Influenza surveillance in birds in Italy (1999-2002): preliminary molecular characterisation of virus isolates

During influenza surveillance activities carried out from 1999 to 2001 in wild ducks, 311 cloacal swabs were collected in Central Italy. A total of 20 avian influenza viruses (AIVs) were isolated, that belonged to eight different subtypes. Five of these subtypes had never been isolated before in the area under study, including two H7N3 viruses obtained from mallards in Autumn 2001. One year after, outbreaks of AI caused by H7N3 LP viruses occurred and rapidly spread among commercial poultry farms in Northern Italy. We compared the H7N3 duck strains with the first two H7N3 turkey isolate, and a high level of similarity between the two viruses was found in all genes, except for the NA. The N3 genes of domestic poultry strains showed a 23-amino acid deletion in the stalk region, indicating an initial adaptation of wild waterfowl viruses to terrestrial bird species. Phylogenctic data are also discussed. This is the first report in which a domestic poultry AIV and its direct wild bird counterpart are described. (C) 2004 Elsevier B.V. All rights reserved.