In the wake of yesterday’s report that credited the Brown Headed Gull with spreading the H5N1 virus from China and Tibet down to Thailand, we get another study that minimizes the impact that migratory waterfowl may have in spreading the virus across long distances.
The study appears in the British Ecological Society's Journal of Applied Ecology, and claims that the global spread of the H5N1 virus through migratory birds is possible . . . but unlikely.
By studying 19 species of waterfowl, and making assumptions as to how long they may be able to carry the highly pathogenic H5N1 virus asymptomatically, these researchers say that there is a `limited window of opportunity’ for the virus to be spread over long distances by migratory waterfowl.
The press release may be read at:
The entire study is available for viewing at the link below:
Potential spread of highly pathogenic avian influenza H5N1 by wildfowl: dispersal ranges and rates determined from large-scale satellite telemetry
- Nicolas Gaidet, Julien Cappelle, John Y. Takekawa, Diann J. Prosser, Samuel A. Iverson, David C. Douglas, William M. Perry, Taej Mundkur, Scott H. Newman
Although a lengthy study, the bottom line is summed up by points 3 & 4 of the author’s summary:
3. Our results indicate that individual migratory wildfowl have the potential to disperse HPAI H5N1 over extensive distances, being able to perform movements of up to 2900 km within timeframes compatible with the duration of asymptomatic infection.
4. However, the likelihood of such virus dispersal over long distances by individual wildfowl is low: we estimate that for an individual migratory bird there are, on average, only 5–15 days per year when infection could result in the dispersal of HPAI H5N1 virus over 500 km.
These results are based, of course, on a limited number of species, and calculations are predicated on assumptions based on the pathogenesis of HPAI in captive birds.
While likely not the last word on the subject, this study offers new insight into the potential of intercontinental spread of HPAI via migratory waterfowl.