U.S. screening for highly pathogenic H5N1 avian influenza in migratory birds

Mar 21 2006

Secretary of Agriculture Mike Johanns, Secretary of the Interior Gale A. Norton and Secretary of Health and Human Services Michael Leavitt have moved to further ensure the protection of people, domestic poultry and wild birds by unveiling an enhanced national framework for early detection of highly pathogenic avian influenza (HPAI) in wild migratory birds in the United States.

This readiness plan and system builds on, significantly expands and unifies ongoing efforts among federal, state, regional and local wildlife agencies. Those agencies have been monitoring and testing for the presence of the highly pathogenic H5N1 virus in migratory birds for several years. The increased efforts come as the spring migration of migratory birds is underway and the spread of avian influenza continues across continents.

Wildlife experts and public health officials have been monitoring the spread of the highly pathogenic H5N1 since it first appeared in Hong Kong in 1997. Since 1998, the Department of Agriculture (USDA) has tested over 12,000 migratory birds in the Alaska flyway and since 2000, USDA has tested almost 4,000 migratory birds in the Atlantic flyway. All birds in these flyways have tested negative for the highly pathogenic H5N1 virus of concern. Since the summer of 2005, the Department of Interior (DOI) has been working with the State of Alaska to strategically sample migratory birds in the Pacific flyway. DOI has already carried out more than 1,700 tests on samples from more than 1,100 migratory birds. There have been 22 avian influenza isolates identified, but none have been highly pathogenic.

"The Department of Agriculture is working on many fronts, with many partners to further strengthen our ability to detect and respond to highly pathogenic strains of avian influenza," said Johanns. "By intensifying our monitoring of migratory bird populations, we increase the likelihood of early detection, which is key to controlling the spread of the virus, particularly in our domestic poultry. Having said that, it's important for the public to know two things; a detection of Asian H5N1 in the United States would not signal the start of a human pandemic; and properly prepared poultry is safe to eat, because proper cooking kills this virus."

Wildlife biologists, migratory bird specialists, veterinarians and epidemiologists from the USDA, DOI and Health and Human Services (HHS), along with the International Association of Fish and Wildlife Agencies, National Association of Public Health Veterinarians and the State of Alaska have developed "An Early Detection System for Asian H5N1 Highly Pathogenic Avian Influenza in Wild Migratory Birds -- U.S. Interagency Strategic Plan."

"We do not know for sure what role wild migratory birds play in the movement of this virus, but the potential exists for them to carry this virus to North America, and we have a responsibility to prepare for that possibility," said Secretary of the Interior Gale Norton. "Working closely with our state, local and federal partners, we can detect and respond to disease events involving wild birds and screen birds for highly pathogenic H5N1 virus. These actions will help us provide an early warning to the agriculture, public health and wildlife communities if the virus is detected in migratory birds."

The ability to effectively prevent the spread of highly pathogenic H5N1 into domestic poultry operations is greatly enhanced by being able to rapidly detect the pathogen if it is introduced into wild migratory birds in the United States. The interagency plan outlines five specific strategies for early detection of the virus in wild migratory birds, including:

• Investigation of disease-outbreak events in wild birds
• Expanded monitoring of live wild birds
• Monitoring of hunter-killed birds
• Use of sentinel animals, such as backyard poultry flocks
• Environmental sampling of water and bird feces

Because Alaska is at the crossroads of bird migration flyways, scientists believe the strain of highly pathogenic H5N1 currently affecting Southeast Asia would most likely arrive there if it spread to North America via migratory birds. Thus, the plan recommends a prioritized sampling system with emphasis in Alaska, elsewhere in the Pacific Flyway and the Pacific islands, followed by the Central, Mississippi and Atlantic Flyways. In 2006, USDA and its cooperators plan to collect between 75,000 to 100,000 samples from live and dead wild birds. They also plan to collect 50,000 samples of water or feces from high-risk waterfowl habitats across the United States.

The wild bird monitoring plan is part of the President's National Strategy for Pandemic Influenza Preparedness. President Bush allocated $29 million in his avian influenza supplemental funding package for implementation of the wild bird monitoring plan.

HHS Secretary Mike Leavitt noted that highly pathogenic H5N1 is still a disease of birds, not people, and that most human cases in other countries have come from extensive direct contact with infected birds or their droppings. He cautioned, however, that scientists are concerned that the virus could develop the ability to efficiently transmit from person to person, and "such a development could trigger a worldwide pandemic."

Leavitt said HHS is using a multi-pronged approach, which includes increased monitoring to spot disease outbreaks at home and abroad; development of vaccines and vaccine manufacturing capability; stockpiling of both vaccines and antivirals; planning at the state and local level, and communications to inform the public.

Noting that the disease could show up in many communities all at the same time, Leavitt called local preparedness "the foundation of pandemic readiness" and said: "any community that fails to prepare -- with the expectation that the federal government can offer a lifeline -- will be tragically wrong." To assist local efforts, HHS is holding planning summits in all 50 states and providing checklists to local and state governments, businesses, schools, home health care providers, faith-based and community organizations and individuals and families.

Historically, wild birds have been natural reservoirs for low pathogenic avian influenza viruses and often show little or no signs of disease. Various forms of low pathogenicity avian influenza have existed in the United States since the early 1900's. They can cause varying degrees of illness in birds and have not posed a public health threat. If a virus mutates or mixes with another avian influenza virus it can become highly pathogenic, causing higher fatality rates in birds. The HPAI strain of H5N1 currently affecting countries in Asia, Africa, Europe and other geographic areas is highly infectious between birds, but has never been found in the United States. Other forms of HPAI have been detected in domestic poultry three times in this country: in 1924, 1983 and 2004. The 2004 outbreak was confined to one flock and eradicated. There were no human illnesses reported in connection with these outbreaks, however the highly pathogenic H5N1 avian influenza virus has caused human illness and death in other countries where people have handled or been in close contact with infected birds.

http://www.usda.gov, http://pandemicflu.gov and http://avianflu.gov/