Ilka Wagner
DVM, MAgr
Equine Veterinary Services
Hearne, Texas

Laminitis, also known as founder, is a disease that has plagued the horse for centuries. As far back as 350 BC, it has been described by horsemen as a crippling affliction that often times led to the horse’s ultimate demise.1 These past records focus primarily on the lameness issues and conformational changes in the horse’s foot affected by chronic laminitis. Historical references also refer to various forms of treatments, both medical and therapeutic shoeing, all in an attempt to alleviate the severe painfulness of the disease and allow the horse to function again in work or sport.1 During the last half of the twentieth century practitioners and horsemen have also begun to recognize and investigate a connection between chronic laminitis and other systemic, or body, changes that occur simultaneously.

 

Ilka Wagner

Dr. Ilka Wagner graduated from Texas A&M University as a DVM with emphasis on equine medicine/lameness. She has been involved with The Hoof Project, established by Dr. David Hood, since 1996 and in private practice since 1997 in Hearne, Texas. Equine Veterinary Services is an ambulatory practice specializing in equine lameness. Ilka has presented papers on laminitis at several national meetings including the American Association of Equine Practitioners, American Veterinary Medical Association and Equine Sports Medicine.

There are four distinct phases to laminitis, 1) developmental, 2) acute, 3) subacute and 4) chronic. These phases, their definitions and descriptions will be addressed individually, followed by a brief discussion of some of the systemic conditions that are associated with horses suffering from chronic laminitis. As stated above, the terms laminitis and founder can be used interchangeably, and will be more distinctly defined by the addition of either acute or chronic.

Developmental Laminitis
Developmental laminitis refers to the stage of the disease that is relatively difficult to diagnose and treat, however critical for prevention of the next stage. This is the time between the initial cause of the laminitis, or “insult” to the foot, and the onset of the painful lameness that is commonly associated with the disease.2 The list of causes for this disease is exhausting. Common causes include grain overload, retained placentas, overwork on hard surfaces, and many more. However, in at least 50% of the diagnosed cases of laminitis the inciting cause is never determined. That is part of what makes this disease such an incredible challenge from a prevention standpoint. This developmental phase has an average duration of 40 hours.3

During this developmental phase, if it can be identified before reaching the acute phase, preventative measures from a medical standpoint should be administered to the horse. This may range from the administration of various drugs to nasogastric intubation of fluids, depending on the inciting cause.

Acute Laminitis
Acute laminitis is defined as that stage in which lameness first appears.2 This can range from a very mild, difficult to notice lameness to such a crippling lameness that the horse refuses to move. It is during this stage that the horse will often take on the classic “laminitis stance” in which the hind limbs are place further underneath the body while the front limbs are extended forward, all in an effort to shift body weight off the toes of the forefeet. During this stage the attachment and position of the third phalanx, or coffin bone, remains unchanged. This phase will typically last for approximately 72 hours, after which the horse will progress into either the subacute or chronic phase of the disease.3

During the acute laminitic phase, treatments should focus on pain management, support of the foot, and medical regimens that encourage proper blood flow to the feet. It should be kept in mind that not only the front feet may be affected, and the rear feet should be evaluated as well. Radiographs are an important diagnostic/assessment tool, while stall confinement is a necessity and trailer rides should be avoided.

Subacute Laminitis
This phase follows acute laminitis and is considered a recovery phase.4 At this stage the acute painfulness of the disease may or may not still be present, but the horse is relatively stable and the coffin bone is still in the correct position, with no demonstration of mechanical collapse. It is at this stage that the horse can either progress to complete recovery or go on to chronic laminitis. The average duration of subacute laminitis is variable, but 8-12 weeks has been suggested as a minimum.3

Treatments during this time should include continued stall confinement, limited activity, support of the affected feet and pain management as necessary. Excessive exercise or turn out, especially during the first few weeks, can cause the horse to progress to the chronic laminitis stage quickly. The goal during the subacute phase is to allow the damaged tissues to heal and prevent permanent mechanical collapse from occurring.

Chronic Laminitis
Chronic laminitis is defined as that time when mechanical collapse of the foot occurs.4 This can be almost immediately following the acute phase, thereby completely bypassing the subacute phase, or may occur several days or weeks following the initial insult. Mechanical collapse refers to the actual movement or separation of the coffin bone away from the hoof wall. This can occur by both rotation and/or sinking of the bone within the hoof capsule. It is in this stage where prevention is no longer an option and therapeutic rehabilitative treatments begin. These patients may or may not fully recover and the time frame can vary from months to the life span of the horse.

During this chronic phase of laminitis, the focus is primarily on realignment of the coffin bone within the hoof capsule, as well as support of the foot in order to allow the damaged tissues to heal in a proper fashion. Pain management is a necessity as well during chronic laminitis in order to help prevent decubitus ulcers from forming and/or tendon contraction from occurring. Exercise management is variable depending on how severely the horse is affected. Finally, radiographic evaluation over time and therapeutic trimming/shoeing are necessary in order to encourage proper hoof wall growth and realignment of the coffin bone. During this stage, radiographs alone should not be used as a prognostic tool. They should be used in conjunction with the overall clinical evaluation of the patient, as many horses can become sound and still demonstrate significant radiographic changes.

Systemic Diseases & Chronic Laminitis
Often times, certain systemic pathologies or specific body types are associated with horses suffering from chronic laminitis. Current research in this area is continuing to grow and is primarily focused on three specific disease pathologies, 1) Equine Metabolic Syndrome, 2) Pituitary Pars Intermedia Dysfunction and 3) Immunopathologies. Much of the research today focused on these diseases is reflective of human research in similar areas.

Equine Metabolic Syndrome (EMS) is a disease commonly associated with obese, easy keeper type horses. Often times these horses have cresty necks, abnormal fat deposition in certain body areas, and abnormal blood work with respect to glucose and insulin levels. Many of these horses also have concurrent chronic laminitis, usually reflecting relatively mild lameness episodes, eventually becoming worse over time. Mares will often not settle or carry a foal to term.5

Pituitary Pars Intermedia Dysfunction (PPID), also often referred to as Equine Cushing’s Disease, is a disease affecting the pituitary gland in the brain and affected horses demonstrate various clinical signs. Included in these are excessive hair coats in summer time, cresty necks, abnormal fat deposition, enlarged abdomens yet not overweight, abnormal lactation in mares, and more. They are also often times suffering from chronic laminitis, again as with EMS, it is frequently insidious and overlooked for some period. These horses can be separated from the EMS horse by various blood work, most diagnostic of which is the dexamethasone suppression test. The PPID horse will most times test positive where an EMS patient will have a normal dexamethasone suppression test. This is important when approaching treatment options for either patient.6

Immunopathologies exist in some chronically foundered horses – including those that may or may not test positive for either EMS or PPID. It has been well established that many chronic laminitic patients have increased responses to allergenic challenges. In addition to this, complaints regarding the appearance of lamenesses post-vaccination are documented with enough frequency that this should be a consideration when establishing a vaccination protocol for the laminitic patient.7

Conclusion
As can be seen by the numerous horses affected by laminitis throughout the world, this can be a very devastating disease. It is physically challenging and crippling for the horse, and emotionally distressful for the owner. Further research in this area must continue in order to more completely understand this disease process and develop preventative measures as well as successful treatments for those horses affected by this disease.

References
Wagner, IP and Heymering H. Historical perspectives on laminitis. In: Vet Clin NA Eq Pract; 1999; 15(2):295-310.
Hood DM, Grosenbaugh DA, Mostafa MB, et al. The role of vascular mechanisms in the development of acute equine laminitis. J Vet Intern Med 1993; 7:228.
Hood DM. Laminitis in the horse. In: Vet Clin NA Eq Pract; 1999; 15(2):287-294.
Hood DM. Perspectives on chronic laminitis. In Hood DM, Wagner IP, Jacobson AC (eds): Proceedings of The Hoof Project. College Station, TX Private publisher, 1997; 21.
Donaldson, MT. Equine metabolic syndrome: What is it and how do I diagnose it? In: Proceedings. 2nd Intern Eq Conf on Lam and Dis of the Foot. 2003, 64-80.
Schott, HC. Pituitary pars intermedia dysfunction: equine Cushing’s disease. In: Vet Clin NA Eq Pract; 2002; 18:237-270.
Wagner IP, Rees C, Dunstan R, et al. A systemic immunologic hyperreactivity to intradermal skin testing in chronically laminitic horses. AJVR 2003;64(3):279-283.

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