H5N1 Confirmed in Fourth Swan in England
Recombinomics Commentary 11:11
January 17, 2008
A fourth swan has tested positive for the H5N1 strain of bird flu, the Department for Environment, Food and Rural Affairs said yesterday.
Defra said the infected mute swan had been collected on January 11 as part of wild bird surveillance in the area.
The Environment Department said there was currently no evidence to suggest the disease was widespread among wild birds in the area, but enhanced surveillance was taking place.
The above comments describe confirmation of a fourth H5N1 infected swan in the Dorset area (see satellite map). The earlier positives included swans collected in December, indicating infected swans have been detected over a two week period, which is evidence of widespread infection among wild birds.
Two of the positives were in swans that had been recent euthanized. One had a broken leg. Detection of H5N1 in live wild birds is rare, but these positives may have been linked to increased levels due to stress in the injured birds, coupled with collection procedures, which involved freezing the birds shortly after they were euthanized.
Prior to the recent four positives, the DEFRA surveillance program had detected H5N1 in a single wild bird, a whooper swan that washed up on the shores of Scotland in 2006.
Earlier media reports had suggested that the current outbreak in mute swans was due to a recent introduction. However, the failure to find wild bird sources for the H5N1 outbreak in free range turkeys in Suffolk, as well as H7N3 and H7N2 outbreaks in the same region in 2006 and 2007, signals caution in the interpretation of negative data generated by the surveillance program.
The H5N1 outbreaks in Germany, France, and the Czech Republic over the summer signaled increased activity in H5N1 in late 2007, early 2008 in Europe. England now has had two outbreaks, and sequence data indicates that the outbreaks are due to independent introductions of the Uva Lake strain. That strain has become dominant and accounts for 2007 outbreaks in the Czech Republic, Germany, France, Krasnodar, Romania, Poland, and probably Rostov.
Expanded testing of the mute swans in the region, including antibody testing, would be useful.
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