A team of researchers recently evaluated a possible treatment for equine bone fragility disorder (BFD) with positive results, giving owners of horses affected by this currently incurable disease a glimmer of hope.
Equine BFD, also known as bone fragility syndrome, has only been identified in horses residing in northern coastal California and has a similar geographic distribution to pulmonary silicosis (a respiratory disease caused by inhaling certain types of silicate dust found in some geographic regions). According to lead researcher Scott A. Katzman, DVM, Dipl. ACVS-LA, an equine surgeon at Cleary Lake Veterinary Hospital in Prior Lake, Minn., BFD is characterized by clinical signs including:
- Generalized stiffness;
- Exercise intolerance;
- Intermittent to severe lameness, depending on disease severity;
- Lordosis (swayback);
- Lateral scapulae bowing;
- Weight loss; and
- Reduced range of motion in the cervical spine.
The cause of the disease remains unknown.
"Historically, treatment for this BFD has been largely symptomatic, relying on systemic administration of non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids, exercise restriction, and relocation to a different geographic region," Katzman said. "Treatment has been generally unrewarding, with only transient improvement of clinical signs."
To that end, Katzman and colleagues elected to test the benefit of using zoledronate--a nitrogen-containing bisphosphonate used to prevent bone resorption in humans--on horses with BFD. Katzman explained that the authors chose zoledronate due to "its increased potency and duration of action" compared to tiludronate (marketed as Tildren), a related medication used previously in a limited number of clinical cases of BFD, with disappointing results. Katzman added that to his knowledge, "The use of zoledronate in horses has not been previously described."
The team employed 10 horses presented to the University of California, Davis, William R. Pritchard Veterinary Medical Teaching Hospital from May 1, 2008, to Oct. 31, 2009. All horses received a BFD diagnosis via clinical signs and bone scan (bone-phase nuclear scintigraphy) findings.
At presentation, researchers carried out a complete physical examination on each horse, which included lameness exams videotaped for post-zoledronate administration comparisons. Katzman said lameness was graded on a 0 to 5 scale (with 0 being no lameness), according to the American Association of Equine Practitioners lameness grading system. Then, researchers bone scanned each horse to evaluate the amount of radiopharmaceutical uptake present.
The researchers administered an intravenous zoledronate infusion to each horse before reexamining the animals six months later.
Key study findings included:
- Researchers found no adverse effects after zoledronate administration;
- Although the researchers allowed NSAID administration post-zoledronate administration, none of the horses necessitated the medications between treatment and the six month evaluation;
- Nine of the 10 horses showed clinical improvement in lameness scores, although lameness did not resolve completely in any horse;
- Eight of the 10 horses had improved scintigraphic findings post-zoledronate administration (the other two horses' scintigraphic findings did not worsen and were similar to initial examination).
"Treatment with zoledronate appeared to be useful for improving clinical and scintigraphic signs of BFD identified in horses in California," Katzman said. "Six months after drug administration, nine of 10 affected horses had an improvement in lameness grade or resolution of clinical signs of musculoskeletal pain, compared with findings at the time of initial examination."
The researchers noted that the current study's limitations include the small number of horses and the lack of a control group. Additionally, Katzman said, "BFD is a progressive, debilitating disease, which suggests the need for treatment at the time of diagnosis in most situations. This is primarily because of the risk of pathological fractures developing in addition to other signs of clinical deterioration, which makes a long-term, placebo-controlled trial difficult to justify to horse owners."
The team noted that further research is needed to better understand zoledronate's pharmacokinetic properties before the drug is used regularly.
The study, "Use of zoledronate for treatment of a bone fragility disorder in horses," appeared in June in the Journal of the American Veterinary Medical Association The abstract can be viewed online.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.