On Thursday four British meetings in Huntingdon, Doncaster, Ffos Las and Chelmsford, were cancelled. The yard in question had runners at jump meetings at Ayr and Ludlow on Wednesday.
Bosses at Dunstall Park announced the move to abandon the Saturday evening meeting as the probe into the outbreak was being investigated today.
Whilst the infected horses had not been racing this week, McCain has had runners at Wolverhampton, Ayr and Ludlow.
Equine flu is a highly contagious respiratory virus which affects horses, mules and donkeys.
What race meetings are cancelled today?
A BHA statement read: "The British Horseracing Authority (BHA) has this afternoon taken the decision that racing will not resume in Britain until Wednesday February 13 at the earliest, including fixtures programmed by the Point-to-Point Authority".
It is the most potentially damaging of the respiratory viruses that occur in United Kingdom equines and disease symptoms in non-immune animals include high fever, coughing and nasal discharge.
The potential spread of the disease and the action to cancel racing has been viewed as necessary in order to restrict, as far as possible, the risk of further spread of the disease. The BHA is presently communicating with yards potentially exposed, to ensure appropriate quarantine and biosecurity measures are put in place and horse movements restricted to avoid potential further spread of the disease.
The sport's ruling body said it had identified yards that could have potentially been exposed today.
The BHA played down fears the British outbreak could be as severe as the one in Australia in 2007, which brought the industry to a standstill in New South Wales and led to the cancellation of Sydney's spring carnival.
A further update on the possible continued extent of disruption is expected from the BHA - with a packed weekend of Cheltenham trials and other big races scheduled at Newbury, Warwick, Musselburgh and in Ireland.
"Key to our decision-making is understanding exactly the status of the horses that we know raced yesterday from the infected yard".