Types of Laminitis and the Treatments

Although we often think that all laminitis is ‘inflammatory’, there are two other kinds of pathology that can start the process of tissue deterioration within the hoof. Laminitis is therefore classed as either ‘inflammatory’, ‘metabolic’ or ‘overload’. In the second of a two-part look at this debilitating condition, Sarah Hogg BA VetMB MRCVS from Paragon Equine explains...

It’s important to pinpoint what type of laminitis is occurring in order to develop a specific treatment plan that will help your horse get back to full health as quickly as possible, and to minimise the chances of recurrence in the future.

Metabolic Laminitis

This is the commonest and possibly the most confusing type of laminitis. Vets have estimated that more than 90% of horses presenting with laminitis as their primary (main) complaint are metabolic cases. There are two underlying conditions involved in metabolic laminitis:

·         Equine Metabolic Syndrome (EMS)

·         Cushing’s Disease (more correctly called Pituitary Pars Intermedia Dysfunction; PPID).

Both conditions mean that horses have an inappropriate response to eating carbohydrate rich food (grass, concentrate feeds, hay and haylage) and produce too much insulin. Because of these high levels or unusually large spikes in insulin, the body becomes less sensitive to it. This is called ‘insulin resistance’.

Equine Metabolic Syndrome

EMS is a complex condition responsible for most cases of metabolic laminitis. It usually affects native pony breeds. Although it’s still unclear exactly how EMS causes laminitis, we think that high levels of insulin following carbohydrate digestion alter the blood vessels and blood supply to the hoof first of all. This then causes an inflammatory response and clinical symptoms. Studies have suggested that many horses with EMS have had subclinical (grumbling) laminitis for a long time before they are diagnosed with it. They are also more likely to suffer from further episodes in the future, so it’s vital that EMS is properly managed to prevent this.

Obesity is known to exacerbate EMS. It can look quite different from how we think of obesity in humans or other animals, where we’d always expect an all-over covering of excess fat. In horses ‘regional obesity’, where fat builds up in just one or two areas such as the crest of the neck or behind the shoulders, can be just as dangerous. Body condition scoring is a uniform way for describing the weight of a horse compared to what their optimal weight would be (see box for more information on how to do this properly).

The good news is there are plenty of ways we can help reduce the effects of EMS. Early diagnosis and management is critical and your vet may suggest a blood test or glucose challenge test to help confirm EMS is present. Weight loss is central to treatment, and a plan should be made for decreasing the calories your pony takes in whilst increasing those burnt through exercise (once any laminitis has completely settled). Learn to body condition score your pony and use a weight tape regularly to record your progress.

The best diet for EMS ponies is hay that has been soaked for at least an hour to reduce soluble sugars, alongside a quality commercial feed balancer fed to replace any vitamins and minerals that are also washed away. Weighing your hay at each feed or sending a sample to a laboratory for nutritional analysis can help you to gain more informed control over your pony’s diet. Your vet will be able to help you decide on a suitable amount of hay to feed for successful weight loss without cutting down too severely. Once EMS is under control, it is often possible to return ponies to restricted grazing.

Metformin is a human medication used in type 2 diabetes that is sometimes used to help treat EMS in horses. Several supplements, from cinnamon to omega-3 fatty acids, have been scientifically tested but none have proved reliably effective so far.

PPID

PPID, more commonly known as Cushing’s disease, is a degenerative condition of the pituitary gland at the base of the brain that occurs as horses get older. A small area of the pituitary gland becomes hyperplastic (grows) or can develop a benign growth called an adenoma. It is a common condition, affecting around 20% of horses over 15 years of age.

Despite being small in size, the pituitary controls many hormonal processes throughout the body, primarily the ‘stress hormone’ cortisol. PPID can have a range of gradually progressive symptoms, including:

·         Weight loss; or muscle wastage

·         Characteristic fat storage: pot-belly, crest, supra-orbital fat pads (above the eye)

·         Hirsuitism (thick, hairy coat) and delayed shedding of winter coat

·         Increased drinking and urination

·         Mouth ulcers

·         Prone to infection (e.g. skin, hoof, respiratory)

Although a clinical exam can be strongly suggestive of PPID, your vet will usually confirm diagnosis with a blood test.

Pergolide is an oral drug that effectively stabilizes most horses with PPID and can help to prevent or reduce further flare-ups of laminitis. Careful dietary management and regular farriery are also key to successful management.

Inflammatory Laminitis

Inflammatory laminitis occurs after the onset of a severe illness. Toxins are produced as a byproduct of inflammation and tissue damage, and travel through the bloodstream to affect all areas of the body – including the hoof.

Severe colic is an example of this kind of illness – when the gut is damaged toxins are released and travel to the feet to cause inflammation and damage in the sensitive laminae which hold the hoof the bone. Eating a lot of concentrate feed can have the same effect. Other examples include mares retaining their placenta after foaling and sepsis, where a bacterial infection overwhelms the body.

When dealing with inflammatory laminitis it’s vital that the original condition is treated alongside dealing with symptoms in the feet. This often includes antimicrobial treatment and strong anti-inflammatories. In the acute (early) stage, ice can be applied to the feet to try and shut down the blood vessels (like when we have cold hands and our fingers go white) to stop further toxins being delivered to the laminae and causing more damage. If a horse is known to be at risk from laminitis and is suffering from a severe systemic illness, your vet may want ice to be applied as a preventative measure.

Overload Laminitis

This is the least common form of laminitis, but it’s important to be aware of as the early stages can be hard to spot. Overload laminitis happens when a horse injures a limb and the leg on the other side is forced to compensate by bearing more weight. The increased load from their bodyweight causes mechanical damage to the laminae and the sensitive tissue again becomes painful and begins to break down.

Overload laminitis is best prevented and treated by supporting the weight-bearing limb. Vets are usually aware of this risk when treating severe lameness, and will help you to make the best possible plan for effective nursing and recovery.

General Treatment

Treatments directed at the foot itself, rather than the underlying cause, are also important. Strict rest, deep bedding, foot supports and suitable analgesia (painkillers) can all be important.

Corrective trimming is crucial in some cases, to get the foot realigned. If this is the case, radiographs (X-rays) can give your vet and farrier more information. Sometimes dramatic re-shaping of the foot is required, with the toe cut back and heel lowered. A good working relationship and open lines of communication between all those who care for your horse can make a real difference to the outcome. Once recovered, regular maintenance farriery should be a part of any laminitis-prone horse’s routine.

During the acute phase of laminitis, a low carbohydrate diet should be considered. Your vet will be able to advise you on this, and on a maintenance diet going forwards.

Finally, don’t be afraid to ask your vet for good recommendations on where you can learn more about laminitis and any underlying disease your horse may have. Most practices have detailed information sheets for owners or will happily point you in the direction of up-to-date online resource.

How to Body Condition Score your Horse

This is a great skill to have in your toolbox! Even if your horse doesn’t have laminitis it can be a useful way to evaluate the natural changes in condition we should see throughout the year (e.g. losing some weight each winter).

Try to score your horse every two weeks – taking a photo on your phone can help as a record of progress. Take particular note of fat at the neck crest, shoulders, tail head and covering the ribs, pelvis and backbone.

SCORE 0 – Emaciated

Sunken rump, angular pelvis, deep cavity under tail, skin tight across ribs and hips, sharp backbone, narrow neck base.

SCORE 1 – POOR

Prominent pelvis bones, sunken rump but some give in skin, deep cavity under tail, ribs easily visible, prominent backbone, narrow neck base.

SCORE 2 – MODERATE

Flat rump running down from backbone, slight cavity under tail, ribs just visible, backbone covered but easily felt, narrow but strong neck.

SCORE 3 – GOOD

Pelvis rounded and covered by fat but easily felt, ribs and backbone just covered but easily felt, no crest (except stallions), firm neck.

SCORE 4 – FAT

Dip along back of pelvis to tail, firm pressure required to feel pelvis and ribs, dip along backbone, wide, firm neck.

SCORE 5 – OBESE

Deep dip along back of pelvis, skin over rump distended, pelvis and ribs cannot be felt, deep dip along backbone, broad, flat back, marked crest with fold of fat.

To read the first part of this article click Laminitis (part1)

What is Laminitis & How Do We Recognise It?

When we think of laminitis, we often picture an overweight pony knee deep in rich spring grass. Although there are risk factors that make some animals more susceptible, laminitis can occur in any horse, pony or donkey of any age or breed at any time of year.

In the first of a two-part look at this debilitating condition, Sarah Hogg BA VetMB MRCVS from Paragon Equine explains ….

Laminitis is a veterinary emergency, so it’s important to be able to recognise the signs. Quick treatment is essential in stopping this painfully debilitating and potentially fatal condition in its tracks, giving horses the best chance of returning to full health.

We usually see laminitis in two states:

Acute laminitis is the initial stage of the disease. Inflammation within the hoof causes heat and pain, which is often severe. Prompt intervention in this phase can prevent long-term structural damage to the foot.

Chronic laminitis occurs when inflammation is not adequately controlled, causing permanent damage to the foot. The outer hoof shows change and careful long term management is required by vets, farriers and owners. Chronic laminitis is often still very painful.

Even if acute laminitis is managed effectively at the time so the disease doesn’t progress, once a horse has suffered from laminitis he will be more prone to future episodes.

Overweight ponies are not the only equines at risk of laminitis

Signs to watch out for

A range of symptoms are associated with laminitis. Not every horse has all of them and whilst some may show them in a subtle way, others can find themselves completely debilitated in alarmingly little time. Horses may show signs in all four feet, although often only the front feet appear affected or are noticeably worse.

Signs include:

        Lameness – varying from a short, ‘pottery’ gait at trot to an inability to walk

-          More lame on hard or uneven surfaces

-          Sensitive when turning, especially in tight circles

-          Hot feet

-          Increased digital pulses

-          Pain when the toe is squeezed

-          Weight shifting from foot to foot

-          Leaning back with front feet extended to reduce the weight in the toes

-          Change in facial expression – ears back, flat nostrils, a tight jaw

-          Increased periods of time lying down.

-          In severe cases, horses may pant or sweat, which can be confused with colic.

-          Changes to the outer appearance of the hoof, e.g. odd shapes, deep horizontal lines or ‘rings’ or widening/separation of the white line (visible underneath the foot)

-          Visible bruising on the base of the foot when trimmed or soreness after trimming

Know-How: How to take a digital pulse

Finding your horse’s digital pulse is a useful first aid tool in many circumstances, but is particularly useful if you suspect laminitis.

Starting with your horse’s front right foot facing towards the back of your horse, place your right index finger on the inside edge of the lower fetlock. Apply a little pressure and slide your finger over the skin around the base of the fetlock until you feel a cord-like structure ‘ping’ under your finger. This is where the artery lies.

There is a similar cord-like bundle on the outer edge of the lower fetlock, which you may be able to feel with your thumb at the same time.

Apply pressure over the bundle to feel the pulse – this is the tricky bit! Too much pressure can squash the artery, preventing you from feeling the pulse. Too little pressure makes it difficult to feel the blood moving. Practice makes perfect, so don’t be afraid to have a go on your ‘normal’ horse.

It can be difficult to tell if the pulse is normal if you haven’t felt many. A ‘bounding’ or ‘rushing’ feel, or a pulse that is easily found is usually warning sign.
However it presents, laminitis is an emergency and requires immediate veterinary attention. Quick treatment is essential in stopping damage from progressing further and helping horses to return to full health.

What happens inside the foot?

The hoof is made up of a hard, insensitive outer layer (horn) and an inner, sensitive layer of softer tissue called the lamellae. The layers are stuck together in a similar way to ‘Velcro’ and hold the pedal (coffin) bone to the hoof capsule.

In laminitis, inflammation prevents a healthy flow of blood and oxygen to these tissues, which become weakened and damaged. In severe cases, damage is so severe that the tissue is no longer able to support the pedal bone in place – this results in ‘rotation’ and ‘sinking’. In severe cases a horse may ‘founder’. Here the bone presses against or even penetrates the bottom of the sole. As the bone shifts the tissue and blood vessels surrounding it are crushed and the outer hoof begins to show signs of chronic change, such as deep rings running around the hoof. Affected feet require long-term management in order to limit damage and begin to try and restore foot balance.

It’s important to remember that by the time a horse starts showing signs of laminitis, these internal changes are already well underway.

Because horses have evolved to remain standing for the vast majority of time, their feet constantly bear weight and the impact of movement. When the soft inner tissue of the foot becomes inflamed within the rigid hoof capsule, it causes unrelenting pain that quickly becomes debilitating.

An x-ray of a hoof affected by laminitis showing rotation
of the pedal bone. In this case the pony was euthanised.

Confirming a diagnosis of laminitis

Although vets are usually able to diagnose laminitis from a clinical examination, x-rays show the degree of change inside the hoof.

Taking foot x-rays is usually a simple procedure. Painkillers are given beforehand to ensure the horse is as comfortable as possible. A marker is attached to the hoof to show where it meets the skin (the coronary band) and pictures of affected feet are taken from several angles.

The images can then be shared with your farrier, and a detailed plan for corrective trimming made.

Know-How: Obel Grading

Vets often use a system called ‘Obel Grading’ as a guide for classifying the severity of laminitis and monitoring progression.

Grade I – Intermittent weight shifting and lifting of feet. Horses aren’t lame at walk but have a stilted gait at trot.

Grade II – Willing to move, but shortened stride. Able to lift feet.

Grade III - Reluctant to move. Unable or very reluctant to lift affected feet.

Grade IV – Extremely reluctant or unable to move. Frequently lying down.

Grade V – Mostly recumbent. Unable to stand for more than a few minutes.

What next?

It’s very important never to force a horse that may have laminitis to walk or exercise. Suspected cases of laminitis should be box-rested with easy access to hay or water (Remember they may not want to walk across the stable!). Keep any stress to a minimum. Your vet will usually advise you to do this over the phone while you wait for them to arrive, and this will usually continue for 30 days or more. A deep bed – ideally non-edible and dust-free – will support the feet and allow the horse to rest by lying down if needed.

Your vet will be able to provide painkillers and foot supports if needed. Any underlying illnesses can also be treated.

Sadly, despite the best efforts of owners, vets and farriers, the only option left in a minority of cases is euthanasia on welfare grounds.

In the next of our expert veterinary posts, we’ll be looking in more detail at the causes of laminitis and how knowing what type of laminitis a horse has can help us prevent recurrence.