US - The US Geological Survey has released additional evidence that western Alaska remains a hot spot for avian influenza to enter North America.
The new report announces that while no highly pathogenic avian influenza viruses have been found in Alaska, the state remains an important area to monitor due to migratory bird flyways from North America and Eurasia that overlap the region.
“Our past research in western Alaska has shown that while we have not detected the highly pathogenic avian influenza virus, up to 70 per cent of the other 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 and lead author of the recent report.
“This is because Asian and North American migratory flyways overlap in western Alaska.”
The designation of low or highly pathogenic avian influenza refers to the potential for these viruses to cause disease or kill chickens. The designation of “low pathogenic" or “highly pathogenic" does not refer to how infectious the viruses may be to humans, other mammals or other species of birds.
Most strains of avian influenza are not highly pathogenic and cause few signs of disease in infected wild birds. However, in poultry, some low-pathogenic strains can mutate into highly pathogenic avian influenza strains that cause contagious and severe illness or death among poultry, and sometimes among wild birds as well.
Past research by the USGS, found low pathogenic H9N2 viruses in an Emperor Goose and a Northern Pintail. Both 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 Mr Ramey.
In the new report, the USGS collaborated with the Yukon Kuskokwim Health Corporation in Bethel, Alaska, and the Southeastern Cooperative Wildlife Disease Study in Athens, Georgia to obtain and test bird samples from Alaska Native subsistence hunters during spring of 2015.
Hunters provided researchers with over 1,000 swabs from harvested water birds, the primary hosts of avian influenza viruses.
Last year, the USGS published an article describing the introduction of highly pathogenic avian influenza into North America at the end of 2014, likely via migratory birds that migrated through Alaska. However, highly pathogenic avian influenza was never documented in Alaska.
The highly pathogenic viruses spread throughout parts of the western and Midwestern US, impacting approximately 50 million poultry. However, those highly pathogenic viruses have now not been detected in North America since July 2015.
This fall, the USGS will sample wild birds at Izembek National Wildlife Refuge. Most of those samples will come from sport hunters.
The new report is entitled, “Surveillance for Eurasian-origin and intercontinental reassortant highly pathogenic influenza A viruses in Alaska, spring and summer 2015” and is published in Virology Journal.