Aidan O'Brien - string has been affected by low-grade infection

Aidan O'Brien reveals low-grade infection has affected some horses in his yard

Horse Racing

Mon September 14, 2026 · 1h ago

Aidan O’Brien revealed at the Curragh on Sunday that a low-grade infection has been affecting some of his string over the last couple of months.

The trainer’s bid to break the record for number of Group One wins in a calendar year has hit the buffers during the period with his strike-rate and runners-to-form measurements the subject of much discussion.

It was a mixed day for the Ballydoyle juggernaut on Saturday, Darkness Falls catapulting himself to Betfred Derby favouritism with a blistering win in the newly-anointed Group One HKJC World Pool Golden Fleece Stakes but a whole host of reverses too including Constitution River in the Royal Bahrain Irish Champion Stakes and Christmas Day and Pierre Bonnard performing well below expectations in the Betfred St Leger.

O’Brien revealed that Christmas Day, a well-backed favourite, had coughed on the way to the start at Town Moor.

“That’s one of those things you’re never prepared for,” the trainer told Racing TV. “Obviously for the last couple of months we’ve been fighting a very low-grade infection in the whole place through all the horses, two-year-olds and three-year-olds. It pops up every now and then and then disappears. It pops up in their blood, pops up in their scopes and you can’t be sure where it is.

“Obviously before we run any horse they’re always blooded and scoped to make sure they’re perfect, but you don’t know. Sometimes when you travel them it brings it out and obviously he (Christmas Day) was a little under-the-weather when that happened and he won’t run again this year and will be put away. Pierre Bonnard is probably the same thing.

“It’s one of those things. It’s been there a couple of months, we’re dealing with it, you have to keep it going, no horses ran until we were 100% sure but sometimes when you travel it brings little things to the fore. There’s never any harm to them after but obviously there’s little things lurking there and we have to be careful.

“Obviously we had the horse yesterday (Constitution River) and it was the same. We ran him back quick after a tough race at York and you’re always conscious of these things. I wouldn’t be taking away from any horse that has beaten them in the last couple of months but it’s there and that’s the way it is. We just have to deal with it and keep moving forward.

“Anyone who has horses knows about these things. We blood so much. You see when there’s a spike in the blood and the SAA level goes right up and then disappears down. Obviously there’s a little thing there which we can’t put our finger on where it is or what it is but it will work through, it always does.

“It's just there at maybe a delicate time but every week that goes by will help them through and the three-year-olds at this time of year are usually the ones who are more prone to it because they have been trained for the Classics and would have had a tough year up to then.

“Obviously, we try and get them to compete in the middle and on against the older horses as well but it’s the way it is, everyone knows about it and we’ll go gentle away and move on. “

Aidan O'Brien reveals low-grade infection has affected some horses in his yard

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