Thursday, November 02, 2006
Study fingers migrating ducks in bird flu spread
WASHINGTON, Nov 2 (Reuters) - Migrating ducks, geese, and swans spread the H5N1 bird flu virus from Russia to Romania, Turkey and Ukraine, researchers said on Thursday.
A careful analysis of the spread of the virus from central Asia into eastern Europe in the autumn of 2005 shows that wild birds, especially mallard ducks, were the chief spreaders of the virus.
“We conclude that the spread of (highly pathogenic avian influenza) H5N1 virus from Russia and Kazakhstan to the Black Sea basin is consistent in space and time with the hypothesis that birds in the Anatidae family have seeded the virus along their autumn migration routes,” the researchers wrote in the journal Emerging Infectious Diseases.
Anatidae include geese, ducks and swans, some of which are killed by H5N1, and other species of which often show no ill effects from the virus but which can spread it. Mallard ducks are the main suspect.
Marius Gilbert of the Free University of Brussels and colleagues used satellite data to figure out the start of the autumn migration, and plotted known seasonal migration pathways against the actual outbreaks of H5N1.
They noted that adult birds can transmit the virus easily to juveniles during the molting season, when they cannot fly, and also noted that the virus can survive in cold standing water—where many species of birds congregate while molting.
“The initial outbreaks of (highly pathogenic) H5N1 virus in Romania, Turkey, and Ukraine occurred close to wetlands frequented by overwintering migratory waterfowl,” they wrote.
“These locations were clearly far from any known location where ... H5N1 virus had been recorded, while the timing and location match the autumn wildfowl migration ahead of the approaching wave of frost.”