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Northern Germany: sea eagle infected with highly contagious bird flu virus
The highly contagious avian influenza virus H5N8 was found in several sea eagles found in northern Germany. The deadly infections pose new challenges for the protection of the threatened birds of prey.
Infected sea eagles found
In winter 2016/2017 there were numerous deaths of sea eagles in northern Germany, in which lead poisoning or a collision with a train could be excluded as causes of death. Instead, 17 sea eagles found in Mecklenburg-Western Pomerania, Schleswig-Holstein, Lower Saxony and Hamburg were infected with the highly contagious bird flu virus H5N8, reports the Friedrich-Loeffler-Institute, Federal Research Institute for Animal Health (FLI) in a current release.
First cases of bird flu in threatened birds of prey
This was demonstrated by Oliver Krone from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), Timm Harder, Franz J. Conraths, Reiner Ulrich and Martin Beer from FLI and other colleagues.
According to the information, the deadly infections with the virus strain H5N8 2.3.4.4b are the first cases of avian influenza in sea eagles and pose new challenges for the protection of the threatened birds of prey.
The study was recently published in the journal "Viruses".
Threat that has been going on for several decades
Avian flu has been threatening wild birds and poultry for several decades. Chickens, geese and ducks as well as other water birds are particularly affected by infections with different strains of the influenza A virus.
Epidemics keep occurring, for example in 1992 in Mexico, 2006 in Central Europe, 2015 in the USA and 2016/2017 again in Europe.
In Germany, tens of thousands of chickens have therefore often had to be culled.
So far, white-tailed eagles (Haliaeetus albicilla) seem to have been spared from infections, although infections have already been detected for individual birds of prey such as the peregrine falcon or the common buzzard.
The investigations of the 17 white-tailed eagles found in northern Germany - 14 of them were already dead and three more showed strong symptoms such as overexcitability and difficulties with coordination - now showed that white-tailed eagles can also become infected.
Analysis of the genetic makeup of the viruses showed that it was not the widespread influenza type H5N1, but the type H5N8.
In addition, by fully elucidating the viral genome, the scientists identified virus strain 2.3.4.4b, which is considered to be highly aggressive for birds.
The virus can cause inflammation of the brain (polioencephalitis) in the animals. Measurements of the lead concentration in the kidney and liver of the sea eagle previously excluded lead poisoning as the cause of death.
Susceptible to infectious diseases
The northern German lowlands and the German Baltic coast are the central habitat of sea eagles in Germany. Its distribution area extends to Greenland in the west and Japan in the east. There are currently 750 breeding pairs in Germany.
In the second half of the 20th century, it was almost exterminated by human persecution and the effects of the DDT insecticide. Stocks have been recovering since the 1980s after the persecution was stopped and DDT was banned.
New threats emerged, such as poisoning from leaded ammunition. The animals are also susceptible to infectious diseases: "Especially in winter, sea eagles feed on carrion and, if available, also water birds," says Oliver Krone from Leibniz-IZW.
“Of course, sick and weak animals are easy prey for the sea eagle. As a result, these birds of prey repeatedly expose themselves to viruses and other pathogens. "
A few more questions unanswered
There are still some unanswered questions for the scientific team, which are now the subject of further research.
For example, it is still unclear why the H5N1 epidemic in 2006 apparently showed no infections in sea eagles and why they were so severely affected in winter 2016/2017.
"The susceptibility to different virus strains could be species-specific," said Franz Conraths and Martin Beer from FLI.
“But it could also be that the differences between the virus strains are decisive. The virus strain 2.3.4.4b appears to be significantly more aggressive for many bird species than previously occurring strains, which is why it may now have also hit the large sea eagles. "
So far, it is unclear whether infections are inevitably fatal to sea eagles or whether the animals can survive the infection - possibly if the strains are not so aggressive - and are subsequently immune.
"The observation that the majority of the 17 animals are young could also indicate immunization," added Krone.
Young animals may be particularly susceptible
“Either young animals, as in other species, are particularly susceptible to infections. Or they belong to the age group that is infected with the flu virus for the first time. If these animals survive the infection, they may be "ready" for further infections, "explains the expert.
"Older animals could therefore be 'immunologically experienced' and have already had one or the other influenza disease, which could make them more resistant to newly emerging strains."
The H5N8 influenza type appears to be less dangerous for humans than the H5N1 type, which infected several hundred people in birds after the epidemics.
Those affected may experience typical bird flu symptoms such as fever, cough and sore throat after an infection.
"So far, no transmission from animal to human has become known for H5N8," said the FLI scientists. (ad)
