production of antibodies against chicken interferon-gamma: demonstration of neutralizing activity and development of a quantitative ELISA.

Four monoclonal antibodies (mAbs) specific for chicken interferon-gamma (ChIFN-gamma) were generated by gene gun immunization and were utilized to develop a mAb-based capture ELISA specific for ChIFN-gamma. Each mAb reacted specifically with both baculovirus and Escherichia coli-derived recombinant ChIFN-gamma in ELISA and Western Blot analysis or natural ChIFN-gamma in immunofluorescence experiments. As determined by competition ELISAs, mAbs 3D5, 4C6 and 3A3 recognized the same or adjacent epitopes on the ChIFN-gamma molecule, whereas mAb 1E12 recognized a distant epitope.

[Inter-species transmission of the influenza virus].

Influenza is an infection of human beings and several animal species. It is caused by influenza viruses which belong to the Orthomyxoviridae family. Type A influenza viruses are the most important as they cause severe epidemics and are responsible of important pathological troubles.

Comparison of biological activities of natural and recombinant chicken interferon-gamma.

In recent years, chicken interferon-gamma (ChIFN-gamma) has been identified and cloned from a chicken T cell line. In this study, recombinant ChIFN-gammma produced in the baculovirus and prokaryotic (Escherichia coli) expression systems were characterized and their activity was compared to that of naturally ChIFN-gamma produced by mitogen-activated splenic T cells. The baculovirus-derived ChIFN-gamma protein (Bac-ChIFN-gamma) proved to have physiochemical properties and biological activities similar to those of natural ChIFN-gamma.

Acute pancreatitis in chickens due to non-virulent Newcastle disease virus.

A non-virulent Newcastle disease virus (strain APMV-1 96/89 VB) was isolated from a broiler chicken from a backyard flock. Using monoclonal antibodies, the virus was shown to be different from the vaccinal virus strains Hitchner, La Sota and Ulster. The virus was shown to replicate in the pancreas of one-day-old specific pathogen-free chickens infected orally, and the histological lesions observed in the pancreas of chickens inoculated with the fourth chicken passage of the virus five to nine days after infection were consistent with an acute pancreatitis.

Newcastle disease outbreaks in recent years in western Europe were caused by an old (VI) and a novel genotype (VII).

Newcastle disease virus (NDV) strains, isolated from outbreaks during epizootics between 1992 and 1996 in Western European countries, were compared by restriction enzyme cleavage site mapping of the fusion (F) protein gene between nucleotides 334 and 1682 and by sequence analysis between nucleotides 47 and 435. Both methods revealed that NDV strains responsible for these epizootics belong to two distinct genotypes. Strains derived from sporadic cases in Denmark, Sweden, Switzerland and Austria were classified into genotype VI [6], the same group which caused outbreaks in the Middle East and Greece in the late 1960's and in Hungary in the early 1980's.

Acute infectious bursal disease in poultry: Immunological and molecular basis of antigenicity of a highly virulent strain.

This study has confirmed, by the use of immunological and molecular tools, that the recent failures of vaccination against infectious bursal disease (IBD) encountered in Europe were not related to antigenic variation, but to increased virulence of the circulating IBD virus strains. Neutralizing monoclonal antibodies (Mabs) showed that the vaccines of intermediate virulence and the pathogenic strain 849VB had a similar pattern of reactivity in ss neutralization tests. Four distinct epitopes could be defined in seroneutralization and addition ELISA tests.

An ELISA for the detection of antibodies to avian nephritis virus and related entero-like viruses.

An ELISA for the detection of antibodies against avian nephritis virus (ANV) and related entero-like viruses was developed. Different antigenic preparations made from chicken kidney cells infected with the G-4260 strain of ANV were compared. Crude antigen obtained by fluorocarbon treatment of infected cells was found to be appropriate and to give reproducible results with antisera directed against ANV and three entero-like particles (ELPs): the Belgian entero PV2 and entero 3, and the Irish ELP-1.

Acute infectious bursal disease in poultry: protection afforded by maternally derived antibodies and interference with live vaccination.

Maternally derived antibodies (MDA) were found insufficient to protect broiler chicks against a highly pathogenic strain of IBDV during the growing period even if the parent flocks had been boostered at point of lay by using oil emulsion vaccines. Whatever the vaccination scheme of the parent flocks, maximum mortality was observed after a challenge performed at 38 days of age in broiler and layer chicks, suggesting that the offspring need to be vaccinated with live vaccines before that age. MDA were demonstrated to interfere with live vaccination but strain D78 was shown to be more efficient as it could establish an infection even at higher antibody levels than the other strains.

Acute infectious bursal disease in poultry: Isolation and characterisation of a highly virulent strain.

A highly virulent strain of infectious bursal disease virus (IBDV) was isolated from the field and propagated in SPF chickens, causing up to 100% mortality. Although it still belongs to the standard serotype 1 IBD viruses, serological typing with monoclonal antibodies showed an antigenic drift in this pathogenic strain. Conventional 'intermediate' IBD vaccines are probably more antigenically related to the pathogenic strain than the mild ones and were effective in protecting SPF chickens against challenge.