Genetic testing, what for ?

Most of you are aware that there are several genetic tests available for the screening of certain “diseases” that our Shelties may carry. They remain expensive and some of you are dubious as to their reliability. Others test their whole kennel, especially where CEA is concerned, sometimes with rather surprising and even gratifying results!! We have resumed the tests already available and others that should be available in the very near future:

CEA (Colley Eye Anomaly)

The gene of this abnormality has been identified and the test has been available for some years already. The test has proven itself and is considered reliable. But this test DOES NOT COVER all types of eye diseases and it is indispensable to complete the genetic test by an ophtalmological examination. In the case of a genetically “affected” subject, it is essential to screen as the stages (1-4 ) are not detected by a genetic test, at the moment at least, even if the laboratories are working on it. In the case of a genetic "CARRIER" or even "NORMAL" (genetically free and non-carrier of the disease) it is indispensable to have your puppies screened at the optimal age of 7 weeks (at the latest 12 weeks) to detect any possible colobomas which are not associated with CEA and which can nevertheless be genetically transmitted. This examination also allows the detection of other congenital eye problems. Dogs should be re-tested at approximately one year old, and always before the dog begins to reproduce; sometimes colobomas are so small that they are not visible at an early age but can appear later. And finally, all breeding stock should undergo at least one additional examination after six years of age to detect the real monster, PRA.

Coloboma

Colobomas are generally associated with CEA, but regrettably there are the other types of coloboma which are not detected by the genetic test for CEA. At the moment there is no genetic test available for colobomas which are independant to CEA but OptiGen is working on this problem.

We have the permission from Sue Pierce-Kelling from the OptiGen laboratory to translate her article concerning these studies (translation available on the French pages). You may read this in our article “CEA and coloboma” or by clicking here.

PRA - Progressive Atrophy of the Retina

For the Shetland Sheepdog, at least for the moment, there is no genetic test available for this eye disease. It is nevertheless the most formidable and guarantees total blindness of the dogs which are afflicted. Laboratories have been researching this disease and the way in which it is transmitted and are still collecting samples worldwide. An article on PRA and the new breakthroughs in research will soon be available on our site.

MDR1

Multi-Drug Resistance. This is not a disease but a medicinal sensitivity that came about with the appearance of the molecule “Ivermectin” on the market in the ‘80s. We are preparing an article on this subject as well as a list of the products that are potentially dangerous for our Shelties. Fortunately, there is a genetic test available to detect this sensitivity. According to the laboratory Antagène, 77 % of Shelties tested by them were shown to be positive for this sensitivity.

Dermatomyositis (DM)

This is a rare inflammatory disease of the skin and the muscles, it is a hereditary illness and known as Canine familial dermatomyositis in dogs. It is known to afflict mainly Rough Collies and Shetland Sheepdogs.

Several theories circulate on the way this serious disease is transmitted. At the moment, at least, there is still no genetic test available to detect carriers or afflicted subjects. However, this work is advancing as researchers have found a locus responsible for the phenotype of the dermatomyositis in Shelties. Thus, genetic studies will show to be interesting in the near future, to try to determine with precision the gene(s) responsible for this disease.

Hip dysplasia

Quite common in Shelties, as in most other breeds, but fortunately due to their small size, lighter weight and strong muscle structure, the symptoms remain much less crippling to Shelties. There is still no genetic test available for this disease but the research is ongoing. At the moment, x-rays are the only screening available.

TO CONCLUDE, research is advancing in the field of canine genetics. Even if our breed remains one of the most rustic and free of disease, it is our duty to assure that it stays this way. Most of the genetically transmitted diseases appeared in pedigree dogs because of our selection and inbreeding. This is normal however, because after all it is necessary to fix a type and to respect a standard. But, as in humans, these 'bad' genes are recessive (it is necessary that both parents are either carriers or affected for the disease to express itself), thus by coupling related dogs we increase the risk of “awakening” certain diseases. Our breed is still very young and the type is still not really fixed. So, be alerted to the dangers. Without wishing to alarm, if we do not want to see our breed becoming as ' fragile ' as other breeds, we should conduct our breeding programmes very conscientiously and in all honesty. Test and screen all of our breeding stock - but also our dogs available at stud and most of all be very open about our results. It is only in this way that we shall avoid problems in the future.

However, if genetic testing remains a means of reliable and very useful screening it is necessary to remain objective. A dog is a whole: health, temperament and morphology. We should not lose sight of one of these three points to the detriment of the others. We should not obsess about one disease and ignore the eventuality of the others. For example, you know that a genetic test for CEA does not guarantee the absence of other eye diseases. If you possess a dog, or lines, which are exempt from such or such a disease, there is a good chance that this dog or his lines will suddenly become very popular for breeders wishing to eradicate this defect from their lines. It is your responsibility to assure that these dogs are also exempt from all other known genetically transmitted diseases.

Genetic testing - a tool, not a weapon.