Equine Cushings Disease (ECD). Also known as “Old Horse disease”, Hyperadrenalcorticism/Hyperadrenocorticism, Pituitary Pars Intermedia Dysfunction (PPID), and “Cushings’”.
Cushings disease is caused by a malfunction of the pituitary or adrenal glands, often caused by a tumour. This gland controls hormone levels and the tumour often results in excess levels of the natural steroid Gluocorticoid being produced which create an imbalance in the horse. The cause of this tumour is currently unknown. Affects horses over the age of 20 (although younger cases are documented) of both sexes. Affects older horses so is becoming more common as horses are now living longer.
Symptoms associated with Cushings include uneven and strong hair growth coupled with moulting problems (i.e., a horse may not lose its winter coat in the spring and have a shaggy appearance). This can cause heavy sweating and an increased thirst. Increased urination is also common. This may also cause a general loss of condition and may also bring in other problems such as Laminitis and other hoof problems specifically hoof infections and abcesses, infections, tooth problems, sinusitis and other problems – mostly due to a suppressed immune system. Muscle tone is quickly lost, especially along the topline and a “pot belly” appears, the horse becomes weak and sleepy and can develop nervous system problems including seizures. Laboured breathing can also occur, as can a “cresty” neck, bulging of the fleshy pads over the eyes, dipped back and infertility. Horses affected by Cushings can also develop insulin-resistent diabetes.
Diagnosis is usually started by noticing the shaggy coat and loss of condition and can be confirmed by blood and urine testing, although an authoritative test may not exist and repeated testing may be required. Urinalysis shows a low specific gravity, x-rays can show an enlarged liver and mineralisation of the adrenal gland and bronchial walls. Ultrasound and CT scanning can help in locating pituitary tumours.
Treatment: Good horse management. Low heating feed, rugging to control body temperature and watch for foot, teeth and infection problems. Medical treatments are usually Pergolide, Cyproheptadine or Phenoxybenzamine which both show positive results, with the former showing more success in the Michigan Cushings Project trials. In some cases a horse may be returned to full health with their help. After diagnosis, the average lifespan for the horse is between 2-3 years, although as previously mentioned a horse cannot be completely cured.
