Endemic Asymptomatic Qinghai H5N1 in Europe
Recombinomics Commentary
October 25, 2007
"It seems that a new chapter in the evolution of avian influenza may be unfolding silently in the heart of Europe," Joseph Domenech, chief veterinary officer of the Food and Agriculture Organization (FAO), said in a statement.
The statement came after German scientists detected H5N1 in dead domestic ducks which had appeared to be healthy.
"Europe should prepare for further waves of avian influenza outbreaks, most probably in an east-west direction, if the virus succeeds in persisting throughout the year in domestic waterfowl," Domenech said.
FAO veterinary experts said they were particularly concerned about the Black Sea area where a high concentration of chickens, ducks and geese is comparable with virus-entrenched Asia.
The above comments acknowledge that the Qinghai strain of H5N1 can asymptomatically infect domestic waterfowl, but once again attempt to discount the role of wild birds in the “silent” spread. The comments mimic those of WHO in the fall of 2004, when H5N1 isolated from a fatal human case in Vietnam was used to experimentally infect domestic ducks. Although the H5N1 was fatal to humans, the lab infected ducks were asymptomatic or had mild symptoms, yet they excreted high levels of H5N1. Thus, clade 1 could be spread by asymptomatically infected domestic birds. Subsequent testing also found H5N1 in asymptomatic chickens.
The natural host for H5N1 is waterfowl, and healthy wild birds carry H5N1 antibodies, signaling non-lethal infections. Detecting Qinghai H5N1 in live healthy birds has be technologically challenging, but isolates or sequences have been obtained from healthy wild birds in Russia and Egypt. These isolates were virtually identical to Qinghai H5N1 found in dead and dying wild and domestic birds in countries west of China, including those in Europe, the Middle East, and Africa.
The detection of H5N1 in asymptomatic ducks in Germany was precipitated by major outbreaks in Germany over the summer, which supported the conclusion that H5N1 was endemic in wild birds in Europe.. The number of wild birds infected approached the numbers reported in early 2006. However, the more recent outbreaks represented a number of independent introductions of H5N1 that were most closely related to H5N1 that had previously been isolated in wild birds, including grebes in Tyve and Mongolia. Most of the positives in Germany were also grebes, and the large numbers led to additional testing on farms. Positives in Bavaria led to testing on farms that were commercially linked to the positive farm, which led to detection of H5N1 in asymptomatic birds.
The testing of the domestic birds included testing for H5N1 antibodies, which isn’t done by various conservation groups which regularly report negative data in wild birds to support the “dead birds don’t fly” mantra used to discount the role of wild birds in the transportation and transmission of H5N1.
The Black Sea area is home to high concentrations of migratory waterfowl in the fall.
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