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News & features archive, 2011

HPAI local persistence and long-distance dispersal is studied


21 January 2011 - Since late 2003, H5N1 highly pathogenic avian influence (H5N1 HPAI) has caused outbreaks primarily in poultry across Africa, Asia and Europe, with wild bird outbreaks most frequently documented in the central Asia flyway and parts of the African-Eurasian flyway. H5N1 HPAI has persisted over several years in many areas and, as of 2011, five countries are considered endemically infected. Viral persistence poses a threat to animal (domestic and wild) and human health, as well as impacting livelihoods and food security of millions of people.

While it has been empirically demonstrated that H5N1 HPAI risk in Southeast Asia is related to domestic ducks grazing openly in rice agricultural systems and human densities, relatively little is known about the interplay between persistence and dispersal. In fact, a hypothesis that had never been studied is that the global persistence of H5N1 HPAI results from the interplay between the high capacity to persist in domestic poultry in localized areas and sporadic long-distance introduction events through migratory birds.

To test this hypothesis, an international team of research scientists from Asia, Europe and the United States expanded previous work on geospatial risk analysis to include South and Southeast Asia, as well as integrating migration ecology data from satellite-tracked wild waterfowl along the Central Asia flyway. Their work and conclusions have been outlined in a journal article titled: “Flying over an Infected Landscape: Distribution of Highly Pathogenic Avian Influenza H5N1 in South Asia and Satellite Tracking of Wild Waterfowl” to be published in EcoHealth.

Briefly, through satellite tracking of Ruddy Shelduck (Tadorna ferruginea) and Bar-headed Geese (Anser indicus), the results from this investigation reveal a direct spatial-temporal relationship between areas identified at highest H5N1 HPAI risk in India and Bangladesh and the wild bird outbreaks that occurred in China from May to July 2009. Furthermore, it points out that domestic duck populations are the main factor delineating areas at risk of H5N1 HPAI spread in domestic poultry is South Asia, thus confirming what was found to be the case in Southeast Asia.

This study underscores the potential for integrating H5N1 HPAI risk modeling with wild waterfowl migration ecology data to map and track hotspots, introduction, persistence and spread of this disease along the Asian flyways. Also, it provides supporting evidence that the dynamics of continental disease transmissions are hinged on a number of persistence areas where large numbers of domestic ducks reside, connected with sporadic transmission through migratory waterfowl.

As the Food and Agriculture Organization of the United Nations (FAO) and its partners move forward with its unwavering support to the ‘One Health’ approach, this type of studies prove to be critically essential to link pernicious emerging diseases with animal populations, husbandry practices, people and agroecological regions around the world.