Wild Birds as Qinghai H5N1 Victims in Germany?
Recombinomics Commentary
June 25, 2007
Statements from proponents and opponents of the role wild birds might
play in the epidemiology of H5N1, are expected:
- Do these German cases reflect a self-sustained infection evolving
within wild bird populations, or have they been infected from
commercial poultry?
- Is the Nuremberg event related, directly or indirectly, to the
recent outbreak in a commercial turkey flock in the Czech Republic?
- Was the source of infection there contact with wild birds or the
other way around (namely, initial Czech infection originating from
infected commercial poultry elsewhere, subsequently infecting wild
birds)?
The above Promed comments appear to be another variation on the migratory birds as victims story widely circulated by various wildlife conservation groups. This story, along with the “dead birds don’t fly” corollary were popular in 2005 after H5N1 was discovered in long range migratory birds at Qinghai Lake in May, 2005. The Qinghai strain was novel and easily tracked, so the “dead birds don’t fly” argument was not viable a few months later when H5N1 infections were reported for the first time in Russia, Kazakhstan, and Mongolia. All three outbreaks involved the Qinghai (Clade 2.2) strain, clearly indicating that H5N1 could be transported and transmitted by migratory birds over long distances.
However, Promed continued posting articles and commentaries suggesting that the H5N1 in poultry was somehow changed, and wild birds became victims of the more virulent H5N1. However, the publication of the H5N1 sequences from a healthy crested grebe in Novosibirsk in 2005 effectively eliminated that argument also.
For those who could not read a gene sequence, the subsequent migration of Qinghai H5N1 to approximately 50 countries in Europe, the Middle East, and Africa effective removed all doubt. None of these countries had previously reported the “Asian” versions of H5N1, which had been circulating in eastern Asia, including China, since 1996. After H5N1 was reported in long range migratory birds at Qinghai Lake, every reported outbreak west of China involved the Qinghai strain. The H5N1 went from Qinghai Lake in China to Erhel Lake in Mongolia and Chany Lake in Russia. The H5N1 then migrated to the Volga Delta, the Danube Delta, and the Nile Delta. Each outbreak involved wild birds and the H5N1 subsequently spread throughout Europe, the Middle East, and Africa. In many countries in Europe, wild bird infections were the only reported infections. In countries that did report H5N1 in poultry, the farm infections were preceded by detection of H5N1 in dead wild birds.
The “dead birds don’t fly” and “migratory birds as victims” stories had been largely discounted, but many still cling to the spread by trade and smuggling. Although there is undoubtedly some short range spread due to legal and illegal movement of domestic poultry or exotic birds, the only convincing example of long range spread was the linkage between H5N1 in Hungary and England, based on the close similarity between isolates from both countries and one commercial operation with facilities in both countries.
However, smuggled eagles detected in Belgium in 2004 did not lead to any reports of Clade 1 infections in wild birds or poultry in any location outside of southeast Asia, and H5N1 detection in exotic birds quarantined in England in 2006 did not lead to any reports of Clade 2.3 infections in wild birds or poultry outside of eastern or southeastern Asia.
The recent questions in the Promed commentary would seem to have been already answered by the description of the turkey farm in the Czech Republic, which was closed and did not involve free range turkeys, reducing the likelihood that the turkeys infected the wild birds in the Czech Republic, which then infected the wild birds in Bavaria.
Instead, the finding of H5N1 in non-migratory wild birds in the summer in Germany suggests that H5N1 has become endemic in the region, and an increased level in the infected birds led to their death and discovery in Bavaria.
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