#5639
Wild water birds (ie. duck, geese, swans, terns, gulls) are the natural reservoir for avian influenzas (including, but not limited to H5N1), and unlike many terrestrial species, can often carry the virus with little or no ill effect.
Avian influenza is primarily a gastrointestinal infection among birds, and it can be spread through virus laced feces deposited in shared ponds and lakes.
The role of wild birds in the spread of bird flu is not without its controversy. Over the years we’ve a number of studies that either implicate migratory birds in the spread of the virus, or minimizes their role.
In September 2010 (see Another Migratory Bird Study) a paper appeared in the British Ecological Society's Journal of Applied Ecology, that claimed that the global spread of the H5N1 virus through migratory birds was possible . . . but unlikely.
In a blog from 2009, called India: The Role Of Migratory Birds In Spreading Bird Flu I wrote about an article entitled Scientists rule out spreading of bird flu by migrant birds in India from Xinhua News.
And in January of 2008, Reuters carried a report called: Don't blame wild birds for H5N1 spread: expert
Despite these dissenting opinions, there have been plenty of other reports that strongly associate migratory birds with the spread of the virus.
A few include:
Korea: Migratory Birds Behind Spread Of H5N1
EID Journal: H5N1 Branching Out
Japan: Hooded Crane Positive For H5N1
FAO: On The Trail Of Avian Influenza
Despite overlapping migratory flight paths, avian strains common in Eurasian birds have yet to appear in North America. Monitoring continues in every year, however.
Which brings us to a fascinating bit of research presented as a doctoral thesis by Ms Yali Si, a graduate student at the University of Twente in the Netherlands.
Using satellite imagery and field tests, Yali Si has worked to determine which grasslands are more likely to attract water birds to feed. She found that the age and quality of the grass affects selection by migratory birds.
Using this information, she has produced risk maps of Europe showing the areas most likely to visited by wild water birds, and therefore most vulnerable to the spread of avian flu.
While demonstrating the feasibility of this method, Yali Si states that additional study will be needed to refine the system and the resultant maps.
For more on this, we have a press release from the University of Twente, and a link to the thesis.
First the press release:
Satellite images to combat avian flu
The entire 139 page PDF of her thesis is available at http://www.itc.nl/library/papers_2011/phd/yalisi.pdf
As the author points out, global environmental change (including climate and land use) has the potential to shift migratory and nesting behavior of wild water birds.
Through the use of GIS (geographic information systems), remote sensing (primarily satellite data), and new spatial techniques scientists will be better able to predict where the avian influenza threat is likely to be the highest.
Which ought to give researchers a better idea where to test for the arrival of new avian viruses, and could serve as a warning to poultry producers of when and where to beef up their biosecurity.
