PPID Up­date

Horse & Rider - - Table Of Contents - By Jen­nifer von Geldern

A dis­ease once known as equine Cush­ing’s is com­mon among se­nior horses. We an­swer your key ques­tions.

Chances are you ei­ther own a se­nior horse deal­ing with a con­di­tion known com­monly as equine Cush­ing’s dis­ease, or know some­one who does. More ac­cu­rately called pi­tu­itary pars in­ter­me­dia dys­func­tion ( PPID), this dis­ease af­fects many horses around the world. Here we’ll talk with Steve Grubbs, DVM, PhD, DACVIM, the equine tech­ni­cal man­ager for Boehringer In­gel­heim Vetmed­ica, Inc., to get the lat­est facts about PPID.

What ex­actly is PPID, and why the name change from equine Cush­ing’s dis­ease?

Dr. Grubbs: There’s Cush­ing’s dis­ease in hu­mans, in dogs, and in horses, and though there are some sim­i­lar­i­ties among those, there are many key dif­fer­ences. When you look at the con­di­tion anatom­i­cally, it’s more pre­cise and de­scrip­tive to call it pi­tu­itary pars in­ter­me­dia dys­func­tion in horses since it’s the pars in­ter­me­dia por­tion of the pi­tu­itary gland where some­thing has gone wrong, hence the term “dys­func­tion.” The name equine Cush­ing’s dis­ease is still com­monly used, how­ever, and may be used in­ter­change­ably.

In the ve­teri­nary com­mu­nity decades ago, we used to think this was a rare con­di­tion found only in older horses. Much new in­for­ma­tion has come out within the last decade, though, and we re­al­ize we’re see­ing horses with PPID much more fre­quently. The con­di­tion has been around for­ever; we’re just rec­og­niz­ing it bet­ter now. There’s been sig­nif­i­cant ad­vance­ment in un­der­stand­ing it over the past five or six years, but there’s still a lot we need to learn. We’ve gained a lot of knowl­edge about what’s go­ing on with PPID horses, but don’t yet know all the answers.

As cer­tain horses age, they ex­pe­ri­ence a de­crease in dopamine pro­duc­tion. In a nor­mal horse, dopamine in­hibits the pars in­ter­me­dia of the pi­tu­itary gland that con­trols the re­lease of many of the horse’s hor­mones. How­ever, in horses with de­creased dopamine, the pars in­ter­me­dia of the pi­tu­itary gland is not in­hib­ited, or kept quiet, enough. When the pi­tu­itary gland be­comes too ac­tive with the de­crease in dopamine, cer­tain hor­mone pro­duc­tion isn’t kept in check, and we be­gin to see the clin­i­cal signs as­so­ci­ated with PPID.

Are some horses or breeds at greater risk for PPID?

Dr. Grubbs: Horse own­ers should know that this con­di­tion isn’t ex­clu­sive to older horses. The more we look for PPID, the more we find it. Yes, it’s more preva­lent in geri­atric horses, but has been iden­ti­fied in horses as young as 5 years of age. One thing is for sure, though: as a horse ages, his risk fac­tor for PPID in­creases.

Stud­ies un­der­way will seek to de­ter­mine if some breeds of horses are more prone to PPID. We’ve tested more than 4,000 horses with at least one clin­i­cal sign as­so­ci­ated with PPID, plus iden­ti­fied more than 66 breeds and crosses that were PPID-pos­i­tive. We saw the con­di­tion most of­ten in Quar­ter Horses, but of course, the Quar­ter Horse dra­mat­i­cally out­num­bers other breeds in the U.S., so that doesn’t nec­es­sar­ily mean they’re more prone to it. We’ve seen PPID in ev­ery­thing from ponies (which have a higher in­ci­dence) to draft horses (a lower in­ci­dence) to ev­ery­thing in be­tween, in­clud­ing Ara­bi­ans, Mor­gans, Thor­ough­breds, and warm­bloods.

What should a horse owner look for as signs of PPID?

Dr. Grubbs: It’s im­por­tant to stay tuned in to your horse’s over­all health, as clin­i­cal signs of PPID at first may be quite sub­tle. Your ve­teri­nar­ian may see your horse only once or twice a year, but you should have daily knowl­edge of your horse’s rou­tines, at­ti­tude, and ap­pear­ance. If and when your ve­teri­nar­ian di­ag­noses PPID, those sub­tleties are ex­tremely im­por­tant for you to men­tion.

In the ve­teri­nary field, the clin­i­cal signs of PPID have been di­vided into early and ad­vanced, but those don’t al­ways cor­re­late to age. Early clin­i­cal

A dis­ease for­merly known as equine Cush­ing’s is com­mon among se­nior horses. We an­swer your most press­ing ques­tions here. By Jen­nifer von Geldern

signs can be found in a 12-year-old horse or a 22-year-old horse.

One of the most com­monly as­so­ci­ated and highly rec­og­niz­able signs of ad­vanced PPID is an ex­tremely long hair­coat all over the body. This coat, which never sheds out or is very slow to shed, is known as hy­per­tri­chosis. In the early stage, though, this may ap­pear as longer hair on just por­tions of the body, such as the neck and legs. It can ap­pear as later-than-nor­mal shed­ding in the early stages, too. If your horse ever seems to be shed­ding later than the al­ready-slick horses around him, it may be worth hav­ing him checked for PPID.

An­other early sign is de­creased ath­letic per­for­mance, and though that can be at­trib­uted to many other con­di­tions, a PPID horse may ex­hibit lethargy in con­nec­tion with the lack of per­for­mance. Loss of mus­cle mass and tone, es­pe­cially across the horse’s topline, is an­other early clue. Mus­cle at­ro­phy in­creases in the more ad­vanced stages of PPID. Since the horse’s im­mune sys­tem is com­pro­mised, a PPID horse is less able to fight off in­fec­tions, so even small sores may not heal as well.

The most con­cern­ing clin­i­cal sign, whether in the early or ad­vanced stage, is lamini­tis, which has the po­ten­tial to cre­ate the most detri­men­tal is­sues for PPID horses. Lamini­tis typ­i­cally ap­pears very grad­u­ally in these horses and of­ten goes un­no­ticed for a pe­riod of time, un­til the horse is ex­tremely sore. Some­times own­ers don’t even no­tice it un­til it gets to the point that the horse is show­ing ob­vi­ous signs of pain. Again, stay­ing vig­i­lant to your horse’s rou­tines and at­ti­tude is crit­i­cal, as this en­ables you to sup­ply the big­ger pic­ture to your vet, in turn al­low­ing him or her to piece all the signs to­gether.

H&R: Can a horse be tested for PPID? If so, what is the pro­ce­dure for that?

Dr. Grubbs: Test­ing for PPID has pro­gressed to a sim­ple blood test. If you think you see any of the early or late clin­i­cal signs of PPID, have your ve­teri­nar­ian ex­am­ine your horse and, if needed, pull blood for test­ing. Pulling blood for rest­ing ACTH (adreno­cor­ti­cotropic hor­mone) lev­els can be con­ducted any time of day and all year long. Thus if your horse shows any of the early or ad­vanced signs, it’s easy to test for PPID.

An older method, the dex­am­etha­sone sup­pres­sion test, checks for the level of a hor­mone called cor­ti­sol in the blood. Re­quir­ing two blood draws on two con­sec­u­tive days and less ac­cu­rate dur­ing au­tumn, it’s less con­ve­nient than the newer test for rest­ing ACTH lev­els, but is still used.

H&R: What kind of life­style man­age­ment changes can help a PPID horse?

Dr. Grubbs: Fol­low­ing the di­ag­no­sis of PPID in your horse, I’d rec­om­mend dis­cussing med­i­cal ther­apy with your ve­teri­nar­ian. Be­yond that, treat­ing the whole horse is the best ap­proach. That be­gins with a thor­ough ve­teri­nary exam and in­cludes con­sci­en­tious den­tal care, par­a­site con­trol, proper nu­tri­tion, and tend­ing to ba­sic com­forts.

Ag­ing horses, more likely to de­velop PPID, also need to have their teeth floated con­sis­tently. Some PPID horses tend to carry too much weight, but of­ten, older PPID horses tend to run too lean. Un­tended teeth can com­pli­cate keep­ing weight on these horses, so es­tab­lish a den­tal rou­tine with your ve­teri­nar­ian.

PPID horses also tend to har­bor more in­ter­nal par­a­sites than healthy horses. Have your ve­teri­nar­ian run a fe­cal count to de­ter­mine type and quan­ti­ties of par­a­sites, then ad­min­is­ter suit­able de­worm­ers on a sched­ule.

Proper nu­tri­tion de­pends greatly on the in­di­vid­ual horse’s needs, and varies from one ge­o­graphic re­gion to an­other. Learn the body-con­di­tion scale, with 1 rep­re­sent­ing the thinnest and 9 rep­re­sent­ing the most obese, so that you can com­mu­ni­cate ac­cu­rately with your ve­teri­nar­ian while es­tab­lish­ing the horse’s diet. (Note: Find the stan­dard Hen­neke body-con­di­tion score sys­tem at bit.ly/

Mon­i­tor­ing in­sulin lev­els is an im­por­tant part of the horse’s meta­bolic pro­file, be­cause in­creased in­sulin puts a horse at greater risk for lamini­tis. In­sulin lev­els can be checked dur­ing the same blood draw that checks for rest­ing ACTH lev­els to de­ter­mine if the horse has PPID. In our study of more than 4,000 horses, 47 per­cent of the PPID-pos­i­tive horses had in­creased in­sulin that needed to be man­aged to help de­crease the risk of lamini­tis.

Some PPID horses with heavy coats will need to be kept body clipped, which helps them reg­u­late their body tem­per­a­ture bet­ter. Tend to the com­fort of these spe­cial horses to make the most of their lives and per­for­mance abil­i­ties, which can be main­tained for many years with care­ful de­ci­sions about their care.

H&R: What does the fu­ture look like for manag­ing PPID?

Dr. Grubbs: There’s a huge amount of in­ter­est in the PPID horse at this time, and right­fully so. A tremen­dous amount of new in­for­ma­tion about the recog­ni­tion, di­ag­no­sis, and man­age­ment of PPID in horses has come to light in the last few years. We’re now rec­og­niz­ing PPID in younger age groups of horses be­cause we’re aware of the early signs and have newer di­ag­nos­tic ca­pa­bil­i­ties avail­able. The big­gest chal­lenge at this point is to get all this newer in­for­ma­tion into the hands of horse own­ers and vet­eri­nar­i­ans who man­age these horses on a daily ba­sis. Horse own­ers see their horses on a daily ba­sis and can re­port any changes that might be PPID-re­lated to their ve­teri­nar­ian. I think we all just want to en­sure that the most ac­cu­rate, up-to-date in­for­ma­tion about PPID gets to horse own­ers and vet­eri­nar­i­ans in a timely man­ner, so we can all work to­gether to man­age the PPID horse in the best pos­si­ble way. It ab­so­lutely re­quires a team ap­proach.

Stay vig­i­lant to your horse’s or­di­nary daily rou­tines and at­ti­tudes to catch early signs of PPID.

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