COLLIE EYE ANOMALY DISCOVERED IN THE NSDTR
Written by Jane Folkman, Chair of the Health and Genetics Committee and reviewed by Dr. Gregory Acland and Jeanette Felix, PhD from OptiGen.
Printed April 2006.
Recently US breeders and several international Toller club Presidents have been notified in a letter from the US club President and Health and Genetics Committee that Collie Eye Anomaly or CEA has been identified as a genetic problem in the Toller. This was determined by various tests performed by leading eye expert Dr. Gregory Acland and his research team with the participation of OptiGen, LLC. Fortunately the CEA mutation test now available for other breeds will became available to the Toller starting April 17, 2006.
CEA can present a range of abnormal eye complications that include, most commonly, Choroidal Hypoplasia or CH, but also coloboma, retinal hemorrhaging and/or detached retinas. For a complete description of these conditions, please refer to the detailed question and answer document CEA FAQ.
The researchers were able to conclude that CEA has been in our breed probably before registration books were closed, when the farm collie was used as a component breed in developing the Toller. As Dr. Acland said, “The Toller did not get this problem from a cracker box. It has likely been passed down from the founding generations of the breed”. This recent research has tied all the pieces together and these relatively rare occurrences now have a clearer genetic explanation.
Breeders and the HGC have known of a few cases of coloboma but had not associated it with CEA until now. We have not seen many cases of CH perhaps due to the fact that as the eye develops, pigmentation in the eye can mask or hide the CH so that by age 2 an eye vet will not be able to see it. This is referred to as the “go normal” phenomenon. However even though the eye appears normal, the CEA affected dog will pass its genes to offspring.
CEA has been determined to be an autosomal recessive trait, inherited in the same pattern as prcd-PRA. This means that if you breed 2 dogs together that carry the gene, 1 in 4 would be affected by the disease and 50% would carry the disease gene. Although the overall carrier rate among sampling has been estimated at this time to be approximately 5%, there are situations where the rate could easily climb much higher (25 to 50%). A possibility of higher carrier frequency exists within a line with affected or carriers already identified.
The recommendation from the researchers as well as the HGC is that breeding stock (sires and dams) should be tested for this disorder. Unfortunately, much like prcd-PRA you will not know if a Toller carries the CEA gene unless you have the DNA test done. But just like with prcd-PRA breeding strategies, breeders can use dogs that carry the gene in their breeding program so long as they are bred to a normal or clear mate. If a breeder has a litter on the ground between the time CEA testing is available and results are known for a sire and dam, the puppies can be examined for CEA between the ages of 7-11 weeks by an eye vet. Again, you will not know if a puppy with apparently normal eyes is a carrier for CEA without the DNA test. However you will know if the puppy’s eyes at that time are affected with CH and/or coloboma.
We need to thank the breeders, owners and researchers for their team effort and their outstanding cooperation. This genetic problem was determined in record time. Researchers were able to use blood samples of affected dogs submitted by owners as well as research prcd-PRA blood available at OptiGen to determine the problem in less than a month at no cost to our club. We are very grateful for their continued help and are extremely fortunate to have their expert guidance. We are also very thankful to the conscientious breeders and owners who called this to our attention and helped pursue solutions with HGC.
HGC members have asked the researchers many questions posed by owners of affected dogs and other members, and have provided a detailed Question and Answer document for you to learn more about CEA in the Toller. Please refer to the CEA FAQ. At this time, there is limited information in the Toller since this is so very new. Researchers and breeders will not have a more accurate picture of CEA in our breed until we have more Tollers tested. And right now we cannot assume that the collie or other breed information holds perfectly true for the Toller.
Testing will provide further information. For a one year period, our partners at OptiGen will CEA test any affected dog for free if you have a diagnosis of CH, coloboma or detached retina by an eye vet and you submit a 3 generation pedigree to them in advance for pre-approval. For more information on this program, contact OptiGen
CLICK HERE to go to the CEA FAQ page.