Equine Cushing’s disease, also known as PPID (Pars Pituitary Intermedia Dysfunction), is a very common, but easily managed disease in horses. It primarily affects ponies and horses over 15 years of age, but has been seen in younger animals. A significant proportion of horses with laminitis – an inflammation of tissues in the hoof – have PPID. All horses are at risk and up to a third of all horses are affected by the age of 20. Diagnosis and treatment can result in a greatly improved quality of life for the horse and is crucial in cases of laminitis if PPID is the suspected cause.
The disease is caused by progressive nerve degeneration in an area of the brain called the hypothalamus. This leads to a reduction in dopamine. Dopamine is important in controlling the secretion of hormones from a part of the pituitary gland known as the pars intermedia. When the pars intermedia is not exposed to enough dopamine, the result is the production of abnormally high levels of hormones.
Symptoms of Cushing’s disease include:
• Laminitis – occurring acutely or in recurrent bouts. This is often unresponsive to treatment until the PPID is controlled
• A hairy coat, which can become thick and curly. This is often preceded by
patchy or late shedding of the coat hair
• Drinking excessively and producing large volumes of urine
• Lethargy – this can be mistaken by owners to be just a normal age-related change
• Loss of muscle, dipped back and a potbellied appearance
• Bulging fat pads above the eyes
• Weight loss
• Excess sweating
• Compromised immune system. Affected horses are more prone to skin, respiratory and dental infections, and parasite infestation
If you recognise any of these symptoms and want your horse or pony to be checked out, a vet can visit. A simple blood test can then be performed to help diagnose PPID.
The most commonly performed test is the ACTH. Affected horses will show a high level of the hormone ACTH. There is no cure for PPID, but the disease can be well controlled with a daily tablet called Prascend. This controls the production of hormones and should be continued for life. Further blood samples will help find and maintain the correct dose for individual horses. Good horse management is also important. This should include clipping hair to improve comfort levels, frequent checks to ensure early identification of wounds and infection, plus regular farriery, dentistry and worming checks.
Jenny Wrangham, Wellsford Vet Clinic