The British Horseracing Authority (BHA) took the decision to cancel racing at Huntingdon and all other British racecourses after it was informed by the Animal Health Trust of three confirmed influenza positives from vaccinated horses in an active racing yard.Horses from the infected yard had raced on Wednesday at courses in Ayr and Ludlow, potentially exposing a significant number of horses from yards across the country and in Ireland. A spokesman for the BHA said: The fact that the cases have been identified in vaccinated horses presents a cause for significant concern over welfare and 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 has worked quickly to identify which yards could have potentially been exposed and identify the further actions required. 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 possible further spread of the disease. A spokesman for Huntingdon Racecourse said all tickets would be automatically refunded within seven working days. Log on to www.thejockeyclub.co.uk\/huntingdon for more information.