Multiyear surveillance of Influenza A virus in wild birds in Portugal
Résumé
This report presents the results of a multiyear (2005-2009) study of avian influenza virus (AIV) occurrence in wild birds in Portugal. A total of 5691 samples from wild birds belonging to 13 different Orders were examined. Ninety three samples tested positive for AIV by matrix RT-PCR, giving a total prevalence of 1.63 %. Twenty one viruses were successfully cultured in embryonated chicken eggs, which represent a rate of viral infectivity in the samples of 22.6 %. Nine subtypes of hemagglutinin (H1, H3-H7, H9-H11) and eight subtypes of neuraminidase (N1-N4, N6-N9) were identified in 20 different combinations. The most prevalent subtypes of hemagglutinin detected were H5, H1 and H4 while for neuraminidase, subtypes N2 and N6 were the most common. The subtype combinations H4N6 and H1N1 were predominant (15.1 %). All H5 and H7 viruses detected in this study are low pathogenic for poultry as determined by the sequence of amino acids at the cleavage site of hemagglutinin. The full-length nucleotide sequences of five H5, one H7 and five N3 genes were phylogenetically analyzed. The Bayesian analysis revealed that all but one of the strains analyzed are closely related to isolates detected in the same period in North and Central European countries. Three H5N3 isolates, all from 2007, form a separate cluster in both H5 and N3 phylogenetic trees. This study provides evidence that various subtypes of avian influenza virus circulate in the country, including subtypes H5 and H7, which may pose a risk to industrial poultry.
Domaines
Biologie animale
Origine : Fichiers produits par l'(les) auteur(s)
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