Predicting catastrophic racehorse injuries

After a string of deadly accidents on horserace tracks in recent years, science has aimed at finding ways to recognize which horses are most at risk of sustaining a fatal fracture. And the work is paying off. According to a team of U.S. researchers, a new blood test can detect certain copies of genes that could flag impending doom.

Racehorses that experience catastrophic injuries (fractures causing death or requiring immediate euthanasia) have a different profile of messenger RNA (mRNA), which can be detected through mRNA expression analysis from a blood test, said Allen Page, DVM, PhD, staff scientist and veterinarian at the University of Kentucky’s Gluck Equine Research Center, in Lexington.

By drawing blood in racehorses from time to time to see how their mRNA profile evolves, caregivers could pick up on clues that the horse is nearing the point of sustaining a catastrophic injury, and thereby choose to take necessary precautions, like changing the training program and seeking more in-depth veterinary examinations Page said.

“We believe that regular mRNA expression analysis in racehorses can help decrease fatal injuries, and we are really interested to see how this research and our findings are received by the racing industry,” he said.

Page and his fellow researchers acquired blood samples from 374 healthy Thoroughbreds just before a race, 205 healthy Thoroughbreds just after a race, and 107 Thoroughbreds within 30 minutes of sustaining a catastrophic injury (just before or just after euthanasia). They also had blood samples from both before and after a race for 37 healthy horses.

Scanning 21 mRNA pre-selected genes they thought might be good biomarkers for pending injury, they identified three which were distinctly different in horses that successfully finished a race and those that broke down with a life-ending fracture. The mRNA copies of Insulin-like growth factor 1 (IGF-1), Interleukin-1 receptor antagonist (IL1RN), and Matrix metalloproteinase-2 (MMP2) were expressed at different rates in the injured horses compared to the healthy horses.

All horses have these three genes in their DNA, so it’s not a genetic test checking for heritability of certain genes, according to Page. Rather, the test looks at what horses’ bodies do with the genes they have—or more specifically, how many mRNA copies the horses are producing.

DNA genes code for protein production, but it’s mRNA that serves as a bridge between DNA and protein production. To do so, the genes have to be transcribed—have copies made—into mRNA. The number of mRNA copies of a gene is linked to how much of the related protein gets produced. And that seems to depend on various circumstances, like the body’s reaction to internal and external events that are heading that horse towards a breakdown. Thus, it seems that horses’ gene transcription process changes upstream from the catastrophic injury. And ultimately, such changes could identify the horses that are about to have such a serious accident, Page said.

“We envision this being a test that is repeated with some regularity since mRNA expression will change over time as horses are conditioned and as a result of underlying injuries,” he explained.

“While that certainly adds cost, we see regular sampling as being a positive, in that we would be able to identify trends in mRNA expression changes within the individual horse,” said Page. “Rather than comparing them against other horses, like we did in this study, we could compare them to their previous samples, likely improving our ability to identify horses at risk for injury.”

Even so, the test can’t be considered all-compassing, Page added. “It probably won’t detect every horse at risk of catastrophic injury, but anything we can do to decrease the injury rate in racing is a step in the right direction,” he said.

The study is published in the Equine Veterinary Journal. It is titled ‘Expression of select mRNA in Thoroughbreds with catastrophic racing injuries’ by
Allen E. Page, Emma Adam Rick Arthur, Virginia Barker Forrest Franklin Ron Friedman, Timothy Grande Michael Hardy, Bruce Howard Emma Partridge, Matthew Rutledge Mary Scollay,John C. Stewart, Alina Vale and David W. Horohov.

The abstract can be found here.