Un­der­stand­ing the Ba­sics of Equine Cushing’s Dis­ease

Clin­i­cal signs, test­ing, treat­ment and pre­cau­tions

Dressage Today - - Content - By Reina Abelshauser with Dou­glas Langer, DVM, MS

Clin­i­cal signs, test­ing, treat­ment and pre­cau­tions

If you see a horse with a long, curly hair coat, it could be a sign of Cushing’s dis­ease in the ad­vanced stages. But the dis­ease can start with much less strik­ing signs. Dou­glas Langer, DVM, MS, who op­er­ates Wis­con­sin Equine Clinic and Hospi­tal in Oconomowoc, Wis­con­sin, says that dres­sage horses are es­pe­cially pre­dis­posed to de­vel­op­ing Cushing’s dis­ease due to the fact that they are of­ten easy keep­ers. Fol­low­ing are things you need to know about the dis­ease and what you can do to catch it early.

What is Cushing’s Dis­ease?

Cushing’s dis­ease is a con­di­tion where the pi­tu­itary gland, also re­ferred to as pars in­ter­me­dia, en­larges in the brain. The pi­tu­itary gland is re­spon­si­ble for reg­u­lat­ing the body’s hor­mones. In a horse suf­fer­ing from Cushing’s dis­ease, there ei­ther is not enough dopamine present or the body is not ad­e­quately rec­og­niz­ing it. This has an ef­fect on the adrenal glands and the kid­neys, and the horse be­comes prone to hav­ing in­fec­tions. In se­vere cases, Cushing’s dis­ease can cause neu­ro­logic dis­ease.

Clas­sic clin­i­cal signs in horses in­clude a long, curly hair coat, a cresty neck, ab­nor­mal fat de­posits and poor shed­ding habits. Some older horses lose mus­cle mass. Most af­flicted horses are older, but younger horses can de­velop Cushing’s dis­ease as well.

Gabrielle Jolin’s 20-year-old, Third Level Hanove­rian geld­ing, Fievel, had all the clas­sic signs of Cushing’s dis­ease when he was di­ag­nosed. “My in­struc­tor and I sus­pected it dur­ing the late win­ter/early spring of 2016 when he was 19,” she says. “His coat wasn’t shed­ding out very well and he was very wooly. He had also lost a lot of topline mus­cle, was sweat­ing ex­ces­sively and was uri­nat­ing quite fre­quently.”

Other more sub­tle in­di­ca­tors in­clude be­ing over­weight as well as aber­rant in­sulin lev­els in the blood. Many Cushing’s horses de­velop lamini­tis. Sore feet af­ter trim­ming can be a symp­tom. “Any horse who gets sore af­ter his feet are trimmed and founders, but there is no ex­pla­na­tion why it hap­pens—80 to 90 per­cent of these horses have Cushing’s dis­ease or Equine Meta­bolic Syn­drome [EMS],” says Langer.

Com­pli­ca­tions from Cush­ings and EMS

Re­searchers have found that although Cushing’s dis­ease and EMS are not the same thing, there is a strong link be­tween the two. Both con­di­tions are linked to in­sulin re­sis­tance, di­a­betes, lamini­tis and/or founder­ing if un­treated. “It is a com­plex of the two that we are of­ten deal­ing with,” Langer ex­plains. “As horses gain weight, EMS con­cerns go up and their in­sulin lev­els tend to rise, which can over time trig­ger a laminitic episode. If the horse is also mildly Cushin­goid, that very quickly can trig­ger a laminitic episode, es­pe­cially if he has joint in­jec­tions with steroids. The joint in­jec­tions can tip the scales,” Langer ex­plains. He adds that founders trig­gered by steroids are usu­ally among the most se­vere cases. If the horse is a can­di­date for joint in­jec­tions, Langer rou­tinely plans on test­ing for both Cushing’s dis­ease and EMS.

“If I am con­cerned about ei­ther con­di­tion—Cushing’s or EMS—I treat the horse with joint med­i­ca­tions that don’t pre­dis­pose him to founder­ing. Hyaluronic acid is a safe joint sup­ple­ment to ad­min­is­ter. Re­gen­er­a­tive ther­a­pies such as IRAP [In­ter­leukin 1 Re­cep­tor An­tag­o­nist Pro­tein], Pro-Stride and platelet-rich plasma are suit­able op­tions as well.” He adds that there is a new med­i­ca­tion for such horses that is cur­rently be­ing used on an ex­per­i­men­tal ba­sis—poly­acry­lamide gel, an

ar­ti­fi­cial joint lu­bri­cant that will be on the mar­ket soon.

Test­ing for Cush­ings and EMS

When sus­pect­ing a horse has signs of EMS, Cushing’s dis­ease or re­ceives steroid in­jec­tions, vet­eri­nar­i­ans ide­ally test the horse’s ACTH and in­sulin lev­els prior to any treat­ment. ACTH stands for adreno­cor­ti­cotropic hor­mone, and its lev­els in­di­cate if the horse has Cushing’s dis­ease. “What we are look­ing for are higher-than-nor­mal ACTH lev­els,” Langer says. “With Cushing’s dis­ease, if the ACTH level is not high and I still sus­pect this dis­ease, we may do a TRH [thy­rotropin-re­leas­ing hor­mone] stim­u­la­tion test to see if there is a nor­mal re­sponse or not.”

Ka­t­rina Hiller, of Wal­worth, Wis­con­sin, ex­pe­ri­enced how joint in­jec­tions can sud­denly trig­ger lamini­tis due to el­e­vated ACTH lev­els in her 17-year-old Olden­burg geld­ing, Toy Sol­dier, whom she has had since he was 3 and whom she has trained to Grand Prix. “He has al­ways strug­gled with his weight,” she says. “I had trou­ble keep­ing the weight off. He al­ways had a cresty neck and fat de­posits. Then, in the sum­mer of 2016, four days af­ter his sti­fles were in­jected with cor­ti­cos­teroids, he sud­denly de­vel­oped lamini­tis. [Re­ceiv­ing the steroid in­jec­tions] was rou­tine for him. I had his ACTH lev­els tested ev­ery year. He was al­ways fine. We tested him af­ter the in­jec­tion and his ACTH lev­els were very high.”

Treat­ment

While there is no cure for Cushing’s dis­ease, drugs can help re­lieve the clin­i­cal signs. Cypro­hep­ta­dine was once the drug of choice for treat­ment. Some horses re­spond well to per­golide (Pras­cend) and some­times it is used in con­juc­tion with cypro­hep­ta­dine. Toy Sol­dier’s ACTH lev­els had im­proved so dra­mat­i­cally on per­golide that Hiller took him off it. “We tried to take him off the med­i­ca­tion. He was OK for about six weeks and then he had another lamini­tis flare-up.”

Jolin’s geld­ing, Fievel, is still rel­a­tively sta­ble with­out med­i­ca­tion. “We have been retest­ing his ACTH lev­els ev­ery spring and watch­ing them. If his clin­i­cal signs worsen or if his lev­els get con­sid­er­ably higher, we will start med­i­cat­ing.”

Pre­cau­tions to Lower the Risks

Although Cushing’s dis­ease can­not al­ways be pre­vented, there are pre­cau­tions you can take to lower the risk. “The most im­por­tant thing is to keep your horse’s weight down, pro­vid­ing proper nutri­tion, which means to feed him only what he re­ally needs,” Langer says. Sugar in­take should be min­i­mized. “Feed­ing too many car­rots, ap­ples or treats is a con­tribut­ing fac­tor. Avoid it in horses that are pre­dis­posed. When you have an easy keeper, it is wise to put on a graz­ing muz­zle when turn­ing him out on pas­ture.

Hiller changed Toy Sol­dier’s diet af­ter the di­ag­no­sis, tak­ing out all sugar, in­clud­ing treats and grass. “We stopped his diet of al­falfa pel­lets, beet pulp and vi­ta­min sup­ple­ments. We had to find a way to give him enough pro­tein and fat with­out the sugar. The sugar caused lamini­tis. I gave him a pro­tein sup­ple­ment safe for meta­bolic horses that re­ally helped to get his mus­cle tone and en­ergy back.” Jolin’s geld­ing, Fievel, is on a con­trolled low­sugar/low-starch diet and stays clipped for most of the year.

Since per­golide is on the FEI list of pro­hib­ited sub­stances, Hiller no longer com­petes her horse. How­ever, she is still school­ing all the Grand Prix move­ments and is par­tic­i­pat­ing in clin­ics, although the med­i­ca­tion has changed her horse’s en­ergy lev­els. “His en­ergy is pretty low. And he got re­ally stiff. He has to have a much longer warm-up time. On days where he can’t work through the stiff­ness, I take him for a hack or let him be and give him more easy stretch days. About twice a week I can school the harder move­ments.” She adds that now that the pres­sure of show­ing is gone, she can fo­cus more on her­self in her rid­ing.

Jolin hasn’t given up her goal of earn­ing her USDF bronze medal with her Cushing’s horse. “It was my first time out at Third Level this past show sea­son and I’m look­ing to im­prove and hope­fully achieve this be­fore I go to col­lege in the fall.”

If you are con­cerned your horse might de­velop Cushing’s dis­ease, you can help min­i­mize its impact. Make sure your horse main­tains a healthy weight and re­duce his sugar in­take. Feed your horse only what he re­ally needs.

If your horse is over­weight or has been di­ag­nosed with Cushing’s dis­ease and needs treat­ment for de­gen­er­a­tive joint dis­ease, pre­vent com­pli­ca­tions by choos­ing joint med­i­ca­tions that are safe for Cushin­goid horses and stay away from cor­ti­cos­teroids. Re­lieve your horse’s Cushing’s signs by keep­ing him on per­golide or cypro­hep­ta­dine. When man­aged prop­erly, horses with Cushing’s dis­ease can lead long and use­ful lives as dres­sage part­ners.

Ka­t­rina Hiller and her 17-year-old Olden­burg geld­ing, Toy Sol­dier

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