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rmi$klnuAs researchers reveal the source of a potentially deadly genetic trait nowit will deal with the legal, ethical and financial repercussions of what

ore than two decades havepassed since Jerry Wells first set

eyes on a Quarter Horse coltnamed Impressive. Even as a

yearling being shown at the In-diana State Fair, it was clear that Impressive was

something special, Wells recalls: Already the hal-ter horse boasted the well-developed hindquar-ters and muscular forearms that would becomethe trademark of his lineage. "You could tell whatan outstanding individual he was," says Wells, aprominent Quarter Horse breeder based in Sul-

phur, Oklahoma. Wells and a partner paid$20,000 that day for Impressive. When they soldhim three months later for $40,000, they feltthey had turned a tidy profit.

But it soon became clear that Impressive's val-ue would be much greater than Wells imagined.Because he was so different from the classic "bull-dog" Quarter Horse prevalent at the time, Impres-sive was a sensation in the halter ring, winning

his age group 31 times in 31 attempts. In thebreeding barn he was just as successful, turningout champion after champion. Many of Impres-sive's progeny bore the same dramatic body-builder physique, and they too became outstand-ing and prolific sires and broodmares: Of the top15 halter horse sires of 1992, 13 were Impressive'sdescendants; even at the age of 23, Impressivehimself was fourth on that list. "I've or.rmed 95

percent of all the top [halter horse] studs in the

Quarter Horse industry over the past 25 years,and he was the best there ever was," says Wells.

"It's very rare to have such a great individual, andto be able to pass that greatness on."

Greatness, unfortunately, is not the only thingImpressive has passed on. He also is linked to a

genetic mutation that only recently has been im:plicated in the rare but burgeoning-and some-times fatal-muscular disorder known as hyper-kalemic periodic paralysis. This particular defectis a dominant condition, which means that at

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carried by tens of thousands of horses, the Quarter Horse industry grapples with howbeen knor,rm as "Impressive S;mdrome."

least half of an affected horse'soffspring will be affected as well.To have such a mutation in a lineas popular and as prolific as Im-pressive's is, in the words of oneprominent Quarter Horse trainer,"one of the most devastatingthings that has ever hit the horseindustry."

Within a few years of Impres-sive's ascendancy to the top ofthe sire's list, halter horse ownersbegan to notice a strange muscu-lar twitching that often left theiranimals temporarily unable tomove. Usually misdiagnosed as tying up or colic,these episodes varied widely in degree and dura-tion, but all had one factor in common: the ani-rrals' pedigrees. As a result, the disorder becameltnorvn informally among insiders as "ImpressiveSr ndrome."

Research funded by the American Quarter Horse Association(AQHA) and the University of Cali-fornia-Davis Equine Research Lab-

oratory subsequently linked theproblem to elevated levels of potas-sium in the blood serum. The dis-

ease became known officially as

hyperkalemic periodic paralysis, orHYPP. But even as researchers atthe leading veterinary schools inthe United States and Canada be-gan publishing articles on the dis-order in professional iournals andthe lay press beginning in the mid-

1980s, the vast majority of Quarter Horse ownersremained unaware of the condition.

All the while, Impressive and his kin contin-ued to breed, to show, to win ribbons and tomake their owners fantastic amounts of money.Most affected horses can be controlled quite well

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Despite hisadvanced age,lmpressive(opposite page)remains one ofthe top halterhorse sires. Atleast 55,OOO

Quarter Horses,Paint Horses andAppaloosas bearhis pedigree. Hisamazing physiqueis believed to belinked to hisgenetic musculardefect.

EQUUS 18s

with medication and a proper low-potassiumdieq therefore, many owners of affected horses

considered HYPP a minor inconvenience in lightof the line's tremendous value. Given the factthat there was no proof that the disorder was ex-

clusive to his family-not to mention the fact

that owners of stock descended from Impressiveincluded some of the most prominent andwealthy individuals in the industry-no one

wanted to be the first to publicly implicate theline. And even later when a breakthrough genetictest removed all doubt, lessening the moral andethical burdens associated with naming thehorse, neither the research community nor theAQHA was eager to lift the lid of this Pandora's

box: Each feared possible legal and financial rami-fications from a sector of the horse industry thatwould be shaken to its foundations.

In the past year, however, pressures both with-in and outside the Quarter Horse industry final1yshattered the secrery surrounding HYPP. The ge-

netic test, m4de available last summer, can identi-fy affeaed horses with virtual certainty. As a re-

sult, many owners of horses descended from Im-pressive have rushed to have their animals tested,hoping that a negative result will protect theirconsiderable investment against the anticipatedbacklash. Breeders have purchased advertise-ments in The Quarter Harse loumal touting theirHYPP-negative test results, and privately haveurged their peers to either test their Impressive-

bred horses or remove them from breeding.From his vantage point, Wells predicts that all

breeders soon will be forced to have all of theirImpressive horses tested, whether they like it ornot. He adds that his own Impressives have beentested, with at least one positive. "I don't knowwhat I'm going to do" with the HYPP-affectedstock, he says. "It's a very serious problem. It'stearing our industry up."

A Decade Of ResearchThe code of silence was formally broken

November 30, 1992, at the annual meeting of theAmerican Association of Equine Practitioners(MEP) in Orlando, Florida. SharonJ. Spier, DVM,PhD, of the University of California-Davis, hadcompleted her presentation on HYPP before a

large audience of fellow veterinarians. Spier con-densed seven years of her own research into ahalf-hour talk, inciuding the most recent devel-

opment: a genetic test developed with Eric P.

Hoffman, PhD, of the University of Pittsburgh,

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tlat pinpoints the exactpoint on the specific chro-mosome at which the mu-tation causing HYPP oc-curs. But while she alludedto the fact that all of heraffected breeding stockwere descendants of a sin-gle sire, Spier stoppedshort of dfi,"ulging hisname.

Immediately followingthe presentation, however,Glenn F. " Andy" Ander-son, DVM, of the EquineVeterinary Associates inBroken Arrow, Oklahoma, stepped up to the mi-crophone and asked her specifically to name thesire. Drawing a deep breath, Spier replied: "I amallowed to say now that the research horses that Iused were descendants of Impressive." Her re-sponse marked the first time that Impressive hadbeen linked publicly with HYPP, though specula-tion and rumor abounded and had become par-ticularly intense following the annual staging ofthe Quarter Horse Congress in October. It alsomarked a watershed in the decade-long investiga-tion into the disease that forever may change thelray in which particularly muscularQuarter Horse halter horses are re-garded.

Research into equineHYPP dates back to 1983,n-henJudy H. Cox, DVM,VS, of Kansas State Uni-venity, began to evalu-ate horses brought tothe school's veterinaryhospital that displayedsigns of muscular weak-ness, combined with highserum potassium levels.Cox did some reading on hy-perkalemia in people, andfound that a "challenge test" canconfirm the condition: Bv administer-ing a low dose of potassium chloride via stomachtube, an affected individual can be induced into a

hsperkalemic episode. This soon became thestandard means of diagnosing HYPP in horses.The potassium challenge had two drawbacks,hort'ever: It was both time-consuming and poten-tially life-threatening to severely affected horses.

So electromyography(EMG) became a usefultool in detecting HYPP. AnEMG involves inserting a

needle electrode into thehorse's muscle to miasurethe electrical activity ofthe muscle fibers. The pro-cess takes less than a half-hour and does not requirethe sedation of the horse.HYPP-affected horses tendto show spontaneous, un-provoked electrical dis-charges. Although these

;JffiUffi,-rcffi electrical irregularities also i

occur in other muscular disorders, and thus donot indicate HYPP definitively, an irregular EMGis considered an effective screening mechanismfor horses who have shown signs of hyper-kalemia.

While Cox pursued the link between elevatedpotassium levels in the bloodstream and episodesof HYPP, Jonathan M. Naylor, BVSc, PhD of theUniversity of Saskatchewan's Western College ofVeterinary Medicine, began studying the mode ofinheritance of the disease. Like Cox, Naylorfound illuminating similarities with the human

form of HYPP-known originally as

adymamica episodica hereditaria-about which academic litera-

ture dates at least to the early1960s. Naylor established a

familial component toequine HYPP consistentwith that already foundin people. He analyzedthe pedigrees of 1 7 hors-es diagnosed with thecondition and found that

all were second- or third-generation descendants of

"a common Quarter Horsesire."Naylor's findings raised the

frightening possibility, since confirmed,that the disease is a dominant trait, and that theproblem could be far more prevalent than previously thought. According to his study, the "com-mon sire'/ had more than 55,000 registered Quar-ter Horse descendants spread over five genera-tions. Naylor says the number of horses affectedby HYPP is at least 14,00O, and could be twice

Sharon J. Spierof the Universityof California-Davis, picturedhere with herown QuarterHorse, Joey,disclosed lastNovember thatall of the HYPP-affected horsesin her researchherd were des-cendants oflmpressive,marking the firsttime that thefamous sire hadbeen linked pub-licly with thedisease.

Recent researchhas linked HYPPto a mutation inthe sodium chan-nel gene. The se-quence of nuc-leotide bases in anormal horse (top"chain"), con-sists of twothymines (inblue) and onecytosine(orange). !nhorses withHYPP (bottomchain), cytosineis replaced byguanine (yellow).The resultingamino acid,leucine, producesthe cellular "leak"that allows sod-ium into the mus-cle fibers, caus-ing them to fireindiscriminately.

EQUUS 185

that number. "The one thing that concerns us is

that there has been selection for this condition

[as breeders sought to produce horses with Im-

pressive's conformation], so the actual number

may be much higher.... In terms of a genetic de-

fect, it's been very successful," Naylor says'

In 1986, during her residency at UC-Davis,

Spier began what would be an ongoing series of

bieeding trials that would ultimately confirm

Naylor's suspicion that HYPP is a familial disease'

Beginnlng with two Quarter Horses, both affected

wiitr ttre disease, Spier produced two colts and

one filly-all affected. Subsequently, she mated

cific mutations of the sodium channel gene caus-

ing HYPP in people. Although he considered it a

"long shot" that the same genetic mutation caus-

ing human HYPP also was responsible for the dis-

ease in horses, Hoffman accepted the challenge'

In surprisingly short order, Hoffman identified

a change in the DNA of affected horses descend-

ed from Impressive. One specific sodium channel

gene was found to be altered identically in every

;ffected animal. Hoffman then discovered the

causative change in the DNA sequence: A single

"letter" out of 30,000 in the gene was different,

causing an amino acid change in the sodium

an affected stallion with 11

normal mares (Quarter

Horses, Thoroughbreds,Standardbreds and Arabi-

ans) and three affected

mares-two of which were

supplied bY Cox. Of the 17

offspring resulting over two

seasons, 10 carried the HYPP

gene; the disease was dis-

tributed evenlY bY gender

and breed. From these re-

sults, Spier concluded that

HYPP was an autosomal

dominant condition: If one

i parent is affected, roughlY

i nalf tne offspring will carry

i the trait; if both Parents are

i affected, at least three-quar-

i ters of their offsPring will be

i affected.: Using this exPanded

i population of horses, SPier

i continued the research bY

i testing the muscle functionsi of normal and affected hors-

i es. It became clear that the

i muscle membrane of affect-

Despate medication and a controlleddiet, Tribute, a son of lmPressive'

suffered lrequent HYPP attacks and

eventually succumbed to the disorder'

channel. The resulting

amino acid leucine-ratherthan the usual PhenYlala-nine-appeared in every af-

fected horse out of roughlY

200 horses tested' And as ithappened, the homozY-

gotes, horses with tr'vo

copies of the defective

gene-one from each Par-

ent-were more seriouslY

affected than the heterozY-

gotes, who had inheritedonly one coPY.

The importance of thisgenetic investiSation was

tremendous. Not onlY did

it show conclusivelY thatHYPP was a heritable disor-

der, it isolated the Preciselocation of the genetic de-

fect that causes it. Thus, itcould be used to detect the

presence of the defective

sodium channel gene, withnear 100 Percent accuracy,

in Impressive-bred horses.

It follows, then, that if ev-

ed horses was more permeable than usual' It was

prone to leak sodium into the cell-thus provok-

ing ttre visible muscular tremors-and to leak

potassium out of the cell and into the blood-

itr"u*. The source of the leak was determined to

be a protein known as the sodium channel (see

, sidebar, "What Is HYPP?").

i Having established that the defective sodium

' channel causes HYPP, and that this defect is

, hereditary, the next step was to determine what

, precise gene is responsible for the defect' Spier

: iontu.t"d Hoffman, who already had studied spe-

ery horse descended ftom Impressive were tested'

and if atl horses with positive HYPP tests were re-

moved ftom the breeding population, then the

gene could be eliminated entirely in a single gen-

eration.

The Specter Of Legal ActionAs word slowly filtered through the Quarter

Horse establishment that something was indeed

amiss with the Impressive line, pressure began to

mount against the AQHA. Although it granted

Spier nearly $47,000 toward her research in

Coufresy, Leslie Salomon

HYPP, the organization was reluctant to make

any formal statements or to require-as many

have urged-that Impressive-bred horses be test-

ed for the genetic defect before being registered or

bred.AQHA Executive Vice President Bill Brewer de-

fends his organization's cautious approach, insist-

ing that until Spier or another scientist came for-

ward with Impressive's name, the AQHA would

have no basis for making a statement or takingaction regarding the stallion or his offspring. Now

that Impressive has been named, he adds, the or-

ganization can decide what action, if any, to take-

A three-paragraph men-tion of Spier's Presenta-tion, including her nam-ing of Impressive, aP-

peared in Btewer's "AQHAUpdate" column in the

January edition of the as-

sociation's official Publica-tion, The Qnrter Horse

Ioumal. And the issue is

sure to top the agenda ofthe AQHA's annual meet-

ing this month. "lt's obvi-

ous that the AQHA has

done a lot for [under-standingl the condition,"Brewer says. "What haP-

pens next is uP to ourboard of directors.'4

Some horse owners feel

the association has been

too slow to inform mem-

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ffiMffiMHYPP can be passed on by either parent. Aheterozygote (H/N) mated with a normal (N/N)

horse should produce 5O percent affectedoffspring (shaded) and 5O percent normal.

When both parents are heterozygotes, roughly25 percent of their get will be homozygotes(H/H), 50 percent will be heterozygotes and 25

percent will be normal.

al people close to the HYPP issue say the chief ob-

stacle facing both the breed registries and the re-

searchers has been the threat of legal action

should they single out Impressive and his descen-

dants. "The AQHA's position is, we don't feel like

being sued," according to one knowledgeable

source. Likewise, the University of California,

wary of lawsuits, took a cautious approach to-

ward HYPP, particularly as it applied to the Im-

pressive line.In fact, the decision to name Impressive was

made only the day before Spier's appearance at

the AAEP convention. But pressure from the vet-lf either parent is homozygous, then all

offspring will be affected, even if the otherparent is normal.

EQUUS 185

Continued on P. 80

erinary communityr horse owners andthe press grew so great that the re-

searchers, the institutions that employthem and the AQHA knew that thehorse's name would have to be re-

leased, if not at the veterinary conven-tion then in the immediate future. The

deciding factor, according to Spier, was

the development of the Senetic test,

which is specific to the mutation foundin her research horses. "It was gettingvery difficult for me to even talk to vet-

erinarians over the phone and not be

allowed to use the stallion's name," she

says. It was especially so from thestandpoint of the accuracy of the ge-

netic test., Thomas Bertrand, legal counsel toi the University of California, says uni-

versity officials concluded that "some-one had to take the initiative" in dis-

closing all relevant facts regardingHYPP and the DNA test. "[The HYPP]

research, which took five years and a

substantial amount of money, is veryvaluable, but its practical applicationrequires identification of the blood-

: line," he says. The university knew thati Spier would probably be asked about: the foundation sire at the AAEP con-

r-rientiory Bertran*adds, and didn3: want the answer to be disingenuous.r "We knew she was going to Florida,"i he says. "We weren't going to have a

i scientist stand up there and PlaYi Richard Nixon."

and, in some cases, relief. Some are notconvlnced that the uproar surroundingHYPP is iustified, pointing out thatfewer than two percent of the QuarterHorse breed carries the trait. Of thistwo percent, however, the vast maiori-ty are halter horses. And Impressive'spopularity has crossed over into thePaint Horse and Appaloosa breeds as

well. As a result, many wonder whetherthe halter industry, which invested so

heavily in Impressive stock, can suryiveif buyers suddenly refrain from breed-ing to any horse bearing Impressive

blood.

"In the last 10 years, everybody has

swarmed toward this bloodiine," notesTerry Sartain, trainer at Meucci Ranchin Senatobia, Mississippi, where several

Impressive-bred Appaloosas are stand-ing. "But I think we're fixing to see anabrupt turnaround. You're going to see

these horses go by the wayside eventu-ally." Sartain says two Impressive-bredhorses at the ranch have died recentlyfrom episodes of HYPP: One mare suf-fered an attack that started as a musclespasm in the flank area and quicklyspread over the shoulder and into herhindquarters. "By that time, the shockset in and she died shortly after that,"Sartain recalls. The entire episode, fromonset to death, lasted just an hour.

Sartain points out that while HYPP

theoretically can be managed with a

low-potassium diet-usually througheliminating alfalfa hay-such a rationis not practical for the high-profile hal-ter horse. "The problem we have is thatthere is no solution to fitting horses forhalter without the use of alfalfa hay,"he says. "Their muscle structure is veryimportant in the show ring. You get

them taut and get the muscle right onthe edge."

Others in the breeding industrydoubt that an anti-Impressive backlashwill occur, simply because too manypeople would be put out of business.

"There would be a lot of people whowould suffer, and suffer gteatly," pre-

dicts Bill Dickerson, owner of Bill Dick-erson Quarter Horses in Moscow, Penn-sylvania. "Other than his grandsire,

Three Bars, Impressive probably has

had more influence on this breed than

any other horse in the world- If you're i

going to eliminate all the laffected] sec- ;

ond- and third-generatron Impressives, i

you're setting the industry back 20 :

years." :

Jim Bob Long, owner of the Long :

Equine Center in Keamey, Missouri, in- :

sists that Impressive's positive at" i

tributes outweiSh whatever undesirable '

baggage comes with them. "This i

bloodline is so good, people are going :

to breed to these horses whether they :

have that defect or not," he says. Long :

contends that no other line of Quarter I

Horse is capable of filling the void that :

would be left should Impressive and i

his progeny fall out of favor. i

One breeder who aPPlauds SPier's :

public unmasking of Impressive is i

Sandy Arledge, owner of Sandy Arledge ;

Quarter Horses in Rancho Santa Fe, i

California. Arledge was the first breeder i

to advertise a negative HYPP test inThe '

Qrurter Horse loumal, and says the re- i

sponse to the ad was mixed' "Most i

people didn't know what it IHYPP] :

meant," she says. "There were a couple i

who knew. And one who didn't care' i

Not knowing is bad, but not caring is :

much worse.D I

Owners: Grief And AngerFor those who own a horse affected

with HYPP, the flow of information is

far too slow. Many veterinarians still

don't know a hYPerkalemic ePisode

when they see one, they say, and aren't

sure what to do even if they recognize

the signs. Misdiagnoses, such as tyingup or colic, are still commonplace, ac-

cording to several owners and trainers,

and horses are suffering as a result'

Lyn Sikorski, of Rochester Hills,

Michigan, had no idea what was wrong

with her Quarter Horse stallion,

Knights Impression, when he collapsed

one day. The previous owner claimed

to have experienced no such problems,

she says, but a check of the horse's vet-

erinary records showed that he had in-

deed collapsed before' "TommY," a

grandson of Impressive, has been kept

on medication for more than two

years, Sikorski reports, with no further

episodes. Still, she feels she should

have known of her horse's condition

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In late December, about a month af-

ter her announcement, Spier andBertrand met with CecilJohnson, Im-pressive's curent owner, to draft astatement that summarizes the re-

search that has been done in HYPP, in-cluding the DNA test and the namingof Impressive. The resulting document,releasedJanuary 5, calls for the testingof all Impressive-bred horses, and ap-

peals to the breeding establishment "toselectively breed HYPP out of existence

before it becomes so widespread thatthis is impossible."

Bteederc: Resignation And ReliefAmong breeders of ImPressive stoc\

the response to Spier's announcementat the AAEP meeting has ranged ftomdenial and indignation to resignation

earlier. "Somebody,s got to bring it outof the closet,,, she says.

Less fortunate was Leslie Salomon ofEncinitas, California, who was fullyaware that her horse, Tribute, sufferedfrom HYpp. ,,I was told when I boughthim that he had Impressive Syndrome,but that it was controlled by [the di_uretic medication] acetazolamide,,, Sa_lomon says. ',And he was particularlybeautiful...a great horse.,, When shepurchased the five-year_old gelding_ason of Impressive-in April 1992, hewas on eight 2s0_milligram tablets aday, but within a month or so he beganexhibiting the classic signs: ,,like waterrippling all over his skin_it was verystrange," she recalls. Tribute,s dosagewas steadily increased until he was at6,000 milligrams a day.

i In late October, Salomon took Trib_

this mutation produced very goodmeat-better than a normal pig's-andtherefore were selected for. But in ho-mozygotes (with both copies of the mu-tant gene), the animal's muscles wouldseize up in response to even slightstress, generating enough heat within a

few minutes to make the pig "cook it-self to death." After much debate, thepork producers decided to screen outthe mutation, says Hoffman, who pre-dicts the Quarter Horse industry will beforced into the same decision.

Arledge agrees that aggressive mea-sures must'be taken against HYPP, evenif some breeders are hurt finarciatly inthe process. "I'm lucky in that I don'thave too many [mpressive horses],"she says. "It would be a devastatingblow to a breeder who has a pasturefulof mares and a barnful of stallions. Butthe ultimate issue has to be the integri-ty of the breed."

Another step toward eliminatingHYPP could take place at the halterring, argues Anderson. If judges stoppedawarding ribbons based purely on mus-cle bulk, he says, then breeders wouldstop producing bulky horses. "Why is itthat the biggest, fattest, most muscle-bound thing is the best?" he asks. Vet-eran halter iudge Mike Perkins, ofOwasso, Oklahoma, says the trend maymove back toward a more well-roundedhorse that is functional as well as stat-uesque. "That's the beauty of the Quar-ter Horse-he can do it all," saysPerkins.

Yet another possibility is for insur-ance companies to require a DNA teston all Impressive descendants beforewriting a policy on the horse. This isnot as simple as it sounds, warns E.W."Butch" Human of Horse InsuranceSpecialists, Inc. in Pilot Point, Texas. Tohave any effect on the breed, any test-ing requirement would need the ap-proval of every insurance company,Human says. Moreover, the opportunities for fraud will be greater than ever ifa horse's financiai viability hinges onthe gene test. More sinister still, ownersof HYPP-positive horses may seek tocollect immediately on their policies byhaving them die "mysteriously," addsHuman. "There are all kinds of ugly

shades of this thing lurking in thebackground."

And What Of ImpressiveHimself?

At Ensign Farms in Edmond, Okla-homa, the Z4-yeatold Impressive re-mains an active stud. He bred morethan 100 mares last year, and his bookfor this breeding season is about thesame. Cecil Johnson, a Las Vegas busi-nessman looking to enter the horsebusiness, purchased Impressive for$1.7 million inJune 1990. LikeJerryWells two decades earlier, Johnson wassmitten by the horse and resolved tobuy him. "When I saw him I iust fellin love with him," Johnson recalls. ,,It

was about a month or six weeks laterthat I found out that he was for sale.Since I wanted to get into the breedingprogram, I wanted the best.,'

When he bought Impressive, John-son says, he was unaware that thehorse was linked to HYPP. He now in-cludes a notification of the disease inthe breeding contract, and plans to

:

provide copies of the fact sheet pre- i

pared by UC-Davis. Johnson says that, i

to his knowledge, Impressive has never i

suffered a hyperkalemic episode. Not i

until late October, at the annual Quar- i

ter Horse Congress, did Johnson realize i

the furor surrounding the syndrome. i

"[t's tol"ally out of hand," saysJohn- :

son. "There are people making mis- i

statements of fact to demean l"he I

horse.... I've talked to hundreds of :

people from all over the world about :

this, and only a few people have even :

a remote idea what it's all abouL. It's i

crazy." :

Johnson says he has cooperatedwith Spier's research in an attempt to"put HYPP in perspective," and hopesto see further scientific inquiry intothe disease-specifically, the mortalityrate of horses affected with HYPP com-pared with other equine diseases."Theveterinarians that I've talked to say it'sminimal-less than one percent of allhorses," he says. "It would be well toeliminate it, but I think hyperkalemiais something we can live with. Educat-ing the people, informing them, is thething that must be done."l

/

/

1ute on a week-long trail ride in themountains. ,,The riding was muchmore strenuous than he was used to,,,she says, "but he rode fine, he traileredfine completely without symptoms.,,But on the moming of December 15,Salomon got a call at work telling herthat Tribute had gone down suddenlyin the field and died. ,,It was the phonecall I never wanted to get,,, she says. ,,I

was told he went down, and within 10minutes he was dead.,, The experiencehas left Salomon ,,brimming with griefand anger," both at the unpredictabili_ty of the disease itself and the fact thatit has lingered for so long.

Seeking A Solution

- How much longer will Hypp linger?If, as Sartain and others predict, Impres_sive-bred horses fall out of favor withthe horse-owning public, the undesir_able trait could be bred out of the euar_ter Horse about as quickly as it was bredinto it. And if, as some concernedhorsepeople advocate, the AeHA setsstrict testing standards for breeding Inr_pressive horses, Hypp could be elimi_nated in a single generation.

Hoffrnan notes that there is ampleprecedent in other species for the euar_ter Horse industry. Several years ago, amutation arose in the pig populationthat caused the muscle disorder malig_nant hyperthermia. Heterozygotes for

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