French authorities plan to expand their culls of ducks reared for the controversial delicacy foie gras as an outbreak of bird flu rips through the southwest of the country, a producers' federation said Thursday.

The highly pathogenic H5N8 virus was first detected in a bird in a pet shop on the Mediterranean island of Corsica in November before spreading to duck farms on the mainland in December.

"The virus is stronger than us. New clusters are constantly emerging," the head of the CIFOQ federation of foie gras producers, Marie-Pierre Pe, told AFP, warning of a "runaway increase" in confirmed and suspected cases.

She said that around 100 clusters had been identified, mainly in the Landes department, a bastion of the foie gras industry, and that the authorities planned to step up culls.

The agriculture ministry declined to comment.

On Tuesday, France's chief veterinary officer, Loic Evain, said that over 200,000 ducks had already been slaughtered and that a further 400,000 birds were set to be culled, out of around 35 million reared each year in France.

The bird flu spreading through southern France is highly contagious for fowl but poses no health risk to humans
The bird flu spreading through southern France is highly contagious for fowl but poses no health risk to humans AFP / GAIZKA IROZ

He described the virus, which is not harmful to humans, as "very, very contagious".

The most recent update from the agriculture ministry, which dates to January 1, cited 61 clusters detected among birds on duck farms and in pet shops. Of these, 48 were in the Landes area.

Pe said the government's strategy of localised preventive culls was "insufficient" which revealed the state's "powerlessness in the face of a virus which is moving faster than us."

The head of the chamber of agriculture, Sebastien Windsor, called Wednesday for "radical measures" to try to restore confidence in export markets such as China which announced Wednesday it was suspending French poultry imports over the outbreak.

Producers of foie gras, a pate made from the livers of force-fed ducks or geese, fear a repeat of the devastation wrought by two previous waves of bird flu in the winters of 2015/2016 and 2016/2017.

Over 25 million ducks were culled in the first outbreak, followed by 4.5 million the following year, causing a steep decline in foie gras production.

The Netherlands, Sweden, Britain and Ireland have also reported bird flu outbreaks since November. Dutch authorities culled some 190,000 chickens in November over the discovery of a highly contagious strain of the virus at two farms.