Industry on avian flu alert as migration for some birds will begin in August.

RIGHT now, in the prairie pothole region of southern Canada and the U.S. Upper Midwest, waterfowl are mingling, raising their young and instinctively preparing to migrate, some leaving as early as August.

All spring and summer, these wild birds, known as puddle or dabbling ducks — such as gadwalls, mallards, pintails, teal and wigeons, to name a few — have shared aquatic habitats, food supplies, brood-rearing responsibilities and — likely — avian influenza.

When those ducks head toward their wintering grounds, they will take different routes. Most will fly south along the Mississippi Flyway, but many will embark east and then merge into the Eastern Flyway. That route will take them over Pennsylvania, Maryland, Virginia, the Carolinas and Georgia to Florida's Gulf coast.

When they stop to rest and feed along the way, infected birds may potentially shed the pathogens that cause disease in their droppings and secretions.

"This strain of avian flu, H5N2 — which has yet to be seen along the Eastern Flyway — usually doesn't make waterfowl sick. In fact, many don't show any symptoms, and it doesn't affect people or other mammals," Margaret Brittingham, a professor of wildlife resources in The Pennsylvania State University College of Agricultural Sciences, said. However, "it does sicken and kill other birds, namely domesticated chickens and turkeys. It has devastated the poultry industry in states such as Minnesota and Iowa along the Mississippi Flyway and Washington and Oregon along the Western Flyway."

Two years ago, migrating waterfowl carried a novel strain of avian influenza out of Asia to breeding grounds in the Bering Sea region of northern Russia, and from there, at least a few ducks are believed to have conveyed it to Alaska, where birds migrating south brought it to the Pacific Northwest, Brittingham explained. It somehow spread east from there.

Along the way, the disease is believed to have evolved to become a highly pathogenic virus that is even deadlier to domesticated poultry.

"Historically, the Eastern Flyway has not been spared by avian flu outbreaks, and there is no reason to expect that the disease won't show up here this time," Brittingham said. "We have had big avian influenza outbreaks in the past. The difference this time seems to be that this strain of the disease is so pathogenic."

The threat has poultry producers in the eastern U.S. bracing for the potential arrival of the deadly virus this fall, hoping to prevent an outbreak similar to that in the Midwest. Thanks to strict biosecurity, avian influenza can be kept out of most poultry barns along the Eastern Flyway, Brittingham said.

How the disease is spread is not entirely clear, she added. Migratory paths vary greatly. Some species, such as pintails, have wide-ranging migratory routes that cross Asia, Russia and North America, while others have much more confined routes.

Brittingham suggested that dabbling ducks are not the only species that pose a risk for spreading avian flu to the eastern U.S.

Although avian flu poses a risk to wild turkeys, raptors and upland birds such as grouse and pheasants, their populations are probably protected by their high susceptibility to the disease and their low density — relative to poultry or waterfowl — on the landscape, according to Dr. Justin Brown, wildlife veterinarian for the Pennsylvania Game Commission and Penn State adjunct clinical associate professor based at the university's animal diagnostic laboratory.

Because wild turkeys, birds of prey and upland birds seem to be so vulnerable to avian flu and are killed quickly by the virus, they are not effective carriers, Brown explained. Additionally, they are spread out, which he said makes a large-scale mortality event unlikely.

"If they are exposed, there will be some mortality, but I'm not expecting that we'll see severe, widespread infection or population-scale impacts," he said.

The Pennsylvania Game Commission intends to conduct disease surveillance in ducks this fall at Presque Isle in the northwestern corner of the state through a collaboration with the University of Georgia, Brown said.

"I would also really like to conduct surveillance at the commission's Middle Creek Wildlife Management Area in Lancaster County (Pa.), but at this point, that is dependent on available funds and what surveillance is being conducted by the U.S. and Pennsylvania departments of agriculture," he added.

Volume:87 Issue:28