Laminitis causes painful inflammation and breakdown of the structures connecting the coffin bone to the hoof capsule in horses' feet. In more severe cases the coffin bone can rotate, causing extreme pain and lameness in the horse that might necessitate euthanasia. Researchers have suggested systemic inflammation might be linked to hoof inflammation, leading one team to study the efficacy of a new anti-inflammatory drug in treating laminitis.
"Horses can develop laminitis rapidly and from multiple causes, but the one common denominator is the development of an inflammatory cascade," said Maimaiti Tuniyazi, doctoral student and research assistant at Jilin University's College of Veterinary Medicine, in Changchun, China. Once this inflammatory cascade begins, veterinarians must stop it quickly to reduce the risk of the horse's hoof structures degrading, he added. Therefore, Tuniyazi and his team set out to study the efficacy of methylated tirilazad, a novel anti-inflammatory drug that might be beneficial when treating laminitis in horses.
Researchers studied 20 3-year-old Mongolian horses with no signs of digestive problems that had not been recently exposed to antibiotics, deworming medications, or been transported over long distances within three months of the study. They carefully monitored each horse's diet to ensure it was balanced for his or her nutritional needs and offered local forage at 2% of body weight on a dry matter basis. They allowed each horse unrestricted access to water and did not provide any additional dietary supplements.
A computer program randomly assigned the horses to four groups: control (no laminitis), laminitis (with no treatment), prophylactic (laminitis with preventive methylated tirilazad administration), and treatment (laminitis with methylated tirilazad treatment).
The researchers then induced laminitis in each horse and applied the associated group treatment, closely observing each horse's Obel score. The Obel grading system helps veterinarians classify and understand the progression of laminitis in horses during diagnosis and treatment. The researchers humanely euthanized any horses in the laminitis groups with an Obel score of III or greater.
In the prophylactic group the researchers administered intravenous (IV) methylated tirilazad for two days prior to inducing laminitis and at the time of induction. In the treatment group they administered IV methylated tirilazad at the first signs of fever or diarrhea (common signs of inflammation) and observable signs of laminitis (such as lameness). The researchers humanely euthanized the horses in each of these groups 72 hours after inducing laminitis to examine the hoof tissues.
Horses treated with methylated tirilazad showed reduced clinical signs of laminitis, such as improved lameness scores and laminar tissue structure. "For horses, (methylated tirilazad) offers a promising treatment that can significantly reduce the pain and lameness associated with laminitis, potentially restoring their mobility," said Tuniyazi. "For horse owners, it could mean a reduction in the emotional and financial burden of managing a horse with laminitis. Veterinarians would gain a new, effective tool in their arsenal to treat this challenging condition, improving outcomes for patients, and potentially reducing the need for more invasive or costly interventions."
Tuniyazi said he and his team believe potential applications for methylated tirilazad might include resolving laminitis episodes more rapidly and treating other conditions where an inflammatory cascade or inflammation and tissue damage are complicating factors. However, he noted that further research is needed to confirm these findings.
Laminitis can be very painful for horses and challenging and expensive to address. Researchers report that methylated tirilazad might provide an efficacious and cost-effective way for veterinarians to treat this crippling disease. However, they acknowledge they need more long-term research across different populations of horses to fully establish the role this new drug might play in treating laminitis.
The study, "Methylated tirilazad may mitigate oligofructose-induced laminitis in horses," appeared in Frontiers in Microbiology in September 2024.