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Everything you wanted to know about Avian
Influenza
Early Detection of the
Asian H5N1 Strain of Avian Influenza in Migratory Birds
Virulence or strength is classified as either low pathogenic avian influenza (LPAI) or high pathogenic avian influenza (HPAI). Most avian influenza subtypes are low pathogenic and cause little or no signs of illness in domestic or wild birds and pose no threat to human health. These subtypes are found every year in waterfowl and other birds. High pathogenic avian influenza viruses are associated with the H5 and H7 subtypes. Some strains of the H5 and H7 subtypes are extremely infectious and fatal to domestic poultry, sometimes posing a threat to human health. The high pathogenic Asian strain of avian influenza (also known as the Asian H5N1 strain and referred by the media as bird flu) has been found in Asia, Europe and Africa. The virus has affected millions of domestic poultry and is receiving great attention within the medical community. It has infected more than 250 people and has resulting in more than 170 human deaths since 1993. Nearly all cases in humans have occurred in circumstances where domestic poultry and people were in close and frequent contact. There is no evidence of sustained human-to-human spread of this virus, but there have been at least three instances where the virus has been transferred from human to human among family members. As of May 2007, the Asian H5N1 strain of avian influenza has not been detected anywhere in North America.
Role
of Migratory Birds in Transmission of Avian Flu
There is no evidence to suggest that migratory birds have transmitted the Asian strain of avian influenza to humans. Indeed, it is highly unusual for an avian influenza to be transmitted directly between different kinds of animals. This strain has been found in pigs, cats, and a few other species, so this heightens the concern that it may also be transmittable to humans. With rare exception, the avian influenza viruses found in wild birds have been low pathogenic forms and have rarely caused signs of illness. Low pathogenic forms of the virus have been detected in at least 105 species of wild birds, although birds of wetland and other aquatic habitats, particularly waterfowl (ducks, geese, and swans), shorebirds (wading birds, gulls, and terns constitute the major natural virus reservoir. However, the highly pathogenic Asian virus, circulating in parts of Asia, Europe and Africa, is easily transmitted among birds. The Asian virus sometimes kills wild birds, including waterfowl, but most seem to survive exposure. These birds become carriers of the disease, e.g., they have the disease but do not show signs of illness and behave normally. These carriers can carry the transport the virus to other locations and affect other wild or domestic flocks. However, in almost every case where wild birds have died from the disease, the source has been traced to infected poultry flocks. There are a few cases, however, where the virus arrived in remote locations where it was more likely transported by wild birds. Although the Asian H5N1 virus can be lethal to wild waterfowl, only a few large die-offs have occurred in the wild. A concern expressed by waterfowl hunters and waterfowl managers is that some groups might advocate culling wild birds to prevent them from spreading the virus. This approach has been reviewed and opposed by international conservation organizations and by public health authorities around the world. Both the Canadian and U.S. Fish and Wildlife Service indicate that such action is out of the question. What about waterfowl hunting seasons? A couple of countries in Europe and Asia closed their spring hunting season this year. However, if the Asian H5N1 virus does show up in North America, not much is likely to change related to hunting seasons. The world’s health experts continue to stress that the Asian virus has never been transmitted from wild birds to humans, so even if a hunter shoots and subsequently handles a bird infected with the Asian virus, transmission of the virus is not likely to occur. Even so hunters should take routine precautions when handling and cleaning game birds. Furthermore, the U.S. Fish and Wildlife Service does not anticipate closing waterfowl hunting seasons based upon what is currently known about the Asian strain of avian influenza. The overwhelming concern with wild birds is that they might transmit the Asian H5N1 virus to domestic poultry. The threat to domestic birds is huge with the potential for devastating economic and food supply implications. Wild waterfowl, however, are not a threat to human health. Wild birds have never been shown to transmit the virus to people, and health officials consider this type of transmission highly unlikely.
Monitoring Avian Flu in Migratory Birds in North America
In 2006, the U.S. Fish and Wildlife Service and U.S. Geological Survey, working in conjunction with the Alaska Department of Fish and Game, collected more than 15,000 samples from 29 bird species in more than 50 locations throughout Alaska. Sampling was expanded to other areas in the lower U.S. and Canada. Wildlife biologists from several federal and state agencies, universities and non-governmental organizations collected more than 84,000 samples from live and hunter-harvested wild birds. They also collected more than 50,000 water and/or fecal samples from high-risk waterfowl habitats across the nation. Highly pathogenic H5N1 avian influenza virus was not detected. However, 16 positives were found for North American H5 and N1 virus strains of low pathogenicity in 10 states. Wild birds, particularly waterfowl, are well-recognized reservoirs of avian influenza viruses of low pathogenicity, and detection of these viruses was expected. In 2007, cooperating agencies plan on collecting a minimum of 50,000 samples from wild birds. In addition, U.S. Department of Agriculture, Wildlife Services (WS) plans to collect 25,000 fecal samples nation-wide to augment wild bird sampling and increase the probability of detecting the Asian H5N1 virus in wild bird populations. Environmental sampling focuses on areas most likely to receive birds from Asia, Europe, and South/Central America. With surveillance efforts in place, there is a good probability the disease will be detected if wild waterfowl carry the Asian H5N1 virus to North America this year. Monitoring Avian Flu in Migratory Birds in
Maryland 2005 and 2006 During 2006-07, Maryland DNR and its partner, USDA WS, sampled more than 1,600 waterfowl during 2006-07. Sampling focused on species that are affiliated with Alaska and the eastern Arctic. Samples included 194 Atlantic Brant, 189 Long-tailed Ducks, 213 Lesser Scaup, 47 Greater Scaup, and 175 Canvasbacks. Waterfowl outfitting services were especially helpful in assisting in obtaining samples of Brant and Long-tailed Ducks. Although plans included sampling tundra swans, low swan numbers and mild winter weather precluded capture and sampling of this species. An additional 1,000 fecal samples were obtained from wild birds by USDA WS. Some 753 additional samples were taken during 2006-2007 in cooperation with Dr. Richard Slemmons at Ohio State University. Waterfowl species included Canada geese (116), Mallards (157), Lesser Scaup (104), Mute Swans (62), Bufflehead (30), Green-winged Teal (20), and lesser numbers of Snow Geese, Black Ducks, Surf Scoters, Black Scoters, Long-tailed Ducks, Ruddy Ducks, American Wigeon, and Common Mergansers. No Asian H5N1 avian influenza virus was found in the Maryland samples. North American H5 virus of low pathogenicity was detected in environmental samples at one site on the Eastern Shore where wild and captive-reared waterfowl co-existed. 2007 Avian Flu Surveillance Plans for
Maryland
Handling Wild Birds Reporting Dead Birds If you do inadvertently have contact with sick or dead wildlife, thoroughly wash your hands with soap and water, taking care to avoid rubbing your eyes, eating, drinking or smoking before washing. If hands are not visibly soiled, alcohol-based hand cleaning products may be used. For More Information about Avian Influenza |