Linda Greaves, Equine Technical Adviser for Boehringer Ingelheim Animal Health, explains why this disease is more common than was previously thought, and advises on various symptoms to look out for and the steps to take to improve your horse’s quality of life. First published in Carriage Driving April 2019
Equine Cushing’s disease is the most common equine hormonal disease in the UK1, 2. It is so common that a horse or pony over the age of 15 has a 1 in 5 chance of developing Equine Cushing’s disease3.
Equine Cushing’s disease is a lifelong progressive condition associated with the reduction of a hormone called dopamine in the horse’s brain. Dopamine acts as an “off switch” for the production of other hormones by the brain. Reduced dopamine levels results in an increase in hormone production by the pituitary gland, and these increased hormone levels are thought to be the cause of the clinical signs associated with Equine Cushing’s disease. The disease is progressive and will advance at different rates in different individuals. This has two important consequences: firstly horses with Equine Cushing’s disease may not always show severe clinical signs, and secondly it is impossible to predict which horses will go on to develop severe symptoms or how quickly this may happen. The early symptoms of the disease may not be an immediate cause for concern for owners. This means that horses may go undiagnosed and untreated for months or even years which can have potentially serious consequences for the horse.
The importance and
challenges of early recognition
Early recognition and diagnosis of Equine Cushing’s disease can reduce the risk of potentially serious consequences such as laminitis or recurrent infections by allowing owners to instigate appropriate treatment and management strategies before severe symptoms are seen in their horse.
One of the challenges that vets and owners face in identifying Equine Cushing’s disease is differentiating the signs of disease from the signs of ageing. Equine Cushing’s disease is predominantly a disease of horses over the age of 10. Studies have shown that owners can often mistake symptoms of Equine Cushing’s disease for normal signs of aging4.
Some clinical signs associated with Equine Cushing’s disease can be particularly difficult for owners to identify. Recent research into owner recognition of laminitis has demonstrated that many owners find it difficult to identify mild episodes of laminitis6.
What are the common signs of Equine Cushing’s disease?
One of the most severe signs of Equine Cushing’s disease is laminitis. This painful and debilitating disease of equine feet is 5 times more likely to occur in a horse or pony that has Equine Cushing’s disease3. Research has found that 90% of diagnosed cases of laminitis are associated with hormonal disease which includes Equine Cushing’s disease5. The signs of laminitis can be divided into two categories: those associated with pain and those associated with visible changes to the hooves. Signs associated with pain can vary in severity from a classic laminitic rocked back or rocked forward stance to a horse that becomes slightly footy after a farrier visit. Similarly, hoof changes may also be subtle such as variation in the width of the white line around the foot or divergent hoof rings where the rings at the heel are wider than those at the toe or more severe such as a change in the angle of the hoof wall or an increased amount of horn at the toe.
Although laminitis is commonly considered the most severe sign of Equine Cushing’s disease, many of the other symptoms can also have a significant impact on the affected horse’s quality of life and ability to continue training. Lethargy can significantly impact the willingness of a horse to work at its full potential which may be further complicated when we consider the muscle wastage associated with Equine Cushing’s disease. While muscle wastage may not always be immediately obvious on visual examination, it may present as a change in the way that tack or harnesses fit the affected individual. It can be a challenge to get a horse with Equine Cushing’s disease looking fit and well for competition when we consider not only this muscle wastage but also the development of a potbellied appearance due to abnormal fat deposits.
Horses with Equine Cushing’s disease can develop a reduced ability to fight infections6, which can lead to recurrent infections such as foot abscesses, respiratory or skin infections. Whilst these infections can interfere with a horse’s training quite significantly, they can also impact on the affected animal’s welfare. As such, the presence of recurrent infections or high worm burdens in older horses may warrant further investigations to rule out underlying disease processes such as Equine Cushing’s disease.
Individual horses may show none, one or several of the many symptoms associated with Equine Cushing’s disease depending on the disease progression and severity. It is therefore important for owners to be aware of not only the signs of Equine Cushing’s disease but also the challenges in differentiating these from the normal signs of ageing especially given that affected horses are often over the age of 10. To help assess your horse or pony for signs of Equine Cushing’s disease you can download an Equine Cushing’s disease checklist at www.careaboutcushings.co.uk. This can help you spot the early signs of Equine Cushing’s disease. If you spot any of the signs described on the check list you should discuss them immediately with your veterinary surgeon.
Why is prompt diagnosis of Cushing’s disease important?
In recent years, a significant amount of time has been spent researching laminitis and it is acknowledged that owners can find it difficult to recognise some of the signs of the disease especially in mild cases7. The majority of owners would recognise laminitis in their horse if the animal was so painful it was unable to walk, had hot hooves and bounding digital pulses and would seek veterinary attention immediately. However an owner may not realise that if their horse or pony was pottery on hard ground or sore following farriery that these could be early signs of the onset of laminitis. In addition to an Equine Cushing’s disease checklist, you will also find a laminitis assessment checklist from www.careaboutcushings.co.uk this can help you spot the signs of laminitis in your horse. If you spot any of the signs described on the check list you should discuss them immediately with your veterinary surgeon.
Laminitis can be extremely challenging and time consuming for owners, vets and farriers to treat. Treatment of laminitis can be vastly expensive depending on the severity of clinical signs seen and the type of treatment required for the patient. X-rays, corrective farriery and medication may be necessary for the animal on more than one occasion, especially if the horse has repeated bouts of laminitis. Bringing horses or ponies back into work after a diagnosis of laminitis can be a long and demanding journey especially if lameness is still observed; full return to normal work may not be possible in every case.
Prompt recognition of signs of Equine Cushing’s disease means that treatment can commence earlier with the aim to reduce the severity, or further development of symptoms. Identifying the disease sooner allows important management strategies to be introduced including farriery, parasite control and dentistry all of which can improve the welfare and quality of life of a horse or pony with PPID
What should I do if I spot the signs of Cushing’s disease?
If you are concerned that your horse or pony may be showing any of the symptoms discussed, you should call your veterinary surgeon for further help and support. If your veterinary surgeon considers it appropriate to investigate further they are likely to suggest a simple blood test. If this blood test indicates that your horse or pony has Equine Cushing’s disease your vet will be able to discuss a licenced treatment with you in addition to important management strategies to maintain your horse’s quality of life.
If your vet recommends testing your horse for Equine Cushing’s disease, vouchers for complimentary blood tests are available from the brand new Care about Cushing’s website https://careaboutcushings.co.uk/. This website also contains a library of information for you to support your horse with Cushing’s, and an online toolkit for monitoring Equine Cushing’s disease.
In summary, Equine Cushing’s disease is a lifelong but treatable condition that can be managed with help and support from your veterinary surgeon. It is important to recognise the early signs of Equine Cushing’s disease so that prompt diagnosis and treatment can optimise quality of life and reduce the risk of suffering associated with the symptoms of this disease.
Equine veterinary surgeon Linda Greaves is an Equine Technical Adviser for Boehringer Ingelheim Animal Health. Before joining Boehringer Ingelheim Linda worked in equine veterinary practices throughout the North of England, where she specialised in equine dentistry. Linda also has a special interest in laminitis and Equine Cushing’s disease, and works closely with the Talk About Laminitis campaign: an educational initiative that raises awareness of the link between laminitis and Equine Cushing’s disease. For further advice: www.careaboutcushings.co.uk
References
1.
Durham AE. (2016) Endocrine disease in aged horses. Vet Clin North Am Equine Pract 2016;32:301–315.
2.
McFarlane D.(2011) Equine pituitary pars intermedia dysfunction. Vet Clin North Am Equine Pract 2011;27:93–11
3.
McGowan TW, et al. (2013) Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses. Equine Vet Journal. 2013;45(1):74-79.
4.
Ireland J, et al.(2012) Comparison of owner reported health problems with veterinary assessment of geriatric horses in the UK. Equine Vet Journal Jan;44(1):94-1005. Karikoski NJ et al. (2011) The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital Domestic Animal Endocrinology 41. 111-117.
6.
McFarlane D, Hill K, Anton J. (2015) Neutrophil function in healthy aged horses and horses with pituitary dysfunction.Vet Immunol Immunopathol. 15;165(3-4):99-106.
7.
Pollard et al (2017) Assessment of horse owners ability to recognise equine laminitis: A cross‐sectional study of 93 veterinary diagnosed cases in Great Britain. Equine Veterinary Journal Vol49, Iss 6. 759-766