Molecular Surveillance of Low Pathogenic Avian Influenza Viruses in Wild Birds across the United States: Inferences from the Hemagglutinin Gene

Abstract

A United States interagency avian influenza surveillance plan was initiated in 2006 for early detection of highly pathogenic avian influenza viruses (HPAIV) in wild birds. The plan included a variety of wild bird sampling strategies including the testing of fecal samples from aquatic areas throughout the United States from April 2006 through December 2007. Although HPAIV was not detected through this surveillance effort we were able to obtain 759 fecal samples that were positive for low pathogenic avian influenza virus (LPAIV). We used 136 DNA sequences obtained from these samples along with samples from a public influenza sequence database for a phylogenetic assessment of hemagglutinin (HA) diversity in the United States. We analyzed sequences from all HA subtypes except H5, H7, H14 and H15 to examine genetic variation, exchange between Eurasia and North America, and geographic distribution of LPAIV in wild birds in the United States. This study confirms intercontinental exchange of some HA subtypes (including a newly documented H9 exchange event), as well as identifies subtypes that do not regularly experience intercontinental gene flow but have been circulating and evolving in North America for at least the past 20 years. These HA subtypes have high levels of genetic diversity with many lineages co-circulating within the wild birds of North America. The surveillance effort that provided these samples demonstrates that such efforts, albeit labor-intensive, provide important information about the ecology of LPAIV circulating in North America.

Assessment of transmission, pathogenesis and adaptation of H2 subtype influenza viruses in ferrets

“…The reintroduction of the H2 subtype into the human population would pose a significant global health threat in a population where the majority of humans now lack anti-H2 hemagglutinin (HA) serologic immunity (Pyhala 1985; Webster 1997; Nabel et al, 2011). Avian influenza virus surveillance provides evidence for the continuing circulation of H2 viruses in wild migratory birds and poultry in live bird markets (Schafer et al, 1993; Piaggio et al, 2012; Chen et al, 2010). In some cases, contemporary H2 viruses have been found to be antigenically related to the early pandemic human viruses (Schafer et al, 1993; Piaggio et al, 2012; Chen et al, 2010).…”

Complex Reassortment of Multiple Subtypes of Avian Influenza Viruses in Domestic Ducks at the Dongting Lake Region of China

“…Wild aquatic birds serve as carriers and transmitters of AIV, expanding the geographic distribution of influenza viruses. In the United States, the active surveillance for AIV in wild aquatic birds initiated in 2006 has revealed that hemagglutinin (HA) gene sequences representing the H4, H8, H10, H11, and H12 subtypes are well established in North America, with no evidence of intercontinental exchange (4). Intercontinental exchange of AIV between the North American and Eurasian lineages has occurred, however, for other subtypes of lowly pathogenic AIV (H1, H2, H3, H6, H9, H13, and H16) over the past few decades (4).…”

Transmission of H6N2 wild bird-origin influenza A virus among multiple bird species in a stacked-cage setting

“…These were the only animals that were intentionally infected during this study. An H6N2 AIV was chosen as inoculum because this subtype has been associated with LBM infections in the U.S. during previous years [5], H6 viruses are prevalent in LBMs in Asia [9], and H6 AIVs are commonly found in the wild bird fauna in the U.S. [10]. The experimental design allowed the assessment of virus transmission occurring downward among cage rows (i.e., top to bottom) and horizontally to adjacent cages.…”