An outbreak of equine flu - which has affected 14 horses in Suffolk - has forced all British racing to be cancelled today and could affect upcoming events including races at Chelmsford City.

The British Horseracing Authority (BHA) announced on Wednesday night that all races would be abandoned after the Animal Health Trust confirmed three positive tests from vaccinated horses in an active racing yard.

It was revealed that the same yard had runners at Monday’s meetings at Ayr and Ludlow.

The BHA statement added: “It was essential that racing be stood down today, and controls on movements of horses be put in place in order to attempt to control the spread of the disease. The decision was taken swiftly last night that this course of action should be taken, once the extent of the issue was known.”

The decision to cancel today’s races at Chelmsford, Huntingdon, Doncaster and Ffos Las, was taken with unanimous support of the BHA’s industry veterinary committee.

A spokesman for Chelmsford City Racecourse said: “Racing today has been abandoned following restrictions imposed by the BHA due to an outbreak of equine influenza (EI).

“All customers who have booked to attend the racing today will be contacted directly by the racecourse this morning. Apologies for any incovenience caused.”

The next fixture at Chelmsford City Racecourse is scheduled for Thursday, February 14, a Valentine’s Day special – but there has been no indication from the BHA regarding the length of time that racing will be cancelled because of the equine flu.

There are no meetings planned at Newmarket until April.

On Monday, February 4 the Animal Health Trust (AHT) confirmed two separate outbreaks of EI in Suffolk. One outbreak affected eight vaccinated two-year-old Thoroughbreds that presented with coughing, nasal discharge and pyrexia.

The second outbreak affected six unvaccinated non-Thoroughbreds. Virus isolation and sequencing analysis is now underway at the AHT and details will be made available soon.

BEVA, the equine veterinary association, said: “Of particular significance is that one of these two recently confirmed outbreaks in Suffolk involves multiple vaccinated horses and provides the first evidence of failure of vaccine effectiveness in the UK related to the recent cluster of EI outbreaks.”

The BHA are still in the early stages of assessing the scale and severity of the outbreak. They are working to identify the extent of the infection and will have more information when further test results are returned today. The results from those tests will not be known until Thursday evening.

What is equine influenza?

A highly infectious disease which affects horses, mules and donkeys caused by strains of Influenza A virus. All horses should be vaccinated and need to receive a booster vaccine every six months.

It is the most potentially damaging of the respiratory viruses that occur in UK equines.