PAIN MAN­AGE­MENT IN THE EQUINE ATH­LETE

Britt Con­klin is an equine vet­eri­nar­ian who is em­ployed by Boehringer-In­gel­heim (the largest equine an­i­mal health provider in the world) and owns a Sports Medicine and Po­di­a­try prac­tice near Amar­illo, Texas. This is the third in­stall­ment of his TR-- ex­clu

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Part 3: Di­ag­nos­ing the prob­lem area—In­ter­nal Is­sues. By Britt Con­klin, DVM

The first ar­ti­cle in this se­ries be­gan the dis­cus­sion of pain in the per­form­ing horse. Last month, we high­lighted com­mon sources of mus­cu­loskele­tal pain caus­ing lame­ness, and iden­ti­fied ways to di­ag­nose where those prob­lems oc­cur. While sound­ness is­sues are the most com­mon lim­it­ing fac­tor in our equine ath­letes, in­sid­i­ous in­ter­nal prob­lems of­ten play a com­pro­mis­ing role, re­duc­ing the full po­ten­tial of our horse’s per­for­mance. The three ar­eas of pri­mary in­ter­nal fo­cus are the res­pi­ra­tory sys­tem, the gas­troin­testi­nal sys­tem, and the en­docrine sys­tem.

The ca­pa­bil­i­ties and scale of the res­pi­ra­tory tract in a horse, though of­ten un­der­ap­pre­ci­ated, is truly re­mark­able. The end goal for this sys­tem, in any crea­ture, is the elim­i­na­tion of car­bon diox­ide in ex­change for oxy­gen, which is nec­es­sary for en­ergy pro­duc­tion in the body’s cells. At rest, an av­er­age horse may take 12 breaths per minute, equal­ing 60 liters (think 30 two-liter bot­tles of soda) of to­tal vol­ume of air in­haled in that minute. In com­par­i­son, at max­i­mal ex­er­cise, the horse may take 120 breaths per minute, and be­cause the lungs ex­pand, have a to­tal vol­ume of 1,800 liters of air in­haled—the equiv­a­lent to six nor­mal-sized bath­tubs of air ex­changed each minute your horse is run­ning at full speed.

While our rop­ing horses don’t run for mul­ti­ple min­utes, any com­pro­mise to the de­mand of the sys­tem can af­fect the over­all per­for­mance of your horse. Dis­ease and in­flam­ma­tion sig­nif­i­cantly re­duce the ex­change of air and, there­fore, com­pro­mise en­ergy to the cells of the body, es­pe­cially large oxy­gen-uti­liz­ing cells, like mus­cle. Viruses like in­fluenza, her­pes, or rhini­tis can dam­age lung tis­sue, and bac­te­ria like strep­to­coc­cus can com­pro­mise lung func­tion by thick­en­ing mu­cous and pro­duc­ing ex­u­date that clogs the air­way. Al­ler­gens, for some horses, can cause asthma-like symp­toms and are cat­e­go­rized by ve­teri­nar­i­ans based on their sever­ity: in­flam­ma­tory air­way dis­ease (IAD), or re­cur­rent air­way ob­struc­tion (RAO). Long-term in­flam­ma­tion may not cause your horse to gasp for air like the hu­man asth­matic, but may cause your horse to cough when warm­ing up, or fa­tigue at the end of mul­ti­ple runs, and seem­ingly have the in­abil­ity to “catch their air,” as if they are out of shape.

To di­ag­nose res­pi­ra­tory prob­lems, ve­teri­nar­i­ans of­ten sam­ple or look at dif­fer­ent parts of the air­way for lab­o­ra­tory eval­u­a­tion. En­doscopy, or “scop­ing,” in­volves putting a cam­era down the horse’s nose to vi­su­al­ize the anatomy of the up­per air­way, and can be used to dif­fer­en­ti­ate po­ten­tial me­chan­i­cal prob­lems in breath­ing from ab­nor­mal struc­tures. Vets may also cul­ture parts of the air­way, look­ing for viruses, bac­te­ria, or fun­gus. A transtra­cheal wash is a tech­nique that al­lows ster­ile ac­cess to the lung for cul­ture, while a bron­choalve­o­lar lavage, or “lung-wash,” col­lects fluid from the lung to look for dis­eases like IAD and RAO.

The gas­troin­testi­nal tract (GI) can also be an un­der rec­og­nized source of pain. The most com­mon is­sue is gas­tric ul­cer­a­tion. Mul­ti­ple stud­ies show that two-thirds of all non-rac­ing per­for­mance horses have ul­cers, and race­horses, in par­tic­u­lar, have up to a 90-per­cent preva­lence rate. One rea­son for this high in­ci­dence is that the horse’s stom­ach is prone to ul­cer­a­tion be­cause sen­si­tive cells from the esoph­a­gus ex­tend down into the stom­ach and are eas­ily “burned” by stom­ach acid. Ad­di­tion­ally, our feed­ing and man­age­ment prac­tices com­pound the prob­lem. Horses were de­signed to graze small amounts of grasses, for­ages, and legumes con­tin­u­ously through­out the day, while mov­ing, which keeps their stom­achs full and buffered, lim­it­ing the splash­ing of acid onto those sen­si­tive cells. In gen­eral, though, horses are fed twice a day, leav­ing large gaps of time for the stom­ach to be

empty and ex­posed to acid, which, un­like in peo­ple, horses pro­duce con­tin­u­ously. Ad­di­tion­ally, grain di­ets tend to evoke a strong acid re­sponse and are di­gested quickly, once again leav­ing the stom­ach vul­ner­a­ble over time to acid ir­ri­ta­tion.

Di­ag­nos­ing ul­cers is done by gas­troscopy, or “scop­ing,” the stom­ach. Ve­teri­nar­i­ans will look for com­pro­mised tis­sues that range from fo­cal mi­nor ir­ri­ta­tion to dif­fuse full thick­ness ero­sions, which can oc­cur in mul­ti­ple ar­eas of the stom­ach. They are very sim­i­lar to blis­ters or burns on your skin, and can man­i­fest in horses in many ways. Horses can be “cinchy,” have box is­sues, back sore­ness, buck­ing fits, weight loss, or ap­pear to be poor-do­ing. Like res­pi­ra­tory dis­ease, ac­cu­rately di­ag­nos­ing and treat­ing ul­cers ap­pro­pri­ately can have a sig­nif­i­cant im­pact on your horse’s health and per­for­mance.

An­other area of in­ter­nal fo­cus that we may not re­al­ize is in­hibit­ing our horses is the en­docrine sys­tem. This sys­tem reg- ulates al­most every ac­tiv­ity in the body. That reg­u­la­tion is man­aged by hor­mones. In ad­di­tion to be­ing re­pro­duc­tive mol­e­cules, hor­mones are mol­e­cules that tell the body to do many dif­fer­ent essen­tial func­tions. When hor­mones are dis­rupted or dis­eased, the re­sult can be detri­men­tal.

For ex­am­ple, in­sulin is a hor­mone that reg­u­lates sugar in the body. If this hor­mone is miss­ing in a per­son, that per­son be­comes di­a­betic. Di­a­bet­ics deal with an en­hanced risk of many detri­men­tal is­sues, from heart dis­ease to di­a­betic neu­ropa­thy, all be­cause one hor­mone is in short sup­ply. In horses, the most com­mon en­docrine dis­ease is Pi­tu­itary Pars In­ter­me­dia Dys­func­tion, or PPID. It is of­ten re­ferred to as Cush­ing’s dis­ease and orig­i­nates from a prob­lem in the horse’s brain. This ab­nor­mal­ity causes a host of hor­mones to be dis­rupted.

The in­ci­dence for PPID in horses is high and in­creases with age. About 20–25 per­cent of horses over the age of 15 have some form of PPID. Some early is­sues we see in horses with the dis­ease are in­creased rates of in­fec­tions (skin, den­tal, feet), ab­nor­mal sweat­ing, in­creased ten­don or lig­a­ment in­juries, mild re­ten­tion of hair coat in the spring and sum­mer, in­fer­til­ity, and lamini­tis. To di­ag­nose the is­sue, ve­teri­nar­i­ans may draw blood for a screen­ing sam­ple, or they may give a drug to stim­u­late the pi­tu­itary gland and then sam­ple the blood for anal­y­sis. Early di­ag­no­sis is key in prevent­ing some of the more life-threat­en­ing is­sues that can oc­cur with en­docrine dis­eases.

Think­ing about all the is­sues that can af­fect our per­form­ing horse can be over­whelm­ing. Mostly, our con­cerns re­volve around the mo­bil­ity of our ath­lete, but care­ful con­sid­er­a­tion should be given to in­ter­nal is­sues that may im­pact the peak per­for­mance of our equine part­ners. Next month, I will dis­cuss the treat­ments that are avail­able for many of the prob­lems we have been learn­ing about.

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