Study shows virus spread through bird migration

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Foreign animal diseases could enter North America through an area of Alaska where waterfowl migration paths converge, according to a study by U.S. Geological Survey researchers.

An emperor goose (Courtesy of Andrew B. Reeves)

“The significance of this study is that it demonstrates that viruses with genes of Eurasian origin can enter North America via migratory birds,” a USGS announcement states.

From 2006-2009, USGS researchers tested for avian influenza in wild birds in the Yukon-Kuskokwim Delta of western Alaska, where birds converge from the Pacific side of the Americas, Central Pacific, and East Asian-Australasian flyways, according to the announcement. The study results were published in July in the scientific article “Genomic analysis of avian influenza viruses from waterfowl in western Alaska, USA” (J. Wildl. Dis. 2013;49:600-610).

The study characterized 90 low-pathogenic avian influenza isolates from 11 waterfowl species and found 35 of those isolates had one to four gene segments of Eurasian origin. Although the sampling was part of a surveillance program for detection of highly pathogenic strains of H5N1 influenza, no highly pathogenic strains were found in any of 24,000 samples from 82 bird species.

“The detection of highly similar genomes in our study indicates viruses are shared within, and to a lesser degree, among species groups on the Y-K Delta,” the article states.

The article notes that avian influenza viruses with entirely Eurasian-origin genomes have not been documented in North America, even though gene segments from Eurasian ancestor viruses have been documented. The USGS announcement notes that the study provided evidence that avian influenza viruses found in Alaska more often have Eurasian genes than do such viruses found in the 48 contiguous states.

The Journal of Wildlife Diseases is available here.