“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 outbreak of avian 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.