First proven fatal bird flu infection in the sea eagle

Northern Germany: White-tailed eagle infected with highly contagious avian influenza virus

In several sea eagles found in northern Germany, the highly contagious avian influenza virus H5N8 was detected for the first time. The deadly infections pose new challenges to the protection of endangered birds of prey.

Infected white-tailed eagle found

In the winter of 2016/2017, there were numerous deaths in northern Germany of white-tailed eagles, in which a lead poisoning or a collision with a train could be excluded as causes of death. Instead, 17 found sea eagles in Mecklenburg-Vorpommern, Schleswig-Holstein, Lower Saxony and Hamburg were infected with the highly contagious avian flu virus H5N8, reports the Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health (FLI) in a recent release.

Researchers have detected the highly infectious avian flu virus H5N8 in white-tailed eagles in Germany for the first time. (Image: Alexander Raths / fotolia.com)

First cases of bird flu among endangered birds of prey

This was proven 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 the FLI and other colleagues.

According to reports, the deadly H5N8 2.3.4.4b virus strain is the first case of avian flu in sea eagles and poses new challenges to the protection of endangered birds of prey.

The study has recently been published in the journal Viruses.

For several decades ongoing threat

Avian influenza has been threatening wild birds and domestic poultry for several decades. In particular, chickens, geese and ducks, as well as other waterbirds, are affected by the infections with different strains of the influenza A virus.

Again and again epidemics occur, for example in Mexico in 1992, in Central Europe in 2006, in the United States in 2015 and again in Europe in 2016/2017.

In Germany, therefore, often had tens of thousands of chickens are culled.

White-tailed eagles (Haliaeetus albicilla) have so far seemed to be spared from contagion, although infections have already been detected for individual birds of prey such as the peregrine falcon or the buzzard.

Investigations of the 17 white-tailed eagles found in northern Germany - 14 of them were already dead and three others showed strong symptoms such as overexcitability and coordination difficulties - now provided evidence that even eagles can become infected.

Analyzes of the genomes of the viruses showed that it was not the widespread influenza type H5N1, but the type H5N8.

Furthermore, by fully elucidating the viral genome, the scientists identified virus strain 2.3.4.4b, which is considered highly aggressive to birds.

The virus can cause encephalitis (polioencephalitis) in the animals. Measurements of lead concentration in the kidney and liver of the white-tailed eagle previously excluded lead poisoning as the cause of death.

Susceptible to infectious diseases

The North German Plain and the German Baltic coast are the central habitat of white-tailed eagles in Germany. Its range extends to Greenland in the west and Japan in the east. In Germany there are currently 750 breeding pairs.

In the second half of the 20th century, he was almost eradicated by human persecution and the effects of the insecticide DDT. Since the 1980s, stocks have been recovering after the persecution ceased and the use of DDT banned.

New threats arose, such as poisoning with leaded ammunition. The animals are also susceptible to infectious diseases: "Sea eagles feed on carrion and, if available, waterfowl, especially in winter," says Oliver Krone from Leibniz-IZW.

"Of course, sick and weak animals are easy prey for the white-tailed eagle. As a result, these birds of prey repeatedly expose themselves to viruses and other pathogens. "

Still some questions unanswered

For the science team still some questions remain unanswered, which are now the subject of further investigations.

For example, it is still unclear why in the H5N1 epidemic in 2006, apparently no infections were detected in sea eagles and why they were so severely affected in the winter of 2016/2017.

"Susceptibility to different viral strains could be species-specific," says Franz Conraths and Martin Beer of the FLI.

"It could also be that the differences between the virus strains are crucial. The virus strain 2.3.4.4b seems to be significantly more aggressive to many species of birds than earlier strains, so it may have hit the big white-tailed eagles as well. "

So far, it is still unclear whether infections for sea eagles are inevitably fatal or whether the animals can survive the infection - possibly if the strains are not so aggressive - and then immune.

"The observation that most of the 17 animals are juveniles may also indicate immunization," adds Krone.

Pups may be particularly vulnerable

"Either young animals, as in other species, are particularly susceptible to infection. Or they belong to the age group, which is infected for the first time with a flu virus. If these animals survive the infection, they may be 'ready' for further infections, "explains the expert.

"Older animals could be 'immunologically experienced' and have already gone through one or the other influenza disease, which could make them more resistant to emerging strains."

For humans, the influenza type H5N8 appears to be less dangerous than the H5N1 type, which has infected several hundred people after the bird epidemics.

Patients may experience typical bird flu symptoms such as fever, cough and sore throat after infection.

"So far, H5N8 has not been known to transmit from animals to humans," said FLI scientists. (Ad)