If your horse has difficulty in losing weight, or suffers from bouts of laminitis, they may be suffering from Equine Cushing’s disease and/or Equine Metabolic Syndrome. The following articles will hopefully help you understand more about these relatively common but often misunderstood and confusing conditions.
What is Equine Cushing's disease?
Equine Cushing's disease, also known as Pars Pituitary Intermedia Dysfunction (PPID) is a disorder of the horses’ endocrine system (hormonal system). Equine Cushing’s most commonly affects pony breeds, but larger breeds can be affected and it is primarily seen in older horses above the age of 15 years.
Equine Cushing's is caused by an enlargement in the pars intermedia (middle section) of the pituitary gland. The pituitary gland is located at the base of the brain and is an important endocrine organ that produces a variety of different hormones. This enlargement of the pars intermedia results in the increased release of several hormones, most notably ACTH (adrenocorticotropic hormone). ACTH causes the adrenal glands (located near the kidneys) to increase the production of cortisol, a type of steroid. It is this overproduction of cortisol that causes the majority of clinical signs seen in this condition.
What does Equine Cushing's look like?
There are many clinical signs associated with Cushing’s disease. Recurrent, and often unexplained, bouts of laminitis along with an abnormal hair coat are two of the most common clinical signs of a horse with Cushing's.
Other signs include a pot-bellied appearance, ravenous appetite, increased urination and drinking, lethargy and a decrease in the immune system seen as recurrent skin and respiratory infections, as well as dental disease and an increased susceptibility to worms. Cushing's horses can also get an abnormal deposition of fat above their eye where normal horses would have a depression (this depression can often be seen moving when a horse chews) and can also show wasting of their skeletal muscles.
Abnormal hair coat can vary from mild changes in shedding pattern to the development of a long (up to 10cm) thick and wavy overgrown coat. This strange coat characteristic is known as ‘hirsutism’ and is due to the enlarged pars intermedia of the pituitary gland compressing the hypothalamus, which is a section of the brain located next to the pituitary gland that regulates body temperature, appetite and seasonal cyclic shedding of hair.
The link between Equine Cushing's disease and laminitis is still not fully understood but it is the focus of extensive research. It is currently believed that the increased levels of circulating cortisol and cortisol-like hormones may play a major role in the development of laminitis, so too might a metabolic state known as insulin resistance, which we will come to later.
How do you diagnose Cushing's disease?
In classic cases (i.e. the older pony with hirsutism and recurrent laminitis) a diagnosis can be made on presentation alone, but not all Cushing's cases have obvious clinical signs - often they are very subtle. When investigating subtle signs, or when a definitive diagnosis is wanted, there are a couple of tests your vet can conduct.
The most common test is to measure resting ACTH. This is a simple once off blood sample that gives fairly reliable results in regards to diagnosis, as well as being used to monitor the progression of the condition once treatment has started. Another common test performed to achieve a diagnosis of Equine Cushing's disease is the Low Dose Dexamethasone Suppression Test. This test involves taking a blood sample from the horse to get a base-line measure of circulating cortisol. After the blood is taken, a dose of dexamethasone is administered into the muscle. Dexamethasone is a steroid that in normal horses will cause suppression of circulation cortisol levels. In horses affected by Cushing's disease the body is unable to respond properly to the injection and cortisol levels remain elevated. A second blood sample is taken about 20hrs after the injection of dexamethasone. If the cortisol levels have not decreased then a diagnosis of Cushing's is made.
Treatment and Management of Equine Cushing's disease
Unfortunately there is no cure for Equine Cushing's but we can help reduce the effects of the disease.
Pergolide is the most commonly used Cushing's medication. It comes in tablet form that can be crushed up and fed in feed or hidden inside a treat and is given once per day. Pergolide is a dopamine agonist (dopamine inhibits the pars intermedia and hence helps to reduce its size and thus reduce over production of cortisol) and has been reported to be up to 80% successful in reducing the severity of signs seen in Cushingoid horses. Other medication such as cyproheptadine and trilostane can also occasionally be considered if results with pergolide are disappointing.
Management is just as important as medicating Cushingoid horses. Frequently inspecting for wounds and the evidence of any kind of infection and ensuring prompt veterinary attention is very important as affected horses may have reduced levels of immunity and often need more intensive and prolonged treatment than other horses. Regular farrier visits and dental checks along with routine vaccinations and a de-worming program involving frequent faecal egg counts are vital to ensure the health of Cushing's affected horses. Simple things like clipping out excessive hair will also go a long way in ensuring the comfort of affected horses especially in hot weather.
This poor little girl is a one year old miniature horse suffering from colic due to a large accumulation of sand in her large colon (see the X-ray showing the sand in the lower abdomen). This occurs as a result of steady ingestion of sand from the paddocks/soil over weeks or months, and can easily go unnoticed until there is enough sand in the bowel to cause significant irritation and obstruction. It also predisposes to enterolith formation (development of “stones” in the intestine) which can lead to further colic and often the need for emergency surgery to remove them.
Fortunately this patient responded very well to pain relief and administration of paraffin oil and psyllium husk – seen here being administered by Drs Hayley Lang, Jonathan Lee and Tom Bayes, and was able to go home a couple of days later and is still doing well.
If you have your horses on sandy pasture, regular preventative measures should be taken to minimise the risk of sand colic. These include feeding any hay or other feed from raised mangers or hay nets (or using mats which are regularly swept to remove the sandy soil) and feeding psyllium (e.g. Sandlube) twice weekly at least. In the greater Sydney region we see most cases of sand colic from the Terrey Hills/Duffy’s Forest and Kurnell regions, but all soil in our part of the world can have relatively high sand content, so it can occur almost anywhere. Sometimes routine radiography of the abdomen is necessary to know how much sand is being eaten and therefore how big a risk sand colic is.
Please contact us via email@example.com (02 0399 7722) or see your usual vet if you would like more information.
REC has just purchased the first Class IV therapeutic laser for horses in Australia. This is the most powerful laser on the market and has greater depth of penetration and shorter treatment times than the Class III lasers many of you may have used before. Class IV therapeutic laser has been shown to increase circulation, reduce inflammation, pain and muscle spasms. It is useful to treat a wide variety of conditions including:
• Tendon injuries
• Ligament injuries, such as suspensory desmitis
• Muscle pain and inflammation
• Osteoarthritis, including navicular syndrome
How does it work?
Laser therapy uses a range of specific wavelengths to stimulate a cascade of events at the cellular level, resulting in:
• Increased oxygen and energy supply to the tissues and accelerated removal of waste products and inflammatory mediators
• Downregulation of pain pathways
• Vasodilation resulting in improved circulation
• Activation of lymphatic drainage (aiding reduction of swelling)
• Reduced formation of scar tissue
Combining deep-penetrating laser therapy with traditional therapeutic regimes accelerates the recovery time for many common lameness disorders in horses. Laser is also an invaluable tool to assist in injury prevention and help maintain
Laser therapy effect is cumulative so each treatment is complementary to the last at a cellular level. Treatment protocols vary depending on whether it is being used for injury treatment or prevention, the type of injury and whether the injury is acute or chronic. The laser unit is portable so treatment can be carried out at your yard. Please contact reception for further information. athletes at their highest level of performance. Training at a high level inevitably results in intermittent pain and soreness. Periodic class IV laser application can allow faster recovery and therefore more efficient training.
We are very pleased to be sponsoring the upcoming NSW State Dressage Championships again at SIEC (Thurs 8th to Sun 11th September). Drs Rachel Salz & Ruth Franklin, along with master farrier Garth Derrig will be giving a free talk on Thursday evening about how to avoid lameness and promote soundness in your horse. It's at SIEC ay 6:30pm & will be a very informative evening, so be sure you attend. The team will be very happy to answer any questions you may have about lameness, shoeing or any other aspect of maximising performance. There's the chance to win a tube of Epiitalis Forte joint supplement & also a free BBQ!
Here are some pics of the team being trained how to use the new scintigraphy unit and our first patient to successfully have a difficult lameness diagnosed.
The screen shot shows a stress fracture of the right humerus. This injury can only be accurately diagnosed with scintigraphy. It is extremely important to establish the correct diagnosis in cases such as this because, if not managed properly, they can easily propagate and become complete fractures with truly disastrous consequences (i.e. euthanasia in almost all cases). With the appropriate treatment almost all horses recover fully and return to full work without further lameness.
1. Group Financial Accountant (Full Time - Equine Industry).
2. Collections Officer (Full Time - Equine Industry).
If you are keen to take your career to the next level apply now for one of these challenging and diverse role by sending your Resume with a properly set out Cover Letter to firstname.lastname@example.org.For more information on each position please see below -
HUGE congratulations to our own Dr Rachel Salz on recently passing the board examinations to become a diplomate of the American College of Equine Sports Medicine and Rehabilitation. This is a massive achievement and represents the highest possible qualification in this field. Well done, Rach – just reward for an enormous amount of hard work & effort!
But wait…. there’s more! Similar congratulations to Dr Josie Leutton on passing the board examinations of the American College of Veterinary Surgeons in Equine Surgery. Like Rachel, Josie started her career as an intern at REC & then stayed on as an associate before becoming our first ever surgery resident. She left REC a couple of years ago to further her career in WA and recently passed the exams to become a registered specialist in equine surgery. Well done, Josie!
In light of the recent spate of positive swab results to ibuprofen in Victoria, Racing NSW has released the following notice warning about the risks and advising that it not be used at any time.
RANDWICK EQUINE CENTRE SYDNEY EVENTING SUMMER CLASSIC THIS WEEKEND 20-12 FEBRUARY AT SIEC.
We are delighted to again be marquee sponsors for the Summer Classic at SIEC this weekend. It's going to be another great weekend with competition up to 3*. We will be in attendance to help if there are any problems and also to answer any questions you may have about your horse. So go along and join in the fun!