Evidence of persistence and multiple genetic modifications of LPAI H7N7 in wild mallards in Poland is supported by phylogenetic studies

Krzysztof Śmietanka (1) , Anna Pikula (1) , Zenon Minta (1) , Wlodzimierz Meissner (2)

1 Department of Poultry Diseases
2 Department of Vertebrate Ecology & Zoology, Avian Ecophysiology Unit

Genetic characterization of the whole genome of four avian influenza viruses (AIV) H7N7 isolated in 3 successive winter seasons (2007-2009) from wild mallards in 3 cities in Poland was performed. All of the tested strains were of low pathogenicity and no molecular markers associated with an increased adaptation to poultry, mammals or resistance to antiviral drugs were found. The major outcome of the phylogenetic studies was that the isolate A/mallard/Poland/446/09 (detected in December 2009) shared a recent common ancestor with A/mallard/Poland/41/09 (isolated in February 2009) in relation to HA & PB1 genes, with A/mallard/Poland/16/09 (found in January 2009) regarding NA & NS genes, and with A/mallard/Poland/01/08 (recovered in December 2007) as regards NS gene. Interestingly, A/mallard/Poland/16/09 and A/mallard/Poland/446/09 were isolated at the same sampling site almost exactly one year apart and that points to resident population of mallards (and other resident waterfowl) as responsible for the perpetuation of AIV in the given area between successive winters. On the other hand, the ornithological data discussed in detail in the paper strongly suggest that the virus transmission between close sites but located in different urban areas is most likely achieved by migratory birds, a fact additionally supported by a close relatedness between different gene segments of Polish H7N7 and AIV detected in wild birds in Europe. A high heterogeneity of the gene pool found in the study is indicative of frequent reassortment events. Additionally, two H7N7 isolates were shown to possess selected genes closely related to AIV detected in domestic poultry in Italy and Czech Republic. This study corroborates the importance of active surveillance in wild birds as a valuable tool of early warning of AI in poultry.

Mots clés: Life Sciences

Domaines: Biologie animale

Krzysztof Śmietanka, Anna Pikula, Zenon Minta, Wlodzimierz Meissner. Evidence of persistence and multiple genetic modifications of LPAI H7N7 in wild mallards in Poland is supported by phylogenetic studies. Avian Pathology, 2011, 40 (02), pp.131-138. ⟨10.1080/03079457.2010.537304⟩. ⟨hal-00687799⟩