Quick Summary
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Phenotype: The presentation of CEA varies considerably. While some dogs may have no obvious clinical signs and present with normal vision all their lives, most affected dogs have choroidal hypoplasia, an underdeveloped vascular layer of the eye. Affected dogs may also present with small eyeballs (microphthalmia), mineralization of the cornea, bleeding inside the eye, detachment of the retina, impaired vision or even blindness due to coloboma of the optic nerve.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, CEA = Collie Eye Anomaly
Breeds appropriate for testing: Australian Cattle Dog, Australian Shepherd, Bearded Collie, Border Collie, Boykin Spaniel, Collie, Lancashire Heeler, Longhaired Whippet, Miniature American Shepherd, Nova Scotia Duck Tolling Retriever, Old-time Scotch Collie, Rough Collie, Smooth Collie, Shetland Sheepdog
Explanation of results:
• Dogs with N/N genotype will not have this inherited form of ocular disorder and cannot transmit this allele to their offspring.
• Dogs with N/CEA genotype will not be affected by this inherited form of ocular disorder but are carriers. They may transmit this allele to 50% of their offspring. Matings between two carriers are predicted to produce 25% of affected puppies.
• Dogs with CEA/CEA genotype may develop this form of ocular disorder and will transmit this allele to all of their offspring.
Sample Collection
Dog DNA tests are carried out using cells brushed from your dog's cheeks and gums. The preferred cytology brushes are sent to you by mail, or you may provide your own brushes. For accepted alternative brushes, click here
We recommend waiting until puppies are at least three weeks old before testing.
Step-By-Step:
- Make sure the dog has not had anything to eat or drink for at least 1 hour prior to collecting sample.
- When swabbing puppies, isolate each puppy from the mother, littermates and any shared toys for 1 hour prior to swabbing. Puppies should not have nursed or eaten for 1 hour prior to collecting sample.
- If collecting samples from more than one dog, make sure to sample one dog at a time and wash your hands before swabbing another dog.
- Label brush sleeve with name or ID of dog to be sampled.
- Open brush sleeve by arrow and remove one brush by its handle.
- Place bristle head between the dog’s gums and cheek and press lightly on the outside of the cheek while rubbing or rotating the brush back and forth for 15 seconds.
- Wave the brush in the air for 20 seconds to air dry.
- Insert brush back into sleeve.
- Repeat steps 5 - 8 for each unused brush in sleeve on a fresh area of cheek and gums. Make sure to use and return all brushes sent by the VGL. In most cases, it will be 3 brushes per dog. If using interdental gum brushes, please note that the VGL requires 4 brushes per dog and only moderate or wide interdental gum brushes are accepted.
- Do not seal brushes in sleeve.
- Place all samples in an envelope and return to the address provided.
ATTENTION:
- Do not collect saliva/drool – the key to obtaining a good sample is getting cheek cells on the swab
- Do not rub swab on the dog’s tongue or teeth – this will result in poor quality sample
- Do not collect a sample from a puppy that has recently nursed – the mother’s genetic material can rub off on the puppy’s mouth and contaminate the sample
Collie eye anomaly (CEA) is a complex heritable disorder of the eye that affects multiple dog breeds, especially herding breeds with Collie ancestry. The disorder causes an abnormal development of the inner structures of the eye, including the vascular and retinal layers. While some dogs may have no obvious clinical signs and present with normal vision all their lives, most affected dogs have at least an underdeveloped vascular layer of the eye, which is commonly referred to as choroidal hypoplasia. Affected dogs may also present with small eyeballs (microphthalmia), mineralization of the cornea, bleeding inside the eye, detachment of the retina, impaired vision or even blindness due to coloboma of the optic nerve.
A 2007 study identified a large 7.8 kb deletion in exon 4 of NHEJ1 gene as associated with CEA in the Collie, Shetland Sheepdog, Border Collie and Australian Shepherd. The deletion includes a region that contains binding sites for several regulatory proteins and is highly conserved across species, indicating it is important for normal development.
The study also showed that this 7.8kb deletion was present and homozygous in affected dogs of two hunting breeds: the Boykin Spaniel and the Nova Scotia Duck Tolling Retriever. However, researchers noted that a CEA-like phenotype seen in the Soft Coated Wheaten Terrier was not associated with the 7.8kb deletion in NHEJ1.
While coloboma of the optic nerve is found as part of the CEA phenotype, studies have also shown that this NHEJ1 deletion is not fully correlated with coloboma in dogs. Some dogs with colobomas did not have the 7.8Kb deletion, indicating that there are other yet unknown and possibly genetic causes for colobomas in dogs.
The original 2007 study showed that two Berger des Pyrenees dogs that had been diagnosed with coloboma did not have the NHEJ1 deletion. In 2018, a study by UC Davis researcher and professor, Dr. Danika Bannasch, showed that only 3 out of 7 Nova Scotia Duck Tolling Retrievers presenting with coloboma of the optic nerve head were homozygous for this 7.8kb deletion, suggesting that this variant is not the sole cause of coloboma in the breed.
The condition is inherited in an autosomal recessive manner, meaning that dogs must have two copies of the disease allele to be affected. Dogs with one copy of the disease allele are normal but can pass on the disease allele to their puppies.
Testing recommendations: Testing for CEA assists owners and breeders in identifying affected and carrier dogs. Dogs with one copy of the CEA allele are normal but are carriers. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing dogs affected by this ocular disorder.
