Section: Causes
It is likely that laminitis may arise as a consequence of numerous different causative factors. Most current information pertaining to the cause of laminitis is based on the laminitis seen in conjunction with intestinal disorders. However, it should be noted that laminitis sometimes occurs in the absence of any intestinal problem and may, in those cases, have an entirely different mechanism.
Some of the well-recognized causes for laminitis are:
Intestinal. Associated laminitis is an intestinal problem that leads to the absorption of specific toxic substances into the bloodstream that cause laminitis. Numerous intestinal problems may cause laminitis and include diarrhea (colitis), colic, ingestion of lush grass, and the consumption of excessive quantities of grain.
Plant Toxins. Several plant species may cause laminitis. Well known examples include Black Walnut and Hoary Alyssum. Horses that are allowed to graze endophyte-infected Tall Fescue are believed to be at increased risk for laminitis. Other unrecognized plant species might also cause or increase the risk for laminitis.
Trauma. Whenever a hoof has been severely traumatized, the resulting inflammation may lead to laminitis. Examples include "road founder," the development of laminitis following hard work on hard ground. (Road founder is important in horses with recently trimmed soft feet that have not been shod). Laminitis occurs in some horses following aggressive trimming, even in the absence of any substantial work.
Bearing Excessive Weight. Whenever a horse must bear all (or most of) the weight of one side of the body on one foot, that foot is at great risk for laminitis. An example of this type of laminitis is the situation that exists when a horse is lame in one limb to the degree that the weight is predominantly borne by the opposite limb. Oftentimes, before the source of pain in the original limb has healed, lameness is evident in the weight-bearing limb because laminitis has occurred as a result of the extra loading.
Inflammation. Another cause is the extension of the inflammatory process during the development of a sole abscess.
Vasculitis. Laminitis may occur during or following recovery from a respiratory infection. Although it is uncommon, some of the infectious agents involved in equine respiratory disease will attack the blood vessels (vasculitis) and, in so doing, interfere with blood flow through the hoof, leading to laminitis.
Glucocorticoid Steroids. For inexplicable reasons, glucocorticoid steroids appear to cause or increase the risk for laminitis in horses. For this reason, this category of drugs is used cautiously in horses. The body's production of its own natural glucocorticoids (cortisol) is sometimes increased (during stress) and this increase in endogenous cortisol appears to lead to laminitis. The syndrome of excessive glucocorticoid effect in the body is known as Cushing's syndrome; laminitis is one of the important clinical manifestations of equine Cushing's syndrome.
Idiopathic. In many instances, a specific reason for the development of laminitis cannot be clearly identified. It is likely that an unseen/unrecognized, mild intestinal disturbance or dietary indiscretion may be the cause.
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