The Kentucky Horse Racing Commission has published the post-mortem review reports for both of the Saffie Joseph-trained horses who experienced sudden deaths at Churchill Downs this spring. The occurrence of two of the statistically unusual deaths within just a few days of each other prompted the commission to scratch Joseph's other horses from races at the track, and Churchill later announced a private property suspension of his entries.
Joseph-trained Parents Pride collapsed after being pulled up near the 3/16ths pole during a race on April 29 and died before emergency veterinarians could evaluate her on-site. Chasing Artie trailed the field in his May 2 race and began to stagger, then collapsed while returning to be unsaddled. He was unresponsive to veterinarians' attempts to revive him, and they decided to euthanize him.
Both horses passed their pre-race veterinary exams, and were described as having “very minimal and routine” veterinary work within the past 60 days prior to their starts, based on medical records. No prohibited or therapeutic substances were found in blood testing for either horse; no urine was collected from either horse for testing, as this becomes logistically difficult after death.
In the case of Parents Pride, pathologists did note some mild to moderate changes in the heart, brain and lungs, including minimal myocarditis but none of those abnormalities were thought to be significant enough to prompt a sudden death.
Dr. Laura Kennedy, the author of the mortality review for Parents Pride, reported that “Myocarditis can be identified in clinically normal racehorses that are euthanized for a variety of reasons, including non-catastrophic musculoskeletal injury.”
“Judgments on the significance of certain findings can vary between laboratories and pathologists,” Kennedy wrote. “The pathologist on this case defines myocarditis to be a significant finding when greater than 30% of the histologic sections exhibit inflammation. In this case, 5% of the sections were affected.”
An examination of organs from Chasing Artie did not reveal any abnormalities in the heart, but did make note of hemorrhage in the lungs, including evidence of previous EIPH. The pathologist did not believe this was significant enough to prompt a sudden death. Hemorrhage or congestion in the lungs and spleen are common findings on horses who have undergone chemical euthanasia soon after exercise, and it's often difficult to tell whether the bleeding was a result of the euthanasia drug, normal exertion, or whether it's something acute that preceded the horse pulling up or stumbling.
Toxicology testing on Chasing Artie did reveal trace amounts of the anticoagulant rat poisons chlorophacinone and diphacinone. The concentrations were detectable but too small to be quantified.
Kennedy wrote that while it's true rodenticides were found in 2016 cases of horses in Southern California suffering from sudden deaths, the levels found in those horses were measured in parts per million. In this horse, the levels were smaller than 50 parts per billion, which led Kennedy to doubt this substance caused the horse's death.
Both horses had stomach ulcers, which is a nearly-universal finding on necropsies of racehorses.
Neither the report for Chasing Artie or Parents Pride establishes a definitive cause of death, which is common in instances of sudden death. One academic study from 2011 showed that only about 43 percent of sudden death incidents ever had a definitive cause of death established.
Mortality review reports are published on the commission's website here. Several, though not all, of the other Churchill deaths also have mortality reviews posted. In each case of musculoskeletal injury, report authors compared the injured horse to uninjured cohorts from the same race to see if there were any abnormalities in age at first work, veterinarian's list history, length of recent layoffs, number of high-speed furlongs, and much more. Most horses were found to be similar to their competition for most factors studied.
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