The British Horseracing Authority has cancelled all racing until Wednesday at least following an outbreak of equine influenza in England.

Thursday's meetings at Ffos Las, Doncaster, Huntingdon and Chelmsford were all called off after it emerged three vaccinated horses from Cheshire-based trainer Donald McCain's yard had tested positive for flu.

The BHA said that while no further positive tests have been received, it can be up to three days before symptoms of the virus emerge, so it will be Monday before it will be possible to make a decision about whether it is safe to resume racing.

Meetings at Bangor, Kempton, Newcastle, Southwell, Lingfield, Newbury, Wolverhampton, Warwick, Uttoxeter, Musselburgh, Exeter, Hereford and Catterick will all be cancelled, with a decision on Monday as to whether racing will go ahead on Wednesday at four venues.

Racing at Thurles went ahead today but the Irish Horseracing Regulatory Board has appealed for Irish trainers and their vets to be aware of the outbreak.

The Racing Post is reporting that over 100 stables in the UK - those which had runners at the Ayr, Ludlow or Wolverhampton meetings attended by McCain horses this week - have been locked down until all their horses have been given the all-clear.

Irish trainers such as Gordon Elliott, who had multiple runners at Ayr, have quarantined those horses as a precautionary measure.

BHA statement

"The British Horseracing Authority (BHA) has this afternoon taken the decision that racing will not resume in Britain until Wednesday 13 February at the earliest, including fixtures programmed by the Point-to-Point Authority.

"The BHA’s veterinary team has today been in contact with more than 50 trainers and veterinarians to allow it to make an informed assessment of the risk of equine influenza spreading. Whilst no further positive tests have been received, at least three more days are required before it will be possible to make a decision about whether it is safe to resume racing.

"The disease can take up to three days before symptoms are visible, meaning it will take until Sunday at the earliest before the BHA can gather all the information required. This approach will allow samples to be collected and assessed by the Animal Health Trust in order that a fully informed decision can be made on Monday.

"This may then allow declarations to take place on Tuesday in time for racing on Wednesday, with 24 hour declarations for all fixtures on this day, should racing be able to resume. Declarations for Thursday would revert to the usual procedures.

"We are grateful to trainers and veterinarians for the rapid flow of information and feedback  we have received today. Because of this, we have been able to make an informed decision earlier than we expected and before we have any test results back from horses from the affected yards that travelled to the three meetings.

"Trainers support a precautionary approach and we thank them for the collaborative manner in which they have worked with us to address this unfolding situation.

"This precautionary approach is intended to ensure we put the health of the horse population and control of the virus first, and avoid any unnecessary risk that might come from returning to racing too quickly. We appreciate the impact that this may have on the sport commercially, but disease control in order to mitigate the risk of further disruption to the sport – and safeguard the health and welfare of our horses – must be a priority.

"A plan will be constructed for the rescheduling of key races – and those which may provide important opportunities for horses to run – which are lost during this period,

"Separately, as a precaution, all of the trainers who had runners at the fixtures at Wolverhampton, Ludlow and Ayr this week have been informed that their yards have been placed under a temporary hold which means that they will not be able to make any declarations until their horses have been tested and cleared."

One area for concern is the fact that the infected horses had been vaccinated against the disease.

"All British racehorses are vaccinated against equine influenza," the BHA said in an earlier statement.

"However, this strain has affected vaccinated horses. The disease may be serious in unvaccinated horses, although symptoms in vaccinated horses are usually mild and transient.

"Symptoms may include a raised temperature, a cough and nasal discharge. It is highly contagious. Humans are not at risk from the virus, though can be transmitters of the virus."

A strain of equine influenza had a devastating effect on Australia in 2007, but the BHA has moved to stress there is little comparison.

"The situation here is not the same as the incident in Australia in 2007. Australian thoroughbreds are not vaccinated against influenza, while British thoroughbreds are, as the virus is endemic in the UK. Therefore an important barrier is in place to prevent the same situation occurring here.

"However, as we have seen in Europe, the virus has affected vaccinated horses in this case. The vaccine should, however, help reduce to a certain extent the effect and spread of the disease in thoroughbreds.

"This is a wider horse health issue, which is not confined to horseracing. Unlike thoroughbreds, the wider horse population in Britain is not vaccinated against equine flu. While the BHA is not specifically responsible for non-racehorses, the general advice to owners would be to contact your vet if you have concerns."