By Susanne Quick
Milwaukee Journal Sentinel
February 9, 2004

As West Nile virus continues to steam-roll its way across North America, killing thousands of wild birds and an Asian bird flu knocks out part of the domestic poultry population in China and Vietnam, a different avian ailment is hitting bald eagles along the lower Wisconsin riverway.

And although the area and scope of the disease are limited - just the lower Wisconsin River and only bald eagles - no one knows what's causing it.

According to state and federal wildlife specialists, the disease generally manifests itself in live animals as grand mal seizures. The birds, who can't stay in the trees because of their jerking and spasms, end up on roadways, in fields or on frozen lakes, where they thrash and roll - seemingly unaware of their surroundings.

"One of the things about this disease," said Julie Langenberg, wildlife veterinarian at the Wisconsin Department of Natural Resources, "is some of these birds can be rescued" because they are unable to fly and don't seem to realize that they are being approached.

However, wildlife specialists warn that people who see eagles in such a state should not approach them, and instead should call the DNR to come rescue the animals.

"You have to keep in mind that these birds are quite strong and powerful," said Marjorie Gibson, executive director of Raptor Education Group Inc. in Antigo. And when they are having seizures, even if they are unaware of their surroundings, they can still injure untrained people.

Four eagles survive illness

Despite the opportunity to save some of the eagles, "a significant proportion of them die - more than half," Langenberg said.

As of this year, 11 eagles are suspected of having succumbed to the disease - although there may be more whose bodies have not been found.

Four survived and are being rehabilitated at Gibson's center in Antigo, where they are watched 24 hours a day, and given anti-seizure medications as soon as they begin having spasms.

"We literally sleep next to them," Gibson said, "so that we're right there if the symptoms start."

Gibson also works to teach the surviving birds how to fly and hunt again.

"It's a long process," she said, often taking a year or more before the eagles can be rereleased.

The disease first appeared during the winter of 1994 and 1995. It then vanished and reappeared in the winter of 2000.

Since then the severity has fluctuated, killing between six and 20 eagles each year.

Although only a small number of eagles seem to be affected - only 11 out of a bumper crop of 614 pairs between Adams and Juneau counties - they're numerous enough to have wildlife specialists concerned, Langenberg said.

"The Wisconsin DNR has taken this problem very seriously," said Carol Meteyer, a wildlife pathologist at the U.S. Geological Survey's National Wildlife Health Center in Madison.

"There is a very small window of opportunity to gain environmental information from the dead carcasses because some years we don't see dying eagles. And when we do, it is only for about six weeks," she said.

No other birds or mammals appear to be involved, Meteyer said.

According to the pathology work done at the Wildlife Health Center, "changes in these birds do not point to any clear cause," she said.

Disease appears swiftly Curiously, both Meteyer and Langenberg say that despite the very big symptom of death, the birds appear to be in good physical condition. They have, "lots of fat, which means that whatever happens, happens relatively quickly," Meteyer said.

Necropsy examinations of the eagles' livers indicate changes that are recent, instead of chronic, she said.

But these changes don't seem to have the hallmarks of any particular disease, poison or contaminant the researchers are aware of.

"As a wildlife forensic pathologist, this disease is fascinating, but also frustrating," Langenberg said.

Lesions have also been found on the brains of some of these birds and are probably associated with seizure symptoms.

"The bottom line is nobody knows what is going on," Langenberg said. "It appears to be a nervous system disease, as evidenced by the presence of seizures."

The DNR and National Wildlife Health Center have conducted investigations to look for infectious agents, environmental pollutants and poisons in the eagles' forage, but so far nothing has surfaced, Langenberg said.

Eagles on the northern Wisconsin River and on the Mississippi don't appear to be affected by this disease.

That indicates that there is something peculiar to the lower Wisconsin contributing to the disease.

Langenberg thinks maybe they are observing a combination of problems - a dab of environmental factors mixed in with a dash of something else.

"I think this kind of situation is only going to become more typical in the coming decades," she said. "It's because of the way we are changing their environment," often in incremental steps, that makes it harder to pinpoint problems.

"I think the eagles are trying to tell us something," she said.

The next step, Langenberg said, is to look for clues on a smaller scale. But with budget tightening at the state and federal levels - as well as funds being diverted to "hotter" diseases such as chronic wasting disease and West Nile virus - the work on the eagles may be delayed.