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U.S., International Scientists Study Disease in Wild Birds

Doves in Shanghai rest near a sign that reads "China." (©AP/WWP)

By Charlene Porter
Washington File Staff Writer

Washington – U.S. and Chinese wildlife scientists are headed to remote Qinghai Lake in western China in early June to conduct a joint project on the presence of a highly pathogenic avian influenza virus in barheaded geese.

An outbreak of the deadly H5N1 virus in these migratory birds on that lake in 2005 served as one of the first clues underlying the theory that the seasonal movements of birds might carry the pathogen on intercontinental journeys.

The Animal and Plant Health Inspection Service (APHIS) of the U.S. Department of Agriculture joins the Chinese Academy of Sciences Institute of Zoology in the project, according to Dr. Tom DeLiberto, APHIS’ national wildlife disease coordinator, who is overseeing the research.

A wildlife veterinarian, DeLiberto told the Washington File that the researchers will be working to answer a number of questions surrounding the discovery of more than 500 dead wild birds at Qinghai Lake in 2005.

“[Is] that virus endemic in that ecosystem?” he said. “If so, where is it reservoired, what species is it in, and is it still an active virus in that ecosystem?”

Qinghai Lake is an important stopping point for migratory birds on one of their Asia-Europe routes. When H5N1 was discovered in wildlife there, some experts theorized that the birds had carried the disease up from the south where they originally were infected.

Months after discovery of that die-off, H5N1 began moving out of Asia in a big way, first appearing in Central Asia, then Russia, then Eastern and Western Europe, the Mideast and Africa. Only about 10 countries reported observations of H5N1 either in poultry or wild birds in mid-2005; now that number is more than 50.

DeLiberto said the American-Chinese collaboration should help wildlife scientists better understand what happens to the virus in a given environment, and whether the virus sustains itself in those environments for long periods.

Also in Asia, APHIS has worked with the U.S. Agency for International Development to help the Cambodian government establish a surveillance program for avian influenza in wild birds. Similar programs are anticipated in other nations of the region.

WILD BIRDS IN NORTH AMERICA

In North America, DeLiberto said his agency is working with counterparts in Mexico’s government to improve surveillance of migratory birds.

The H5N1 virus has not appeared in the Western Hemisphere since the bird pandemic began in Asia in late 2003, but some observers expect it to appear there at any time, given the rapid movement of the pathogen across Eurasia in 2006.

Mexico’s wild-bird surveillance currently is not as comprehensive as that conducted by the United States and Canada, DeLiberto said, so the effort now being planned will scale up the Mexican program to help ensure the first appearance of H5N1 in North America will be detected rapidly.

“We will be able to get a continentwide view,” the U.S. wildlife veterinarian said. “If this virus enters North America in wild birds, we’ll be able to have a perspective on the entire continent.”

Bird migratory flyways on the Atlantic and Pacific coasts are being watched as possible routes for the introduction of H5N1 into North America.

Even though wild birds have received significant attention as the transcontinental transporters of highly pathogenic avian influenza, DeLiberto said, poor biosecurity measures are also a highly likely means by which the virus can be carried from one area to the next.

The H5N1 virus can be carried from one place to another via the transport of domestic birds, or it might survive in mud that is carried from one farm to the next on a vehicle fender or a farmer’s shoe. The virus also can be carried on feathers plucked from infected birds, or on empty cages in which the animals once were kept.

DeLiberto said genuine vigilance is needed to prevent transmission of the virus through poor biosecurity.

The veterinarian represented the United States at a May 30-31 international scientific meeting on avian influenza and wild birds sponsored by the Food and Agriculture Organization of the United Nations and the World Organization for Animal Health. (See related article.)

That meeting concluded with recognition from the 300 scientists involved that H5N1 has been mainly spread through the poultry trade, both legal and illegal. At the same time, an FAO summary of the meeting says specialists from more than 100 nations attending acknowledged that migrating birds have played and will likely continue to play some role in transporting the virus.

International animal health officials urge developed nations to provide greater assistance for the improvement of veterinary services in developing countries in order to improve wildlife surveillance as a key to early detection of disease.

For ongoing coverage of the disease and efforts to combat it, see Bird Flu (Avian Influenza).