Cushing’s Disease and EMS in horses
Cushing’s Disease in horses is also known as Pituitary Pars Intermedia Dysfunction (PPID). It is a disease that involves the pituitary gland in the brain. This gland produces a hormone called ACTH which stimulates the adrenal glands to produce cortisol. These increased hormone levels lead to the signs seen in a horse suffering from Cushing’s disease.
What are the signs of Cushing’s disease?
- Long, wavy coat
- Bulging fat pads above eye
- Increased thirst
- Increased urination
- Failure to lose winter coat
- Increased sweating
- Increased skin infections, sinus infections, parasites
What horses are affected by Cushing’s disease?
This disease mainly affects older horses, but can be found in horses over the age of 10. The average age of a horse developing signs of Cushing’s disease is 19. Ponies are more likely to be affected than horses, and mares and geldings are equally affected.
How is Cushing’s disease diagnosed?
Your vet will assess your horse clinically. They will consider their age, breed and symptoms shown. If suspicious, they will test for the hormone ACTH. Unfortunately, this test can be unreliable in less obvious cases and therefore other tests such as a TRH stimulation can be done to further assist diagnosis.
How do I treat Equine Cushing’s disease?
There is only one drug licensed for treatment of Equine Cushing’s disease in the UK. This is a drug called pergolide and is sold as either Prascend, Pergoquin, or pergolide paste. This drug is reportedly effective in 65-85% of cases. Treatment is lifelong as the disease is not curable. There are some side effects (as all medicines have) such as diarrhoea, inappetence and depression. These should be discussed with your vet. Not all owners will treat the disease and will mainly depend on how severe the symptoms are in their horse. If symptoms are mild such as a long coat, some owners will elect to manage these instead e.g. clipping the hair off. If there are more serious consequences of underlying Cushing’s disease such as laminitis, it will always be advised that the disease should be treated in addition to other management tools.
What is Equine Metabolic Syndrome (EMS)?
Equine metabolic syndrome (EMS) is a disease caused by the dyregulation of insulin in the horse. This means the horse is unable to manage their insulin levels and in that sense is like Type 2 diabetes in humans. It was previously known as Peripheral Cushing’s Disease.
What causes Equine Metabolic Syndrome?
Insulin dysregulation is caused by the inability of insulin to instruct cells within the body to take up glucose. Insulin normally helps control glucose levels in the bloodstream. When malfunctioning, the glucose is not moved out of the bloodstream into the cells and therefore the body tries harder to push it into the cells by releasing even more insulin. This insulin resistance (i.e. inability to exert it’s effect on the cells) is created due to hormones released by fat cells. This then leads to altered metabolism and more fat being laid down further compounding the insulin resistance. The excess glucose in the blood has a detrimental effect on blood vessels. In the horse the blood vessels of the hooves are mainly affected. Any breed can be affected, but native breeds such as Shetlands, Welsh and Dartmoor ponies are more likely to develop the disease. This is a disease that is created/caused by humans. It is caused by incorrect management of horses with regards to their feed and exercise management.
What are the signs of EMS?
- Obesity – cresty neck, fat pads behind shoulders, around tailhead
- Laminitis – this can be seen as active lameness caused by laminitis, but can also be identified as poor hoof quality, divergent hoof rings, being ‘footy’, widened white lines
What is the difference between EMS and Cushing’s Disease?
- EMS horses tend to be younger to middle aged
- Horses with Cushing’s disease usually have multiple signs eg long hair coat, laminitis, excessive sweating, excessive drinking
- Cushing’s horses have dysfunction of a gland in their brain which can be tested for
How is EMS diagnosed?
EMS can be suspected by clinical examination and confirmed by blood tests. Blood can initially be checked for insulin and glucose levels. If still concerned but not confirmed by the initial blood tests, your vet may recommend a test called an Oral Glucose Tolerance Test. The horse is fed glucose and a blood sample is taken 2 hours after this to measure the glucose and insulin levels in response to glucose being fed. Your vet may also be suspicious of Equine Cushing’s disease so may test for this too. It is possible for your horse to have both Cushing’s disease and EMS. If laminitis is present, your vet may also take xrays to assess the severity of the damage. Read our blog on laminitis here!
How do I treat EMS?
The main way to treat this condition is for your horse to lose weight. This is normally in the form of restricting calories and increasing exercise. Feeding a diet low in sugar alongside rationing hay at a weight of 1.5% of their body weight. If this does not lead to weight loss, the percentage can be reduced to 1.25% and then 1%. If your horse has laminitis, it may not be possible to exercise them and therefore diet alone is relied upon. Exercise is vitally important if safe to do so. It has been shown that aerobic exercise allows the body to handle dietary sugars more efficiently.
Due their inability to handle sugars effectively, these horses need to avoid grazing during dangerous periods of grass growth when the shoots are full of fructans. Some horses need to be completely removed from their pasture during this time. Others just need to have their grazing restricted.
Managing your horse’s weight
This should be done as a normal part of equine management. This should involve weighing your horse once a month. This is ideally done using a weigh bridge but weigh tapes can also be used effectively. A horse with EMS initially may need to be reassessed every 2 weeks to make sure the horse is losing weight. Weight loss should be slow and steady, as rapid weight loss can lead to serious metabolic conditions.
Some great advice from Dengie and feeding the horse and pony with Equine Cushing’s Disease and EMS.
In some cases, medicines such as Metformin and Levothyroxine have been used to assist weight loss but should only be used if management is optimal and can only be done under veterinary guidance.
Please remember, EMS is a preventable disease. It is entirely caused by lack of dietary restriction and exercise, leading to obesity in the horse. The consequences of this syndrome can be life threatening and therefore should not be underestimated.