Patuxent Wildlife Research Center
Victims and Vectors: Understanding wild migratory birds and their role in highly pathogenic avian influenza transmission
Diann Prosser, USGS Patuxent Wildlife Research Center
Wild bird marking, Qinghai Lake
Ruddy Shelduck (Tadorna ferruginea) with 30g solar GPS satellite transmitter
The goal of this project is to study the potential risk of highly pathogenic avian influenza (HPAI) transmission between wild and domestic waterfowl within China be combining field data, satellite telemetry, remote sensing, and modeling techniques. The project focuses on 2 regions within China: Qinghai Lake, northcentral China and Poyang Lake, southeastern China.
Qinghai Lake, the largest salt water lake in China, is an important breeding ground for colonial nesting waterbirds located on the Qinghai-Tibetan Plateau. Qinghai Lake is strategically located for connecting avian species from multiple flyways and provides breeding and stopover habitat for migrants from southern China, the Tibetan Plateau, Siberia, Europe, and potentially pan-arctic species as well. Qinghai Lake is the location of the largest outbreak of avian influenza in wild birds – in 2005 over 6500 wild waterbirds died from HPAI in an area reportedly devoid of domestic poultry. This event spurred global debate over the potential role wilds play in the spread of HPAI, particularly raising the question if wild birds could migrate with the disease and spread it long distances along migratory corridors.
Poyang Lake is an important wintering ground for wild waterfowl, and an area of intensive free-grazing duck and goose farming. Poyang Lake is the largest fresh water lake in China, and consists of a complex, dynamic integration of rice paddy agriculture and natural wetlands. The potential for wild and domestic bird overlap is high in this region.
1. Examine the migration routes and wintering areas of wild migratory birds captured at Qinghai Lake NRR, China.
2. Examine the movements and virological status of non-migratory wild waterfowl within the Poyang Lake NRR and adjacent agricultural areas.
3. Determine the movements of wild migratory waterfowl away from the Poyang Lake NRR and their virological status to assess potential avian vectors and victims of H5N1 HPAI.
4. Create a geospatial model of HPAI transmission risk between domestic and wild birds in China
We have utilized satellite telemetry to determine wintering locations and migration patterns (timing, routes) for wild waterfowl in China. In 2007 and 2008, 29 bar-headed geese (Anser indicus) and 14 ruddy shelduck (Tadorna ferruginea) were marked at Qinghai Lake. Fifteen migratory ducks (teal, wigeon, garganey) and 16 non-migratory ducks (mallard, chinese spotbill) were marked at Poyang Lake.
Analyses of telemetry data are ongoing. Daily updated maps of telemetry locations can be viewed at:
Bar-headed goose (Anser indicus)
Scott Newman (UN FAO) performing health exam prior to marking, Poyang Lake 2007.
Transmission Risk Modeling
Our project will fill a major gap in knowledge through the creation of geospatial data layers for wild waterfowl and domestic poultry populations at multiple spatial and temporal scales across China. We will use these data layers to produce a spatially explicit model of HPAI H5N1 transmission risk between domestic and wild birds in both winter and summer seasons. By studying the ecological and epidemiological relationships where the disease is currently active, we will be better equipped to frame a response if the disease disperses to North America. We will also begin to understand the role wild avian species play in the year to year perpetuation of the most entrenched HPAI yet experienced in modern times.
Background information on Avian Influenza
The emergence of highly pathogenic avian influenza (HPAI), H5N1, throughout Asia, Europe, and parts of Africa has caused major global concern regarding a potential pandemic as well as serious economic loss within the poultry industry. Avian influenza is an RNA virus of the family Orthomyxoviridae, which includes five genera: Thogotovirus, Isavirus and influenza types A, B, and C. Type A influenza is the most commonly distributed of the group and can cause infections ranging from subclinical to lethal in its hosts. The natural hosts of type A influenza are birds (hence the name, avian influenza or bird flu), although mammals such as humans, horses, pigs, cats, weasels, and seals have also acquired infection from this virus. H5N1, an especially virulent form of type A influenza, emerged in south-east Asia in late 2003 and infected large numbers of domestic chickens, turkeys, and ducks. HPN1 is alarming due to its high virulence in poultry and ability to spread through a number of hosts, including over 40 wild bird species. The currently circulating Asian HPAI H5N1 virus is not easily passed from birds to humans in its present form, and human-to-human transmission is extremely rare. Antigenic shift within this virus could result in efficient and sustained human-to-human transmission causing a worldwide pandemic.
Wild waterbirds, particularly those within the orders Anseriformes (waterfowl) and Charadriiformes (shorebirds and gulls) are the natural hosts and reservoirs for the low pathogenic form of AIV, which is replicated in the intestinal tract, shed through feces, and transmitted via the fecal-oral route. The role of wild birds in the transmission of H5N1 currently remains unclear. It appears the primary mode of spread in Asia has been in the poultry trade, but migratory wild birds are recognized as a secondary source of spread (3 of 21 countries). In Europe, where the disease has occurred more recently, wild birds have been implicated as a primary source of observed outbreaks (20 of 23 countries). In April 2005, the largest known outbreak of HPAI in wild birds occurred in north-central China at Qinghai Lake - an area devoid of domestic poultry. Over 6000 colonial nesting waterbirds died within a two month period, including six percent (3300 birds) of the world’s population of bar-headed geese (Anser indicus), 1300 great cormorants (Phalacrocorax carbo), 930 great black-headed gulls (Larus ichthyaetus), 570 brown-headed gulls (Larus brunnicephalus), and 150 ruddy shelduck (Tadorna ferruginea). As HPAI H5N1 mutates, there is potential for wild birds to survive and distribute the disease locally or along migratory routes. Given the potential for wild birds to contribute to the spread of disease through interaction with domestic poultry in commercial and backyard farms within Asia, it is critical to determine the most likely places for H5N1 transmission.
Online resources: www.nwhc.usgs.gov/disease_information/avian_influenza/
IN THE NEWS“Understanding Global Avian Influenza Transmission Pathways Through Ecology: USGS Maps Possible Transmission Routes for Avian Influenza”, USGS Top Stories Science Pick, September 2011
“Do Wild Birds Play a Role in the Spread of Highly Pathogenic Avian Influenza (HPAI H5N1)?”, GeoHealth Newsletter, Summer 2011
“Migrating Birds May Spread Deadly Virus”, Frontiers In Ecology Dispatches, May 2011
“New Research Suggests Wild Birds May Play a Role in the Spread of Bird Flu”, March 2011
“In China’s Backcountry, Tracking Lethal Bird Flu”, Science News, October 2010