Ducks offer clues to avian influenza risk

Low clouds and showers of rain drift over the Thief Lake Wildlife Management Area as a crew of two in a small boat splashed ashore with dozens of ducks in plastic crates.

The ducks were caught in barley-baited traps out on the water.

The crew carried the grumbling ducks to a processing facility set up on two pickup trucks parked with their tailgates open. Forceps, syringes and swabs are ready to hand.

Minnesota DNR biologist Ciara McCarty reaches into a box and grabs a blue-winged teal.

McCarty notes the leg band number and the duck’s age and sex.

This is part of the Minnesota Department of Natural Resources’ annual waterbird banding initiative. About three thousand ducks are caught each year and fitted with a numbered aluminum leg band. When hunters turn in the tapes, it helps biologists track migration patterns and bird deaths.

But a subset of these ducks are also tested for bird flu.

“Swabs test the bird for active virus and then blood samples are tested for antibodies in the blood,” McCarty explained.

This is a multi-agency effort. The team catching the ducks and running the gang work is DNR.

Timothy White, US Department of Agriculture wildlife disease biologist, collects fecal and throat swabs here to test for highly pathogenic avian influenza.

The swabs are sent to a laboratory in Missouri. All positive results are confirmed by the National Veterinary Services Laboratories in Ames, Iowa.

This is part of a national surveillance effort.

“By taking this national approach, we can get information not only from here, but also as it moves along the trajectory in different states,” White said.

“It helps us understand what’s going on in the wild,” he said. “And we can share that information with poultry producers, and maybe it will help them make other management decisions to protect their flocks.”

Minnesota sees a lot of ducks. According to the DNR, 60 percent of migratory birds in North America transit the state during the spring and fall following the Mississippi River Flyway.

Researchers are excited to learn more about the highly pathogenic bird flu virus, as the current variant is not behaving like previous outbreaks.

This virus has continued to circulate throughout the summer killing many more wild birds compared to previous outbreaks.

There are many viruses in the landscape, making this surveillance important, said Julianna Lenoch, USDA National Wildlife Disease Program coordinator.

“The most important thing we need to understand is that the virus is still circulating, which bird species are carrying it, and what flight routes they may be returning to as we look at fall migration and birds returning over North America,” she said.

Lenoch says poultry producers did a great job earlier this year to reduce the impact of the virus by implementing strong biosecurity plans, and those plans should be taking action now.

“I wouldn’t wait for it to be spotted near you. Our evidence at the moment is that this virus is quite widespread and quite present, so all our poultry lovers are encouraged to maintain this level of biosecurity,” she said.

The Minnesota Board of Animal Health reported nearly a dozen cases of bird flu in commercial and backyard poultry flocks this month.

According to Lenoch, at least two variants of the highly pathogenic H5N1 virus are circulating in North America. One entered on the east coast, the other on the west coast.

Viruses mutate and mingle all the time, and experts want to know what might have changed over the summer.

“What’s important for us now is to understand if we’re seeing these viruses mixing,” Lenoch said. “If these tribes and these bird migration routes converge, could we possibly see the emergence of a new virus in North America? That might help us understand what we might be looking at for fall risk.”

“The landscape is fraught with risk when you’re a bird out there,” said Bryan Richards, the emerging disease coordinator at the US Geological Survey National Wildlife Health Center. “The virus is out there, it remains a threat, it hasn’t gone away. And I think the evidence suggests we’ll be seeing more of that in the fall.”

The virus has continued to kill wild birds throughout the summer and hit colonial nesting birds like terns and pelicans hard, Richards said. The virus has also been found in a range of mammals, from young red foxes in Minnesota to a black bear in Canada, and earlier this month the first case in a dolphin in Florida.

“And now we are at the beginning of autumn migration, so the birds are on their way. And those birds coming back from the northern latitudes, we’ll have to see what they bring with them,” Richards said.

As the USDA conducts surveillance in 49 states for the virus responsible for the outbreak that has killed more than 40 million turkeys and chickens statewide and nearly 3.5 million domestic fowl in Minnesota this year, other researchers are taking a deeper look.

At the Thief Lake Wildlife Management Area, Alinde Fojtik prepares to draw a blood sample from the carotid artery of a duck immobilized on the tailgate of a pickup truck.

“It tells us whether or not they have the antibodies to the virus,” she explained. “They carry it or just have the antibodies from previous infections.”

Fojtik is a research associate with the Southeastern Cooperative Wildlife Disease Study at the University of Georgia.

She travels the Mississippi Flyway collecting waterfowl samples. The project has collected samples in Minnesota since 1998 and annually since 2005, accumulating a vast body of data on the variety of influenza viruses that have co-evolved with waterfowl over thousands of years.

“We’re tracking low pathogenic avian influenza viruses so we can see what’s naturally occurring in the populations,” Fojtik explained. “We’re trying to establish the normal trend of the flu and then we’ll see if anything’s changing, if anything’s different.”

So the swabs and blood samples collected here in northern Minnesota will not only help track the risk of the current deadly bird flu virus, but also help provide context so scientists can see the big picture of how these ubiquitous viruses are changing in waterfowl .