HPAI outbreaks along the East Asian flyway are related to latitude and poultry density, not to core migration corridor or wetland habitats
| 01 April 2010 ľ A recently published study that uses a newly developed Brownian bridge spatial analysis methodology found that highly pathogenic avian influenza (H5N1 HPAI) outbreaks reported along the East Asian flyway were related to latitude and poultry density but not to the core migration corridor or to wetland habitats used by migratory waterfowl. These findings suggest that there are temporal mismatches between the timing of reported outbreaks and wild duck movements.
Given that the Guangdong province in China has been pinpointed as the epicentre of H5N1 HPAI, it was deemed critical to better understand disease transmission dynamics between wild and domestic birds in this area. Poyang Lake is the largest freshwater body in China and it lies within the East Asian flyway. This lake is situated near Guangdong and represents a migratory corridor as well as a significant congregation site for waterfowl. Herein there are surrounding rice fields and free-grazing poultry flocks that interact with wild waterfowl, a situation that has been said to be largely conducive to avian influenza transmission across the poultry-wildlife sectors.
Scattered yet recurrent reports of H5N1 HPAI in healthy wild ducks at Poyang Lake, Qinghai Lake, and other locations globally, have raised concerns about the potential of resilient free-ranging wild birds to disseminate the virus over short and long distances. However, the lack of information about the migratory ecology of wild ducks has hindered understanding of the role these birds play in connecting regions that host and report H5N1 HPAI outbreaks throughout Asia.
In view of this information deficit, during 2007 and 2008, a group of research scientist from different countries mounted satellite transmitters on wild ducks at Poyang Lake to examine the location and timing of spring migration and to identify any spatiotemporal relationship with H5N1 HPAI outbreaks reported in this area.
The study included wild duck species such as the Eurasian wigeon (Anas penelope), the northern pintail (Anas acuta), the common teal (Anas crecca), the falcated teal (Anas falcata), the Baikal teal (Anas formosa), the garganey (Anas querquedula), the mallard duck (Anas platyrhynchos), and the Chinese spotbill (Anas poecilohyncha), a group of waterfowl that could play a role in transmission, based on their ability to serve, in general, as reservoirs of low pathogenic avian influenza viruses .
Satellite signal-based tracking maps indicate that these wild ducks [excluding the last two species] followed the East Asian flyway along the Chinese East coast to breeding areas in Northern China, Eastern Mongolia, and Eastern Russia yet none migrated West toward Qinghai Lake [the site of the largest wild bird epizootic], thus failing to demonstrate any relevant migratory connection to the Central Asian flyway.
Data analyses used novel approaches to integrate ecological information to better inform epidemiological investigations seeking to explain, predict and understand the spread of avian influenza viruses. The Emergency Centre for Transboundary Animal Diseases (ECTAD) at the UN Food and Agriculture Organization (FAO) will continue to actively collaborate with national governments, research centres, diagnostic laboratories, and universities to further elucidate the dynamic evolution of transboundary diseases in diverse ecological landscapes that include wildlife, livestock and people.
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