Wigeons (Dabbling ducks) – Credit Wikipedia
Although we saw the announcement from the government of the Netherlands on Monday of the discovery of 2 wild ducks (wigeons) carrying the H5N8 avian flu virus, there still are unanswered questions over how the virus ended up in Western Europe – 8 thousand kilometers from where it emerged in Korea last January.
Despite a lack of hard evidence, the most plausible answer right now is via migratory birds who may have shared their Siberian summer nesting grounds with infected birds coming up from China or Southeast Asia.
As you can see by the flyway graphic above (credit FAO), Siberia serves as a confluence for several international migratory bird flyways, providing an plausible environment to disseminate the virus.
This (machine translated) press release from Erasmus University.
H5N8 bird flu virus found in wild birds
On Monday 24 november 2014 are POO H5N8 widgeons in which the avian flu virus samples collected from was encountered. The sampling of wild bird monitoring in the context of H5N8 is a collaboration between the Erasmus MC and the Dutch Institute of ecology (NIOO-KNAW) particularly ducks, geese and swans are tested. Ducks, geese and swans are a natural host of ordinary mild variants of bird flu.
A group of 150 widgeons are 52 poo poo in which two samples samples collected the virus has been detected. The Eurasian wigeons stood on a grassland between Kockengen and Kamerik in the municipality Woerden, Utrecht province. The part of the bird flu virus of the widgeons that is examined, is genetically almost identical to the virus that has previously been found in a poultry farm in hekendorp.
Eurasian wigeons are ducks that especially in the winter come in large numbers in Netherlands for. More than 60% of the Northwest – European population wintering in Netherlands. It is expected that the wintering numbers of widgeons still in the next month will increase. The largest numbers of widgeons are observed in wetlands in the West, but also more to the East along the great rivers of Netherlands. Recently, the bird flu virus found in a Germany H5N8 teal. Will be more intensively in Netherlands teals also tested for the presence of H5N8 avian flu virus.
Or the virus also occurs at other wild bird species is still being investigated. The past few weeks have more than a thousand birds tested for the presence of bird flu H5N8. In sampled wild ducks, teals, pintails, shovellers, krakeenden, greylag geese and mute swans H5N8 avian flu virus was not detected.
More research is needed to find out how often the virus is common among H5N8 widgeons and other wild birds. In the presence of Eurasian wigeons H5N8 indicates that there should be additional attention in poultry holders regarding the hygiene to prevent further outbreaks and incursions. It does not make sense to take measures with regard to populations widgeons and other wild birds.
The detection of the virus in Eurasian wigeons has no direct impact on public health. The virus is not found in people who have had close contact with infected poultry.
The following excerpts come from a report posted today by the Netherlands Institute of Ecology:
How did the virus reach the Netherlands?
The answer to this and related questions is as yet unclear. Bird flu can be spread through the transport of poultry, poultry products and fertilizer, as well as by wild birds - both migratory and resident. The evidence so far does not point to any single route the virus might have travelled.
Without certainty on this point, it is extremely difficult to take effective measures both now and in the longer term.
Teal in Germany
On the German island of Rügen, six wild ducks were tested for bird flu that had been shot some 50 kilometres away from an outbreak on a turkey farm. Three turned out to have been healthy, two carried mild strains of the virus and one - a teal - was infected with H5N8. This German teal was the first wild bird in Western Europe confirmed to be a carrier, although the fact that it was flying around normally seems to suggest it wasn't very ill.
The German discovery does not settle the question of how H5N8 spread to Europe: the sick teal could have become infected through 'spill-back transmission' (see above). It is worth noting that no traces whatsoever of H5N8 bird flu have been found in samples from duck decoys as part of regular Dutch and European monitoring programmes.
Wild birds from Southeast Asia do not migrate to Western Europe. Their main point of contact with 'our' migratory birds is when both groups stop over in their breeding grounds in Siberia. It is possible that H5N8 was transmitted there, and that it reached Europe through some kind of relay involving more than one species of bird.
Samples from waterbirds in the Arctic have so far not produced any evidence of widespread infection, past or present. But monitoring in this area would need to be stepped up significantly before any conclusion can be reached.
Latest research into infection among wild birds
If migratory or other wild birds are indeed responsible for spreading H5N8, it should not be too hard at this stage to find traces of the virus in nature. That is why research teams from the Erasmus MC, NIOO-KNAW, the Centre for Avian Migration and the Dutch Centre for Field Ornithology set to work right away after the outbreak, taking samples from the surrounding area and analysing them.
NIOO-researchers have mainly collected fecal samples from mute swans, Bewick's swans and various species of ducks. They have also taken throat and cloacal swabs from mute swans, as well as some blood samples.
On 1 December, deputy Economic Affairs minister Sharon Dijksma announced that feces of two wigeons near Kamerik (province of Utrecht) were found to contain traces of H5N8 bird flu.