2006-03-07-With avian flu spreading, US to expand its testingUnderstanding Avian Influenza
2006-03-07-With avian flu spreading, US to expand its testing
The U.S. government, bracing for the possibility that migrating birds could carry a deadly strain of bird flu to North America, plans to test nearly eight times as many wild birds this year as have been tested in the past decade.
Starting in April, samples from 75,000 to 100,000 birds will be tested for the virus, mainly in Alaska, as part of a joint effort of the departments of Agriculture and Interior, along with state Fish & Wildlife agencies. That's a jump from the 12,000 birds tested since 1996, the USDA's Angela Harless says.
The expanded program, which will include birds in the Pacific islands and on the West Coast, reflects growing concern that the virus, highly pathogenic A (H5N1), which has spread across Asia and Europe, could arrive in North America as soon as this spring and be carried into the western continental USA by fall.
"I would expect" the virus to arrive in North America, USDA Secretary Mike Johanns says. It could enter in other ways, he says, including smuggling of infected pet birds or fighting cocks, but the chance that it could be carried in with the spring migration "is definitely a possibility."
A disease of birds, not humans
If tests find the virus in birds in North America, it would not signal the start of a human pandemic, because it still primarily is a disease of birds, he says. The virus was first found in birds in China in 1996. It moved into people for the first time in Hong Kong a year later and now has turned up in 39 countries.
Since December 2003, at least 175 people have been infected, and 95 have died, most of them after having close contact with infected chickens but not wild birds. Scientists say the virus hasn't developed the ability to spread easily from person to person. If that happens, it could start a pandemic.
Of four major bird migratory patterns, or flyways, in North America ? the Pacific, Central, Mississippi and Atlantic ? the Pacific flyway is of greatest interest now, says Frank Quimby of the U.S. Department of the Interior. "The Pacific flyway is the most likely route, because birds that winter in Asia migrate in spring to Alaska." Alaska, with its wetlands and coastal areas, is a kind of Grand Central Station for bird species.
"Alaska is the crossroad of bird migration pathways," says Rick Kearney, wildlife program coordinator for the U.S. Geological Survey. "With the coming of the spring migration season, we are increasing surveillance" in partnership with federal, state and local agencies. "We shall be collecting samples from live migratory birds and samples from hunters."
Birds on the Asian flyway could arrive in Alaska in April and May, says Nicholas Throckmorton of the U.S. Fish & Wildlife Service. "That could be the moment when wild birds bring Asian bird flu to Alaska. As those birds spend the summer breeding in Alaska, they could pass it to birds that migrate south in the fall," he says. He added that if the virus arrives in Alaska, the agency doesn't expect it to move south until sometime between August and November.
To test the birds, scientists capture them in nets, take swabs from the throat or cloaca (posterior opening) and send the samples to the U.S. Geological Survey's National Wildlife Center in Madison, Wis. If any test positive for H5N1, confirmatory testing will be done at the USDA's National Veterinary Services Laboratories in Ames, Iowa. USDA spokeswoman Angela Harless says as many as 18,000 samples a day can be tested. Tests also will be made on birds killed by hunters in Alaska this spring, and in Oregon, Washington and California during the fall, Throckmorton says.
To bird experts, avian flu is nothing new. There are at least 144 types of bird flu viruses, most of which don't kill the birds. Only two types, H7 and H5, have become highly pathogenic, killing three out of five chickens infected, Throckmorton says. In Asia, the H5N1 virus "went from wild birds to domestic poultry, evolved in poultry and reinfected wild birds," he says. Now more lethal than it was, it kills some wild birds, but not all. "It's proven wild birds can carry this virus and not have illness."
What if it is found in the USA?
If the virus is detected in wild birds in North America, there will be no massive killing of them to contain it, because experts, including those from the World Health Organization, the World Organisation for Animal Health and the USDA, agree that destroying birds is not an effective control method. What would happen, Kearney says, is health experts and people involved in agriculture would be put on alert and warned to make sure poultry are separated from wild birds.
Some scientists say the focus on wild birds is misplaced. "Migratory birds are probably the least likely way avian flu is going to enter the Western hemisphere," says Peter Marra, a bird ecologist at the Smithsonian Institution in Washington, D.C.
The more likely route into the USA, he says, is through the pet trade and the movement of poultry, legally or illegally. "Migratory birds are innocent bystanders," Marra says. "I don't doubt (they're) moving the virus. I just don't think they're the primary movers."
Poultry industry on guard
The USDA has banned importation of live birds or bird products from countries where the virus has spread. Birds that are legally brought into the country are tested for H5N1 and other bugs, and they're held in quarantine for 30 days. But experts warn that illegal trade in birds and the smuggling of wild birds or fighting cocks could provide an entry.
Richard Lobb of the National Chicken Council says poultry farmers have been warned that "if you have hired help, make sure they don't have fighting birds at home. That is the only way it would get into commercial poultry."
If it spread into domestic poultry, it could threaten the USA's $43-billion-a-year broiler industry, but Lobb says there are precautions in place, from routine testing of every flock to extensive farm bio-security measures. An outbreak on a farm would be quickly detected, contained and extinguished, he says.
"We're not complacent by any means," he says. "It is the No. 1 issue in the industry."