Three major advances in our understanding of laminitis in horses are highlighted by researchers in a recently published review.
First, laminitis is now considered to be a clinical syndrome associated with a disease that affects a number of organs and tissues, or affects the body as a whole or altered weight bearing rather than being a discrete disease entity.
Next, laminitis associated with the endocrine system, known as endocrine laminitis, is now believed to be the predominant form in animals presenting primarily for lameness.
Third, from a series of studies led by University of Liverpool researcher Professor Cathy McGowan in conjunction with veterinary pathologist Janet Patterson-Kane and PhD student Ninja Karikoski, it was shown that microscopic changes in the hoof lamellae were subtle in comparison with previous descriptions. But, most importantly, there was evidence of a prolonged subclinical phase in at least some horses, as evidenced by the development of divergent hoof rings visible on the hoof wall.
These hoof rings may signify a vital window of opportunity for horse owners and their veterinary surgeons to recognise and apply therapeutic intervention before painful laminitis occurs.
Under the microscope it was clear that instead of severe basement membrane failure (as had been proposed based on experimental models in severely systemically ill horses), stretching and elongation of the lamellar cells is an early and key event in the disease, and this knowledge will inform research directions in the future.
These simple but important paradigm shifts have several implications, the main one being that an accurate diagnosis of the associated systemic disease (most commonly endocrine disease) would be pivotal for laminitis management, prognosis and the prevention of recurrence.
The review, titled “Paradigm shifts in understanding equine laminitis”, has been published in The Veterinary Journal.
Laminitis is one of the most serious diseases of horses, ponies and donkeys. It is a painful condition of the tissues (lamellae) that bond the hoof wall to the pedal (coffin) bone in the horse’s hoof.
Severe and recurring cases can cause chronic painful lameness or result in the horse being destroyed to prevent further suffering.
For the past decade, researchers led by McGowan, from the university’s Department of Equine Clinical Science and Institute of Aging and Chronic Disease, have systematically investigated the form of laminitis caused by hormonal dysregulation – endocrine laminitis.
She led ground-breaking research that showed laminitis was directly caused by insulin, an important hormone involved in dietary glucose control, which overturned previous held theories of laminitis.
This new knowledge has paved the way for improving the veterinary industry’s understanding of the disease, and improving future research and treatment.
McGowan’s understanding of abnormal insulin regulation stemmed from her work as a veterinary specialist where she has treated many horses and ponies with endocrine disease. She noticed that what they had in common was abnormal insulin regulation.
“These findings completely change the way we think about a very important disease in horses,” McGowan says. “This is very important to the equine industry and veterinary profession and will be the basis of future research directions.”
Paradigm shifts in understanding equine laminitis
J.C. Patterson-Kanea, N.P. Karikoski, C.M. McGowan