Equine Cushing's disease: Treatment and case discussions (Proceedings)


Equine Cushing's disease: Treatment and case discussions (Proceedings)

Aug 01, 2009

Management of pituitary pars intermedia dysfunction (PPID) in equids consists of improved husbandry, including adequate nutrition and limiting competition for feed, body-clipping, dentistry, and appropriate treatment of concurrent medical problems. In addition, specific treatment with the dopamine agonist pergolide can improve quality of life and reverse many clinical signs of the disease in PPID-affected equids. Treatment with both pergolide and cyproheptadine, in the author's experience, may also prove beneficial in more advanced cases. For patients with chronic laminitis, appropriate trimming or shoeing and judicious use of analgesic medications is also necessary. Although many nutritional supplements and nutraceuticals have been advocated for use in equids with PPID, none have established data to support their claimed benefits. Finally, due to the expense of lifelong medication, a decision of whether or not to treat affected horses with pergolide should be made on a case-by-case basis in consideration of the client's goals for the patient.

Husbandry and nutritional considerations

Management of equids with PPID initially involves attention to general health care along with a variety of management changes to improve the condition of older animals. In the earlier stages of PPID, when hirsutism may be the primary complaint, body-clipping to remove the long hair may be the only treatment required. Next, since many affected animals are aged, routine oral care and correction of dental abnormalities cannot be overemphasized. In addition, assessment of diet and incorporation of pelleted feeds designed specifically for older equids (e.g., senior diets) should be pursued. In the author's experience, aged horses both with and without clinical signs of PPID can easily gain 50 or more pounds within 3-4 weeks of placing them on a Senior feed.

Sweet feed and other concentrates high in soluble carbohydrate are best avoided (unless that is all that they will eat), especially when patients are hyperinsulinemic, hyperglycemic, or both. Also, affected equids may need to be separated from the herd if they are not getting adequate access to feed. Unfortunately, because the abdomen may become somewhat pendulous, weight loss and muscle wasting in more severely affected animals may not be well recognized by owners. In these instances, measurement of body weight, or estimation with a weight tape or body condition score, are important parameters to monitor during treatment.

Whether or not it is "safe" to allow PPID-affected equids to graze pasture as a forage source remains controversial. Pasture, especially lush spring and early summer pasture, should be considered similar to feeding concentrates high in soluble carbohydrates and many veterinarians recommend that PPID-affected equids NOT be turned out on pasture. In my opinion, it is important to assess the overall condition of the patient. If the horse or pony is considered overweight and has abnormal fat deposits, supportive of insulin resistance, pasture turn out would not be recommended. Instead, feeding grass hay at 1-1.5% of the body weight daily would be the preferred forage diet and animals that are overweight clearly do not need an additional "low starch" concentrate feed. However, if body condition is somewhat poor, strategic grazing for several hours per day can be a useful way to increase caloric intake and produce weight gain. Again, caution is advised and access to lush spring or early summer pasture should be avoided or at least limited to one or more shorter periods per day.

Figure 1 Photographs of the front feet of a pony with pituitary pars intermedia dysfunction and chronic laminitis: left, initial evaluation (September, 2006); middle, 5-month re-examination (February, 2007); right, 14 month re-examination (November, 2007). Despite a visual appearance to the hoof that may actually seem worse over time (e.g., lower hoof angle after 5 months), the below video clips reveal a marked improvement in lameness. In addition, hoof conformation was nearly normal after a year of treatment and corrective hoof care.
Since the major musculoskeletal complication of PPID is chronic laminitis, regular hoof care is essential to lessen the risk of flare-ups. It is important to emphasize to clients that starting medical treatment for PPID (i.e., pergolide) may not lead to complete resolution of the pain and intermittent hoof abscessation that accompanies chronic laminitis, due to the damage to the laminar bed that has previously been sustained. Further, intermittent use of non-steroidal anti-inflammatory drugs, primarily phenylbutazone, may be necessary. Although flare-ups of chronic laminitis remain a leading cause for a decision for euthanasia in PPID-affected equids, it also warrants emphasis that a combination of medical treatment for PPID along with regular hoof care can lead to substantial clinical improvement (Figure 1). Finally, because many PPID affected patients may have secondary infections (e.g., sinusitis, dermatitis, and bronchopneumonia), intermittent or long-term administration of antibiotics, typically a potentiated sulfonamide, may be necessary.