How does the highly pathogenic bird flu virus spread to new countries?
Might the domestic bird trade be responsible? Or is it wildfowl? Since last year, a team from CIRAD has been working on wildfowl. To date, the virus has not been detected in healthy wild birds, but many dead or dying birds have been found near infection foci. Are they victims or reservoirs? In all likelihood the former, but the latter hypothesis cannot be ruled out. Six healthy ducks carrying the virus - out of a total of 4600 tested and in a particularly severely infected zone - were found in China in January 2005.
In 2005 and 2006, migrating birds were often under suspicion. However, their migration corridors and periods did not necessarily correspond to the virus spread patterns seen in recent years. To clarify matters, researchers are now plotting comprehensive, accurate flight plans. To this end, with FAO funding, they are fitting birds with small Argos transmitters. This equipment will provide a large number of data and fill the gaps in information on the subject. Migration has already been studied in detail in Europe and Asia, but this is far from the case in Africa, where monitoring is limited to counting the populations in each country or ringing birds, despite the fact that some five million ducks from Eurasia winter in Subsaharan Africa and there are more than four million African ducks that fly between the different regions of the continent.
In particular, the transmitters will provide information on the number of migration stages and where the birds stop off during migration. In fact, they stop off in humid zones propitious to pathogen transmission, where the different species mix with one another. The study should also provide more general information on migration: travelling times and the ecological and manmade factors that determine the stops.