Migration Routes a Factor in Bird Flu Fight

Each fall, millions of birds make the marathon migration south along the Pacific Flyway, winged phalanxes landing amid the swamplands and rice paddies of the Sacramento Valley.

Walter Boyce wants to ensure they’re not carrying unwanted baggage this year.

Scientists like Boyce look to the skies and see the possibility that bird flu might migrate from Asia along with geese and ducks.

Boyce, head of the UC Davis Wildlife Health Center, sees it as a sort of biological domino effect, passing from bird to bird as they head south for winter.

He hopes the feared H5N1 virus, the deadly variant that has prompted concern of a worldwide pandemic, won’t come with them.

“It’s not going to make it here easily,” said the bearded and soft-spoken scientist. “If you just look at the flyway maps, there’s not a lot of overlap between the Asian birds and those of North America.”

But at the tip of Siberia, the transcontinental populations do intermix while fattening up on summer plains of wild grasses and grains. Scientists from UC Davis and several other universities are attempting to act as a sort of early warning system.

Routine testing in British Columbia resulted in the discovery of a farm duck with a nonlethal strain of the virus, the Canadian Food Inspection Agency said Sunday. Health officials quarantined the farm, east of Vancouver, and plan to cull about 60,000 head of poultry as a preventive measure.

Health officials around the world have been on the watch for the Asian strain of the H5N1 virus that experts fear may mutate so it is easily transmitted among humans and possibly cause a pandemic. There are nine known N strains of the H5 virus.

Finding bird flu, Boyce said, could prove akin to locating a needle in a haystack.

In Alaska, the scientists took 4,000 samples as the birds migrated through the state. In Ohio, 500 have been tested. In California, the UC Davis surveillance program expects to test 2,000 birds.

Many will be ducks and other wild fowl shot by hunters. Scientists are also testing crows, magpies and other resident birds that could act as a biological bridge to spread influenza from migratory flocks to domesticated birds, including those in California’s crowded commercial poultry ranches.

With millions of birds on some of the Central Valley’s industrial chicken and turkey farms, Boyce said, any infection “would be like throwing a match on gasoline.”

That possibility brought veterinary technician Yvette Hernandez and Grace Lee, a Wildlife Health Center research associate, to a gravel road in rural Davis one recent morning, on a hunt for birds.

In the middle of the road, the pair placed a smorgasbord of dog kibble, cat food, walnut-and-raisin cornbread, hard-boiled eggs and cheesy rice snacks to lure in a few winged test subjects.

The scientists took up their posts in a small car parked up the road. A few dozen feet from the bait, a net gun lay in wait, tethered to a remote control trigger in the car.

After a couple of hours punctuated by birds swooping in for a look and then fleeing, Lee and Hernandez got what they wanted.

A pair of yellow-billed magpies settled in for a feast.

With the flick of a switch, a 10-foot-wide nylon web shot from the gun and settled over the two birds. The scientists delicately untangled the irate birds, wings thrashing. They stowed the magpies in separate pillowcases and hung them from a clothesline slung between a couple olive trees.

Each magpie got the same treatment. Blood was drawn. Cotton swabs dabbed each little beak and fecal vent.

Before sending them winging on their way, the scientists outfitted each bird with a tiny radio transmitter cinched to its back with a doll-sized harness.

The magpies seemed stunned as they flapped off. “When we let the crows go,” Lee noted, “they’re just screeching.”

The nation’s avian surveillance effort is expected to get a big funding boosting next year, with more than $11 million requested by the U.S. Department of the Interior. For now, the federal government has been left scrambling to tap into existing university projects, including the one at UC Davis.

At the lab, the results don’t come quickly.

Researchers inject live chicken eggs with the samples. If the chicken embryo dies within 48 hours, more tests are performed to see what sort of virus is present.

It takes weeks to months to get any results, eliminating any chance of a real-time warning that the most feared form of bird flu has arrived.

UC Davis scientists running the project -- funded with $75,000 culled from an existing federal grant -- can’t afford speedier tests. The bird flu surveillance effort is an outgrowth of a broader research project started a couple of years ago to study West Nile virus and other diseases with possible links to avians.

“Our work was originally crafted as a research project with no need for speed,” said Carol Cardona, a UC Davis poultry expert. The evolving concerns about bird flu “caught everyone flat-footed. We’ve never seen a virus like this,” jumping from wild birds to poultry and back so readily.

When the results arrive, the scientists expect to see something typical along the world’s flyways. Like humans, birds harbor various flu viruses. In a normal year, up to 30% of the birds are infected with some sort of virus along the Pacific Flyway, which stretches from Alaska through South America.

Scientists just hope they won’t see the H5N1 virus there.

The virus originated in Asia. First identified in 1997, H5N1 has sickened at least 125 people in four countries, killing 64.

All of those afflicted had contact with chickens and other domesticated birds. There are no documented cases of humans catching the flu from wild birds. (Scientists say there’s no reason, for now, to avoid visiting duck ponds or tending backyard bird feeders.)

But flu viruses can quickly evolve, prompting concern this strain could eventually go from person to person, spreading around the globe.

Though migratory birds are suspected of helping spread H5N1 from Asia to Europe, Boyce said he suspects that cargo transport of infected chickens and other poultry may have assisted the movement.

Scientists are just beginning to understand some of the foibles of H5N1 in the wild, Boyce said. It appears to be able to survive days in the water, spread by a fowl’s excrement. Ducks and geese are the main hosts, but gulls, herons, egrets, terns and other shorebirds also can harbor the virus.

If it lands in America, the influenza could ripple outward, spread by crows, magpies and other species. Crows typically spend their lives in a 10-mile radius, but a virus could jump from ring to ring, spreading over time.

Wild birds aren’t the only threat. Boyce noted that imported exotic birds also could introduce H5N1 or some deadly variant to America. So could imported poultry.

For now, Boyce said, “it’s not here, and it may never get here.”

The most threatening transmitter wouldn’t be birds, he added. If the virus mutates as feared, thousands of people who arrive from Asia each day at California airports could dwarf any peril from the birds, Boyce said. “That’s a lot more direct link.”