Interspecific exchange of avian influenza virus genes in Alaska: the influence of trans‐hemispheric migratory tendency and breeding ground sympatry

Abstract

The movement and transmission of avian influenza viral strains via wild migratory birds may vary by host species as a result of migratory tendency and sympatry with other infected individuals. To examine the roles of host migratory tendency and species sympatry on the movement of Eurasian low pathogenic avian influenza (LPAI) genes into North America, we characterized migratory patterns and LPAI viral genomic variation in mallards (Anas platyrhynchos) of Alaska in comparison to LPAI diversity of northern pintails (Anas acuta). A 50-year band recovery data set suggests that unlike northern pintails, mallards rarely make trans-hemispheric migrations between Alaska and Eurasia. Concordantly, fewer (14.5%) of 62 LPAI isolates from mallards contained Eurasian gene segments compared to those from 97 northern pintails (35%), a species with greater intercontinental migratory tendency. Aerial survey and banding data suggest that mallards and northern pintails are largely sympatric throughout Alaska during the breeding season, promoting opportunities for interspecific transmission. Comparisons of full genome isolates confirmed nearcomplete genetic homology (>99.5%) of seven viruses between mallards and northern pintails. This study found viral segments of Eurasian lineage at a higher frequency in mallards than previous studies, suggesting transmission from other avian species migrating inter-hemispherically or the common occurrence of endemic Alaskan viruses containing segments of Eurasian origin. We conclude that mallards are unlikely to transfer Asian origin viruses directly to North America Correspondence: John M. Pearce, Fax: 907 786 7020; jpearce@usgs.gov.

Spread and Persistence of Influenza A Viruses in Waterfowl Hosts in the North American Mississippi Migratory Flyway

“…This result is especially relevant for surveillance projects conducting surveillance for highly pathogenic strains in wild birds (74). Given the degree of reassortment in AIVs observed here, surveillance sites for strains of interest (e.g., HPH5N1, HPH7N3, and LPH7N9) are ideally situated within migratory routes, although gene segments from any one of these viruses may be found in other flyways (61,(75)(76)(77). While targeted surveillance efforts are necessary for rapid responses to disease threats, continued longitudinal studies examining the persistence and evolutionary patterns at regional sites are essential for elucidating the natural history of these viruses in their wild bird hosts (78,79).…”

Adaptive Heterosubtypic Immunity to Low Pathogenic Avian Influenza Viruses in Experimentally Infected Mallards

“…Previously described primers for H3 [28], H4 [29], H10 [30] and H14 [31] were used for subtype identification.…”

Reassortment of Influenza A Viruses in Wild Birds in Alaska before H5 Clade 2.3.4.4 Outbreaks

“…Interhemispheric movement during spring 2014 (or earlier) is most plausible given the circulation of the Eurasian ancestor of North American clade 2.3.4.4 during December 2013–May 2014 (95% highest posterior density October 2013–January 2015) (Figure 1, panel A), an event that preceded introduction. The presence of overwintering birds in Alaska, a known area for influenza exchange between East Asia and North America ( 7 , 8 ), might enhance opportunities for viruses originating in Eurasia to reassort with LPAI in local bird populations. Mallards from this study are a prime example of an overwintering population, occupying urban ponds that remained thawed because of human activity, which allows some birds to remain in southcentral Alaska from September through April, when many migratory waterfowl have since flown south.…”