Laminitis and how to recognise it

We are all looking forward to Spring approaching. However, it is important to be vigilant to both prevent and quickly recognise laminitis, particularly in those ponies prone to the disease.

What is laminitis and what causes it?
Laminitis is defined as ‘acute laminar degeneration’. The laminae are the sensitive tissues that attach the hoof wall to the pedal bone. When these become inflamed the horse will be very painful and the pedal bone can rotate and/or sink.

Laminitis can have many different trigger factors (often there is another underlying disease process):
• Pasture-associated laminitis (too much carbohydrate)
• Hormonal
o Equine metabolic syndrome
o Cushing’s disease
• Systemic bacterial overload (endotoxaemia). These horses will be very sick eg retained fetal membranes or grain overload.
• Concussion – ‘road-founder’
• Overloading of contralateral limb eg severe lameness
• Administration of steroids as medical treatment for another disease

Why is laminitis still so common and who is at risk?
Laminitis has been documented since the Roman times and although we know a lot more about it it’s certainly not disappearing any time soon! An increasing population of horses and ponies are being kept in luxury conditions primarily as pets rather than athletes. This along with them living to an older age increases the number of animals that are both obese and/or have an underlying hormonal disease, which are major risk factors for laminitis. Risk and trigger factors significantly increase the chance of a horse contracting laminitis but it is important to realise that no horse is exempt.

What are the clinical signs?
Laminitis can be divided into acute and chronic. The signs are usually seen in the forelimbs but laminitis can develop in any combination of limbs.

Acute:
• Reluctance to move
• Weight shifting
• The classical ‘laminitic stance’ standing with the forelimbs out infront of them and leaning back onto the hind legs
• Increased digital pulses
• Heat on the hoof
• Pain in the toe region on hoof testers.

Chronic:
Abnormal hoof growth leads to (see picture):
• Divergent growth rings
• Long toe
• Flat sole
• Overgrown heel conformation 


Foot of a chronic laminitic that has not been cared for sufficiently. The long toes and divergent growth rings (arrow) are particularly evident.

What ‘first aid’ action should you take, and what treatment will the vet provide?
It is important to communicate with your vet to arrange a visit as soon as possible so that the right medication and additional tests are prescribed. Until the vet arrives it is important that the horse or pony is moved to somewhere with a lot of foot support and without access to excessive food so a stable with deep bedding and soaked hay is perfect.  Speak to your vet before giving your horse any pain relief such as ‘Bute’. Although this may be the best course of action a vet should always examine the horse first prior to treatment.

The vet’s diagnosis is based on history, type of horse and clinical signs. The most likely additional tests are:
• X-rays of the feet - to assess pedal bone separation, rotation, sinking and bone remodelling (see picture)
• Blood tests for Cushing’s disease and Equine Metabolic Syndrome are appropriate in some cases. These vary in their accuracy and can be discussed with your vet. 

X-ray of severely affected laminitic foot showing pedal bone rotation (R); pedal bone sinking (D); pedal bone remodelling (blue arrow) and pedal bone separation from the hoof wall as seen by a gas shadow (green star). 

Treatment for acute laminitis is a medical emergency. It requires a combination of pain relief medication eg phenylbutazone (‘Bute’), foot support and nutritional management as prescribed by your vet. Depending on severity and cause acepromazine  (‘ACP’) can also be given primarily to dilate blood vessels and increase blood supply to the laminae. 

Immediately after an attack strict rest for several weeks is vital to prevent further damage to the weakened laminae. Soft, deep bedding should always be provided and a decrease in nutrition should be considered. For example, soaking hay for an hour in warm water decreases the amount of sugars available by 50%.

How can involvement of the farrier benefit the horse?
Farriery is an essential part of long-term laminitis treatment. Communication between the vet and farrier is essential for best recovery and x-rays can be helpful for the farrier to optimise treatment. The aims of farriery post laminitis is to
• Reduce toe length and heel depth. This reduces the pedal bone rotation angle and reduces shearing forces on the laminae.
• Provide frog support to spread the weight bearing surface and reduce pressure on the toe – traditionally a heart bar shoe is used. 

This is a long process and no ‘quick fixes’ should be expected but consultation between your vet and farrier is essential for best results. Sometimes repeat X-rays are necessary to assess the progress. 

Managing a horse or pony that has had laminitis in the past 
This is a crucial part of treatment as once one episode has occurred the laminae are weakened and more prone. A calorie (particularly sugar) restricted diet and treatment of any underlying hormonal disease are the two most important areas to address:

Weight management
Overweight horses are at much higher risk of laminitis so it is important to know your horse’s ideal weight and how much he actually weighs. A weigh scales is the best way to determine your horse’s weight but the use of a weigh tape can be useful to monitor bodyweight trends - it is easy to look with ‘rose-tinted glasses’ when it comes to your own horse!  Another way to monitor a horse’s condition is to use a Body Condition Score (BCS) system such as the Henneke BCS with a scale from 1-9 (Henneke et al., 1983).  

A feed programme can then be compiled with your vet or a nutritionist to suit your horse’s needs based on his ideal weight and exercise regime. For example a maintenance diet for a 500kg horse in light exercise would in theory require 2-3% of it’s body weight in dry matter so aprroximately 12-15kg of hay or grass with an additional balancer to ensure intake of all the necessary vitamins and minerals. For weight loss, which is often necessary, this would be reduced to 1.5% of the horse’s ideal body weight and for laminitic cases it is necessary to make an extra effort to reduce sugar levels in the horse’s diet for example by soaking hay for an hour. HOWEVER like humans all horses have different metabolism and requirements so the most important thing is to FEED TO IDEAL BODYWEIGHT RATHER THAN TO THE TEXTBOOK

Hormonal conditions associated with laminitis
Hormonal conditions are a vast area of research. The two most common ones in horses are Pituitary Pars Intermedia Dysfunction (PPID), which is known as Cushings, and Equine Metabolic Syndrome.
Cushings is a benign tumour of the pituitary gland that ends up in excessive production of a hormone called ACTH and consequently cortisol and insulin. Through different pathways this affects multiple body systems causing classic Cushings signs such as a long curly coat as well as a predisposition to laminitis.
Equine Metabolic Syndrome tends to be a disease of obese horses and ponies that develop insulin resistance because enzymes produced by the fat prevent the normal regulation of insulin. Unlike diabetes it doesn’t seem to cause high blood sugar levels but does predispose the horse to laminitis.

The exact mechanism by which these diseases cause laminitis is still unclear and is an ongoing area of research.

What is the prognosis for recovery?
Prognosis for recovery is very dependent on severity and whether an underlying cause can be addressed. Horses with a mild episode that is caught quickly, have an underlying trigger factor diagnosed and treated and is managed appropriately long term have a good prognosis. Sadly many horses and ponies get such severe or recurring episodes of laminitis causing irreversible pedal bone rotation and sinking that cannot be managed and the debilitating disease is so severe euthanasia is the kindest option. 

Prevention
Prevention is always better than cure. Sometimes this is not possible but the risk can be significantly reduced, particularly for pasture-associated laminitis. Three easy and important ways to reduce this risk are:
Make sure your horse is the correct bodyweight.  If necessary put your horse on a diet and increase his exercise regime.
Reduce the intake of lush grass for horses at risk. Particularly with Spring approaching grazing may need to restricted, either with reduced paddock size or time out grazing. Grass on a frosty morning is particularly high in the sugars that predispose to laminitis so not turning out at this time is beneficial. Grazing muzzles can also be useful.
• Talk to your vet about testing for the hormonal diseases if you are suspicious that your horse has one of these. Successful treatment can significantly reduce the chance of your pony becoming laminitic. 

In conclusion, laminitis is a debilitating but sadly common disease which has severe welfare implications. Careful management to prevent an attack is always best but not always possible. However, quick recognition of the early signs is also key for a better long term prognosis. So enjoy the Spring warmth (when it comes!) but with it be aware of the signs of laminitis, particularly in those high risk horses and ponies. 

References
Henneke; Potter GD; Kreider JL; Yeates BR (1983). Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet 371-2.

Dr Hannah Chase MA VetMB PGCert MRCVS
Hannah graduated from Cambridge in 2015 and immediately carried out an internship at Oakham Veterinary Hospital. This was followed by travelling for a few months including volunteering with The Gambia Horse and Donkey Trust. She is now working at Severn Edge Veterinary Clinic in Shropshire as an ambulatory vet. 

 

 

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