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Rauw F.,Avian Virology and Immunology Unit | Gardin Y.,British Petroleum | Palya V.,CEVA Phylaxia | Anbari S.,Avian Virology and Immunology Unit | And 4 more authors.
Vaccine | Year: 2010

The continuous outbreaks of fatal Newcastle disease (ND) in commercial poultry flocks demonstrate that current vaccination strategies are not fully efficacious and should be improved by new generation of vaccines. In this context, maternally immune conventional layer chickens were vaccinated in ovo with a turkey herpesvirus recombinant expressing the fusion (F) gene of NDV (rHVT-ND) and/or at day-old with an apathogenic enterotropic live ND vaccine co-administrated or not with chitosan by oculo-nasal route. The induced vaccinal immune responses and conferred protection against a challenge with a circulating NDV velogenic viscerotropic strain were evaluated. The innovative rHVT-ND/live ND-chitosan vaccination regimen provided the best protection against mortality and morbidity as well as the strongest reduction of virus shedding that could be related to the higher measured cellular immune response and digestive antibody-mediated immunity. © 2009 Elsevier Ltd. All rights reserved.

Rauw F.,Avian Virology and Immunology Unit | Gardin Y.,CEVA Sante Animale | Palya V.,CEVA Phylaxia | van den Berg T.,Avian Virology and Immunology Unit | Lambrecht B.,Avian Virology and Immunology Unit
Avian Pathology | Year: 2014

The recurrent outbreaks of fatal Newcastle disease (ND) in commercial poultry flocks throughout the world indicate that routine vaccinations are failing to sufficiently induce the high levels of immunity necessary to control ND. There is a need for vaccination programmes that could be initiated at 1-day-old for mass application and which would induce a long-lasting immunity, with no need for a booster vaccination at a later age. In this context, the duration of immunity delivered by a vaccination programme including a recombinant herpesvirus of turkeys expressing the F gene of ND virus (rHVT-ND) and live ND vaccine at 1-day-old was compared with a classical programme that included a conventional live and an inactivated ND vaccine at the same age in commercial layer chickens. The humoral, cell-mediated and local immunity were followed weekly and birds were challenged with a viscerotropic velogenic ND virus strain at 6 and 10 weeks of age. We determined that immunity induced by the vaccination programme involving the rHVT-ND vaccine was more protective than that provided by the conventional vaccine-based regime. This might be related to a T-helper type 1 (Th1) cellular-driven immunological response, in contrast to the T-helper type 2 (Th2) humoral-oriented immune response provided by the current conventional vaccine-based vaccination programmes. © 2013 Houghton Trust Ltd.

Claes G.,Avian Virology and Immunology Unit | Marche S.,Avian Virology and Immunology Unit | Dewulf J.,Ghent University | Van Den Berg T.,Avian Virology and Immunology Unit | Lambrecht B.,Avian Virology and Immunology Unit
Epidemiology and Infection | Year: 2014

Aquatic wild birds are often carriers of low-pathogenic avian influenza viruses (LPAIVs). If H5 and H7 LPAIVs are transmitted to poultry and have the opportunity to circulate, a highly pathogenic AIV may arise. Contact with aquatic wild birds is one of the most important ways in which these LPAIVs can be introduced into poultry flocks. In this study, the transmissibility of a duck-originated H5 LPAIV between ducks and chickens was analysed in a series of animal experiments, using different transmission routes. Results indicate that the outcome of virus intake by chickens exposed to infectious ducks depends on the way the virus is presented. Faecally contaminated drinking water proved to be the most efficient route by which the virus can be transmitted to chickens. The results from this study also suggest that some duck-originated H5 LPAIVs may be introduced to poultry but do not have the potential to become established in poultry populations. Copyright © Cambridge University Press 2013.

Marche S.,Avian Virology and Immunology Unit | Van Den Berg T.,Avian Virology and Immunology Unit
Avian Diseases | Year: 2010

Since the emergence of the highly pathogenic avian influenza H5N1, avian influenza surveillance has been expanded in Europe. The serologic monitoring of domestic poultry is usually accomplished using the reference hemagglutination inhibition (HI) test for the detection of H5 and H7 subtypes. However, as the number of tested sera has been increasing, there is a need for another serologic method that could be used as a preliminary screening test. A comparison of four enzyme-linked immunosorbent assay (ELISA) tests (two indirect and two competitive) was conducted, and they showed good specificity and higher sensitivity than the HI test. The selected ELISA tests were then tested using approximately 800 field sera representative of different poultry species, and a simulation was done to determine the best strategy for screening. The first strategy was testing both gallinaceous and nongallinaceous sera with a competitive ELISA and using the HI test for H5 and H7 as a confirmatory test. The second strategy was testing only gallinaceous bird sera with the indirect ELISA with confirmatory H5 and H7 HI and all nongallinaceous sera by the H5 and H7 HI test. In the Belgian poultry context, the best strategy seems to be the use of a blocking ELISA as the primary screening tool to test all the poultry sera, followed by confirmation by H5 and H7 HI test subtyping. © 2010 American Association of Avian Pathologists.

Domanska-Blicharz K.,National Veterinary Research Institute | Minta Z.,National Veterinary Research Institute | Smietanka K.,National Veterinary Research Institute | March S.,Avian Virology and Immunology Unit | Van Den Berg T.,Avian Virology and Immunology Unit
Avian Diseases | Year: 2010

Persistence of H5N1 high pathogenicity avian influenza virus (HPAIV), isolated during the epidemic in wild birds in Poland in 2006, was evaluated in three water samples derived from the sources known to host wild water birds (city pond, Vistula river mouth, and Baltic Sea). The virus was tested at two concentrations (104 and 106 median tissue culture infective dose per milliliter) and at three temperatures (4 C, 10 C, and 20 C), representing average seasonal temperatures in Poland. All tested water samples were filtered before virus inoculation, and one unfiltered sample (Baltic seawater) was also tested. Infectivity was determined twice a week over a 60-day trial period by microtiter endpoint titration. The persistence of the virus varied considerably depending on its concentration and also on physico-chemical parameters of the water, such as temperature and salinity. Avian influenza virus survival was the highest at 4 C and the lowest at 20 C. Prolonged infectivity of the virus in Baltic seawater (brackish, 7.8 ppt) was also seen. In distilled water, the virus retained its infectivity beyond the 60-day study period. Interestingly, a devastating effect of the unfiltered fraction of seawater was seen as the virus disappeared in this fraction the quickest in all studied combinations; thus, biologic factors may also affect infectivity of HPAIV. © 2010 American Association of Avian Pathologists.

Marche S.,Avian Virology and Immunology Unit | Van Den Berg T.,Avian Virology and Immunology Unit
Avian Diseases | Year: 2010

Early detection of highly pathogenic (HP) strains of avian influenza, especially the HP H5N1, is important in terms of controlling and minimizing the spread of the virus. Several rapid antigen detection kits that are able to detect influenza A viruses in less than 1 hr are commercially available, but only a few of them have been evaluated. In this study, four commercially available rapid tests for veterinary usage and two tests for human usage were evaluated and compared. The evaluation of the detection limits of the different tests established with serial dilution of HP H5N1 indicated that most of them have a detection limit of about 105 to 106 50% tissue culture infectious dose/ml. None of the tests was able to detect virus in oral and cloacal swabs 24 hr post-experimental infection of specific-pathogen-free chickens with HP H5N1. However, 48 hr postinfection, almost all of the rapid tests were able to detect infected birds (dead or alive). Moreover, organs were also successful samples for detection of H5N1 with the rapid tests. Unexpectedly, the specificity was not very high for some tests. However, in general in this study, the tests for veterinary usage showed better sensitivity. To conclude, these tests offer good indicative value in the event of an outbreak, but as a result of their low sensitivity and some aspecific reactions, test results always need to be confirmed by other methods. © 2010 American Association of Avian Pathologists.

Ingrao F.,Avian Virology and Immunology Unit | Rauw F.,Avian Virology and Immunology Unit | Lambrecht B.,Avian Virology and Immunology Unit | Van den Berg T.,Avian Virology and Immunology Unit
Developmental and Comparative Immunology | Year: 2013

Infectious Bursal Disease (IBD) is caused by a small, non-enveloped virus, highly resistant in the outside environment. Infectious Bursal Disease Virus (IBDV) targets the chicken's immune system in a very comprehensive and complex manner by destroying B lymphocytes, attracting T cells and activating macrophages. As an RNA virus, IBDV has a high mutation rate and may thus give rise to viruses with a modified antigenicity or increased virulence, as emphasized during the last decades. The molecular basis of pathogenicity and the exact cause of clinical disease and death are still poorly understood, as it is not clearly related to the severity of the lesions and the extent of the bursal damage. Recent works however, pointed out the role of an exacerbated innate immune response during the early stage of the infection with upregulated production of promediators that will induce a cytokine storm.In the case of IBDV, immunosuppression is both a direct consequence of the infection of specific target immune cells and an indirect consequence of the interactions occurring in the immune network of the host. Recovery from disease or subclinical infection will be followed by immunosuppression with more serious consequences if the strain is very virulent and infection occurs early in life. Although the immunosuppression caused by IBDV is principally directed towards B-lymphocytes, an effect on cell-mediated immunity (CMI) has also been demonstrated therefore increasing the impact of IBDV on the immunocompetence of the chicken. In addition to its zootechnical impact and its role in the development of secondary infections, it may affect the immune response of the chicken to subsequent vaccinations, essential in all types of intensive farming. Recent progress in the field of avian immunology has allowed a better knowledge of the immunological mechanisms involved in the disease but also should give improved tools for the measurement of immunosuppression in the field situation. Although satisfactory protection may be provided by the induction of high neutralizing antibody titres, interference from parental antibodies with vaccination has become the most important obstacle in the establishment of control programs. In this context, recombinant HVT and immune complex vaccines show promising results. © 2013 Elsevier Ltd.

Marche S.,Avian Virology and Immunology Unit | Lambrecht B.,Avian Virology and Immunology Unit | Van Den Berg T.,Avian Virology and Immunology Unit
Avian Diseases | Year: 2010

Viruses of all subtypes may be introduced into domestic poultry, but only H5 and H7 low pathogenicity avian influenza viruses can mutate during circulation in poultry and emerge as high pathogenicity avian influenza variants. It is therefore essential to monitor the field situation continuously to detect low pathogenicity notifiable avian influenza (LPNAI) as soon as possible. With the emergence of the highly pathogenic H5N1, markers of infection of avian influenza are becoming more and more significant. They are important as early warning systems, and they can also be valuable tools as companion tests of vaccines (differentiating infected from vaccinated animals), but they might also be informative about the evaluation of the degree of adaptation and the timing of infection. Therefore, several experimental infections of specific-pathogen-free chickens were conducted to follow the kinetics of antibody responses against the hemagglutinin, the neuraminidase, the nucleoprotein, and the M2e after infections with LPNAI viruses isolated from waterfowl or already adapted to chicken. Overall, the immune responses against the different antigens showed similar kinetics in the different infected animals, but they were lower when the animals were infected with AI viruses originating from waterfowl, and the kinetics of the M2e antibodies was quite different. Indeed, it was rather shorter and disappeared more rapidly (approximately 35 days postinfection) compared to the kinetics of the other antibodies. Therefore, the detection of the antibodies against M2e peptide could be an interesting tool to detect recent infection, and these preliminary results indicated that the production of M2e antibodies might be correlated with the degree of adaptation of LPNAIs. © 2010 American Association of Avian Pathologists.

Lardinois A.,Avian Virology and Immunology Unit | van den Berg T.,Avian Virology and Immunology Unit | Lambrecht B.,Avian Virology and Immunology Unit | Steensels M.,Avian Virology and Immunology Unit
Avian Pathology | Year: 2014

Chicks possess maternally derived antibody (MDA) against pathogens and vaccines previously encountered by the dams. This passive immunity is important in early life, when the immune system is immature and unable to fight off infection. On the other hand, MDA can also affect the development of the immune system and interfere with vaccination against avian diseases such as Newcastle disease (ND) and avian influenza (AI). The effect of MDA is generally investigated by studying the progeny of vaccinated dams, which is time-consuming, poorly flexible and expensive. Moreover, the antibody titres obtained are not homogeneous. In this study, a model was developed to offer a faster, more reproducible and cheaper way to study passive immunity in specific pathogen free chickens by injection of a polyclonal serum into the egg yolk at embryonic day 14, combined with an intraperitoneal injection at day 1. A satisfactory model, with consistent, homogeneous antibody titres, as well as persistence close to natural passive immunity, could be obtained for ND virus. On the other hand, the application of this optimized protocol in an H5 AI context induced only a low artificial passive immunity compared with that described in the literature for the progeny of AI vaccinated dams. This artificial model should facilitate future studies regarding the effect of passive immunity on vaccine efficacy at a young age and its effect on immune system development. © 2014 © 2014 Houghton Trust Ltd.

Claes G.,Avian Virology and Immunology Unit | Welby S.,Center for Control of Veterinary Diseases | Van Den Berg T.,Avian Virology and Immunology Unit | Van Der Stede Y.,Center for Control of Veterinary Diseases | And 4 more authors.
Epidemiology and Infection | Year: 2013

SUMMARY In this study, shedding and transmission of three H5/H7 low pathogenic avian influenza viruses (LPAIVs) in poultry was characterized and the impact of floor system on transmission was assessed. Transmission experiments were simultaneously conducted with two groups of animals housed on either a grid or a floor covered with litter. Transmission was observed for H5N2 A/Ch/Belgium/150VB/99 LPAIV. This virus was shed almost exclusively via the oropharynx and no impact of floor system was seen. Transmission was also seen for H7N1 A/Ch/Italy/1067/v99 LPAIV, which was shed via both the oropharynx and cloaca. A slight increase in transmission was seen for animals housed on litter. H5N3 A/Anas Platyrhynchos/Belgium/09-884/2008 LPAIV did not spread to susceptible animals, regardless of the floor system. This study shows that environmental factors such as floor systems used in poultry barns may act upon the transmission of LPAIVs. However, the level of influence depends on the virus under consideration and, more specifically, its principal replication sites. Copyright © Cambridge University Press 2013.

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