New Type Of Avian Influenza Virus Found In Antarctic Penguins
Chicken and other farm birds are known carriers of avian influenza virus. But now it seems that penguins in faraway Antarctica may also be susceptible to this virus. In a first study of its kind, an international team of researchers found a new strain of avian influenza virus in a group of Adélie penguins from Antarctica. The researchers have described the virus in a study published this week in mBio®, the online open access journal of the American Society for Microbiology, according to a press release Tuesday.
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Previous studies on penguins have found influenza antibodies in blood samples taken from penguins but this is the first time that an active virus has been found in bird species in Antarctica says study author and Associate Professor Aeron Hurt, PhD, a senior research scientist at the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia.
The research was conducted on penguins in Admiralty Bay and Rada Covadonga in the Antarctic in January and February 2013. Swabs were collected from the windpipes and posterior openings of 301 Adélie Penguins and blood samples were taken from 270 of these penguins.
Using a laboratory technique called real-time reverse transcription-PCR, the researchers found avian influenza virus (AIV) genetic material in eight (2.7 percent) samples, six from adult penguins and two from chicks. Seven of the samples were from Rada Covadonga. The researchers were able to culture four of these viruses, which proved that live infectious virus was present. On further analysis of the samples, the researchers found all viruses were H11N2 influenza viruses that were highly similar to each other.
But the researchers were in for a surprise because when they compared the full genome sequences of four of the collected viruses to all available animal and human influenza virus sequences in public databases, they realized that this virus was something completely new. Says Hurt, "When we drew phylogenetic trees to show the evolutionary relationships of the virus, all of the genes were highly distinct from contemporary AIVs circulating in other continents in either the Northern or Southern Hemisphere."
Four of the gene segments were most closely related to North American avian lineage viruses from the 1960s to 1980s. Two genes showed a distant relationship to a large number of South American AIVs from Chile, Argentina and Brazil. Using a molecular clock to incorporate the evolutionary rate of each AIV gene segment, the researchers estimated that the virus has been evolving for the past 49 to 80 years without anyone knowing about it. Hurt is unsure if the evolution has occurred only in Antarctica or elsewhere too.
Moreover the virus is thought to be exclusive to birds since 16 percent of penguins (43 of 270) were found to have influenza A antibodies in their blood and a group of ferrets who were exposed to the virus as part of the experiment were not affected. So, its highly unlikely that the virus infects mammals.
Even though the virus is fairly benign and does not cause illness in penguins, the bottom line is that a virus can get into even remote Antarctica and spread among the populations there. "It raises a lot of unanswered questions," says Hurt, like how often AIVs are being introduced into Antarctica, whether it is possible for highly pathogenic AIVs to be transferred there, what animals or ecosystems are maintaining the virus, and whether the viruses are being cryopreserved during the winters.
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