After a lull of a month and a half, the virus has begun to flare up again since early May in the Southwest, contaminating more than 70 farms, especially in the Gers.

Each time, infected animals (mainly palmipeds) are slaughtered, preventive slaughter of healthy animals nearby is decided, and poultry production is permanently disrupted.

The repetition and scale of crises related to avian influenza (more than 20 million poultry slaughtered in 2021-2022 in France, already more than six million in 2022-23) have convinced European countries to imagine a vaccine strategy.

In France, an experiment was launched last year, around two vaccine candidates developed by Boehringer Ingelheim and Ceva Santé Animale.

They aim to protect Mulard ducks, bred for foie gras, from the virus. European neighbours are testing vaccines in other poultry species.

The French experiment involved a few thousand ducks, vaccinated or not. They were euthanized at the end of the process.

The "favorable results provide sufficient guarantees to launch a vaccination campaign as early as autumn 2023," the Ministry of Agriculture wrote on its website.

The virus circulating in France and around the world was inoculated into a fraction of the ducks, previously vaccinated, to measure how well they excreted the virus, and whether they could still contaminate their congeners.

No airborne transmission

"Vaccination has made it possible to have very little shedding of the virus in inoculated animals," whether by respiratory or digestive tract, summarized to AFP Béatrice Grasland, head of ANSES's national reference laboratory for avian influenza Ploufragan-Plouzané-Niort.

The two vaccines, with "very similar" results, have also "almost stopped direct transmission" - when animals are in close contact - and "abolished" indirect transmission, by air, that is to say potentially from one barn to another.

The two vaccines, with "very similar" results, have also "almost stopped direct transmission" © GAIZKA IROZ / AFP/Archives

When animals were not vaccinated, "an inoculated animal infected another animal every two hours," the researcher explained.

Conversely, those who were vaccinated were "almost not" contaminated by their neighbor "even in direct contact, in the same park, with the droppings" infected.

"It's very effective," Grasland said, noting that under these conditions, "normally the epidemic does not start."

When asked, the French laboratory Ceva, whose vaccine is RNA, simply indicated that it had applied for marketing authorization from the National Agency for Veterinary Medicinal Products. It also responded to the call for tenders of the Ministry of Agriculture, which announced in April a "pre-order of 80 million doses".

According to the ministry, the France plans to vaccinate ducks (Mulard type but also Beijing and Barbary - the latter being rather bred for their meat) because of their "particular role" in the dynamics of the epizootic.

Ducks are very sensitive to the virus and excrete it in the environment even before they show symptoms, contributing to a low-noise spread of avian influenza.

The vaccination of "future laying pullets" is also envisaged, says the ministry, "in order to preserve egg production capacities (...) and given the weakening of the sector during past crises".

Vaccination raises technical questions (will we have enough doses, but also staff to inject them and ensure post-vaccination surveillance?), economic (who will pay?) and diplomatic questions, with poultry professionals fearing that export markets will close if animals are vaccinated.

© 2023 AFP