“On the coast, we have never observed such a hecatomb of wild birds.” Terns, seagulls, gulls, greylag geese… Pierre Thellier still can’t get over it. This person in charge of the national nature reserve of Platier d’Oye, in Nord-Pas-de-Calais, counts the corpses which have accumulated since the beginning of the month. “Last week, we already counted 1,433 terns for a total of 1,671 birds, all species combined” he testifies to Science and Future. Blame it on the heat wave? Not even. The culprit of this carnage is none other than the H5N1 virus. It is known for its role in avian influenza, called by specialists “avian influenza”. This highly contagious viral disease affects domestic and wild birds. Since October 2021, it has killed no less than 383,000 wild birds worldwide, according to the World Organization for Animal Health. And the figure is probably underestimated: sick and dead birds are difficult to track.
However, this avian influenza epidemic is not the first that seabirds have had to deal with. “It could happen from time to time that a duck or a swan was contaminated but it remained quite anecdotal and it was always in the winter period” note Pierre Thellier. But this year, the bird flu lasted much longer than usual, until the spring and summer period. However, spring and summer correspond to the period of reproduction in birds. It is therefore a time when individuals are very close to each other. Problem: simple contact with an individual infected with the H5N1 virus is enough to infect another individual. “It is catastrophic since the individuals are in colonies and live in promiscuity. The transmission of the virus is therefore very strong. From the moment you have a few sick individuals, the virus will only spread between the birds. We are witnessing a real epidemic of avian influenza”, alarm the reserve manager. To limit the spread of the virus, the project manager and his team sent as many corpses as possible for rendering (slaughtering of animals unfit for consumption). But they couldn’t do much more.
A unique phenomenon
France is not the only country affected: “en Belgium is also a disaster” says the project manager. The virus has also killed cranes in Israel, Dalmatian pelicans in Greece and Gannets in Canada and the United Kingdom. And it’s not going to get any better: “we will soon enter the post-nuptial migration period and infected birds from the North risk infecting birds from the South”.
For the Royal Society for the Protection of Birds (RSPB), the largest organization for the protection of animals in Europe, it would be the worst epidemic bird flu ever recorded. In previous years, H5N1 outbreaks remained localized. But this year, the disease is spreading like wildfire. The World Organization for Animal Health also notes that the phenomenon is unusual in terms of the mortality rate, the number of species affected and the diversity of the geographical areas affected.
Yet the virus is not new.
–
“On the coast, we have never observed such a hecatomb of wild birds.” Terns, seagulls, gulls, greylag geese… Pierre Thellier still can’t get over it. This person in charge of the national nature reserve of Platier d’Oye, in Nord-Pas-de-Calais, counts the corpses which have accumulated since the beginning of the month. “Last week, we already counted 1,433 terns for a total of 1,671 birds, all species combined” he testifies to Science and Future. Blame it on the heat wave? Not even. The culprit of this carnage is none other than the H5N1 virus. It is known for its role in avian influenza, called by specialists “avian influenza”. This highly contagious viral disease affects domestic and wild birds. Since October 2021, it has killed no less than 383,000 wild birds worldwide, according to the World Organization for Animal Health. And the figure is probably underestimated: sick and dead birds are difficult to track.
However, this avian influenza epidemic is not the first that seabirds have had to deal with. “It could happen from time to time that a duck or a swan was contaminated but it remained quite anecdotal and it was always in the winter period” note Pierre Thellier. But this year, the bird flu lasted much longer than usual, until the spring and summer period. However, spring and summer correspond to the period of reproduction in birds. It is therefore a time when individuals are very close to each other. Problem: simple contact with an individual infected with the H5N1 virus is enough to infect another individual. “It is catastrophic since the individuals are in colonies and live in promiscuity. The transmission of the virus is therefore very strong. From the moment you have a few sick individuals, the virus will only spread between the birds. We are witnessing a real epidemic of avian influenza”, alarm the reserve manager. To limit the spread of the virus, the project manager and his team sent as many corpses as possible for rendering (slaughtering of animals unfit for consumption). But they couldn’t do much more.
A unique phenomenon
France is not the only country affected: “en Belgium is also a disaster” says the project manager. The virus has also killed cranes in Israel, Dalmatian pelicans in Greece and Gannets in Canada and the United Kingdom. And it’s not going to get any better: “we will soon enter the post-nuptial migration period and infected birds from the North risk infecting birds from the South”.
For the Royal Society for the Protection of Birds (RSPB), the largest organization for the protection of animals in Europe, it would be the worst epidemic bird flu ever recorded. In previous years, H5N1 outbreaks remained localized. But this year, the disease is spreading like wildfire. The World Organization for Animal Health also notes that the phenomenon is unusual in terms of the mortality rate, the number of species affected and the diversity of the geographical areas affected.
Yet the virus is not new. Influenza appeared decades ago in China in intensive poultry farming. The latter have greatly favored the appearance of diseases, as explained for Science and Future Thierry Boulinier, dresearch director at the CNRS in Montpellier, at the center for functional and evolutionary ecology: “by maintaining poultry in very dense farms with plenty of hosts, individuals were able to transmit the virus very easily. The latter was able to evolve in very pathogenic forms, until killing its host.“ Since 1996, the virus has been circulating worldwide in wild and domestic birds, evolving as it moves from host to host. This season, scientists do not yet fully understand why the epidemic is even worse than in previous years.
And according to Thierry Boulinier, the epidemic is not about to stop: “between the colonies, there are particularly intense movements, especially when the young are about to take flight. For example, in kittiwakes, chicks tend to roam between colonies before migrating. It should therefore last until the colonies are empty. And we also don’t know what will happen next year because once the virus is present in populations, it can persist.“
One more threat
Cull poultry infected with bird flu – 16 millions have been decimated in France since November 2021 – will therefore not have been enough this time. This deadly disease therefore adds to the threats that already weigh on many populations of wild birds. In competition with the industrial fishing, seabirds are finding it increasingly difficult to feed themselves, when they are not ingesting plastic. Some individuals may also become trapped in drift fishing nets. Species introduced to the islands, such as rats, can also attack eggs and chicks. Not to mention the climate change which considerably disturbs marine life. Furthermore, the reproductive rate of many species of seabirds is also slow: “In normal times adults have a very good survival rate unlike chicks and usually that’s enough to maintain populations. But if the virus kills the adults, the colonies can quickly be very affected” says the research director. These are all factors that increasingly endanger the survival of many populations of seabirds.
–
