Commentary
H5N1 Swan Surveillence in England Raises Concerns
Recombinomics Commentary 12:36
June 13, 2008
BIRD flu tests will be carried out today on seven swans found dead in a river near Caernarfon.
The carcasses were discovered floating in the Seiont not far from the town’s historic castle.
Locals alerted harbour master Richard Jones on Wednesday, and his team recovered three dead swans in the morning, followed by four more in the afternoon.
Yesterday the team were back at the riverbank after residents reported another swan appeared to be ill.
Mr Jones said he was initially advised by Defra that the government would not test for bird flu in cases involving less than 10 dead wild birds.
He was advised to safely bag up the birds in black bin liners and throw them into a waste bin.
The above comments raise additional concerns regarding H5N1 surveillance. The lack of testing and reporting has been a concern for the past several years, and recently has received additional attention due to Indonesia’s comments on reducing reporting frequencies on human H5N1 infections. Although this announcement has received a great deal of attention, the under-reporting of H5N1 in birds and humans is widespread.
England has a surveillance program, but as noted above, the level of testing is a major concern. When H5N1 reports were widespread in western Europe in early 2006, England reported one H5N1 positive swan that washed up on the shores of Scotland. That isolate was closely related to H5N1 detected in Sweden, Denmark, and northern Germany, suggesting that the level of H5N1 in England was significantly higher than the one reported positive.
More recently England has had confirmed outbreaks in free range turkeys in Suffolk as well as the Abbottsford swannery. The reports of H5N 1 positive wild birds in the vicinity of the swannery extended over two months and involved 10 swans and a Canada goose (see satellite map). The limited reporting on the sequences of the first four isolates indicated the isolates were all clade 2.2.3, but there was considerable genetic diversity, indicating the swans were infected through multiple H5N1 introductions. The swans were collected individually under an enhanced surveillance program, and none were linked to clusters of 10 or more wild birds.
The testing requirement of 10 or more wild birds significantly limits testing. Many of the H5N1 positive birds in Europe have been swans, due in part to their size which leads to easy identification on an unusual event. The initial instructions to simply discard the carcasses raises serious questions about the surveillance program, which has had limit success in detecting H5N1 or H7 in wild birds in England.
The flawed surveillance programs remain causes for concern.
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