By Julia Shrubb MA VetMB CertAVP(EM) MRCVS
www.ashbrookequinehospital.co.uk 01565 723030
Laminitis is an extremely common condition which has been recognised in domestic horses for thousands of years. The disease can result in extreme pain, chronic debilitation and may even necessitate euthanasia (putting the horse to sleep). Recent research has increased our understanding of the disease, but there is still a lot that is not completely understood. This article aims to provide an overview of laminitis, updates on treatments and its prevention.
What is laminitis?
Laminitis simply means inflammation of the laminae. The foot contains two sets of laminae which interdigitate forming the supportive structure of the pedal bone. In laminitis, these structures become damaged and weaken, allowing movement of the pedal bone within the hoof capsule. The accumulation of inflammatory products within the solid hoof capsule causes severe pain. Unfortunately the horse has to stand on this damaged structure, further increasing the pain.
Signs of laminitis
Although laminitis is a systemic (whole body) disease, the signs seen are usually associated with the feet. Some horses are slightly footsore and reluctant to turn in tight circles; others will be unwilling to stand. The horse may shift its weight back, resulting in the classic laminitic stance, but may also shift weight from foot to foot or be reluctant to move or lift a leg. These movements are all attempts to reduce weight transfer through the laminae. Although the front feet are most commonly affected, the disease can affect any single foot or often all four feet. Usually the hooves will feel warm to touch, especially around the coronary band. There may also be an increased digital pulse felt at the back of the fetlock. Occasionally there will be an obvious depression in the skin just above the coronary band. Some equines are so painful that they will have increased respiratory and heart rates and even sweat. Unfortunately by the time signs of laminitis are seen, significant damage will have occurred within the feet.
What causes laminitis?
Studies are ongoing to further understand the risk factors and causes of laminitis. Laminitis has long been associated with ingestion of lush grass in overweight ponies and in horses with Cushing’s disease. Recently it is has been discovered that this is linked with high insulin levels.
Laminitis can also be secondary to severe systemic illness when toxins are absorbed in to the blood stream e.g. in mares that do not pass their placenta after foaling or severe diarrhoea.
Which equines are at risk of laminitis?
Ponies have evolved to live on poor quality grasslands so unfortunately the ‘ideal’ good quality, lowland grass can precipitate this horrible disease. Many of our native breeds have a genetic predisposition to insulin resistance, and therefore laminitis. Being overweight is a big risk factor, but we commonly see laminitis in all types of horses and in lean animals. Laminitis is traditionally seen in the spring but we see cases throughout the year
The most common underlying cause of laminitis is Equine Metabolic Syndrome (EMS), a disease associated with resistance to insulin. These horses tend, but not necessarily, to be overweight and suffer from repeated bouts of laminitis. Often these ponies have a cresty neck, which is strongly linked with insulin resistance. EMS can be diagnosed with a blood sample which detects an inappropriate excess of insulin. This condition is fully reversible with dietary management and exercise. In some cases, human medication used in people with type II diabetes may be helpful.
Older horses with Cushing’s disease are also very prone to laminitis, which often responds poorly to treatment if the Cushing’s is not controlled. If your vet is suspicious of Cushing’s in a case of ongoing laminitis, they will advise testing for the disease as treatment can result in a dramatic improvement in the laminitis.
A simple clinical examination by the vet will usually be sufficient to diagnose laminitis, without the need for costly diagnostic techniques. Hoof-testers will be used to test for foot pain. The pain response is usually most severe over the sole in front of the frog as this is the area that the pedal bone will exert most pressure on if it is rotating. X-rays may be taken to assess the position of the pedal bone, allowing a more accurate prognosis to be given and these will also aid remedial farriery.
Acute cases of laminitis should be treated as veterinary emergencies, because appropriate and aggressive treatment will improve the outcome. Any identifiable cause of laminitis should be addressed such as removal of a retained placenta after foaling or testing for Cushing’s disease or EMS. The horse should not be walked or travelled unnecessarily as movement will increase the amount of damage. Strict box rest on a deep shavings bed is essential as this provides mechanical support by packing into the sole of the foot. Frog supports may be applied by the vet to provide additional support.
Your vet will assess each case individually but most require anti-inflammatory painkillers. These will increase comfort and should reduce inflammation within the laminae. Acetylpromazine gel is sometimes used to help blood flow to the damaged laminae in the early stages. This drug will also provide mild sedation, reducing movement round the stable and thus reducing stress on the weakened laminae.
Grass and all high starch and sugary foods, including apples, carrots and most mixes should be removed from the diet. The mainstay of the diet will be soaked hay; soaking reduces the soluble sugar levels whilst preserving the fibre content.
Once the horse becomes more comfortable, farriery is critical to a successful outcome. Plastic ‘imprint’ shoes are increasingly used to provide frog support. These also eliminate the need to nail on shoes which can cause further concussion and damage to the laminae. As the laminitis improves, metal heart bar shoes may be used for long term support.
The prognosis depends on the severity of the disease, whether the pedal bone has moved and how long the horse has been affected. The prognosis is worse if the pedal bone has sunk rather than rotated; however, the vet will be able to advise on each case individually. If the laminitis is only mild, complete repair may occur within two to three months. Some cases will require box rest and medical treatment for many months and will continue to be prone to subsequent bouts of laminitis. It should always be remembered that such long-term treatment will be costly and may not result in a cure. Sadly some severe cases do require euthanasia on welfare grounds.
As laminitis is such a horrible disease, prevention is always better than cure. Diet and exercise are key to preventing laminitis, especially if an individual has metabolic syndrome. Exercise has been shown to significantly improve insulin resistance. Limiting starch and sugar in any hard food is also very important. There are now a range of non-mollassed chops and sugarbeets and specially designed mixes available.
Cushing’s disease cannot be prevented, but prompt diagnosis and treatment is vital in prevention of laminitis secondary to Cushing’s disease.
Laminitis is a painful and debilitating disease. With prompt and aggressive treatment, many cases make a good recovery, although this may be protracted. Unfortunately in some cases, the degree of pedal bone displacement and pain is so severe, euthanasia is the only option.