The outbreak of avian influenza among Mute Swans in Southern Europe is most likely to have been caused by swans coming from Eastern Europe. Infected swans from the same south-east European population (see attached chart) were already detected in the Caspian and Black Sea region in November and December.
The migration of this population is dependent on the severity of winter weather in the east of their wintering range, and the exceptionally cold weather in January in these regions has caused a more extensive migration than usual. Individuals, including infected swans from this population moved to the southern and western borders of their wintering range into Greece and southern Italy. There is certainly very unlikely to be a link with the recent outbreaks in Nigeria.
The possibility of a further spread in the EU depends at least partly on the actions taken by EU-governments. As long as the infection stays within these swan populations, it will probably remain in some wetlands areas and die out soon. Infected swans die within days.
A danger and a worry is that of transmission of the virus by swans to other, migratory waterbird species. Mute Swans mix readily with other waterbird species and large numbers of waterbirds will be moving north and east through southern Europe in March and April. The wild Mute Swans of this population don’t normally visit parks and cities like the swans in Western Europe, which makes dissemination to domestic birds a relatively low risk. However, if the infected swans are disturbed and fly to other areas or if they are able mix with domestic birds, a rapid further dissemination by poultry transport might occur, as appears to have happened in Turkey.
It would be advisable for The EU to
1) install an effective surveillance system for mortality in wild and domestic birds. Unusual mortality should be investigated immediately.
2) Minimise disturbances of wild birds, such as hunting, as it will make the birds fly to other areas.
3) Prevent any contact between wild and domestic birds; for instance by regulations regarding free range poultry.
4) Control all transport of poultry and poultry products in regions around outbreaks.
In this light, bans on keeping of poultry out of doors, transport bans an hunting bans are all wise precautions which will help to combat a further spread.
As these measures have huge implications for society, implementation of such policies should be considered in consultation with the animal health sector and with the hunting, transport and poultry sectors affected.
Programme manager avian influenza
+31 (0)6 50601917
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Wetlands International is a global organisation that monitors the migration of millions of waterbirds annually. At this moment, the organisation conducts several programmes fro the EU and FAO to understand the possible spread of the avian flu among wild birds.
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