Equine Cushing’s disease (ECD) is a hormonal disease of older horses caused by a benign growth of the pituitary gland at the base of the brain.The pituitary, a marble-sized gland at the base of the brain, is responsible for the regulation of almost all of the body's endocrine systems, in fact, it's sometimes referred to as the "master gland".
Horses are generally over 15 years of age when diagnosed but the disease has been recorded in horses as young as seven years old. There are a number of hormones involved, all which act to cause the loss of cortisol circadian rhythm, resulting in chronically increased cortisol levels.
Ponies seem to be more prone to developing laminitis with this disease but here is no overall breed or sex predilection.
Signs of equine Cushing’s disease
There are many signs of Cushing’s disease in horses. Often signs increase over time. They include: - Heavy hair growth that may be curly and doesn’t shed normally - Excessive sweating (including heat stress in hot humid conditions) - Increased thirst and urination - Muscle wasting - Lethargy and poor performance - An increased susceptibility to infection (particularly sinusitis, teeth and hoof infections) - Slow healing wounds - Pot-bellied - Increased appetite - Weight loss (which may be hard to detect under the curly coat) - Mucky eyes and sheath - Fat pads around the eyes, along crest of the neck, above the tail and in sheath area) - Abnormal season or infertility in mares (a mare's estrous cycle might be suppressed or abnormal, and she might even produce milk without being pregnant.)
A horse with Equine Cushing disease or Cushing’s Syndrome will show one or more signs and not every affected horse will show every sign.
The treatment of these horses and ponies relies on a form of hormonal replacement therapy.The most effective drug currently available is called Pergolide, which acts to stimulate the production of the depleted hormone, Dopamine, which controls the affected part of the pituitary gland.Most ponies and horses can be maintained on this drug for as little as $1.50 - $3.00 a day. They are initially monitored every 6-8 weeks to ensure the dose is correct to start hair shedding, muscle and weight gain and improvement in demeanour. Treatment will need to be administered for life as the drug is not a cure.
The other aspect of Cushing’s disease treatment is management. These horses are very susceptible to large worm burdens, infections, weight loss and laminitis, especially if they are not being treated medically. Therefore regular worming, teeth checks, shoeing every 6-8 weeks and keeping vaccinations strictly up to date is therefore recommended!Good quality diets that will not exacerbate any laminitis and in a form which they can use, as they are not good in digesting food as the young adult horse. Pellet diets that have been heat processed or steam extruded instead of grain mixes are much better for them.The energy is in an easy form for digestion and is digested completely in the small intestine and if large amounts reach the large bowel can cause laminitis.Good quality Lucerne chaff and hay provide the protein required and as long as it isn’t too lush, doesn’t cause laminitis.