In a new study published in the Journal Virology on March 31, 2015, scientists from the U.S. Geological Survey and U.S. Fish and Wildlife Service harnessed a new type of DNA technology to investigate avian influenza viruses in Alaska. Using a “next generation” sequencing approach, which identifies gene sequences of interest more rapidly and more completely than by traditional techniques, scientists identified low pathogenic avian influenza viruses in Alaska that are nearly identical to viruses found in China and South Korea. This publication provides even more evidence of this intercontinental avian influenza exchange program.
The viruses were found in an area of western Alaska that is known to be a hot spot for both American and Eurasian forms of avian influenza. “Our past research in western Alaska has shown that 70 percent of avian influenza viruses isolated in this area were found to contain genetic material from Eurasia, providing evidence for high levels of intercontinental viral exchange,” said Andy Ramey, a scientist with the USGS Alaska Science Center and lead author of the study. “This is because Asian and North American migratory flyways overlap in western Alaska.”
In this study, led by the USGS, low pathogenic H9N2 viruses were found in an Emperor Goose and a Northern Pintail. Both of the H9N2 viruses were nearly identical genetically to viruses found in wild bird samples from Lake Dongting, China and Cheon-su Bay, South Korea.
“These H9N2 viruses are low pathogenic and not known to infect humans, but similar viruses have been implicated in disease outbreaks in domestic poultry in Asia,” said Ramey. “There is no commercial poultry production in western Alaska and highly similar H9N2 virus strains have not been reported in poultry in East Asia or North America, so it is unlikely that agricultural imports influenced this result.”
The finding provides evidence for intercontinental movement of intact avian influenza viruses by migratory birds. The USGS recently released a publication about the detection of a novel highly pathogenic H5N8 virus in the U.S. that is highly similar to the Eurasian H5N8 viruses. This suggests that the novel re-assortment may be adapted to certain waterfowl species, enabling it to survive long migrations. That virus, and associated strains, has now spread from early detections in wild and domestic birds in Pacific states to poultry outbreaks in Minnesota, Missouri and Arkansas.
“The frequency of inter-hemispheric dispersal events of avian influenza viruses by migratory birds may be higher than previously recognized,” said Ramey. While some of the samples for the project came from bird fecal samples collected from beaches at Izembek National Wildlife Refuge, most of the samples came from sport hunters.
“For the past several years, we’ve worked closely with sport hunters in the fall to obtain swab samples from birds and that has really informed our understanding of wildlife disease in this area,” said Bruce Casler, formerly a biologist with the USFWS Izembek National Wildlife Refuge and a co-author of the study.