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Bearded Collie Health

Collie Eye Anomaly

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Collie Eye Anomaly (CEA)

What is CEA?

Collie Eye Anomaly (CEA) is an inherited condition that causes abnormalities in the back of the eye. It is found in Rough, Smooth, and Border Collies as well as a number of non-Collie breeds including Shetland Sheepdogs, Australian Shepherd Dogs, and Lancashire Heelers.

The primary defect in CEA goes under the technical name of choroidal hypoplasia (CH). The choroid is an important layer of tissue lying under the retina which is rich in blood vessels delivering oxygen and nutrients to the retina. Hypoplasia means under-development. Choroidal hypoplasia manifests itself as a pale patch at the back of the eye near the optic nerve. The pale colour is due to localised lack of the dark pigment normally found in the retina and choroid. Blood vessels in the affected area are also abnormal in number and shape.

In most dogs with CEA, choroidal hypoplasia is mild and has little noticeable effect on the dog’s eyesight. However, two more serious CEA defects are known: a cleft (called a coloboma) in or near the place where the optic nerve enters the back of the eye; and retinal detachment, with or without haemorrhage. Either of these can cause blindness in the affected eye.

Choroidal hypoplasia and colobomas are congenital but not progressive (meaning they are present at birth and do not deteriorate over time). Retinal detachment is a complication associated with colobomas. It is rare and often one-sided and generally occurs before 2 years of age.

How widespread is CEA in Beardies?

For well over 60 years it was thought that Bearded Collies were free from CEA. However in 2012 the first confirmed occurrence of CEA was reported in the breed. Following the news the Joint Breed Liaison Committee (JBLC) decided it was important to find out how widespread the CEA/CH gene was within the breed. Working through the Animal Health Trust (AHT), a sample set of Beardies with a wide variety of pedigrees representing the UK breeding population was identified and DNA tested.

The results showed one dog out of 59 tested was affected and 5 other dogs were found to be carriers. In a completely random sample, this frequency of affected and carrier dogs would indicate an incidence of CEA/CH in the population of between 3 and 4 affected dogs per thousand (0.35%) and a carrier frequency of 11.16%. However, the actual frequency of the abnormal gene is likely to be lower than this because the sample included the affected dog, its parents and three other relatives.

It appears from current evidence that the abnormal gene came into the breed through a single dog in the relatively early years of the breed. The dog in question and its descendants were relatively little-used in breeding and not prominent in the show scene. As a result the abnormal gene has a comparatively restricted distribution within the overall population, although a number of dogs were exported and have living descendants overseas.

How is CEA caused?

Choroidal hypoplasia is caused by abnormalities in a single gene. The exact cause of the more serious defects is not yet fully understood although it is known they are not caused solely by the CH gene. The most likely explanation is there are other independently acting “modifier” genes that influence CEA/CH gene expression. The good news for breeders is that the choroidal hypoplasia gene is key. Dogs that do not have two copies of the CH mutation will not develop any CEA defects. This means that breeders can manage inheritance of the condition as if it was caused by a single gene.

CEA/CH is a recessive condition. This means that if a normal copy of the gene has been inherited from one parent, the normal copy is sufficient to prevent the effects of an abnormal copy of the gene inherited from the other parent from being expressed.

Dogs inheriting only one copy of the abnormal gene are known as carriers because although they appear normal, the abnormal gene is in their cells and can be carried through to the next generation. Carriers can produce affected dogs if bred to an affected dog or to another carrier. Affected dogs have two copies of the abnormal CEA gene, one inherited from each parent, and they will always pass on the abnormal gene to their progeny.

What tests are available for CEA?

The only reliable way of identifying carriers and affected adults is by DNA testing. The CH gene has been identified by geneticists and a genetic test can now be done using a sample of the dog’s DNA collected from a buccal (cheek) swab or a blood sample. The DNA test is a patented process and is offered commercially by OptiGen laboratories in the USA.

The Future

A growing number of UK Beardies have been DNA tested for CEA/CH since the AHT survey and the results from approximately 170 dogs have been made publicly available by their owners. No further affected dogs have been found, and no carriers apart from dogs which share the same common ancestor as the dog first identified as having CEA.

Provided this situation continues, it is feasible to work towards removing the abnormal CEA/CH gene from the breed. The following actions have been taken.

  • The dog identified as having CEA is not being bred from. His only sibling (a bitch) and his mother have both been spayed. The carrier status of his sire has been recorded in KC records.
  • The JBLC has undertaken world-wide communication with owners of Beardies who share recent common ancestry with the affected dog, to inform them of the situation and offer help in testing their dogs. CEA test results for overseas Beardies can be found on KC site, Irena's site and BCX.
  • The Kennel Club has approved a new official DNA testing scheme for CEA/CH in Bearded Collies. The results will be added to the dog's registration details, can be viewed on the Kennel Club’s Health Test Results Finder  and will appear on the registration certificates of any future progeny of the dog.
  • To encourage genetic testing and reduce its cost, the Breed Clubs have organised a number of 20/20 OptiGen test clinics (for every 20 dogs sampled, a 20% test discount is given). The JBLC is encouraging further testing, particularly in dogs that are to be bred from, to make sure no other cases of CEA exist.

The AHT is to re-evaluate the incidence of the gene within the breed using data from all the dogs that have now been tested, so that the JBLC can make any further recommendations necessary.

In the interim, the advice to breeders is that they should refrain from breeding with carriers, but if carriers are used then they must be mated to clear dogs, the resulting progeny should ALL be DNA tested before they are sold and the pedigrees of any carriers produced should be endorsed so that their progeny are not eligible for registration.

Last updated: 15 June 2015