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Arabian Horse World Letters to the World

Gene and Sue Mathews, West Hills, California
From December 1997 Issue

It is mid-fall now, three months after the Canadian Nationals where our stallion Eqynox was named the unanimous Champion Stallion, and we have just had confirmed the fact that he and his sire Myrlyn have tested out to be carriers of the autosomal recessive trait known as SCID.

As this discovery developed, we also tested Myrlyn's dam, Mystic Charm, our foundation mare, to find that she was the primary carrier in our breeding program. It is clear to us, therefore, that the responsible horses in both stallions' pedigrees precede Mystic Charm, and we need look no further to trace the origin of the recessive gene as it relates to Myrlyn and to his son.

This has been a bad news/good news circumstance for us. The bad news is that we are faced with the necessity of making a public statement about the test results - the good news is that there is, finally, a test. Indeed, the best possible news is that there is a test.

The existence of the test, as administered by VetGen Laboratories, permits us to stand these horses at stud with certain cautions to the mare owners who would wish to take advantage of the gene pool they represent. Any mare owner who wishes to breed to Eqynox or his sire will be asked to have his mare(s) tested by VetGen, and we will accept only mares who have tested clear. We will then never have a SCID lethal foal ascribed to either stallion.

Obviously, since he has been the more successful in the showring, Eqynox is the focus of this statement. Most of the available literature published since the introduction of the testing procedure supports our position. At the top of the page of the release from VetGen Labs is the following:

"We recommend the continued breeding of highly desirable carriers to clear animals for several generations, thereby maintaining the gene pool and ridding Arabians of SCID over time."   ( * See addendum below.)

It is not hubristic of us to put Eqynox in that category of "highly desirable." He has been, perhaps quietly, unanimous champion more than once in his ten-show career. Unanimous in Canada in 1997, unanimous at the Buckeye in 1996 as a three-year-old, unanimous in 1994 at Region 12 in the Yearling Sweepstakes, 1997 Region 14 Champion Stallion and Reserve Champion English Pleasure Junior Horse in Detroit. We leave it to those who have seen him in the ring to judge his qualifications.

As I have poured over the literature on SCID since we received the results of the tests (and believe me, I have been well motivated to do so), there are two cogent statements that leapt to my eye:

1. Breeding a carrier horse to a clear horse (stallion to mare, mare to stallion) will never result in a lethal foal.

I would like here to quote Michael Bowling's statements made in Arabian Horse World July issue: "With carriers identified, carrier stallions with excellent qualities need not be lost to the breed, just bred to clear mares." And in the October World, Bowling further stated: "Once the disease is stopped from killing foals, the gene is just a DNA sequence. It can now be dealt with at our leisure.... In fact, now that the test is in our hands the whole subject can be relieved of its negative emotional burden."

2. Geneticists say it is unwise to banish carriers of recessive traits because it would narrow the breeding pool, weeding out the good genes as well as the bad. It would also raise the risk of other recessive traits emerging. This in EQUUS magazine, September 1997.

This quote was published in a question and answer section of the article and unattributed, but in a conversation I had with John Duffendack, president and CEO of VetGen, the only testing lab for SCID, I read him the quote, and he acknowledged that he had made that statement himself. Jeff Sloan, a VetGen director, is quoted thus: "The lethal gene can be bred out without losing access to those great horses that happen to be carriers. Now that the technology exists and is available, it's up to the individual breeder and to the collective industry to use it wisely." (Arabian Horse World, July 1997.)

Which brings us back to Eqynox and how this information applies to him. He is, in our opinion, a great horse and he will, we are convinced, be a great sire, not just of purebreds but also of National Show Horses. That he is a carrier is because of the carriers in his pedigree who preceded him, and they would not have been bred on if they had not been great horses. There is, in the majority, a number of great clear horses back there also, some of whom may (or may not) have had carriers in their background.

It might be appropriate to interject here that Mystic Charm, the initial carrier in our program, has a daughter who has been tested clear, and she in turn has given us a yearling colt (by another sire) who will be heard from.

So, if we could have been omniscient when we brought Mystic Charm into our breeding program and known that she would have given us a carrier son and grandson, we think, seeing Eqynox (and also being clairvoyant about the testing program), we would do it all again, just for the privilege of being able to breed a horse of his caliber.

We would like to conclude (if you have had the patience to stay with us this far) with an anecdote about the faith that people have had in what we've had to deal with.

One year ago, Lynda Entratter (Jabar Arabians, Alpharetta, Georgia), bred one of her mares to Myrlyn. We saw the resultant filly at her farm in June of this year - a beautiful filly. By September, that filly had died, a SCID lethal. Subsequent to that we started testing our horses, and we got the verdict. Lynda, God bless her, had been through hell with the loss of that foal, and when we talked with her last she said "I want to breed to Eqynox." "He is a carrier too," we said.

"I know that, but I am going to test all my mares, and select one to be bred to Eqynox." And then she added, "I want to put a National Champion Eqynox foal in the ring for you."

Thank you, Lynda, this has not been easy. We have been advised by some not to stand out there and make this statement alone. But, there it is. We hope that all of you who read this, and do your own homework will have as much faith as Lynda Entratter.

*Addendum from VetGen Laboratories:
There is now a definitive test for the Severe Combined Immunodeficiency "SCID" gene in Arabian horses. This test unequivocally determines if an animal is affected, a carrier or clear of the mutant gene. Testing is easy and highly accurate, and can be performed at any point in time in the life of the animal with a simple cheek or lip swab or blood sample. The major and most important implication is that now there is no guesswork in avoiding SCID offspring.

Since SCID is an autosomal recessive disease, matings between two clear animals as well as matings between a clear and a carrier animal will never produce an affected animal. By definition, carriers of genes for autosomal recessive disorders are completely free of clinical signs of the disease. That is, carriers do not have any negative consequences to their health or performance. If two carriers are mated, there is a 25 percent chance that the foal will be clear, 50 percent chance that it will be a carrier and 25 percent chance that it will be affected, a chance not worth taking. Prior to the advent of molecular genetic testing for autosomal recessive disorders, the only way an animal was identified as carrier was when he or she produced an affected offspring. The traditional recommendation in veterinary medicine would be gelding of these animals to prevent other affected offspring being produced. However, this is no longer necessary and not in the best interest of the breed. Carrier animals who have all the desirable traits for which the breed is known can now be mated to other tested animals who are clear and then never produce an affected foal. Similarly, their offspring can be tested and appropriate matings set up in the next generations without the breed ever suffering the loss of another foal to SCID. In this manner, the breed still continues to benefit from all of the outstanding traits that a carrier animal may possess. Thus, the economic value of the animal should not be affected by being clear or carrier.

From January 1998 Issue
Karen Eads, Crescent Moon Arabians, Westfield, Indiana

We would like to commend Gene and Sue Mathews of Stage Coach Ranch for their courage and responsibility in announcing the SCID carrier status of their stallions, Myrlyn and his son Eqynox (Arabian Horse World, December 1997).

If the carrier status of breeding stallions is known, mare owners will have the opportunity to only breed mares who have tested clear, to those carrier stallions. This will be an effective way to maintain a diverse gene pool whilst ensuring foals no longer die from SCID.

Thank you, Gene and Sue, for opening a public dialogue on this important issue.

Jessica Snyder, Stoughton, Wisconsin:

The issue of whether or not to remove SCID carriers from the gene pool is one that I'm sure most Arabian owners are debating. It seems to me that the development of a test has removed the cloud of fear, scandal, and death that the gene used to present to Arabian breeders. After all, the problem with the SCID gene is the potential to lose foals. Now that we have the power to avoid foal loss through testing and intelligent breeding, the gene should no longer be an issue.

As a future breeder, I will be seeking out people like Gene and Sue Mathews. Their treatment of the issue is one that I hope will stand out as an example for others in the breed to follow: they are responsible enough to test their horses for the SCID gene, honest enough to be public about the results, and intelligent enough to understand that carriers are still capable of making a positive contribution to the breed. Kudos to them, and to other breeders who are acting in a similar fashion.

While discussing responsible breeders, let me simply add a note of support about your "Foundation Breeders" series. The features are proof that Arabian Horse World can still be the source of solid information that all Arabian owners and breeders can appreciate. I intend to compile each breeder's "ten commandments"; they are truly words to live by. Three cheers for switching perspective and reminding us that breeding quality Arabians involves more than booking to the latest show winner.