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Does influenza A affect body condition of wild mallard ducks, or vice versa?

January 1, 2009

Low pathogenic avian influenza (LPAI) viruses are well documented to circulate within wild waterfowl populations (Olsen et. al. 2006). It has been assumed that these infections are benign with no subsequent effects on life-history parameters. The study by Latorre-Margalef et al. (2009; hereafter L.-M. et al.) represents an important step, as they attempt to test this assumption in wild birds. L.-M. et al. captured migrating mallards (Anas platyrhynchos) at a staging area and tested them for the presence of avian influenza A virus (IAV). They related IAV infection status to body mass and duration of time spent on the staging area. Overall, the study is well designed with impressive sample sizes and the analyses are carefully conducted and presented. However, in discussing these results, the authors assume causation based upon correlation and, although they acknowledge the possibility of immunosuppression during migration due to reduced energy stores, they do not discuss it as a possible explanation for their findings. Below, we consider several of the major findings by L.-M. et al., providing alternative explanations for the results. Because the L.-M. et al. study design is correlational, it is not possible to use their data to distinguish between their interpretations and our alternative explanations.

Publication Year 2009
Title Does influenza A affect body condition of wild mallard ducks, or vice versa?
DOI 10.1098/rspb.2008.1962
Authors Paul L. Flint, J. Christian Franson
Publication Type Article
Publication Subtype Journal Article
Series Title Proceedings of the Royal Society B: Biological Sciences
Index ID 70003500
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center; National Wildlife Health Center