Written by Adam Duerr & Fletcher Smith
January 11, 2009
The Center for Conservation Biology recently joined the national surveillance program for early detection of avian influenza. Highly pathogenic avian influenza (strain H5N1) is a form of bird flu that when contracted by people, domestic birds, or wild birds, can be deadly. Biologists throughout the world have worked extensively to determine how this lethal strain may affect the human population and identify potential routes in which the disease may enter the United States through domestic or wild birds. In the realm of wild birds, efforts include analyzing migratory routes and monitoring key populations to provide the earliest possible detection of the disease. This early detection will provide state and federal agencies the longest possible lead time to implement response plans to protect human health.
Waterfowl and shorebirds are natural reservoirs of avian influenza. Low pathogenic strains of the virus cycle through these populations, but typically do not cause human disease. Genetic drift (mutation) allows these low-pathogenic strains to infect other species of birds including domestic poultry or waterfowl. Additional genetic drift can then increase the virulence of the strain, causing disease or death in the new hosts and infection in other species including humans. After these changes occur, the virus may move back to wild bird populations that transport the virus to new areas during their natural movements. Genetic changes to the virus are thought to have occurred in Asia in 1995-96, with outbreaks that caused death in domestic poultry, wild bird populations, and humans since then.
Monitoring for early detection of highly pathogenic avian influenza in wild bird populations in the United States is focused on species that are most likely to carry the virus. Primary species include those that migrate directly to areas where highly pathogenic avian influenza has been identified in wild or domestic birds, such as areas of Asia where outbreaks have occurred. Secondary species include other birds whose breeding or migration range overlap with primary species, which may allow for transmission of the disease to secondary species. Given migration routes of wild birds, waterfowl and shorebirds from Alaska are thought to be the most likely species to become infected in North America. A second potential route is through Europe, where the highly pathogenic virus was detected in a duck. In both situations waterfowl and shorebirds migrate from breeding grounds located in northern Alaska and Canada through areas in Asia and Europe.
CCB’s sampling focus is migratory shorebirds. Target species include whimbrel, black-bellied plover, dunlin, least sandpiper, western sandpiper, and semi-palmated sandpiper. Western sandpipers and at least some whimbrel that stop in Virginia while migrating breed in Alaska. The exact breeding locations of the other species are not known, but could include Alaska or northern Canada. The Center for Conservation Biology is pairing our understanding of conservation concerns for shorebirds with participation in the national surveillance effort for highly pathogenic avian influenza. This pairing allows us to collect important data on shorebird populations in Virginia that will further their long-term conservation.
Monitoring for highly pathogenic avian influenza in shorebird species provides CCB the opportunity to simultaneously further our knowledge of the biology of the target species. We are doing this by banding and collecting data on each bird captured. Morphological measurements, or physical measurements, of each bird (bill and wing lengths) will help CCB to characterize populations that move through Virginia. For example, populations of whimbrel that breed in Alaska are larger than populations from northern Canada (see CCB’s Whimbrel Migration page). Banding birds will help us understand how these shorebird populations change through time by providing a means to track the survival of individual animals.
There are several concerns about populations of shorebirds, including observed declines in some species. Dunlin, black-bellied plovers, and whimbrel have been identified as species in need of conservation in Virginia and Maryland. In general, the conservation community is also concerned that populations of birds breeding in the high arctic are or may experience population declines, especially in light of ecological changes associated with global warming. These concerns extend to the shorebird species that are targets for surveillance of avian influenza. Thus, knowing the migratory pathways throughout the life cycle of these birds is vital in developing conservation strategies. Further, baseline monitoring through banding shorebirds will provide a means to detect changes in their populations over time.