Veterinary officials closed the Weidenpesch racetrack on Monday after one horse tested positive for equine infectious anaemia, an exotic viral disease which is often fatal. All 300 horses at the track and stables will have to stay there for the next three months.
The incident means that the track will remain closed for the last two race days of the season, as well as the charity race day due to be held on October 3, and the Winter Favourite Prize, scheduled for October 14.
At least 15,000 people were expected to attend each of the meets, the Kölner Stadtanzeiger newspaper said on Tuesday.
Danedream will also not be able to take part in the Prix de l'Arc de Triomphe in Paris on Sunday. She won it in a track record time last year and by one of the largest-ever winning distances.
Patrick Barbe, racing manager for Danedream's part-owner, Teruya Yoshida, said there was nothing wrong with Danedream but the rules could prove impossible to overcome.
"At the moment, Danedream is very well and has not been infected," said Barbe.
"There is only one horse that has gone down with the illness and is stabled on the other side of the racecourse.”
But the rules mean that no horse can enter or leave the stables while they are under quarantine.
The Peter Schiergen-trained star was favourite to emulate Alleged's feat of 1977 and 1978 on Sunday at Longchamp racecourse.
Danedream's withdrawal leaves a field of 18 in the race - though horses can also be supplemented on Thursday at a cost of €100,000– with Japanese raider Orfevre now generally the 3/1 favourite.