Hereditary Defects Advice - Deafness

Deafness in dogs should be easily detected if it is bilateral - in other words, it occurs in both ears. A bilaterally deaf puppy is unresponsive to even loud noises, and will use mainly visual cues to interact with its environment. Unilaterally deaf puppies are only deaf in one ear, and can often compensate for this so well that they can react in exactly the same way as puppies with normal hearing. The only way to reliably identify a unilaterally deaf puppy is to carry out a Brainstem Auditory Evoked Response (BAER) test. Unilaterally deaf puppies, on the whole, can lead normal lives, however studies have shown that if they are bred from, the incidence of unilateral and bilateral deafness in their progeny is greatly increased.

Border Collies have also been noted as being particularly prone to middle aged onset deafness – initially they are known to have normal hearing, however sometimes as early as 4 years of age, they lose their hearing. Testing and investigation is currently underway in the United States for a possible genetic basis (pers. comm. Judith Skerritt).

BAER testing can be carried out on adult dogs before they are used for breeding, or on puppies before they leave the breeder. It gives a clear result, and is not reliant on any conscious response from the dog. Some dogs and puppies may find the procedure slightly stressful, and require a light sedative, however many remain totally relaxed throughout the procedure. During the test, a headphone is placed over one ear, which sends a series of clicks into the ear. If the hearing in that ear is normal, sensors placed around the head pick up signals which then generate a waveform on the screen of the equipment that should show characteristic peaks and troughs. The procedure is then repeated for the other ear.

The Animal Health Trust (AHT) has been reviewing results for Border Collie BAER tests, and has found an incidence of 3.6% of bilateral or unilateral deafness in the breed. This is significantly higher than the incidence of deafness in the canine population as a whole, which is estimated at 0.025%. At the AHT, analysis of the pedigrees and certain physical characteristics - such as the extent of white markings, the merle gene and the presence of blue eyes - are being correlated with BAER results and DNA sampling, in order to find the cause of deafness in the breed. The more data that is obtained, the quicker the answer will come. All results are kept in the strictest confidence, and no individual persons or dogs will be identified in the findings.

BAER testing centres are relatively few and far between in the UK. A list of the places carrying out the testing can be found at the end of this health section. Costs can vary, but may be around £25 - £50, depending on whether sedation is required.