Linkage test (DNA based) - CEA/CH (Collie eye anomaly / Choroidal hypoplasia)

Please note that this is a linkage test - find out what this means below.

Details about the disease

CEA/CH causes abnormal development of the choroid - an important layer of tissue under the retina of the eye. Since the choroid layer does not develop normally from the start, the primary abnormality can be diagnosed at a very young age.

Clinical signs

The clinical effects vary greatly among affected dogs within one breed, between parent and offspring and even within a litter. Most often the disease presents as a mild form in affected dogs and the presence of the disease can only be detected upon ophthalmologic examination; the dog retains normal vision throughout life. However, dogs with mild disease can produce severely affected offspring. The severe form of the disease presents with related problems with the health of the eye that can result in serious vision loss in some cases.

How is it inherited?

The disease is described as an autosomal-recessive condition. This means that a dog must inherit two copies of an abnormal gene (one from its mother and one from its father) before its health is affected. A dog that inherits only one copy of the abnormal gene (from its mother or its father) will have no signs of the disease, but will be a carrier and may pass the gene on to any offspring.

What is a linkage test?

Most DNA tests identify whether your dog has a specific genetic mutation that causes a disease. Linkage tests do not do this, instead they find parts of unrelated DNA that are almost always inherited with the genetic mutation. Linkage tests may not be as precise as other DNA tests, but they can still be highly accurate. Laboratories will often estimate how accurate their test is. The accuracy of a linkage tests depends on the links between marker DNA and the actual mutation being maintained (i.e. them continuing to be inherited together).

Why do laboratories create linkage tests rather than regular DNA tests?

Laboratories may offer linkage tests for three main reasons:

  1. Sometimes scientists are unable to find the exact gene that causes a disease, but they are able to find sections of DNA that are somehow linked to, and inherited alongside it
  2. It may be technically difficult to find the mutation and it may be easier and cheaper to look at and determine linked markers instead
  3. The test for a particular genetic mutation is patented by a specific laboratory and may not allow others to offer this test, or may ask that they pay to offer it. In these circumstances some laboratories may create a linkage test so that they can offer the test to their clients

Which laboratories test for this condition?

A list of laboratories that offer CEA/CH linkage tests can be found below.

Laboratories that send a copy of your dog's results straight to The Kennel Club, so you don't have to.
Laboratories Contact details
Animal Genetics (UK) Phone: 01726 247788
Email: Animal Genetics
Web: www.animalgenetics.eu

Where will your dog's results be published?

DNA test results from these laboratories are sent directly to The Kennel Club and are recorded on to the dog's record in the registration database, and are published:

How to responsibly breed from your DNA-tested dog

If, once your dog is DNA tested, you would like to find out what their DNA test results mean, or how to select the right mate to avoid producing affected puppies, then please read our breeding advice and DNA testing information.

How to find out if a potential mate has been DNA tested

The Kennel Club’s Health Test Results Finder allows you to find the results of DNA tests carried out as part of The Kennel Club's official DNA testing schemes for any dog on The Kennel Club’s Breed Register.