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. 2012;7(11):e49002.
doi: 10.1371/journal.pone.0049002. Epub 2012 Nov 7.

Birds and viruses at a crossroad--surveillance of influenza A virus in Portuguese waterfowl

Conny Tolf  1 , Daniel Bengtsson, David Rodrigues, Neus Latorre-Margalef, Michelle Wille, Maria Ester Figueiredo, Monika Jankowska-Hjortaas, Anna Germundsson, Pierre-Yves Duby, Camille Lebarbenchon, Michel Gauthier-Clerc, Björn Olsen, Jonas Waldenström
Affiliations

Birds and viruses at a crossroad--surveillance of influenza A virus in Portuguese waterfowl

Conny Tolf et al. PLoS One. 2012.

Abstract

During recent years, extensive amounts of data have become available regarding influenza A virus (IAV) in wild birds in northern Europe, while information from southern Europe is more limited. Here, we present an IAV surveillance study conducted in western Portugal 2008-2009, analyzing 1653 samples from six different species of waterfowl, with the majority of samples taken from Mallards (Anas platyrhynchos). Overall 4.4% of sampled birds were infected. The sampling results revealed a significant temporal variation in the IAV prevalence, including a pronounced peak among predominantly young birds in June, indicating that IAV circulate within breeding populations in the wetlands of western Portugal. The H10N7 and H9N2 subtypes were predominant among isolated viruses. Phylogenetic analyses of the hemagglutinin and neuraminidase sequences of H10N7, H9N2 and H11N3 virus showed that sequences from Portugal were closely related to viral sequences from Central Europe as well as to IAVs isolated in the southern parts of Africa, reflecting Portugal's position on the European-African bird migratory flyway. This study highlights the importance of Portugal as a migratory crossroad for IAV, connecting breeding stationary waterfowl with birds migrating between continents which enable transmission and spread of IAV.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. (A) General migration routes of ducks across Europe , including birds migrating from north eastern summer areas to southern wintering grounds in Southern Europe, and Africa.
Different bird species and populations use different migratory routes, stop over locations, and winter locations. (B) Sampling locations in Portugal utilized in this study.
Figure 2
Figure 2. Temporal variation in IAV prevalence among Portuguese ducks during the period 2008–2009.
(A) Overall temporal variation in IAV prevalence among sampled ducks. (B) The percentage of IAV-positives among juvenile and adult ducks in Portugal. Prevalence numbers are derived from sample screenings where IAV was detected by RRT-PCR.
Figure 3
Figure 3. Bayesian phylogenetic tree showing relationships among H10 influenza A viruses isolated in this study and publicly available sequences from GenBank.
The clades containing Portuguese and North American sequences are indicated, and Portuguese isolates are shown in bold. The tree is rooted at the midpoint and numbers at nodes indicate posterior probability support. The scale bar indicates substitutions per site.
Figure 4
Figure 4. Bayesian phylogenetic tree showing relationships among H11 influenza A viruses isolated in this study and publicly available sequences from GenBank.
The Portuguese sequence is shown with bold font and the clade containing North American sequences is indicated. The tree is rooted at the midpoint and numbers at nodes indicate posterior probability support. The scale bar indicates substitutions per site.
Figure 5
Figure 5. Bayesian phylogenetic tree showing relationships among H9 influenza A viruses isolated in this study and publicly available sequences from GenBank.
The clade including the Portuguese sequences, as well as some well-established H9N2 linages (Korea, G1 and Y280) are indicated. In addition, isolates associated with infections in humans and swine have been indicated by underlining and italics, respectively. The tree is rooted at the midpoint and numbers at nodes indicate posterior probability support. The scale bar indicates substitutions per site.
See this image and copyright information in PMC

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