BAER Hearing Tests for Dalmatians

It’s common knowledge that Dalmatians have a genetic predisposition to congenital or inherited deafness. It appears to be linked to the gene that controls spotting. While the totally deaf puppy is fairly easy to diagnose by watching its reactions to a loud noise when it is away from other dogs, it is not so easy to tell with pups that are deaf in one ear (known as unilaterally deaf or a "uni").

Before the ready availability of the BAER test we used to watch a pup which we suspected of being deaf in one ear and call it when it was out on it’s own somewhere. In the simplest terms if it looked up it wasn’t deaf but if it obviously couldn’t tell where the noise had come from when walking one particular way, there was a good possibility that it was deaf in one ear. We also select for dark eyes in our breeding, avoiding using any dog that has a blue eye or indeed was related to a dog with a blue eye. We do not penalise any dog or bitch for their relationship to a patched animal or for being heavily spotted. Fortunately these factors have been shown to reduce the incidence of deafness in dalmatians (1). By using these methods we have successfully bred many litters with what we believe to be an extremely low genetic predisposition to deafness. However, there comes a time in any breeding program when one needs to outcross to maintain vigour and no matter how hard you research the proposed sire, and no matter how honest the owner is, there is still a possibility that there is the deafness time bomb in the sires genes ready to creep back into the breeding stock.

Our solution to this problem:

1. all the pups we breed in future will be BAER tested
2. all our present breeding stock would be BAER tested

So what is this BAER test? BAER stands for Brain-stem Auditory Evoked Response. In this test the animal is anaesthetised and tiny probes, inserted under the skin in the animals head, are connected up to a piece of electronic equipment. The equipment is zeroed, switched to active left or right and within a few moments, the dog's response to the signal appears on the screen. This is then repeated for the other ear. The whole procedure takes less than five minutes per pup although, because of the more intense anaesthetics necessary for larger dogs, their testing and recovery can take a little longer. That's it; the pups come-to in a little while and appear no worse for wear; into the Ute and drive home. An example of a BAER Test Certificate issued by the University of Sydney for a pup in our recent 'A2' litter is shown on the left.

So why do we test all the pups in a litter, why not save money and only test the one(s) we are going to breed from? Whilst the other factors we have discussed previously cannot be ignored, deafness in Dalmatians appears to be the results of the activity of the extreme white spotting allele (form) of the s gene known as (sw). It is believed that where a non-pigmented area occurs on the skin inside the ear during the pups foetal stage, development of the ear is inhibited and deafness results quickly afterwards. If we are to reduce the incidence of this occurrence it is not sufficient to know that any one dog was fortunate enough to have pigment at the ear during the critical stage, it is necessary to know what percentage of all dogs subject to the same conditions were fortunate. Then over time we can select, improve on the percentage and reduce the likelihood of deafness.

Obviously the more information we as breeders collectively have on the stock available, the sooner we will contain this scourge. We have decided therefore to publish the results of all our testing hoping to encourage other breeders to do likewise. Our puppies are tested after they have been microchipped for identification to ensure that the results of the test can be unequivocally linked to the relevant puppy. If you are buying a puppy from a breeder and they are not BAER testing the puppies, ask why not? The test is now inexpensive and available in three states in Australia, and does not harm the puppy if conducted correctly. Some breeders will argue that their puppies have been home tested - remember this is unreliable and will not diagnose puppies that are unilaterally deaf.

For another good article on BAER testing in Australia visit Lukius Dalmatians and read about Rebecca Woiwade's experiences.

References:
(1) Dalmatian Dilemma by Dr Bruce Cattanach available on the National Dalmatian Council (Australia) website.

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