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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. Source


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. Source


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. Source


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. Source


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. Source

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