Two racing stables in Ireland have been locked down over equine influenza fears in recent weeks while the sport has continued there, The Guardian can reveal. The trainers involved have not been named by the authorities, in order to encourage other trainers to come forward if they fear they may have EI cases on their premises.

One of the two stables is once more sending runners to the track, tests from its horses having shown that the disease is no longer present. The other remains in quarantine until such time as swabs from its horses also test clear.

It emerged on Sunday night that horses at a second British stable, this time in Newmarket, have tested positive. Four cases of the highly contagious disease were discovered among the swab samples provided by the trainer Simon Crisford.

The news from Ireland appears to illustrate a more pragmatic approach to handling the EI outbreak being taken in Ireland than in Britain. However, Irish officials point to what they say is a key difference, that there has not been a case in Ireland of a horse testing positive shortly after mixing with other runners at a racecourse, as has happened in Britain.

“These were isolated, discrete events,” said Lynn Hillyer, chief veterinary officer at the Irish Horseracing Regulatory Board. “The cases that we’ve had have not been racing. The trainers have shut down their yards and they haven’t had runners. That’s a key difference. There hasn’t been the racecourse risk of transmission that the British Horseracing Authority have had to face.”

Hillyer, a former BHA employee, praised British officials for acting so promptly on Wednesday evening to notify their Irish counterparts that horses at Donald McCain’s Cheshire stable had tested positive. That enabled them to contact Irish trainers who had runners at Ayr that day, where McCain also had runners; those Irish horses were stopped from returning to their own stables and have since been kept in isolation.

“We were able to act quickly in response to that information,” Hillyer said. “The BHA didn’t have that luxury. The horses had gone home. So it really is apples and pears.”

Racing has continued in Ireland, at Naas on Saturday and at Punchestown on Sunday, with increased biosecurity measures at each racecourse and a message to all trainers that they should be giving their charges a flu vaccination booster. Hillyer said her risk assessment of the situation could change, “if we had evidence that we had increased numbers of cases very rapidly, or if we had horses that were very sick despite having been vaccinated recently”.

Runners and riders at Punchestown on Sunday. Photograph: David Fitzgerald/Sportsfile via Getty Images

However, she insisted that the trainers so far affected could not be named. “Absolutely not. I want to encourage the trainers here to deal with matters in the same way these two yards I know of did. I liaised with their vets and have complete confidence in their vets.

“I really, really would like Irish trainers to understand that reporting and diagnosis is critical. If they have something that they think could be flu, looks like flu, might be flu, please treat it like flu. The key thing is to deal with it, take it seriously and then we can all get rid of it and move on.”

Anonymous testing is conducted by the Irish Equine Centre near Naas. In contrast to the situation in Britain, Irish racing has no rule requiring trainers to notify the regulator of any EI cases, though this is likely to come under review. The IHRB issued a new rule on Friday, that all runners must have had a flu vaccine within the previous eight weeks in order to be allowed to race.

British-based runners are not presently allowed to compete in Ireland, as a result of the EI outbreak which has so far put 174 British stables on lockdown. However, Hillyer said that could change if the BHA’s own assessment of the situation changed.

The BHA is due to make an announcement on Monday night as to whether the sport can resume from Wednesday.