On a warm spring night everyone in the barn is eagerly awaiting a new foal's arrival. The wait is rewarded with the birth of a big, strong, and beautiful colt. During the next 12 months the foal thrives. The owners dream of having a future champion until one morning the farm manager notices the colt's gait is abnormal, and he looks somewhat incoordinated (ataxic) in his hindquarters. The veterinarian comes out to the farm, examines the yearling, and takes standing radiographs (X rays) of the cervical vertebrae. Assessment of the radiographs and the clinical signs lead to a diagnosis of wobbler syndrome and a guarded prognosis for any sort of successful athletic career.
A standing cervical radiograph showing a horse with Wobbler syndrome.
This scenario is one that occurs all too often but, with participation from the equine community, University of Kentucky researchers hope to learn more about the genetics behind the disease.
Wobbler syndrome is a disease that affects the horse's nervous and musculoskeletal systems. It is characterized by a structural narrowing of the vertebral canal in the neck that can produce severe neurologic deficits through cervical spinal cord compression. The cause is thought to be multifactorial with genetics, high planes of nutrition, trauma, rapid growth, and decreased copper/increased zinc levels all potentially important.
The possible role of genetics, in particular, is interesting and remains somewhat controversial. A pedigree analysis several decades ago suggested that inherited genes were involved, yet breeding studies have not demonstrated a clear pattern of inheritance. Do genetic determinants exist? Is it a single gene or multiple genes? Are there interactions between genetic and environmental (management) variables? Perhaps more relevant in the immediate term, however, is whether there is any hope that we will be able to answer these questions and elucidate the role of genetics in this disease?
The answer to the last question is "yes"--there is now a new reason to be hopeful. With completion of the equine genome sequencing project and the subsequent development of a genetic research tool based on analyzing a type of DNA variation known as single nucleotide polymorphisms (or SNPs), researchers can study genetic associations in the horse with much greater sensitivity than previously possible. Two University of Kentucky veterinarians at the Gluck Equine Research Center--Jennifer Janes, DVM, PhD, and James MacLeod, VMD, PhD, John S. and Elizabeth A. Knight chair, professor of veterinary science and director of UK's Equine Initiative--are currently conducting an SNP-based research study to pinpoint genes that might contribute to the cause and progression of wobbler syndrome.
However, assistance from the horse community is critical to identifying additional cases. If you know of a horse with wobbler syndrome and would like to contribute to the study, contact Janes by e-mail at firstname.lastname@example.org.
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Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.