Aidan O’Brien reveals mystery ‘infection’ has been tearing through Ballydoyle and leading to horses running poorly

KILDARE, IRELAND – SEPTEMBER 13: Aidan O’Brien poses during Irish Champions Festival Day 2 at Curragh Racecourse on September 13, 2026 in Kildare, Ireland. (Photo by Alan Crowhurst/Getty Images) Credit: Getty AIDAN O’BRIEN has revealed a worrying ‘infection’ has been tearing through Ballydoyle for more than two months – leading to a number of his biggest horses running poorly. The legendary trainer stressed that every horse is scoped and has their bloods checked before running to make sure they are OK. Aidan O’Brien revealed Ballydoyle have been fighting a ‘low-grade infection’ ripping through the yard over the past two months Credit: Sportsfile Saffie Osborne made history as the first woman to win a Classic after her St Leger victory on Highwayman – which came after O’Brien’s big fav Christmas Day flopped having coughed Credit: PA But he said the entire squad has been at risk from the ‘low-grade infection’. It came after it was confirmed St Leger favourite and Derby hero Christmas Day coughed on his way to the start of the Doncaster feature. The 7-4 fav finished ninth of 11 – behind 100-1 Rebel Rocker – while stablemate Pierre Bonnard could only manage sixth as Saffie Osborne made Classic history on Highwayman. Constitution River put up much more of a fight in the Irish Champion Stakes but ran out of puff in the closing stages to finish third having been sent off 11-8 favourite. O’Brien confirmed he was OK but will be given antibiotics as a precautionary measure. There have been plenty of highlights, with the awesome Sun Goddess, Darkness Falls and Scandinavia all claiming Group 1s last weekend. But it’s clear the bug has been a huge cause of concern for O’Brien, who spoke about it yesterday at the Curragh. He said: “For the last couple of months we’ve been fighting a very low-grade infection through the whole yard, two-year-olds and three-year-olds. Most read in Horse Racing “Every now and then it pops up in their bloods and scopes. “Before we run every horse, they’re blooded and scoped to make sure they’re perfect, but you don’t know. “There’s a little thing there, but we can’t put our finger on where it is or what it is. “It was with them all, through the whole place. “We blood them and scope them and if all that is right, and everyone is happy, we let them run. “But sometimes you don’t know until they travel. “Ronan (Whelan) said he (Christmas Day) coughed going to the start. “He just said he ran out of gas going to the furlong marker. “Horses do those things a lot of the time at home. It’s like yourself when you get up in the morning, you could have a phlegmy throat and give a few coughs and that’s it. “What do you do? Stay in bed if you have a flu or a cold? “You ask an athlete do you not run, or not race, if you have a flu or feel a bit chesty? It’s just not the way the world is. “It’s there and they are working through it and it will disappear. “I only said it because Ronan brought it to the fore yesterday and the horse ran the way he did. “It was just to make everyone aware of it. It’s not a big issue.” FREE BETS – GET THE BEST SIGN UP DEALS AND RACING OFFERS Commercial content notice: Taking one of the offers featured in this article may result in a payment to The Sun. You should be aware brands pay fees to appear in the highest placements on the page. 18+. T&Cs apply. gambleaware.org. Remember to gamble responsibly A responsible gambler is someone who: Establishes time and monetary limits before playing Only gambles with money they can afford to lose Never chases their losses Doesn’t gamble if they’re upset, angry or depressed Gamcare – www.gamcare.org.uk Gamble Aware – www.gambleaware.org Find our detailed guide on responsible gambling practices here. Comment now