Britain's horse racing industry remains on tenterhooks following an outbreak of equine flu with next month's showpiece Cheltenham Festival the focus of attention.

All race meetings in Britain have been cancelled until Wednesday and three more cases of equine flu were confirmed on Friday at the stables of trainer Donald McCain.

The four-day Cheltenham Festival, the fourth most attended sporting event in Britain which attracts over 320,000 visitors, is due to start on March 12.

“We are in contact with the British Horseracing Authority (BHA) on this matter, who are handling it on behalf of British Racing and providing regular updates,” a spokesman for the Cheltenham race course said.

“The Festival isn't for five weeks and we hope that the BHA's early actions will resolve this matter quickly.”

The British racing industry is worth STG 3.45 billion ($A6.29 billion) a year and horse racing is the second most attended sport in the country with about 5.7 million people going to meetings each year.

Cheltenham is also worth about STG 100 million to the local economy in the county of Gloucestershire.

The Grand National is due to take place in Liverpool on April 5 and could also be under threat if the disease is not brought under control.

An estimated 600 million people worldwide watch the race at Aintree which attracts 140,000 visitors.

Vaccination against equine influenza is mandatory for all racehorses and equines used competitively for other sports like showjumping.

The particular concern with the current outbreak is that the horses which tested positive were vaccinated against the disease.

This has raised fears that a new strain of flu is present but because it takes three days for symptoms to become visible, the BHA will not be able to draw definite conclusions until Sunday at the earliest.

Trainer Dan Skelton is preparing 20 horses for Cheltenham.

“The authorities are working hard to get it back as quickly as possible,” Skelton said. “This goes wider than just competition and participation though.

“It is a health thing for horses so we have to put that first and foremost. It's worrying that it is happening in horses that are vaccinated and it's not doing the job. I feel that we are in competent hands and it is being handled really well.”

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