The death of Kentucky Derby winner Barbaro brought sharply into focus the challenges that laminitis brings. The champion racehorse survived and recovered from a catastrophic leg injury, only to succumb to laminitis. Laminitis can occur in any breed of horse, of any size, at any age. The prevalence of laminitis among horses, combined with the incomplete understanding of the disease, along with the emotional and economic costs, all contribute to the frustration felt by veterinarians, owners, trainers, and caregivers when confronted with this dreaded disease.

Sometimes referred to as “founder,” an old nautical term used to describe a sinking ship, laminitis is a severely debilitating, tremendously painful disease of the soft tissues (laminae) that connect the hoof wall (the outer part of the hoof that you see) to the coffin bone (the skeletal bone that exists inside the hoof). If not treated quickly, it can cause permanent and painful changes in the foot that leave little option but to euthanize the animal in some cases.
The anatomy of the horse's foot yields clues as to why these animals are susceptible to laminitis. The horse is a single-toed animal, and the last bone, or phalynx, of the digit (foot) is encased in multiple layers of a tough protein called keratin, the same stuff our fingernails are made of. These protective layers comprise the hoof and are supplied with nutrients by a complex system of microscopic blood vessels. A good way to understand laminitis is to think of the healthy coffin bone as "Velcroed" to the inside of the hoof wall by interlocking sensitive and insensitive laminae. When the Iaminae become inflamed, the sensitive tissues underneath the hoof wall become excruciatingly painful as the layers of hoof wall, or laminae, separate-the horse is then said to have laminitis.

Although the condition usually affects only the front feet, it may involve all four feet. Both acute and chronic forms occur. The laminae become inflamed because of congestion of blood and accumulation of toxins in the hoof region resulting from any of several causes:

• Pasture or grain (carbohydrate) overload
• Colic
• Endotoxins in the blood
• Uterine infection or retained placenta
• Metabolic disturbances such as insulin resistance or Cushing’s disease
• Obesity
• Excess weight-bearing on a supporting limb (opposite a limb with a severe injury)
• Infection of the blood (septicemia)
• Infection of the lungs
• Enterocolitis (inflammation of the small intestine and colon)
  

Owners and caregivers should learn to recognize the following, very characteristic appearance of a laminitic horse:

• Shifting of weight from foot to foot
• Slight stiffness of gait
• Reluctance to move
• Classic founder stance: all four feet forward , so hind feet carry more weight
• Warm feet, bounding digital pulse
• Sweating, high heart and respiratory rates
• Lying down and not wanting to get up

Any horse showing these signs should be seen immediately by a veterinarian to confirm the diagnosis and start emergency treatment which may not only save the horse’s performance career, but also his life.

The goal of treating laminitis is to first treat the primary disease that caused it, then try to limit the inflammation and structural damage that is occurring. Because the exact sequence of events leading to damage in the foot has not been completely figured out, treatment can be controversial. Most agree however, that a nonsteroidal anti-inflammatory (NSAID) medication like phenylbutazone or "bute" should immediately be given to reduce inflammation, since this seems to be a common factor in all laminitis cases. Other medications that may be used include vasodilators like acepromazine, anticoagulants, and antiendotoxins.

The next step is providing mechanical support to the foot, to ensure even blood flow to all the tissues and try to prevent rotation or sinking of the coffin bone. Some do this by stalling the horse in sand or deep bedding, which provides soft, even support across the whole bottom of the foot. Others prefer to attach special shoes to the bottom of the foot to provide "arch support," to elevate the horse’s heels, and to encourage breakover in a certain area of the foot. Again, most agree that stall rest is critical, at least for the first few days.

The veterinarian and farrier must work closely together to provide treatment to the laminitic horse both in the acute and chronic phases. Baseline and follow-up radiographs allow the healthcare team to measure the damage and accurately place and replace support devices. Day to day monitoring of the horse’s condition will help minimize the risk of repeated episodes of acute laminitis and allow owners and caregivers to detect problems as they arise. It is therefore important for owners and caregivers to be aware that the management of chronically foundered horses can be very difficult, frustrating and time consuming, but that in many cases, dedication can lead to amazing results.

Despite substantial research over the last three decades that has investigated numerous pathways involving the onset and development of laminitis, a complete knowledge and understanding of this disease has yet to be achieved. Effective preventative and therapeutic management strategies continue to remain elusive. A complicating factor is that the disease process is encased within the hoof wall, and many technologies used in other research areas are not easily useful or adaptable for effective study of this disease. The technology and resources required to advance the knowledge in this area are expensive. And because the disease is unique to horses, the research technology must be developed exclusively for the horse.

Laminitis is among the most devastating, and unfortunately one of the leading causes of death and lameness in horses. Hundreds of horses will be diagnosed with laminitis each day. It has been listed by the American Association of Equine Practitioners (AAEP) as one of the most important diseases afflicting horses and the highest priority for funding for further research. Laminitis research is vital to unraveling the unanswered questions about the disease and developing reliable preventative and therapeutic measures, for all of the equine population.

References:

www.aaep.org
www.smartpakequine.com/laminitis.aspx
www.petalia.com