Hereditary Defects Advice - Collie Eye Anomoly (C.E.A.)

Collie Eye Anomaly (CEA) is an inherited eye disease which manifests itself as a lesion on the back surface of the eye near the optic nerve. This lesion can be seen as a pale patch (Chorioretinal Hypoplasia - CH) which is easily visible to a vet carrying out an eye test on puppies less than seven weeks of age. After this age, changes in the eye can hide the patch, making it harder to see, which is why there have been some instances of CEA failure puppies ‘going normal’ at a later test. It is uncommon for affected dogs to lose their sight except in the most severe cases, however the disease can be inherited by the offspring of an Affected or Carrier parent.

CEA, as the name suggests, is most common in Collie breeds such as the Border, Rough and Smooth Collies, as well as Shetland Sheepdogs, Australian Shepherds and Lancashire Heelers.

In Border Collies, the mode of inheritance for CEA is known – it is passed on as a recessive gene. This means that in order to be Affected by CEA, a dog needs two copies of the gene – one from each parent. Therefore both parents must be Carriers or Affected in order to pass on the condition. In the past, to find out whether a dog was a Carrier or not, it was possible to carry out a test mating with a known Affected dog. If this resulted in any Affected puppies – the dog is a Carrier. However this test was not foolproof, as there was only a 50% chance of getting Affected puppies in a test mating from a Carrier, and some dogs may have been thought to be Clear when they were not. Also, it sometimes resulted in the production of CEA Affected puppies which might have to be culled or placed in pet homes at the risk of going blind - the morals of this were dubious.

There are now two ways to screen for CEA, and the BCCGB strongly recommends the use of both in order to reduce the incidence of CEA in Border Collies. Firstly, there is a DNA test available, so it is possible to ascertain whether your dog is Clear, a Carrier, or whether it is Affected. Secondly, is the eye test – this is most usefully carried out at between 5 and 7 weeks of age. If you are buying a Border Collie puppy, ensure the breeder has had this done, (even if the parents are genetically Clear). It is not recommended that anyone breeds from an Affected dog, however Carriers can be bred from if they are mated to a known Clear dog. This may result in some of the puppies being Carriers, so it would be wise to DNA test all the puppies so that the CEA status of each is known.

“It is worth emphasising that CEA is a congenital condition that can be diagnosed as soon as eye examination is possible and that it is diagnosed with greatest accuracy in young dogs. There is little doubt that, in those breeds examined under the Eye Scheme, litter screening, combined with genetic testing, is the best way of attempting to establish clear lines” from BVA Publication ‘Hereditary eye disease in dogs’. Reprinted from In Practice, January 2008 (updated January 2010).

Eye testing can be done by a vet who is a member of the BVA Eye Panel – a list of these vets is available at the end of this health section. The dog needs to have eye drops to relax and dilate the pupil, and the vet will examine the back of the eye. This only takes a few moments and causes the dog no discomfort. The routine eye exam costs £48.00 per dog, £41.00 for 2-24 dogs, and if a group of over 25 dogs is assembled for testing, it costs just £29.00 each. The routine eye exam will also check for other eye problems such as PLL and CPRA (both explained in more detail below) and can pick up other abnormalities such as cataracts. Glaucoma, however, must be screened for in a separate test. Puppy eye tests cost £45.00 per litter of 5 or less puppies, or £9.00 per puppy in litters of 6 or more puppies.

DNA testing for CEA status of dogs is carried out by Optigen (www.optigen.com). The Optigen website contains all the details of how to submit samples, including an online submission form, along with details of where clinics are being held - attending one of these for the blood draw and bulk sample delivery will help to reduce the cost.