Eye Tests for Dogs and the DNA CEA Test – A Discussion

The following was written for inclusion in the ISDS Trials Programmes in 2007.

The ISDS requires that all dogs for breeding over two years old pass the British Veterinary Association (BVA) (or ECVO or suitable equivalent) eye examination for two types of eye disease – Collie Eye Anomaly (CEA) and Central Progressive Retinal Atrophy (CPRA also called PRA). If breeding when under two they must have a CEA pass.

Both these diseases are inherited from parents and this Society has introduced testing and breeding controls to help improve the eye health of the Border Collie. One example of a rule is that if pups or young dogs are found to be affected by the disease then their parents are prevented from breeding until further information is known.

There are two problems with such a rule. Firstly, if the disease is not detected until the dog is much older it might have sired, or whelped, many dozens of pups who could pass on the defect. Secondly, removing large numbers of dogs from breeding can distort, or damage, the gene pool available to the breed making it weaker in some other characteristic.

In practice, we are not so concerned about CPRA as it occurs very rarely. CEA however, is much more prevalent. Around 25% of ISDS collies will have one defective CEA gene and these are called Carriers. It is important that Carriers do not breed together because some pups will have defective eyesight.

What to do for the better?
The ISDS Border Collie is in a better position for removing this CEA defective gene than many other dog breeds. There is now a DNA (genetic) test that can be done by a laboratory called Optigen. They can test the dog’s blood and say with very high confidence whether the dog is CEA Normal, or CEA Carrier (one defective gene), or CEA Affected (both genes defective and liable to show disease symptoms).

The Society has written about DNA CEA testing in its magazine and issued new Rules. But the subject is complicated and it is easy to get confused. This brief article does not repeat all the detailed rules, but it will help you understand how to find a suitable sire for any bitch.

Trials Programme information

In previous years the Society used to put ‘NFB’ (Not For Breeding) in the Programme next to any dogs that were prevented from breeding, and this would include parent dogs that had ‘pup failures’ for CEA. Even if it was a super trial dog, if it said NFB you could not use it as a stud dog. Now, with the DNA CEA test being available we cannot say that. The DNA result may permit breeding to continue.
For this year, we are only listing in the Programme dogs that have actually failed the BVA Eye Examination for CEA – i.e. they are Affected. It may be that you will find none in the programme. There will, however, be many dogs running that are CEA Carriers. They are perfectly fit and healthy and, as I mentioned earlier, statistics suggest it will be around 25% of the listed dogs that are Carriers. These will be only known of if they have either produced CEA Affected pups, or have a DNA CEA result that shows Carrier.

Since DNA CEA testing is often voluntary there is a view that it is not fair to list Carriers in the programme that belong to responsible breeders, while those who keep results secret will be unlisted.

So how do you find a suitable sire?
If you have your bitch’s blood DNA CEA tested the result will most probably come back Normal, or there is a 25% chance the result will come back a Carrier (there is a very remote chance it could be Affected and an eye test has not picked this up before because it is mild or has ‘gone normal’).
If the result is Normal then your bitch will never produce Affected pups, no matter what the condition of the sire was. If your bitch is a Carrier than you must be very careful to only mate her with DNA Normal sires.

If your bitch is CEA Normal and you use a CEA Normal sire then this is the best condition since you will be totally confident that ALL the pups will be CEA Normal. The Society will even say so on the pup Certificates, and you can expect such pups to be in greater demand.

The ‘golden rule’ is not to go hunting for CEA Normal sires, but first to seek a suitable ‘top dog’ and then ask the owner if he or she knows what the CEA status is. If the sire status is unknown then you are breeding ‘in the dark’; if CEA Normal then that is very good news; if CEA Carrier then that is not the end of the story – if it is a good stud dog you can and should consider breeding from it.

Can we breed from Carriers?
A very simple answer – yes.
Let us imagine that there is a Top trialling dog here in the programme, that wins all the time but it has recently been confirmed as a CEA Carrier. I will explain how your Society is using the DNA CEA test to help these top dogs breed, while gradually eradicating CEA from the collie population.
Because the Top sire owner is a responsible breeder, when the sire produced some pups that were CEA failures last year he would have had the DNA CEA test done to confirm he is a Carrier. That owner will then advise all owners of bitches who come to him that they need the DNA CEA test for their bitch and a Normal result. Any litter will then have an average 50% Normal and 50% Carrier pups and the Society will register all the litter once they are microchipped. When anyone wants to breed from those pups they will also need a DNA CEA test first. If a super, good pup turns out to be one of the Normals then the Top sire’s good genes have been passed down, but the CEA gene has gone. In the old days, the top dogs would have to stop breeding. Now, the good genes can be passed on to keep improving the dog.