Abstract
Although continental populations of avian influenza viruses are genetically distinct, transcontinental reassortment in low pathogenic avian influenza (LPAI) viruses has been detected in migratory birds. Thus, genomic analyses of LPAI viruses could serve as an approach to prioritize species and regions targeted by North American surveillance activities for foreign origin highly pathogenic avian influenza (HPAI). To assess the applicability of this approach, we conducted a phylogenetic and population genetic analysis of 68 viral genomes isolated from the northern pintail (Anas acuta) at opposite ends of the Pacific migratory flyway in North America. We found limited evidence for Asian LPAI lineages on wintering areas used by northern pintails in California in contrast to a higher frequency on breeding locales of Alaska. Our results indicate that the number of Asian LPAI lineages observed in Alaskan northern pintails, and the nucleotide composition of LPAI lineages, is not maintained through fall migration. Accordingly, our data indicate that surveillance of Pacific Flyway northern pintails to detect foreign avian influenza viruses would be most effective in Alaska. North American surveillance plans could be optimized through an analysis of LPAI genomics from species that demonstrate evolutionary linkages with European or Asian lineages and in regions that have overlapping migratory flyways with areas of HPAI outbreaks.
Highlights
Current surveillance programs for detection of highly pathogenic avian influenza (HPAI) viruses focus on monitoring avian populations for mortality events and the sampling of live wild and domestic birds (Munster et al 2007; Komar and Olsen 2008)
RNA segments from North American avian influenza viruses have been observed in guillemots (Uria aalge) in Europe (Wallensten et al 2005) and waterfowl in Asia (Bean et al 1992; Liu et al 2004), North American RNA segments were found in a South American influenza virus isolated from cinnamon teal (Anas cyanoptera; Spackman et al 2007), and some Asian lineages of the N8 RNA segment were more similar to North American virus isolates from northern pintails (Anas acuta) than to other Asian reference samples (Koehler et al 2008)
We found no evidence of Asian lineage genes within California isolates for the 177 RNA segments of the M, NP, NS, PA, PB1, and PB2 genes
Summary
Current surveillance programs for detection of highly pathogenic avian influenza (HPAI) viruses focus on monitoring avian populations for mortality events and the sampling of live wild and domestic birds (Munster et al 2007; Komar and Olsen 2008). Previous molecular surveys have revealed substantial levels of sequence divergence among continental populations of low pathogenic avian influenza (LPAI) viruses in Europe, Asia, and North America (Ito et al 1995; Widjaja et al 2004) and, less studied, South America (Pereda a 2009 The Authors Journal compilation a 2009 Blackwell Publishing Ltd 2 (2009) 457–468 et al 2008). This broad-scale genetic differentiation among continents yields a methodology based on phylogenetic assignment to identify intercontinental virus exchange (Webster et al 1992; Widjaja et al 2004) and indicates that intercontinental dispersal of LPAI viruses is relatively rare (Webster et al 2007). RNA segments from North American avian influenza viruses have been observed in guillemots (Uria aalge) in Europe (Wallensten et al 2005) and waterfowl in Asia (Bean et al 1992; Liu et al 2004), North American RNA segments were found in a South American influenza virus isolated from cinnamon teal (Anas cyanoptera; Spackman et al 2007), and some Asian lineages of the N8 RNA segment were more similar to North American virus isolates from northern pintails (Anas acuta) than to other Asian reference samples (Koehler et al 2008)
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