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H5N1 Confirmed in Fifth Swan in England
Recombinomics Commentary 09:11
January 20, 2008
A fifth swan at a sanctuary in Dorset has tested positive for the virulent H5N1 strain of bird flu, environment department Defra has said.
Mr Houston said: "There are still four or five dead swans which have been picked up - and for which there are no test results as of yet."
The above comments describe the fifth confirmed H5N1 swan in Dorset, England (see satellite map). Although media reports indicate H5N1 in not widespread in the area, the above average death rate coupled with five confirmed positives over a three week period, suggest that H5N1 is widespread.
Prior to the recent outbreak, Defra had detected H5N1 in one wild bird over a two year period. The whooper swan was found on the shores of Scotland in 2006. Although the H5N1 was closely related to H5N1 circulating in northern Germany, Sweden, and Denmark, the DEFRA surveillance system only detected on positive wild birds. The program also failed to detect H5N1 in wild birds associated with the earlier outbreak in Suffolk in free range turkeys. Thus, the detection of five positives in three weeks signals widespread infections in the wild bird population.
Detection of H5N1 in wild birds has been difficult. No healthy wild birds have tested positive. Although two of the first three H5N1 positives were in euthanized swans, these samples were collected under favorable conditions, which included swans frozen short after they were euthanized. Swans that die in the wild decompose, which reduces H5N1 detection. Two of the recent dead swans were not tested because of decomposition issues.
The H5N1 levels in two positives from the euthanized birds may have also been elevated because of stress. The Qinghai strain of H5N1 has E627K, which is linked to optimal replication at 33 C. The body temperature of birds is 41 C, so factors which lower the bird’s body temperature will increase H5N1 levels.
Currently, swans are dying at approximately one per day, which is above normal because temperatures in the area have been warmer than usual. Therefore more H5N1 positives swans are expected.
Recombinomics Paper at Nature Precedings