Plans are already in place to salvage races lost to the shutdown in Britain caused by equine influenza as authorities try to identify the strain of the disease.

The British racehorse population is vaccinated against EI but after three confirmed cases on Wednesday, the British Horseracing Authority has shut racing down for at least a week.

Brant Dunshea, the BHA's chief regulatory officer, says it is possible it is a new strain.

"We're not certain as yet that the vaccinations haven't worked, but there are suspicions that this particular strain of the vaccine could in fact be non-prevalent in Europe and it could be a strain that circulates in North America," Dunshea said.

"Non-racehorses have tested positive for this strain in recent weeks.

"We have absolutely no understanding of what the source may be at this particular time. The Animal Health Trust has been fantastic in working with us to help us understand what might be happening."

Dunshea told Sky Sports Racing the authorities were also trying to reschedule races ahead of next month's showpiece Cheltenham jumps festival.

"We've already had numerous discussions about rescheduling Newbury this weekend at the request of trainers and we can work with racecourses who are behind us - not just key races but races for all grades of horses," he said.

"The training community has been incredible, their collaboration has been fabulous."