Large H5N1 Cull in Suffolk England
Recombinomics Commentary
November 22, 2007
Officials will cull a total of 68,000 birds on Grange farm at Hinderclay Road, Redgrave - 56,000 ducks, 9,000 turkeys and 3,000 geese.
Mr Buchanan said that the flocks have been declared a “dangerous contact” because the five seasonal workers who operated the Redgrave Park, Grove, Hill Meadow, Stone House and Bridge farms were lodging in a mobile home on Grange farm.
Redgrave Poultry, a sudsidiary of Woodbridge-based Gressingham Foods, moved the workers in to a local bed and breakfast on Tuesday last week, as per Defra's guidelines to minimise movements on to and off farms.
The above detail describes the circumstances surrounding the largest cull in the H5N1 outbreak in Suffolk. Although no H5N1 positives were found at the Grange farm, all birds at the farm were culled because of a “dangerous contact”. This cull was based on past experiences, which show that false negatives can be generated in H5N1 testing.
Although the index farm, Redgrave Park, tested positive, the closest farm (see satellite map), Grove Farm tested negative, even though there were dead turkeys on the farm. Similarly, Hill Meadow tested positive, even though positive birds at the farm were clinically healthy.
The reported positives have been limited to turkeys, which may be linked to the sensitivity of the test. DEFRA, like most agencies, has failed to detect H5N1 in live wild birds, even though H5N1 in dead and dying wild birds have been widely reported, including the strain in England, which is closely related to isolates from wild birds in Germany, France, and the Czech Republic.
Consequently, culls were carried out at five “dangerous contact” farms, even though H5N1 was confirmed on only one, and warnings have been issued for wild birds, even though H5N1 has not been detected in wild birds. The only H5N1 positive wild bird detected by DEFRA was in a swan that washed up on the shores of Scotland. However, at that time H5N1 was being detected in dead and dying wild birds in Denmark, Sweden, Germany, and France, strongly suggesting that H5N1 in Great Britain extended beyond the one positive in April, 2006.
Although negative results have little value, positive results frequently lead to sequence data and the isolation of the H5N1 virus. Isolation allows for full sequencing, which then creates very reliable data on the genetic origins of the virus. Such analysis has shown that the strain in England is related to outbreaks in multiple countries in Europe over the summer, as well as a more recent outbreak in Krasnodar. The complete sequence of the Krasnodar isolate has been made public, and like the descriptions of the isolates in Europe, is most closely related to H5N1 from a massive outbreak in the summer of 2006 at Uva Lake in Mongolia and adjacent regions in Tyva in southern Siberia in Russia.
In that outbreak, sequences from multiple H5N1 isolates from grebes, swans, and golden eyes were made public and these isolates form a distinct branch on the clade 2.2 (Qinghai strain) phylogenetic tree. All H5N1 west of China has been the Qinghai strain, although continued evolution has created multiple sub-clades of clade 2.2.
Such analysis shows that the vast majority of H5N1 outbreaks west of China are caused by multiple independent introductions of H5N1 from wild birds.
Media Links
Recombinomics Presentations
Recombinomics Publications
Recombinomics Paper at Nature Precedings