14.02.2017

The detection of HPAIV H5N8 in 26 European countries (listed chronologically by date of report: Hungary, Poland, Croatia, Switzerland, Austria, Germany, Denmark, the Netherlands, Sweden, Finland, France, Romania, Serbia, Great Britain, Greece, Bulgaria, Montenegro, Slovak Republic, Italy, Ireland, Czech Republic, Slovenia, Spain, Portugal, Macedonia, and Belgium) and the rapid distribution of the virus indicate a further highly dynamic spatial spread of the infection. The number of cases reported from various parts of Europe increases daily; often also birds kept in zoological gardens and animal parks are affected. In Germany, the case numbers in wild birds and the number of outbreaks in bird holdings (69) have reached an unprecedented level.
WILD BIRDS
While in the 2014/2015 outbreak HPAIV H5N8 was only sporadically detected in healthy appearing wild birds (three mallard ducks, one common teal and one sea gull), currently a large number of dead water birds and carrion-eating birds of prey, e.g. buzzards, white-tailed eagles and sea gulls, is found. So far, the virus has been detected in 47 different bird species including species belonging to the categories diving ducks, grebes, sea gulls, swans, in isolated cases dabbling ducks (mallard duck), geese, birds of prey and also carrion-eating songbirds (e.g. crows). The fact that HPAIV H5 has also been detected in healthy water birds or in their feces leads to the assumption that wild birds can excrete the virus without developing disease or dying. It must be concluded that there is an ongoing HPAI H5N8 epidemics among wild water bird species and that the dead birds found possibly represent no more than the tip of the iceberg.
Infected but asymptomatic wild birds as well as birds during the incubation period continue to be mobile virus carriers. Many water bird species (e.g. geese, swans, some duck species) move between cropland (particularly grassland, maize stubble and winter rapeseed and grains) where they feed during the day and waterbodies where they rest during the evening and night. They can excrete the virus with the feces and contaminate the respective surfaces and waterbodies. Furthermore, predators (mammals such as foxes and martens, but also birds of prey and crows) may break up carcasses of dead waterfowl and carry away parts of the carcasses or inner organs with high virus loads, thus causing a considerable contamination of the environment. Persons and vehicles accessing contaminated areas may spread the virus and introduce it into poultry holdings.
If the frosty weather continues, further dynamic migratory movements of birds must be expected. Most water bird species flee from the cold, i.e. they move to ice-free waterbodies. Such weather conditions can lead to a spread of the infection among wild birds in inland areas and in Southern Europe.
POULTRY AND ZOOS/ANIMAL PARKS
In Germany, HPAIV H5N8 so far has been introduced into 54 poultry holdings and 15 zoos/animal parks. Almost all of these holdings are located in areas where increased numbers of dead HPAIV-positive water birds have been found. In the affected animal parks, mostly water birds with possible contact to wild waterfowl were affected. In most poultry holdings, direct or indirect introduction via contaminated material (shoes, vehicles, objects) is the most likely route of infection. The risk of introduction by purchased poultry, feed and drinking water has been negligible in all outbreaks investigated epidemiologically by the FLI. Most outbreaks in affected holdings were primary outbreaks which did not spread any further; three cases however are highly likely to be secondary outbreaks. In all locations where contacts between wild birds and domestic poultry are possible infections can be introduced and distributed and new sources of infection can develop.
PHYLOGENETIC ANALYSES
Genetic analyses show a similarity