Rood & Riddle co-founder Dr. Tom Riddle dies at 74
Bottom line
Version 1 — Brief
Dr. William Thomas “Tom” Riddle, DVM, co-founder of Rood & Riddle Equine Hospital and a widely respected leader in equine reproductive medicine, died September 20, 2026, after a long illness. He was 74. Riddle helped build Rood & Riddle after joining Bill Rood in 1982, and the practice went on to become one of the best-known equine hospitals in the U.S. He was also recognized across the profession for being the first to identify and report the 2001 abortion outbreak that became known as mare reproductive loss syndrome, or MRLS. (thoroughbreddailynews.com)
Why it matters: For veterinary professionals, Riddle’s legacy reaches beyond one hospital or one specialty. His work on equine theriogenology helped shape reproductive care in mares, and his early recognition of MRLS contributed to a response that linked the syndrome to eastern tent caterpillars and informed farm-level risk reduction in Kentucky. Colleagues also credited him with mentoring generations of equine veterinarians through internships, continuing education, and hands-on training in reproduction. (roodandriddle.com)
What to watch: Memorial services are scheduled for September 28 and 29 in Kentucky, and the equine profession will likely continue reflecting on Riddle’s influence on mentorship, reproductive medicine, and practice-building. (thoroughbreddailynews.com)
Version 2 — Full analysis
Dr. William Thomas “Tom” Riddle, DVM, co-founder of Rood & Riddle Equine Hospital and a leading figure in equine reproductive medicine, died on September 20, 2026, after a long illness. He was 74. His death closes a chapter for one of the most influential names in equine practice, particularly in Kentucky, where Riddle’s work in theriogenology and his role in building Rood & Riddle made him a fixture in both referral medicine and farm practice. (thoroughbreddailynews.com)
Riddle’s professional story is tightly linked to the rise of Rood & Riddle itself. According to the hospital’s biography, he graduated from Wake Forest University in 1974 and the University of Georgia College of Veterinary Medicine in 1978, then trained and worked at Spendthrift Farm before joining Bill Rood in Lexington in 1982. The pair later built out the Georgetown Road hospital campus, helping turn what began as an ambulatory practice into a major equine referral and specialty center. (roodandriddle.com)
He was best known scientifically for his role in the 2001 mare reproductive loss syndrome outbreak. Rood & Riddle says Riddle was the first person to recognize and report the abortion outbreak, and University of Kentucky materials describe MRLS as a previously unrecognized disease that caused widespread foal loss in Central Kentucky. UK says the outbreak led to an estimated loss of 30% of the 2001-2002 Thoroughbred foal crop and roughly $340 million in economic losses, before research tied the syndrome to eastern tent caterpillars and helped produce practical prevention guidance for farms. (roodandriddle.com)
That combination of clinical observation and field relevance helps explain why Riddle carried such weight in equine medicine. His Rood & Riddle profile lists leadership roles including president of the Kentucky Association of Equine Practitioners, the Society for Theriogenology, and the Theriogenology Foundation. The hospital also noted his clinical interests in uterine culture and cytology, early twin management, fetal sexing, and diagnostic ultrasound of the mare reproductive tract, all core areas for reproductive-heavy equine practices. (roodandriddle.com)
Industry reaction has emphasized not only Riddle’s expertise, but also his steadiness as a mentor. In a 2024 AAEP award announcement, The Horse reported that Riddle received the association’s Distinguished Educator–Mentor Award, recognizing his impact on the development and training of equine practitioners. The same report said many of the interns he guided went on to theriogenology residencies, board certification, and mentoring roles of their own. In Thoroughbred Daily News, longtime colleague John Williams called him a “quiet giant” and “gentleman,” underscoring the personal regard that accompanied his clinical reputation. (thehorse.com)
Why it matters: For veterinary professionals, especially those in equine, food animal, or mixed practice settings with a strong ambulatory culture, Riddle’s career is a reminder that influence in veterinary medicine often comes from three places at once: careful clinical observation, institution-building, and mentorship. His early recognition of MRLS shows how frontline practitioners can trigger major disease investigations. His role in growing Rood & Riddle shows how specialty care can evolve from local practice roots. And his teaching legacy matters at a time when workforce development, intern support, and sustainable career pathways remain central concerns across veterinary medicine. (roodandriddle.com)
There’s also a broader workforce angle here. In equine medicine, where recruitment and retention have long been pressure points, high-credibility mentors can shape not just individual careers, but the pipeline into advanced training and referral practice. Riddle’s recognition by AAEP for mentorship suggests his influence extended well beyond his own caseload, reaching into how future veterinarians learned reproduction, ethics, and professional standards. That kind of legacy is harder to measure than a publication list, but it can be just as durable. (thehorse.com)
What to watch: In the near term, the profession will likely see formal tributes from equine organizations and training programs, while memorial events in Kentucky on September 28 and 29 provide the first public markers of remembrance. Longer term, Riddle’s death may prompt renewed attention to the clinicians who built modern equine referral practice, and to how their mentorship models can be carried forward for the next generation. (thoroughbreddailynews.com)