The Impact of Migratory Flyways on the Spread of Avian Influenza Virus in North America

Abstract

Background: Wild birds are the major reservoir hosts for influenza A viruses (AIVs) and have been implicated in the emergence of pandemic events in livestock and human populations. Understanding how AIVs spread within and across continents is therefore critical to the development of successful strategies to manage and reduce the impact of influenza outbreaks. In North America many bird species undergo seasonal migratory movements along a North-South axis, thereby providing opportunities for viruses to spread over long distances. However, the role played by such avian flyways in shaping the genetic structure of AIV populations remains uncertain. Results: To assess the relative contribution of bird migration along flyways to the genetic structure of AIV we performed a large-scale phylogeographic study of viruses sampled in the USA and Canada, involving the analysis of 3805 to 4505 sequences from 36 to 38 geographic localities depending on the gene segment data set. To assist in this we developed a maximum likelihood-based genetic algorithm to explore a wide range of complex spatial models, depicting a more complete picture of the migration network than determined previously. Conclusions: Based on phylogenies estimated from nucleotide sequence data sets, our results show that AIV migration rates are significantly higher within than between flyways, indicating that the migratory patterns of birds play a key role in viral dispersal. These findings provide valuable insights into the evolution, maintenance and transmission of AIVs, in turn allowing the development of improved programs for surveillance and risk assessment.

Assessing the role of live poultry trade in community-structured transmission of avian influenza in China

“…Although we found evidence for continuous geographic viral spread among poultry populations in China (Fig. 1), few studies of the spread of AIVs by wild birds at the intracontinental scale (i.e., the contribution of migratory flyways) have found an effect of geographic distance (18,24,25). This might result from the qualitatively different movement patterns of migratory birds and domestic poultry.…”

The Ecology and Evolution of Influenza Viruses

“…More controversial is how avian influenza viruses are structured within the continental scale, and the precise role played by "flyways" or the specific migratory routes used by birds. Despite some counter suggestions (Bahl et al 2013), there is relatively strong evidence that influenza A viruses in North American birds tend to spread in patterns that loosely respect the geographical boundaries imposed by avian flyway (Lam et al 2012;Fourment et al 2017).…”

Migratory birds as vehicles for parasite dispersal? Infection by avian haemosporidians over the year and throughout the range of a long‐distance migrant

“…Migratory animals may be key players in the spread of parasites and in the structuring of assemblages (Altizer, Bartel, & Han, ; Garamszegi & Møller, ; Viana, Santamaría, & Figuerola, ). In particular, migratory birds may be vehicles for the dispersal of parasites among widely separated geographic areas (Altizer et al., ; Fourment, Darling, & Holmes, ; Rappole, Derrickson, & Hubálek, ; Waldenström, Bensch, Kiboi, Hasselquist, & Ottosson, ) and could play an important role in the transmission of parasites among species at breeding and wintering grounds (Cohen, Auckland, Marra, & Hamer, ; Fuller et al., ; Hellgren et al., ; Klaassen, Hoye, Nolet, & Buttemer, ; Levin et al., ; von Rönn, Harrod, Bensch, & Wolf, ; Valkiūnas, ; Waldenström et al., ). For example, in the Nearctic–Neotropical migratory system, millions of birds travel between temperate breeding and tropical nonbreeding areas, potentially allowing parasites to extend their geographical and host ranges (Durrant et al., ; Ricklefs, Fallon, Latta, Swanson, & Bermingham, ; Ricklefs et al., ); this may account for the broad distributions of some parasite lineages (Fallon, Fleischer, & Graves, ).…”