British Horseracing Authority chief executive Nick Rust has warned a 'three to six-month problem' might have become reality if the national governing body chose to 'play Russian roulette' with its response to the equine flu outbreak.

He insists that the initial decision to cancel all racing for six days following confirmation of three positive cases at Donald McCain's yard will ensure the shut-down lasts no longer than "a few weeks at most".

"We've got to get a hold of it quickly," Rust said on ITV's Good Morning Britain.

"If we play Russian roulette with the evidence we've got, we could have a problem for three to six months and no one would thank us for that.

"First and foremost, we have no sport without healthy horses."

Asked what a worst-case scenario might still be, with the Cheltenham Festival less than five weeks away, Rust said: "We have a 'war-room' - we have 20 vets employed at the BHA, forensic investigation, a lab in Newmarket that is processing hundreds of tests now.

"We hope we've got a hold of it quickly and that by Monday we'll be in a position to make another call.

Concerns grew on Thursday when it became clear the three horses to test positive had also been vaccinated.

"Vaccinations never work 100%. Racehorses are among the best looked-after animals in the country - they are super athletes," added Rust.

"We're on top of this quickly. We are not concerned that we are facing a (superbug) mutation issue here."

Champion trainer Nicky Henderson reported on Friday morning that the BHA's urgent action plan to test all horses is already underway.

"I'm nervous - it will be very interesting to see if any other horses have been challenged by it," he told BBC Radio 5 Live.

"We are all totally vaccinated - rigidly, it's compulsory.

"Unfortunately, I'm told that actually there is only 40% of the horses in Britain are actually vaccinated - because horses outside racing, there is no jurisdiction to say you have to be vaccinated.

Like all his fellow Cheltenham hopefuls, Henderson is wary of time running short.

"The worst part of it is that we are starting to miss races that were part of the horses' preparation.

"We're just going to have to pray it will all go ahead as normal, and this will blow over as quick as it's come in."