Dres­sage Health

Deal­ing with your horse’s al­ler­gies

Dressage Today - - Content - By Ken­neth L. Mar­cella, DVM

Equine asthma Syn­drome

It is dif­fi­cult to know what to call it—chronic ob­struc­tive pul­monary dis­ease (COPD), heaves, re­cur­rent air­way ob­struc­tion (RAO), sum­mer-pas­ture as­so­ci­ated ob­struc­tive pul­monary dis­or­der, bro­ken wind, al­ler­gic bron­chi­tis, in­flam­ma­tory air­way dis­ease or the all-in­clu­sive, more re­cently sug­gested “equine asthma”—but it is very easy to spot when a horse is af­fected by it. Such a horse will be cough­ing and wheez­ing with la­bored res­pi­ra­tory ef­forts. A dis­tinct nasal flar­ing will be noted along with a deep con­trac­tion of the ab­dom­i­nal mus­cles with each breath. Af­fected equine ath­letes will be thin (from all the mus­cu­lar ef­fort needed just to breathe) and will be re­sis­tant to or to­tally un­able to ex­er­cise and per­form. A closer ex­am­i­na­tion with a stetho­scope will re­veal in­creased lung sounds, of­ten with whis­tles or crack­les heard, in­di­cat­ing the pres­ence of mu­cus in the air­ways and pos­si­bly dam­ag­ing fib­rin de­posits in lung tis­sue. Not all horses with equine asthma will be af­fected to this de­gree, but all horses with this con­di­tion will find breath­ing dif­fi­cult and should be treated be­cause of the pro­gres­sive na­ture of the dis­ease. Left un­treated, equine asthma will se­verely re­duce your horse’s abil­ity to per­form and can progress to be de­bil­i­tat­ing, if not fa­tal.

Equine asthma is com­mon. The num­ber of horses af­fected with some type of se­ri­ous asthma is es­ti­mated to be 14 per­cent in the north­ern hemi­sphere. This num­ber is an ag­gre­gate of all the types of asthma and there is on­go­ing re­search look­ing to get per­cent­ages for each in­di­vid­ual type of asthma (e.g., COPD ver­sus RAO ver­sus sum­mer pas­ture-as­so­ci­ated al­ler­gic bron­chi­tis, etc).

It is cur­rently thought that equine asthma re­sults from a hy­per­sen­si­tiv­ity to in­haled al­ler­gens sim­i­lar to what oc­curs in hu­man asth­mat­ics. There is some in­her­ited com­po­nent to this dis­ease and a large en­vi­ron­men­tal fac­tor as well. Cer­tain plants, grasses, trees and weeds re­lease pollen at spe­cific times dur­ing the year. This pollen con­tains count­less num­bers of al­ler­gens that ir­ri­tate and stim­u­late the im­mune sys­tem and, in spe­cific in­di­vid­u­als, gen­er­ate an ex­ag­ger­ated sys­temic re­sponse. The mu­cous lin­ing of the bronchi (the large air­ways in the lungs) swells, be­comes thicker and pro­duces fluid that closes or ob­structs the air pas­sages. The horse must work to breathe and over time this re­sponse dam­ages the elas­tic na­ture of these air­ways and the horse must now use his mus­cles to force air out of the lungs.

Horses can be af­fected by other al­ler­gens as well and dust, air pol­lu­tants, mold, an­i­mal dan­der, fly sprays, smoke and smog, clean­ing chem­i­cals and many other sub­stances can trig­ger an asth­matic re­sponse. This wide ar­ray of causes and the var­i­ous times of the year when and lo­ca­tions where al­ler­gens may be present help ex­plain the many names that have been given to equine asthma over the years.

Own­ers can pro­vide a sig­nif­i­cant amount of help to their asth­matic horses sim­ply by be­ing ob­ser­vant. Does your horse cough and breathe with more dif­fi­culty when in the stall or in the pas­ture? Does your horse cough more when eat­ing round-bale hay or af­ter be­ing put in a stall with fresh shav­ings? Is it harder to ex­er­cise your horse on dry, dusty days or does your horse per­form worse in hot, hu­mid weather?

We know that hay and straw are sig­nif­i­cant sources of al­ler­gens and can cause most asth­matic horses dif­fi­culty. Some horses, on the other hand, are more af­fected by grass al­ler­gens and cough more at pas­ture while oth­ers are more sen­si­tive to dust and there­fore find breath­ing more dif­fi­cult when in a stall. Watch­ing and record­ing those sit­u­a­tions that make your horse cough and strug­gle to breathe can lead you to be­ing able to iden­tify your horse’s unique asthma trig­gers and then to de­vel­op­ing a treat­ment/man­age­ment pro­gram to help.

Treat­ment for horses with asthma must in­cor­po­rate both en­vi­ron­men­tal and med­i­cal man­age­ment. One with­out the other will sim­ply fail. When deal­ing with asth­matic horses, hay should not be stored above stalls and dusty, moldy

hay in all forms should be avoided. Soak­ing and/or wet­ting the hay to re­duce al­ler­gens can be help­ful for some horses. Barns and stalls should be clean and free of dust. Straw or pine­shav­ing bed­ding is of­ten not tol­er­ated by horses with asthma. Low-dust bed­ding is pre­ferred in these re­ac­tive cases. Most own­ers look­ing to re­duce dust from shav­ings will wet their shav­ings or use a com­mer­cial low-dust prod­uct such as wood pel­lets or any one of the hun­dreds of equine pel­leted bed­ding prod­ucts on the mar­ket. Peat moss is also a good al­ter­na­tive to use. It seems dusty, but the par­ti­cles are so large that they do not get deep in the lungs and are very low in al­ler­gens.

The two most com­monly used types of med­i­cal man­age­ment for equine asthma are cor­ti­cos­teroids and bron­chodila­tors. Bron­chodila­tors are a class of drugs that can be given by mouth or in­haled through the nose. Drugs such as al­buterol and clen­buterol func­tion by open­ing up, or di­lat­ing, the large air­ways in the lungs, al­low­ing for more air­flow. Many peo­ple use in­halers with these drugs to treat their asthma, and equine air masks and ver­sions of in­halers for horses are also now avail­able. Cor­ti­cos­teroids are pow­er­ful anti-in­flam­ma­to­ries that help re­duce swelling and com­bat the ex­ces­sive im­mune re­sponse that is at the root of equine asthma cases. Dex­am­etha­sone can be given orally or by in­jec­tion and it is of­ten used in se­verely re­ac­tive asthma cases be­cause of its strong and rapid re­sponse rate. It can have neg­a­tive ef­fects, how­ever, and is not a long-term asthma so­lu­tion. Pred­nisolone is not as strong a cor­ti­cos­teroid but it also does not have as many se­vere side ef­fects and it of­ten be­comes a part of an equine asth­mat­ics treat­ment pro­gram. Aerosolized and in­haled cor­ti­cos­teroids, such as be­clometha­sone and flu­ti­ca­s­one, re­quire less of a dose be­cause they are di­rectly de­liv­ered to the area (the bronchi and air­ways) that are most se­verely af­fected.

Truly suc­cess­ful equine asthma treat­ment pro­grams in­cor­po­rate el­e­ments from all as­pects of breath­ing man­age­ment. The en­vi­ron­ment must be con­sid­ered and all steps must be taken to in­crease air­flow and re­duce al­ler­gen ex­po­sure. Dres­sage work may be avoided on smoggy days or done in an airy, open field rather than in a dusty ring. Hay might need to be soaked be­fore feed­ing and dusty round bales should be re­moved from the pas­ture. Bron­chodila­tors and cor­ti­cos­teroids may be used as needed to con­trol in­flam­ma­tion and in­halers may be added to fur­ther aid breath­ing. Many horses strug­gling with equine asthma can be suc­cess­fully man­aged and can con­tinue to show and com­pete. It re­quires ded­i­ca­tion from the owner, how­ever, and a long-term com­mit­ment to keep­ing this se­vere and pro­gres­sive dis­ease un­der con­trol.

Equine asthma can be trig­gered by a va­ri­ety of al­ler­gens. Hay and straw, for ex­am­ple, are SKINKĂECNě SOTREGS OH CĚĚGRIGNS CNF ECN ECTSG MOSě CSěJMCěKE JORSGS FKĘETĚěX

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