Screening for Highly Pathogenic H5N1 Avian Influenza in Migratory Birds

'An Early Detection System for H5N1 Highly Pathogenic Avian Influenza

in Wild Migratory Birds - U.S. Interagency Strategic Plan'

Mar 20, 2006, 00:00 ET from U.S. Department of Agriculture

    WASHINGTON, March 20 /PRNewswire/ -- Avian Influenza (AI) is a virus that
 is naturally found in wild birds, particularly in certain species of waterfowl
 and shorebirds. Occurrences of an H5N1 highly pathogenic avian influenza
 (HPAI) virus overseas have heightened concern regarding the potential impact
 on wild birds, domestic poultry and human health should it be introduced into
 the United States.
     To understand the differences and potential threats to U.S. bird
 populations, this fact sheet provides definitions, a historical perspective
 and an outline of the U.S. Department of Agriculture (USDA) and U.S.
 Department of the Interior (DOI) efforts to detect the H5N1 HPAI virus in wild
 migratory birds.
     AI viruses are classified by a combination of two groups of proteins found
 on the surface of the virus: hemagglutinin proteins (H), of which there are 16
 (H1-H16), and neuraminidase proteins (N), of which there are 9 (N1-N9). There
 are 144 possible combinations or subtypes based upon this classification
     Wild birds, in particular certain species of waterfowl and shorebirds, are
 considered to be the natural reservoirs for avian influenza viruses. These
 subtypes that naturally occur in wild species usually cause little or no
 disease. However, domestic birds are generally more susceptible to avian
 influenza virus and mutation or recombination of a virus acquired from wild
 birds can increase its disease potential in these domestic birds.
     AI strains also are divided into two groups based on the pathogenicity of
 the virus -- the ability of the virus to produce disease.
     Low Pathogenicity Avian Influenza (LPAI): Most AI strains are classified
 as low pathogenicity and cause few clinical signs in infected birds. LPAI
 generally does not pose a significant health threat to humans. However, LPAI
 is monitored because two strains of LPAI -- the H5 and H7 strains -- can
 mutate into highly pathogenic forms.
     High Pathogenicity Avian Influenza (HPAI): This type of avian influenza is
 frequently fatal to birds and easily transmissible between susceptible
 species. The strain that is currently of concern in Asia, Europe, the Middle
 East and Africa is the H5N1 HPAI virus.
     Since 1997 when it first appeared in Hong Kong, federal wildlife experts
 and public health officials have been monitoring the spread of the highly
 pathogenic H5N1 virus.
     Since 1998, USDA, in partnership with the University of Alaska, has tested
 over 12,000 wild migratory birds in the Alaska flyway and almost 4,000 wild
 migratory birds in the Atlantic flyway. All birds have tested negative for the
 highly pathogenic H5N1 virus.
     DOI and USDA stepped up wild bird monitoring and testing programs when the
 highly pathogenic H5N1 virus spread throughout Southeast Asia and Russia.
     Since summer 2005, DOI biologists have been working with the State of
 Alaska to sample migratory birds for H5N1 in the Pacific Flyway. DOI has
 tested more than 1,700 samples from more than 1,100 migratory birds. There
 have been 22 avian influenza isolates identified, but none have been highly
     In August 2005, as part of the President's National Strategy for Pandemic
 Influenza Preparedness, the USDA and DOI convened a joint working group with
 the U.S. Department of Health and Human Services (HHS), State of Alaska and
 the International Association of Fish and Wildlife Agencies to develop a
 national strategic plan for early detection of H5N1 HPAI should it be
 introduced into North America by wild birds.
     The interagency strategic plan, developed by wildlife disease biologists,
 veterinarians and epidemiologists, provides a unified national system for
 conducting H5N1 HPAI monitoring of wild migratory birds throughout the United
 States. The plan serves as a guide to all federal, state, university and non-
 governmental organizations involved in avian influenza monitoring by providing
 standard procedures and strategies for data sampling, diagnostics, and
     The plan targets bird species in North America that have the highest risk
 of being exposed to or infected with highly pathogenic H5N1 because of their
 migratory movement patterns. Key species of interest include ducks, geese, and
     If wild birds are or become able to effectively move the disease over
 great distances, scientists believe introduction of H5N1 into the United
 States would most likely occur in Alaska, where there is significant mixing of
 Asian and North American birds. Therefore, the interagency strategic plan
 recommends a prioritized sampling system with emphasis first in Alaska, the
 Pacific Flyway and Pacific Islands, followed by the Central Flyway,
 Mississippi Flyway and Atlantic Flyway. The five strategies are:
     1.) Investigation of morbidity/mortality in wild birds: The systematic
 investigation of significant numbers of sick or dead birds offers the highest
 and earliest probability of detection, if the highly pathogenic H5N1 virus is
 introduced into the United States by migratory birds. Biologists and
 veterinarians in state and federal wildlife and natural resource agencies and
 animal health agencies and organizations, are prepared to detect and respond
 to such discoveries. In the event that a highly pathogenic H5N1 is detected in
 wild birds, USDA will identify and monitor domestic poultry and swine
 operations in the area and minimize contact between the wild birds and
 domestic animals.
     2.) Monitoring live, apparently healthy wild birds: This effort targets
 wild birds in North America that represent the highest risk of being infected
 with highly pathogenic H5N1 avian influenza, because of their migratory
 movement patterns. Species that will be sampled include birds that migrate
 directly between Asia, Oceania (including Hawaii, U.S. Pacific Territories and
 Freely Associated States) and North America, and birds that might be in
 contact with species from areas in Asia with reported avian influenza
 outbreaks. This includes sampling live-captured, apparently healthy wild birds
 to detect the presence of highly pathogenic H5N1 virus. Data collected in
 Alaska will be combined with data from additional bird captures to provide a
 broad species and geographic monitoring effort. In 2006, DOI, USDA and their
 cooperators plan to collect 75,000 to 100,000 samples from live and dead wild
     3.) Monitoring hunter-killed birds: Hunter check stations operated by the
 FWS and state natural resource agencies for waterfowl hunting provide an
 opportunity to collect additional samples to test for the presence of highly
 pathogenic H5N1 and other subtypes of avian influenza. These samples
 supplement the targeted monitoring samples from live wild birds and focus on
 species that are most likely to have been exposed to highly pathogenic H5N1
 viruses in Asia; have relatively direct migratory pathways from those areas to
 the United States via Alaska or directly to the Pacific Coast; or that mix in
 migratory staging areas in Alaska with species that could bring the virus from
 Asia. Collection of samples from these species will occur at hunter check
 stations in the lower 48 states, as well as Alaska, during hunting seasons in
 areas where these birds gather during migration or over-wintering. Samples
 also will be collected from wild birds taken by native Alaskans during the
 spring subsistence hunt. USGS, FWS and USDA are working with the four
 Migratory Bird Flyway Councils to enhance sampling plans for hunter-killed
     4.) Use of sentinel animals: There are two groups of animals used as
 sentinels in avian influenza monitoring programs that could provide early
 detection of the highly pathogenic H5N1 virus along migratory flyways in the
 United States. Poultry flocks reared in backyards (raised for noncommercial
 purposes) have been evaluated for diseases of interest to nearby commercial
 poultry operators as a monitoring method. Also, duck flocks can be placed in
 wetland environments where they may commingle with wild birds. The ducks are
 then monitored and tested for avian influenza viruses.
     5.) Environmental sampling of water and bird feces: Waterfowl release
 avian influenza viruses through the intestinal tract and the virus can be
 detected in both feces and water in which the birds swim. This provides a
 means of virus spread to new avian hosts and potentially to poultry or other
 livestock. Analysis of both water and fecal material from waterfowl habitat
 can provide evidence of avian influenza circulating in wild bird populations.
 In 2006, USDA and others plan to collect 50,000 samples from high-risk
 waterfowl habitats across the United States.
     In addition to providing an early warning system for disease occurrence in
 U.S. wild birds and domestic poultry, the monitoring data will be used to
 create a national database that incorporates and tracks all avian influenza
 data collected from wild birds in the United States. The database will be
 available to all agencies, organizations and policymakers involved in avian
 influenza monitoring and response. The data collected in this system will be
 used by scientists to develop a better understanding of the movement of avian
 influenza viruses among wild and domestic animals, improve risk analyses and
 target monitoring strategies to track regarding future avian influenza spread.
     Additional Information:
     USDA Bird Flu Information
     News Release: USDA, DOI And HHS Expand Screening For Highly Pathogenic
 H5n1 Avian Influenza In Migratory Birds
     News Release: Wild Bird Plan: An Early Detection System for Highly
 Pathogenic H5N1 Avian Influenza in Wild Migratory Birds U.S. Interagency
 Strategic Plan
     Fact Sheet: United States Prepares For Highly Pathogenic H5N1 Avian
 Influenza In Wild Birds
     Also See: &

SOURCE U.S. Department of Agriculture