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SCID Carriers Can Be Used For Breeding

By: Lorraine Taylor Picture of a horse named Kariq

Much has been written about Severe Combined Immunodeficiency (SCID) but it would appear not enough. Breeders are still putting their heads in the sand, ignoring its existence - that is, until it affects them personally.

For weeks I thought about writing this article as I became more and more sure of what we were dealing with. I began writing in a slightly less than rational state whilst waiting on the arrival of our vet to end Kariq's short life.

I suspected that I might, before submitting this article for publication, possibly scrub some of what I'd written, but at the time putting my thoughts on paper seemed the most constructive thing I could do. Somehow it helped to ease the frustration, anger and certainly the sadness I felt particularly that morning. You see, I had just had a call to advise that my six and a half week old foal had been positively identified as suffering with SCID. It was all the more unfortunate because I had taken the better part of five weeks to arrive at a definite resolution to the illness that had best beset the stud.

Worse still was the knowing that this situation could have been avoided. The death of foals from SCID can be controlled if breeders positively identify carriers and make informed decisions. There is a definitive test that can determine the SCID status of a horse and it has been available in the United States for over a year through VetGen, which company has an agent, GenTest, in Australia. The cost is not inhibitive. Currently, depending on the number of horses tested, cost can be as low as $100.00 and results are usually obtained within a couple of weeks.

Some will argue the test is possibly open to corruption by some unscrupulous breeders, because the sample for testing can be taken by the owner/breeder alone. It seems to me, however, that by doing so that person could leave him or herself open to legal action if later it were found the testing they had allegedly done was in fact flawed and the results advised for a particular horse false or erroneous.

At the time of writing, testing for this most insidious disease is not legally available in Australia. All samples provided to GenTest are forwarded to VetGen in the United States. I have, however, been advised that the CSIRO hope to patent a test in the near future which hopefully might be a part of the mandatory blood typing our horses currently undergo before being bred. My thanks to The Arabian Horse Society of Australia Limited and Dr. Kevin Bell for their advice. My thanks also to VetGen and their staff who, once apprised of the facts that I had a live but very sick foal, speedily conducted the necessary testing and promptly advised us of the results.

A second picture of Kariq the horse A third picture of Kariq the horse

On the monetary issue alone, to breed and then medicate a sick foal can cost anything from $1,000.00 to $4,000.00 and more, so $100.00 to $300.00 (for one horse) is a small price to pay to eliminate the risk of producing SCID foals. Breeders need to be cognisant of the fact that carriers may continue to breed without fear of producing a SCID foal if only horses are tested prior to breeding and the carrier is bred to a non-carrier. SCID foals can only result from the breeding of two carriers and not from the breeding of a carrier with a non-carrier. If a carrier is bred to a carrier the odds are one in four of breeding a foal that will die of SCID. Two in four foals will become carriers, and one of the four will be unaffected.

There are some particularly beautiful Arabians that are carriers and their owners, rather than concealing the fact and running the risk of reproducing a SCID foal should, in my opinion, openly acknowledge the fact and selectively breed the affected horse.

By breeding carriers to non-carriers breeders can preserve the unique and positive characteristics of some exceptional horses, who are carriers, without risk of producing a SCID foal whilst at the same time, over several generations, aiding in breeding out the undesirable gene. Though there is a 50-50 chance of producing another carrier there is certainly no risk of producing a SCID foal.

Conjecture perhaps, but it has been suggested that prospective horse owners, because of SCID and the unknown, have decided to invest their time, money and emotions in other breeds of horses.

The foal, whose misery has ended, was exotic. His name 'Kariq' means extraordinary, and that he was. Visually he was correct in every way and his temperament was faultless. As the affliction progressed so did my admiration for Kariq. Such was my respect for the foal that I determined, should he survive, that I would have him gelded and he would remain permanently at Kyang. His appeal was catching. Everyone who saw him was wowed.

A fourth picture of Kariq the horse His memory will remain and should I have the opportunity to breed again to his sire I will ensure that the mare I breed to him is not a SCID carrier. I feel no bitterness, only frustration and anger at my own ignorance. I didn't even consider the possibility that the mating we so enthusiastically arranged could end up in a tragedy. Even though it is so evident that the SCID gene lies hidden in a great number of prized Arabians, the prospects of a disastrous mating was never discussed or even considered. Don't contribute to this demise of the Arabian horse. Conformation defects are obvious. However, outward appearances give no hint of the genes that could surreptitiously produce the tragedy of the SCID foal.

Reprinted here with permission of the Author ©
This Article was published in the March, 1999 Issue of