Cushing's and Equine Metabolic Syndrome

Cushing’s Disease

There is a distinct impression that there is more Equine Cushing’s around than there used to be but the reality is that more horses are being tested and treated for it than in previous years.

What is Cushing’s disease?

Equine Cushing’s also known as PPID which stands for Pituitary Pars Intermedia Dysfunction, is a hormonal illness that affects horses and ponies and also other species such as dogs. PPID is caused by progressive nerve degeneration in part of the brain called the hypothalamus and this results in a decrease in the secretion of a substance called dopamine. Dopamine is important in the control of the pituitary gland, specifically, the part called the pars intermedia, hence the name of the disease. The pars intermedia controls the production of two hormones called ACTH and cortisol.

Cushing’s disease results in a weakened immune system so horses are more prone to infections and wounds can take longer to heal, it also had other symptoms. It tends to be associated with old horses but in fact horses in their teens can test positive for Cushing’s, and some even younger than that. Cushing’s comes with a bucket load of symptoms or sometimes, none at all.

Common symptoms may include:-

  • Increased thirst and urination
  • Abnormal coat changes so unexpected growth at odd times of the year,
  • sometimes this may include a long or curly coat but these signs tend to be
  • associated with horses who have had the disease for some time
  • Recurrent infections, particularly in the hoof and the skin
  • Lethargy and depression
  • Muscle wastage, typically a pot-bellied appearance and lack of top line
  • Laminitis
  • Excessive or patchy sweating

How do you determine if your horse has Cushing’s disease?

A simple blood test will confirm the diagnosis. The lab has a reading or level, a different one for every day each month and the results will be presented to you as a numeric level as against the lab level. If your horse’s level is higher than the lab level, then they have tested positive for Cushing’s.

The lab levels vary from day to day and month to month. The most sensitive time to test the horse is in September and October when the reducing daylight hours begin to affect the pituitary gland. Some horses clearly exhibit symptoms of Cushing’s disease whereas others do not. Equally, some horses show classic signs of the illness but test negative; Equine Cushing’s is not an inevitability of old age. The main thing is you can’t always tell by looking.

What is the treatment for Cushing’s?

Treatment is by tablet with a drug called Prascend. The tablet is scored in the middle and can be snapped in half quite easily. Ongoing blood tests are required to monitor the levels as they will rise and the dosage of Prascend may need to be adjusted in line with this.

Because of the increased risk of laminitis associated with Cushing’s disease, it is recommended that affected horses are fed as a potential laminitis risk, so a diet with a naturally occurring sugar level of no more than ten per cent. There are lots of feed companies who offer appropriate feeds particularly for veteran horses which fall into this category.

Can affected horses still be ridden?

Many horses continue to work, sometimes at a very high level, with the appropriate medication and management. Some horses, if they are elderly, may have other issues which force retirement rather than Cushing’s disease. Each horse needs to be viewed holistically and treated as an individual case.

Research into Cushing’s Disease

As more horses and ponies are tested, large quantities of data are becoming available to scientists about this illness. Every time your vet sends in a blood sample to test for Cushing’s disease, they have to give the horse’s age, height and breed so it is hoped that all this data will eventually be able to produce useful conclusions going forward for horse owners. Already the increased awareness of the disease and the use of Prascend combined with non-steroidal anti-inflammatory drugs such as Danilon, mean that many horses are living to much greater ages with excellent quality of life.

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