Managing your horse with Cushing’s Disease

13th July 2018

Your horse has been diagnosed with PPID – what causes it and what are the signs?

• PPID or equine Cushing’s disease is a hormonal disease caused by changes in the pituitary gland (which is found at the base of the brain). PPID refers to this abnormality.
• It becomes increasingly common with age and is thought to affect more than 20% of horses over the age of 15. It is very uncommon in horses below 15 years of age.
• Horses and ponies with PPID don’t produce enough of a chemical (neurotransmitter) called dopamine, and this means that the pituitary gland becomes unregulated and produces too many hormones.
• The exact mix of abnormal hormones varies a lot between cases, hence the variety in clinical signs associated with the disease, including:
o Laminitis / recurrent laminitis.
o Hypertrichosis (an abnormal hair coat which can range from mild changes in coat shedding or colour during the early stages of disease, through to a curly overgrown coat in the later stages).
o Loss of muscle condition, a pot-belly and a wasted topline.
o Abnormal fat distribution such as Fat pads around the eyes (peri-orbital fat), tail head, crest and behind the shoulders.
o Excessive/patchy sweating.
o Increased drinking and urination (often first detected as a very wet bed).
o Lethargy/poor performance.
o Recurrent infections e.g. foot abscesses, sinusitis.
• PPID is a degenerative condition which means it progresses over time and we need to keep monitoring it even after diagnosis to make sure that we keep it under control

How is PPID diagnosed?

• The simplest and most common test for PPID is the basal or resting ACTH test. This is a blood test taken by your vet that usually provides a clear answer.
• All hormone tests are prone to variation and sometimes the results of the ACTH test are not clearcut. In the case of the ACTH test, periods of stress, pain or illness can cause false readings.
• If this happens to your horse then your vet may recommend re-testing after 3-6 months, or performing an alternative test called a TRH stimulation test.

TAL ImageMy horse has been diagnosed with PPID – what now?

• The treatment of choice for PPID is pergolide mesylate and this is the active ingredient of Prascend.
• Prascend is the only licensed drug available to treat PPID in horses. The use of other unlicensed drugs has been reported but they have not been shown to be as effective.
• The required drug doses for treatment of PPID will vary between cases but the starting dose is standard and based on your horse’s bodyweight. • Treatment should be evaluated after 1-3 months by a combination of repeat blood sampling for basal ACTH and reassessment of clinical signs. Clinical monitoring alone for improvement of clinical signs is not recommended. This is because some problems, such as predisposition to laminitis or infection, can only really be detected when a serious problem actually occurs (such as a painful episode of laminitis or tricky infection).
• We therefore recommend that plasma ACTH is rechecked approximately 4 weeks after initiating treatment.
• If clinical improvement or lab results are not noted, then the dose of Prascend will be increased and blood sampling repeated again approximately 4 weeks after the dosage change. Where there is specific concern over laminitis risk, then additional blood testing may be carried out at this time to help quantify this risk.
• You can help to monitor your horse’s response to treatment by checking hair coat changes, water intake and bedwetting (when stabled), body condition, laminitis/ lameness and general demeanour
• In some cases, Prascend can cause horses and ponies to go off their food and appear depressed – this is normally a transient problem but if this is the case please contact your vet immediately to discuss a reduction in dosage • Once the signs have been successfully controlled, horses should be assessed at least monthly for clinical deterioration by owners (it can be tricky to notice gradual changes and actually planning a check over yourself helps) as well as twice a year by blood testing.
• Some horses will remain stable on the starting dose of Prascend for many years whilst others may need several dosage adjustments.
• Owner care and husbandry is even more important for PPID cases – in particular ensuring adequate nutrition, dental care, exercise level and worming treatment. Many cases are geriatric and all of these become even more important.
For 2018 the lab fees for ACTH testing for diagnosis and monitoring of cases already diagnosed with PPID are free of charge. If you combine testing with one of our zone visits then careful monitoring of clinical cases need not be prohibitive. If you have any questions please contact us on 01939 260251 (Baschurch) or 01978 664459 (Wrexham)