Phylogenetic Analysis of H5N1 in Suffolk England
Recombinomics Commentary
November 14, 2007
The origins of the recent H5N1 outbreak in Suffolk, England has attracted considerable interest. The outbreak provides additional evidence for the involvement of wild birds in the spread of H5N1 in Europe. The affected population is free-range turkeys which mingle with wild birds on a large ornamental lake on the farm. The recently released OIE report describes the death of 200 turkeys prior to the start of the ongoing cull, indicating the infections were recent since most of the birds died three days ago. The farm has not introduced birds in the past four weeks, further implicating the wild birds that intermingle with the domestic poultry.
However, the most compelling data comes from the sequences of isolates from the farm. Officials from the Department from Environment Food and Rural Affairs have indicated that the H5N1 is most closely related to clade 2.2 isolates from summer outbreaks in wild birds in the Czech Republic and Germany. The German sequences have been described by reports from the Friederich-Loefler Institute. These reports indicate the German isolates are most closely related to isolates from Tyva/Mongolia, which were collected from wild birds (grebes and whooper swans) dying in a massive H5N1 outbreak in the spring of 2006. Although these isolates are part of a larger group that includes isolates from Afghanistan, which is part of a larger group that includes isolates from Russia, Azerbaijan, India, Italy, Iran, the Tyva/Mongolia isolates are clustered on a distinct branch of hemagglutinin or neuraminidase (NA) phylogenetic trees.
As noted earlier, a recent isolate from Krasnodar also maps to the Tyva/Mongolis branch, and that isolate also has NA G743A, although this polymorphism was not present in the 2006 isolates from Tyva/Mongolia, or any of the more distantly related isolates from 2006.
The presence of the Tyva/Mongolia clade 2.2 sub-clade in the turkeys in England therefore adds addition support implicating wild birds in the spread of H5N1 in Europe because the vast majority of isolates in this group were from wild birds in Russia, Mongolia, Germany, and the Czech Republic.
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