Mammals are affected too: bird flu causes mass mortality

Mammals are affected too
Avian influenza causes mass deaths

In the shadow of the Corona pandemic, another virus is spreading: H5N1, also known as bird flu virus, killing millions of animals worldwide. It also infects litter mammals. Experts are concerned that the virus can also be transmitted to humans.

Some holidaymakers at Easter may have noticed it while walking along the coasts and waters: dead waterfowl, and sometimes several birds a few meters away. However, millions of birds have been dying for months unnoticed by most people – not only in Germany and Europe. The cause of mass deaths among ducks and geese as well as swans, robins and cranes is avian influenza, which is caused by the H5N1 virus. The current wave of infection with the highly pathogenic H5N1 virus is unprecedented with its rapid spread and extremely high frequency of outbreaks in poultry and wild birds and represents a potential ongoing threat to humans, write Michael Weil and Ian Barr of the University of Melbourne in the journal Science.

Transmission of the pathogen from birds to humans has been rare in the past two decades and persistent person-to-person transmission has not yet been documented — but highly pathogenic avian influenza viruses pose a potential epidemic risk, scientists warn. Further adaptation to the currently circulating form of the virus could increase its ability to transmit efficiently from person to person.

So far, the Friedrich Loeffler Institute (FLI) on the island of Rim knows only the case of a 79-year-old man from southwest England who, at the beginning of the year, contracted bird flu. which are currently circulating after direct and prolonged contact with sick poultry. The UKHSA has warned against touching sick or dead birds.

Mammals are injured more than usual

Transmission to meat and scavenging mammals such as foxes and otters has been demonstrated in the current H5N1 wave. The number is higher than in previous waves of infection, according to the FLI at the request of the dpa. “It remains unclear whether this is due to the increased exposure of mammals to the circulating virus or to an increased ‘supply’ of virus-infected bird carcasses.” No mutations showing increased adaptation to mammals or humans were found.

The Federal Research Institute FLI, which is responsible for animal health, spoke of the “strongest bird flu epidemic ever” in Germany and Europe at the end of last year. Radar Bulletin said in March that outbreaks and individual cases in poultry and wild birds in Europe were still being reported nearly every day. According to FLI, from fall 2020 to April 2021, Europe experienced its worst wave of bird flu to date.

Knots on the Danish North Sea coast.

(Photo: Photo Alliance/Zunar)

Since the end of 2021, tens of thousands of dead birds have been found again on the coasts of northern Europe, FLI reports. Since then, hundreds of geese and swans have been reported in France, and several thousand dead nodes have been found in the Netherlands. An estimated 10 percent of the goose barnacles living there died on England’s west coast, and hundreds of Dalmatian pelicans have already died in Greece this year. There are reports from Israel that nearly 10,000 cranes are dying in a national park in the Hula Valley. They come to Israel as migratory birds from southern Europe to stop there on their way to Africa.

First cases in North America as early as 2021

“Surprisingly, it turned out that the virus was transmitted to North America via the North Atlantic in the summer of 2021, most likely by wild birds,” FLI said. At the beginning of the year, the first infections were detected in northeastern Canada. “From there, the virus spreads south along the eastern seaboard of the United States in a rapid epidemic and also westward across the board.” It has already crossed the Mississippi River and in some cases reached the Pacific coast. Hundreds of cases of infected wild birds were detected, and poultry farms were also significantly affected. “More than 30 million birds have already been killed in the United States.”

In Europe, hot spots for infection among poultry are currently found in France, the United Kingdom, Hungary and Italy, according to the FLI. In Germany, there are still significant infections in wild birds, but outbreaks are relatively few in protected birds, especially in commercial poultry farms. The exact reason is unclear, perhaps better security measures to prevent the virus from entering situations may have played a role.

A threat to humans and animals

In wild birds, the pathogen threatens entire populations, especially those already endangered, Weil and Barr warn. There must be a continuous investment in the monitoring of wild birds and poultry, as well as the people at the human-bird interface. To reduce the risk, it makes sense to take measures such as reducing the size and density of the stock and avoiding poultry production in areas where there are many waterfowl.

Technically bird flu Bird flu, occurs mainly in wild waterfowl. Pathogens have specific proteins on their surface, designated by the abbreviations H (for haemagglutinin) and N (for neuraminidase) and that occur in different subtypes (H1 to H16 and N1 to N9). So the name H5N1 means the mixture of H5 and N1 proteins on the surface of the variant.

A distinction is also made between low-pathogenic and highly pathogenic variants of avian influenza. Low-pathogenic forms, such as H5 and H7 subtypes, which cause almost no symptoms or mild disease symptoms, can develop into highly pathogenic variants by genetic changes. The term avian influenza is used to refer to such forms, which often wipe out whole flocks of poultry. Some types of bird flu can be transmitted to humans and – in rare cases so far – cause fatal disease.

Only two subtypes of H – H5 and H7 – have repeatedly emerged as highly pathogenic avian influenza (HPAI), Will and Barr explain in “The Science.” This typically occurs when low pathogenicity H5 or H7 viruses are transmitted from wild birds to poultry, where the H protein changes. “Although the N subtype may play some role in virus transmissibility, it does not determine disease severity.”

There are hardly any vaccinations in Europe

Vaccination of poultry against influenza often provides insufficient protection due to the large variability of the virus, unlike for example China, it has not been widely used in the European Union. According to the FLI, it’s also possible that vaccines from highly pathogenic forms of H5 have been around for some time to be effective against the current H5N1 virus. “However, there is currently no suitable vaccine approved for use in domestic fowl in Europe.” Field trials to test specific vaccines have begun in several EU member states, and options for using the vaccines are being discussed at the EU level.

According to Will and Barr, the currently circulating strain of H5 originated in Asia as early as 1996 and is called the Gänse/Guangdong lineage. Variants based on this disease have spread to Asia, the Middle East, Africa and Europe, hundreds of millions of chickens, turkeys and domestic ducks have been culled and more than 600 human cases of H5N1 have been recorded. The later form now circulated appears to be much less dangerous to humans.

According to Will and Barr, it is still unclear on which characteristics of the virus the massive spread among birds depends. The variant could infect a wide range of wild birds or cause a higher viral load, resulting in easier transmission.

Human-to-human transmission of bird flu remains highly unlikely, Willie and Barr write. We hope it stays this way: as with Corona, it would be virtually impossible to control the virus if there was such an adaptation and the virus spread through the air from person to person.

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