THE USEFULNESS OF DNA EXAM FOR THE “CEA”

The eye problem called “Collie eye anomaly” (or CEA, an acronym for the term Collie eye anomaly) is a canine genetic disorder characterized by incomplete development of the choroid, the highly vascularized layer of the eye that supplies the retina with blood and nutrients. .

This anomaly is one of the most common ophthalmological problems in dogs, and causes a decrease in vision throughout life, in extremely variable degrees: some dogs may be slightly affected, with small loss of vision, but in other animals the disease is severe and leads to complete blindness caused by retinal detachment.  

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CEA can be diagnosed through an eye exam performed between 5 and 10 weeks of age, at which age the animal still has normal vision; Ideally, the test should not be performed after 12 weeks of life, due to increased pigmentation in the eye, which can make the anomaly more difficult to detect and result in a false negative test. This type of assessment provides early diagnosis of CEA, but it does not have the ability to predict how quickly vision loss will occur, nor if it will occur completely.

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Despite the name, the disease is not characteristic of just one breed: it occurs both in Collie-related breeds (Short-haired Collie, Long-haired Collie, Border Collie and Shetland Shepherd), and more rarely in Australian Shepherd, Beagle, Dachshund , German Shepherd, and Poodle, among other breeds. In Brazil there are no prevalence studies, but European studies show that it is in the short-haired Collie that the anomaly reaches its highest prevalence (37% of animals), while in breeds such as the Shetland Shepherd and the Australian Shepherd the prevalence of animals affected is lower (up to 13%), although still very high.

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As it is a recessive disease, dogs can only have the anomaly if they are puppies of two dogs carrying the mutation. However, these carriers are absolutely asymptomatic at any age, including an eye exam performed at the correct age of the puppy. Thus, the only way to detect two carrier animals, which when bred together will have 25% of the litter with CEA, is through DNA testing for CEA.

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Some international studies show a high prevalence of asymptomatic carrier animals, which reach up to half of the dogs of some breeds, which demonstrates the importance of this genetic test.

After the test results, the breeder does not need to be obliged to remove all carrier animals from breeding, as these animals can continue to be bred with normal animals (detected as non-carriers in the DNA test).

This type of approach guarantees that the litter will be born healthy and that dogs produced in this controlled way will never have CEA. Thus, the DNA test for CEA, now available for the first time in Brazil, contributes to increasing the quality of breeding of breeds such as Collie, Border Collie, Shetland Shepherd, Australian Shepherd, Beagle, Dachshund, German Shepherd, and Poodle. .

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This exam is being carried out by the Linkgen Laboratory, a pioneer in the use of the technique of DNA analysis in the veterinary area. It has thus contributed both to the identification of animals and to the diagnosis of genetic diseases in several species.

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The exam can only be requested by the breeder/associate panel, where the whole process is systemic and direct with the laboratory, it can be done together with the DNA PROFILE.