Deafness in DogsDeafness at birth (known as congenital deafness) is often inherited in some breeds. How this condition is inherited is not fully understood but is believed to be controlled by many different genes, possibly with additional breed-specific risk factors.
Double Merle dogs (homozygous, both parents are blue merles), for example, are highly likely to suffer from hearing and vision impairments and in some cases complete blindness and deafness. Deafness and hearing impairment happens due to lack of hair pigment produced in the inner ear.
The BAER (Brainstem Auditory Evoked Response) test is used to check the hearing of a dog. The test checks if the brain responds to noise (usually a clicking sound) and is a reliable way to see if a dog is deaf and to what extent. The test does not measure the full range of a dog's hearing, it only checks noises in the normal human range (some dogs will test as 'deaf' but can still hear very high-pitched noises).
In addition to identifying bilaterally deaf dogs early in life, this testing will identify unilateral deafness. Dogs that are deaf in one ear are thought to have the same genetic variant(s) as dogs that are deaf in both ears. Your dog could be deaf in one ear, and it can go undetected for years because dogs compensate and adapt so well and so will pass on their deafness gene.
Unfortunately, at the moment not enough is known about congenital deafness to offer any firm breeding advice. However, scientists believe that it may be possible to reduce the risk of producing deaf or bilaterally deaf puppies by only breeding from bilaterally normal hearing parents.
Ask your vet where you can find a BAER test centre.
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Amber Marie Westwood* has a Cardigan Welsh Corgi female that is deaf and here is what she writes:
Photo courtesy Amber Marie Westwood
Siren is deaf in both ears although she is not a double merle. I've even been asked if I'm certain Siren is deaf - "she acts like a normal dog!" - anyone who has spent more than five minutes with her can tell! She can react to noise stimuli just like any other dog... but it's an illusion. She relies on social learning from other dogs to know that something has just happened, or can feel the vibrations, air pressure changes, and temperature. She also watches out for shadows and reflections.
You can notice that puppies react to noises from 3 weeks old, and this is also the age that bilaterally deaf dogs can be detected by having them BAER tested. They will be distant, disengaged, oblivious and distracted unless a visual or vibration stimulation is provided. Dogs with very white ears, and pink pigment inside will be at more risk than dark pigments - this is known as Whitehead (which is what we believe is the culprit for Siren's deafness). It's unfortunately not a gene that can currently be tested for, but we're working on it! We will also find out soon via Embark (£159 DNA test) to see if she has the deafness gene, which will mean that one of her parents or grandparents passed on the gene.
*) Amber Marie Westwood is a very talented artist and designer. You can find many items with your favourite breed on https://ambermariestudio.com
Read also: Life with a Deaf Dog