Wild geese that fly with the moon on their wings could be leaving more than a pleasant memory behind.
A recently released study from the Global Consortium for H5N8 and Related Influenza Viruses said migrating wild birds have the potential to move highly pathogenic disease around the world and infect domestic poultry and people.
“Enhancing surveillance in wild birds where migratory flyways overlap, particularly the Arctic, could provide an early warning system for the spread of new viruses,” said the report involving scientists from 32 institutions worldwide.
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Researchers investigated how a subtype of bird flu called H5N8 spread around the world following outbreaks in South Korea that began in early 2014. It spread to Japan, Europe and North America, causing outbreaks in 2014 and 2015.
Scientists analyzed migration patterns of wild birds found to be infected with the H5N8 virus.
They compared the genetic code of viruses isolated from the sick birds collected from 16 countries and determined that the H5 strain of viruses developed new characteristics by mutation and reassortment with other avian flu viruses.
Ducks, geese and shore birds carry a number of avian influenza viruses in their intestinal tracts. It is only when the H5 or H7 subtypes of the virus get into domestic poultry, usually because of breaches in biosecurity, that some of these viruses can evolve into a deadly form, said veterinarian John Pasick.
Known as highly pathogenic avian influenza, these deadly strains can kill up to 100 percent of the birds they infect within a few days.
“Ducks and geese are the natural reservoirs for these viruses but not the highly pathogenic forms,” said Pasick, a specialist in swine and avian diseases with the Canadian Food Inspection Agency.
‘The highly pathogenic forms of either H5 or H7 tend to spill over from domestic poultry and back into the wild population,” he said.
Common teals and northern pintail ducks seem the most likely carriers because their migratory paths take them from Asia, across the Bering Strait and into North America.
British Columbia had outbreaks in late 2014, which were eventually linked with the later epidemic in the United States that resulted in the loss of 48 million birds. The outbreaks coincided with the northward migration of birds in the early spring.
The CFIA analyzed all the virus genes of the B.C. outbreak and found good evidence that half of the 12 outbreaks came from wild waterfowl.
In 2007, a case was found at Regina Beach, Sask., on an isolated farm. Follow-up investigations identified potential sources for introducing the virus, including withdrawing water from a dugout.
The water was normally treated, but the system broke down and coincided with the disease at a time when wildlife may have landed there, said Pasick.
Maintaining strict biosecurity at all times is critical, he said. This time of year presents a higher risk because birds are moving south to their wintering areas.
“They are marshalling in large groups. There can be thousands of them and if these happen to be close to poultry farms, there is a potential risk for introducing the virus, especially if biosecurity measures aren’t appropriate,” he said.
The virus is often shed in bird feces. Research has found tens of millions of virus particles in a small amount of bird feces.
“Sometimes it doesn’t take much to infect an individual animal,” he said.
The viruses may be present every year, but the percentage of ducks carrying these two strains may vary from year to year.
“There is some cyclical activity, and we find some years there are higher H7 viruses present than in other years,” he said.
H5N1 influenza infected people in Hong Kong in 1997.
“People have been treating it very seriously for a long time and still to this day it is being watched closely because it could have pandemic potential,” he said.
More surveillance of wild birds has been conducted since the major outbreaks to see if the highly pathogenic form was still circulating in wild birds. There was a single report in a mallard duck in Alaska this summer.
“We don’t know what that means. It is just one detection,” he said.
The CFIA biosecurity practices recommendations include:
- protecting poultry feed and water from coming into contact with wild birds, particularly ducks and other wild waterfowl
- controlling the movement of people, live birds, equipment and vehicles on and off the farm
- routinely and frequently watching for signs of disease because early detection is crucial to limiting the severity of an avian flu outbreak and early signs may include behavioural changes
The CFIA offers more detailed biosecurity outlines at http://bit.ly/2cZPljp.
barbara.duckworth@producer.com
