Laminitis is a frightening word for horse owners. The causes are many, the treatment is difficult, and the prognosis is uncertain. While laminitis can present as common lameness or discomfort, the best action at any sign of distress is immediate intervention and early treatment from an experienced veterinarian. Palm Beach Equine Clinic’s Dr. Samantha Miles recently discussed some of the causes, treatments, and outcomes of this disease.
What is Laminitis?
Laminitis is a complicated disease of the hoof that can develop for a variety of reasons. The lamina is a connective tissue that suspends the pedal (coffin) bone in the foot, and holds the whole hoof capsule together. If there is inflammation of the lamina, that suspension breaks down and the coffin bone becomes very unstable. The bone can tip forward and rotate, causing the hoof to “sink”. The deep digital flexor tendon (DDFT) also attaches to the coffin bone and pulls on it. When the DDFT pulls against the lamina, it can increase the downward rotation of the bone and have very painful and devastating results. In severe cases, the bone will rotate through the sole of the hoof, causing irreparable damage that leads to euthanasia.
What Causes Laminitis?
How laminitis develops is a difficult and multi-factorial question. One of the major causes understood more in recent years is metabolic disease. Horses that develop insulin resistance have decreased blood flow that can cause a laminitic episode in the foot. Obesity, insulin resistance, and subsequent laminitis form Equine Metabolic Syndrome. It is most commonly seen in ponies, but can affect any equine.
Though not a common problem in South Florida due to the poor quality of grass, most of the country sees a rise in laminitis cases during the spring seasons. Due to high levels of sugar in lush grass, many horses develop metabolic issues during these times that add to insulin resistance and decrease insulin sensitivity.
Another cause of laminitis is steroids, but Dr. Miles emphasized that this is really horse dependent. Some horses do not tolerate steroids well, and other horses can take a lot of steroids for various medical issues with no complications. Ponies seem to be the most sensitive to steroid induced laminitis. It is not the most common cause of laminitis, and Dr. Miles emphasized that this is not a reason to exclude the use of steroids in many cases.
A very serious and fast acting cause of laminitis is any illness that causes gram-negative bacteria to die off in the horse, such as colitis (severe diarrhea). When the gram-negative bacteria are dying, it can cause the release of endotoxins that will damage the lamina. These cases are a big concern for treating veterinarians because the horse can develop laminitis very fast, and early intervention is the only chance for prevention. However, these cases can be challenging to treat and can end in fatality.
Dr. Miles stated, “Sometimes laminitis just happens randomly, and we can’t find a reason unfortunately. It can happen in just one foot and be severe, and we just don’t know why it came about.”
This pony had an acute episode of laminitis coupled with metabolic disease that caused one foot to rotate fairly rapidly with the other foot intact. The line of the pedal bone should be parallel to the hoof wall line, but it has rotated so that there is a larger space between the tip of the coffin bone and the hoof wall versus the coffin bone at the coronary band and hoof wall. Photo courtesy Palm Beach Equine Clinic.
What are the Symptoms?
“Laminitis presents itself in many different ways,” Dr. Miles noted. “Usually the horse will not want to walk or move forward. Sometimes caregivers will think the horse is showing signs for colic because he/she will not get up. It usually presents with immobility.”
Another major sign is increased digital pulses in the feet. The veterinarian will often hoof test the horse and find sensitivity in the toe with hoof testers (depending on how severe it is). Shifting lameness is often seen, where the horse shifts from one front foot to the other front foot, and back and forth.
If a horse founders in all four feet, which is usually seen in more severe cases like colitis, they will lean their hind end against the wall, almost trying to dog-sit against the wall because they are trying to get the pressure off their hind feet, but their front feet are also sore. Horses find ways to compensate and relieve pain.
Changes in the feet will develop in either severely acute or chronic cases. In chronic laminitis cases, the horse will develop rings in the hoof, which can only be seen over a long period of time. Rings can also develop with nutritional deficiencies and other causes, but one can see a difference in rings caused by laminitis. Called “divergent rings”, the laminitic rings tend to separate towards the heel, so there is a bigger space between the rings at the heel than there is at the toe.
With severely acute cases, when the hoof sinks, a shelf or indentation may become visible on the coronary band, but that usually will not be seen right away.
How is Laminitis Diagnosed?
How quickly laminitis develops depends on the cause and how quickly the owner/veterinarian takes steps to slow the progression will depend on the treatment steps. Metabolic causes tend to be more insidious in onset. Colitis cases can progress in a matter of 24 hours to rotated or sunken if severe.
At Palm Beach Equine Clinic, the advanced imaging capabilities are extremely helpful in diagnosing and tracking the progress of laminitic changes. The veterinarian can take side view x-rays of the feet that show the shadow of the lamina. In these images, the veterinarian is able to see where the bone sits and if there is any rotation present. In some cases, the veterinarian may also take MRI images of the foot to track any changes.
“We measure angles and see what degree of rotation is present, and then we can track that over time to find out if a horse has stabilized or is still actively rotating,” Dr. Miles explained. “It usually takes a few days for rotation to occur from the onset of pain, so we take baseline radiographs because we want to see the deviation from the normal radiographs on day one as the disease progresses. We take another set of images a week after that to see if it has stopped rotating. We will take a set every week until we know that it is stable.”
This horse had severe rotation of his pedal bone through the sole of the hoof, very close to the ground. This is a chronic case with an acute episode that triggered the rapid rotation.
What is the Treatment?
In acute cases, the horse will have all feet iced for at least the first 48 hours to decrease inflammation. Dr. Miles noted that icing is only really useful in acute cases. In the chronic cases that have been happening over time, the veterinarian would want to increase the blood flow to the foot, and icing is counterproductive to that.
Other treatments include administering Acepromazine, which decreases anxiety in horses and dilates the blood vessels, which increases the blood flow to the foot. A similar drug called Pentoxifylline also increases blood flow to the feet.
Horses are generally put on Phenylbutazone (Bute) for pain management and anti-inflammatory effects. In some acute cases, the horse will also be given DMSO, which binds to any free radicals or bi-products of inflammation that are circulating in the body that can cause more damage, and assists to excrete the bi-products in the urine.
The next step is to elevate the heel. PBEC has created its own frog support pads for the temporary acute stages that seem to be very successful in relieving some of the pain. When the foot is more stable and has stopped actively rotating, the horse will then receive more advanced corrective farriery for long-term foot support.
“I think the thing about laminitis is that it is very variable and it is a day-by-day process,” Dr. Miles stated. “There is no prediction, unfortunately, on how it plays out. People always want to know how bad it is, and if the horse is going to be able to perform again, and the fact is we do not know until that time comes. It is one of those horrible diseases. We have had some weird cases this year, some really tragic looking ones, that have come back, and other ones that did not look that bad that didn’t make it. My best advice is to call the vet as soon as any lameness or discomfort is recognized. Early intervention is the best option because the condition can deteriorate so quickly. The earlier the intervention, the better off the horse will be.”
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Article courtesy of Jump Media