Cushing's Disease:

I have met several horses with Cushing’s Disease. Oddly, most of the horses were Arabians, but there doesn’t seem to be a genetic link to the disease—at least not yet. The others were ponies. One horse I knew lived to a ripe age, giving children riding lessons before being retired. Sadly Cushing’s can’t be cured, but it can be controlled.

Other Names for Cushing's Disease:

Pars Pituitary Intermdia Dysfunction, PPID, Equine Cushing’s Disease, ECD

Causes of Cushing's Disease:

Cushing’s Disease in horses typically develops as the horse enters its senior years. Most horses who develop Cushing’s Disease are over the age of eighteen although it is possible to see Cushing’s in much younger horses. There are two known causes for Cushing’s Disease. An adenoma or non-cancerous tumour can develop in the pituitary gland area of the brain. Or, neurons in the hypothalamus can begin to break down. In both cases, the pituitary and adrenal glands become enlarged and start producing more hormones than they would normally produce. This excess of hormones causes an increase in the amount of cortisol produced. This excess of cortisol is responsible for the many of the symptoms seen in horses with Cushings. Cushing’s Disease can occur in almost any mammal, including dogs and humans.

Symptoms:

The most obvious symptom of Cushing’s Disease is hirsutism. Even during the hottest summer months, horses with Cushing’s will carry a very thick, often curly coat.

At first it may appear the horse doesn’t shed out completely in the spring, or may start to shed out and re-grow a long coat at odd times of the year. On horses with Cushing’s that I’ve seen the hair looks furry, faded and dead, but is still firmly anchored, unlike winter coat that falls out easily. Horses may develop other symptoms to some extent, or may not develop certain symptoms at all. It really depends on how they are maintained and how long they live. These symptoms can include.

• A distended pot belly
• Problems gaining and keeping weight on.
• Increased water intake and urination.
• Laminitis
• Increased number of tooth or hoof abscesses.
• Sweating due to long coat.
• Lethargy
• The estrous cycle in mares becomes infrequent and fertility is decreased.
• Suppressed immune system. Healing and recovery from illness or injury takes longer.
• Increased risk of infection.
• The hollow above the eyes is filled, rather than concave.

Because many of these symptoms are also common to conditions such as Equine Metabolic Disorder, it’s important that a veterinarian makes a final diagnosis.
Treatment:

Good basic care is essential of the horse with Cushing’s Disease. A regular vaccination and parasite control program is essential. Your veterinarian will advise you of an appropriate de-worming schedule. Any injury or illness should be treated immediately, as small problems can quickly escalate when a horse’s immune system is not working well. It may be more comfortable during the warmer months to keep the horse’s coat clipped short and of course, keep hooves trimmed regularly. Horses with Cushing's will require a special diet, similar to horses with Equine Metabolic Symptom, avoiding high-energy (sugar) feeds and emphasizing high fat and fiber feeds.

There are drugs that will help alleviate the symptoms, but there is no cure. A veterinarian can recommend the best strategy for care and medications.

Prevention:

Because this is an age related condition, there is not a lot the horse owner can do to avoid it. It appears the incidences of Cushing’s Disease is on the rise, but this may be because our increased understanding of horse health is giving them a longer life over all. Because the disease can progress very slowly, early signs may be misconstrued for something else. The sooner Cushing’s is recognized, the earlier any adjustments in care can be made, or medication to control the symptoms can begin.