Q. My 18-year-old mare was just diagnosed with PPID (pituitary pars intermedia dysfunction, formerly known as equine Cushing’s disease). My vet prescribed her pergolide, the mainstay treatment, but are there any management changes I can make as well to help keep her healthy?
A. This is a great question! Optimizing management practices and preventive health care is an important component to promote the best outcome for horses with PPID. While old horses in general benefit from enhanced preventive care, those with PPID have a greater need for careful monitoring and preventive interventions due to the debilitating effect PPID has on immunity, exercise tolerance, thermoregulation, and wound healing. PPID is a catabolic disease, meaning it causes horses to lose weight (particularly muscle mass) and, if not addressed, might result in horses in poor condition. Horses with PPID don’t shed completely or don’t shed their winter coat on time. This could cause horses to be less able to tolerate higher temperatures or more likely to develop skin diseases like rain rot. Some PPID horses have increased water consumption and, consequently, increased urine output. About one-third of horses with PPID are at risk of developing the hoof disease laminitis. Suspensory ligament breakdown is also reported more commonly in PPID horses.
How To Manage Horses With PPID
Several management recommendations can help avoid these complications in horses with PPID. First are the basics: good diet, dentistry, and parasite control are essential to help avoid excessive weight loss. There is no one correct way to feed a horse with PPID appropriately and, over time, as the disease progresses, the dietary needs of individual horses change. Therefore, work with your veterinarian or equine nutritionist to tailor a diet that addresses your horse’s needs. Schedule regular assessments to review and update the diet plan as needed. Ensure the horse has adequate time to eat without competition from other herdmates. Many aged horses are slow eaters, due to poor dentition or arthritis of their mandibular (jaw) joints. Learn to body condition score your horse, and do that monthly. This will help you recognize if your horse is starting to lose weight and will give you an opportunity to intervene before the weight loss is severe. Regular dental evaluation is critical. Loose teeth, sharp points, and tooth root infections are more common in older horses with PPID, leading to pain when eating, quidding, and weight loss. Internal parasites are also more common in horses with PPID, so regular fecal examinations with strategic deworming are needed.
Many horses when treated with pergolide will start to shed more normally, but if your horse is still carrying a long coat, body clipping might be necessary to tolerate higher summer temperatures. At a minimum, keep the horse well-groomed and watch for the development of any skin diseases. If your horse is one that is drinking and urinating more, an ample supply of fresh water is essential. Stalls will need to be cleaned and bedded more often. As the immune system is less competent in horses with PPID, these horses are at greater risk of developing both foot abscesses and lower airway disease that can be initiated by standing in wet, urine-dense bedding for long periods.
Horses with PPID are immunocompromised. Therefore, take precautions to reduce their exposure to pathogens by housing them remotely from horses that are traveling and showing. Despite having a suppressed immune system, immunization is still effective at protecting PPID horses from disease. Continue to vaccinate your aged PPID horse, working with your veterinarian to design an appropriate vaccination plan.
Finally, but perhaps most importantly, watch for any signs of foot pain (e.g., a reluctance to move or lift their feet or a stiff, short-strided gait) in horses or ponies with PPID that also have a history of equine metabolic syndrome (EMS) or obesity. Laminitis is a life-threatening complication of both EMS and PPID that is best treated when caught early.