What is CEA?

Overview

Collie Eye Anomaly (CEA), also known as Choroidal Hypoplasia, occurs in a number of breeds of dogs, one of which is the Border Collie. It is an inherited disease in dogs, with recessive mode of inheritance, therefore controlled by genes which are expressed in offspring only when inherited from both parents. Dogs which carry the genetic mutation, known as 'Carriers' are normal but will pass the mutation on to an average of 50% of their offspring, therefore puppies which inherit two copies of the genetic mutation will develop CEA, and will be 'Affected'.

The ISDS recommends eye testing is carried out in accordance with the approved British Veterinary Association (BVA) Scheme, or ECVO or other approved veterinary certificate, in its effort to improve the breed's health.

Symptoms

CEA is caused by improper development of the eye. CEA symptoms can vary from dog to dog, it affects the retina, choroid, and sclera. For some dogs it can be a mild disease, with thinning in the choroid layer of the eye, and the dog's vision remains normal. In severe forms of the disease, depending on the size and location, it can cause serious loss of vision due to holes or pits in different layers of the eye, but it rarely leads to complete blindness.

A thinning, poorly developed choroid is present at birth and can therefore be detected in puppies, early examination between the ages of 5 and 12 weeks is important, but the test can be conducted in dogs at any age.

Breeding Outcome

The genetic status of dogs can be used to determine breeding outcomes when different combinations are mated. Mating a Clear dog with another Clear dog will produce 100% Clear offspring. Mating a dog that is a Carrier with a dog that is Clear will produce 50% Carriers and 50% Clear offspring. Mating a dog that is a Carrier with another dog that is also a Carrier will produce 25% of the offspring as Affected, 50% as Carriers and 25% as Clear.

Summary

by Professor Sheila Crispin and Dr Cathryn Mellersh

The BVA/KC/ISDS Eye Scheme as it relates to the Border Collie is based on the best available evidence of inherited eye disease in this breed. Currently three inherited eye diseases are listed and certified on the basis of an eye test (clinical examination), they are Collie Eye Anomaly (present from birth), Central Progressive Retinal Atrophy (Retinal Pigment Epithelial Dystrophy) and Primary Lens Luxation (both of which develop in later life). Other possible inherited conditions being investigated include primary glaucoma, early onset cataract and progressive retinal atrophy.

DNA testing (laboratory examination) determines the normal, carrier or affected status for CEA only.

It is wrong to suggest that there is a choice of either eye testing or DNA testing, the tests are complementary not interchangeable and whereas eye testing can detect all the conditions listed above, as well as newly emerging conditions, current DNA testing can only detect CEA.

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