France on Monday began Europe's only vaccination campaign against bird flu in ducks, hoping to avoid mass culls of millions of birds that have dearly cost the industry in recent years.
"There's high pressure from the virus, but vaccination should mean we only face individual cases, avoiding the tidal wave sweeping through farms," said Jocelyn Marguerie, poultry chief at the SNGTV farm vets' association.
The two-jab course for ducklings -- starting at 10 days old -- is obligatory in farms raising more than 250 birds from October.
Producing livers for foie gras or meat, France's duck sector is especially sensitive to the virus.
The birds shed it before symptoms ever appear, allowing it to spread unchecked.
France's poultry population saw a wave of bird flu in 2015-17 and has suffered almost constant outbreaks since 2020 -- although there are currently no disease hotspots.
Discovery of a case means culling for the whole farm and others nearby, disrupting production for the long term and bringing a heavy financial toll for farmers.
"I've been caught up in four culls since 2016. I hope we'll get back to being unscathed. (Vaccination) has to work!" said Thierry Dezes, who raises ducks in the southwestern Landes region and plans to jab some 5,000 ducklings.
Vets expect a total of around 60 million ducks should be vaccinated by summer next year.
France's first 24 million doses will come from pharmaceutical company Boehringer Ingelheim, meaning the government will have to invite tenders for more supply.
But the campaign is not going uncontested.
One farmer in the Landes region told AFP that she had customers "calling to tell me they don't want meat from vaccinated ducks" -- asking to remain anonymous to protect her business.
And on export markets, the fear is that immunisation could mask bird flu circulating unnoticed in the duck population.
A senior official at Japan's ministry of agriculture told AFP that Tokyo would suspend imports of French poultry products after the vaccination campaign had started.