Laminitis, EMS and Cushings – diseases all horse owners need to be aware of

By Hannah Ellis, BVMBVS, MRCVS. Glenythan Vet Group.

Equine, small animal and farm vet Hannah Ellis graduated from Nottingham University in 2016. Brought up in Derbyshire, she moved to Glenythan as a new graduate.

A keen horse rider, she has a rising 2-year-old New Forest/American Paint cross called Toby and a 4yo pure New Forest Leo.

Hannah lives on a croft with her ponies, a small flock of sheep, poultry and bees alongside two dogs and three farm cats. She is also a volunteer with Gordon RDA.

Glenythan Vet Group was established in 2007 when Castle Vets in Ellon and Polesburn Vet Centre in Methlick merged. They deal with small animals, farm animals and horses, run rheir own out of hours on-call service and work closely with Aberdeen Veterinary Referrals.

Laminitis – the scourge of springtime and underlying conditions

AS WE come into the Spring, and hopefully the grass starts to grow, so does the risk of laminitis for our horses and ponies. Laminitis can affect all shapes and sizes, so it’s not just our fat ponies that are at risk.

There can be many contributing factors to a laminitis diagnosis including mechanical stress, underlying endocrine disease, the use of some drugs, for example, steroids and, of course, diet.

Feeling for a digital pulse (above) and assessing the foot with hoof testers (below).

Acute laminitis can come on very quickly and usually seen in the Spring when we get a flush of fresh grass. Chronic laminitis is more commonly found in older equines or those that have an underlying metabolic disease.

Horses and ponies often stand with their weight shifted back on their hindlimbs and have bounding digital pulses in their lower legs. When hoof testers are applied, they are very sensitive all over the foot.

Initial treatment for laminitis can include box rest on a deep shavings bed, pain relief, soaking hay and management of any underlying disease. In more chronic cases, radiographs of the feet are often recommended to assess for any rotation of the pedal bone and assist the farrier in the trimming of the feet.

Laminitis is a complex disease that is often multi-factorial and it is therefore very important to discuss any episodes with your vets.

Cushings Disease (Pituitary Pars Intermedia Dysfunction)

Around 20% of horses over the age of 15 in the UK have been diagnosed with Cushings, but this is not necessarily a condition that only affects older horses.

Cushings is a condition that gets worse with time and the symptoms that we see are related to hormonal changes due to a problem within the pituitary gland. We unfortunately cannot cure this disease but can help to manage the symptoms.

A horse with Cushings.

We do not see all the clinical signs in every horse – it may just be one or two small changes that you notice as an owner or are picked up on during a routine visit.

Some of the signs that we see include:

-        Curly coat                                           - Delayed shedding

-        Laminitis                                             - Recurrent infections

-        Lethargy                                              - Polydipsia (increased drinking)

-        Polyuria (increased urination)            - Muscle wastage

-        Abnormal fat deposits                        - Abnormal sweating             

Initial diagnosis of Cushings is usually by a blood sample to check ACTH levels. ACTH is produced by the pituitary gland. It is likely that this sample will need to be sent to an external lab to be analysed with the results usually taking a few days to come back.

We would not usually take this sample in times of stress, for example during an acute laminitis flare up, as that can affect the results. Horses with Cushings produce an increased amount of ACTH so a ‘positive’ sample is higher than the normal range.

ACTH levels in a healthy horse vary throughout the year, therefore the ‘normal’ values change. Values are naturally higher in the autumn months.

Example of a lab report for a pony that is being treated for Cushings with Pergolide.

Sometimes a horse will produce a normal or grey zone ACTH test but there might still a strong clinical reason for suspecting Cushings.

We can then look at further tests including a TRH stimulation test. Thyrotropin Releasing Hormone (TRH) stimulates the pituitary gland to produce ACTH. This test takes a little longer than the ACTH sample and it also requires 2 or 3 blood samples and an injection of TRH.

Horses with Cushings will have an exaggerated response to the ACTH levels after the TRH injection compared to horses without the disease. It is not recommended to do this test between July and November. 

We use a drug called pergolide to manage the clinical signs of Cushings. This is a once daily tablet which is produced by a couple of different drugs companies under different names and is only available on prescription from a vet.

Once started the medication is usually lifelong. ACTH levels are monitored 4-6weeks after any dose change to ensure that they are having the required affect and six monthly check-ups are also required to monitor ACTH levels.

Equine Metabolic Syndrome (EMS)

Equine metabolic syndrome is another hormonal disorder often seen in overweight horses and ponies. Horses with EMS are unable to regulate their insulin which can lead to an increased risk of laminitis.

Commonly, horses with EMS deposit fat in abnormal places such as above the eyes, behind the shoulders and around the crest. We can also see difficulty in losing weight, lethargy and reduced fertility.

Insulin is involved with regulating glucose metabolism and blood glucose levels. Horses with EMS produce other hormones that reduce the ability of the body to respond to insulin leading to higher blood sugar levels. This leads to more insulin being produced, but the body is still unable to respond to it.

Diagnosis of EMS is important to help to prevent recurrent, chronic laminitis. A simple blood test to measure insulin and glucose levels can be used initially.

If these levels are high it is a good indication that the horse has EMS. Horses and ponies should ideally be starved for six hours prior to the blood sample but if that is not possible, then no hard feed should be fed in that time.

If the results are normal but EMS is still suspected, a dynamic test which evaluates the insulin response in the body can be performed:

Oral sugar test:

1.     Starved blood sample is taken for basal insulin levels.

2.     0.45ml/kg sugar syrup is administered orally.

3.     Blood sample taken 60-90mins later to evaluate insulin levels.

The oral sugar test can help to diagnose insulin dysregulation early, sometimes even before clinical signs have appeared.

Management of EMS includes dietary control and exercise to reduce weight, improve insulin sensitivity and lower the risk of laminitis.

Horses and ponies with EMS require a low sugar, high fibre diet to minimise insulin spikes. It is important to restrict grazing grass especially during the high-risk periods in the spring – this could involve a combination of grazing muzzles and track systems which also encourage movement.

Even low sugar hay may need to be soaked. Regular exercise is one of the most important ways to improve insulin sensitivity and to help with weight loss. Exercise does not necessarily need to be ridden as in-hand walks, lunging and long reining can all be sensible alternatives.

Whilst commonly seen in general practice, each horse or pony can present differently so it is important to discuss any concerns with your vet so an individual plan can be made.

Glenythan Vet Group have practices in Ellon and Methlick. Their website is https://www.glenythanvetgroup.com