The allegations, angrily denied by the resort, were made by trade unions who said managers had hushed up the discovery to avoid scaring off visitors. The row came amid what experts are describing as an avian flu psychosis after the arrival of the H5N1 virus.

In France, police officers have been sent to shoot wild ducks, the fire service has been inundated with requests to pick up dead pigeons, and cockerels banned from fighting are allegedly expiring from apoplexy.

The scare reached Disneyland when two unions, the French Democratic Workers Confederation and Workers’ Force, said staff has seen a dead swan in the adventure park.

Although there was no suggestion the swan had fallen victim to bird flu — or even proof that it had actually existed — the report featured prominently on the radio news.

The resort, which attracts 12 million visitors a year, denounced the claims as “unacceptable lies.” A spokesman said the only birds found dead on the site were a sparrow and pigeon, which had succumbed to natural causes. Disneyland accused unions of making up the swan scare story to put pressure on management during wage negotiations.

The confirmation yesterday of two new cases of bird flu in cats on the German Baltic Sea Island of Rügen provoked fresh concerns from animal welfare societies.

Hundreds of cats have been abandoned in France and Germany over the past two weeks. “A lot of owners pretend they have suddenly developed an allergy to cat fur,” a worker at the French Society for the Protection of Animals said.

In Marseilles riot police sealed off an industrial estate where a dead swan with the H5N1 virus was found last weekend. Pet owners near by were told to keep cats indoors and dogs on a lead.

Anne-Marie Pigache, a council worker in nearby Saint Mitre, said 30 people had asked her to dispose of her backyard chickens. She had refused.

The French poultry industry has lost €130 million (£90 million) as a result of the bird flu scare, with 46 countries banning French fowl and foie gras and a 30 per cent slump in domestic sales. One supermarket is now offering a buy-one-get-one-free deal for roast chicken.

Cockerel breeders said they, too, were suffering after the authorities banned fights. Jean Louis Hoyez, president of the French Club of Northern Fighting Cocks, said: “These animals are bred for their aggressiveness, and when they can’t fight, they just die of apoplexy.”

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