I lived with a deaf dog back in my veterinary school days. He was a pretty classic case of congenital/hereditary deafness — a merle Australian Shepherd that also had vision loss. His owner kept him safe, and he was living a pretty normal and happy canine life, despite his disabilities.
Hereditary deafness in a dog or cat is one of those rare cases when a veterinarian is sometimes able to make a diagnosis as he or she is walking through the exam room door. Dogs with the merle, piebald, or extreme white piebald genes are all at higher than average risk for being born with hearing deficits, as are cats with the “white” gene. Deafness is linked to the genes giving these individuals the coloration we have selected for over the years. An unintended consequence if there ever was one.
Dr. George Strain, professor of neuroscience at the Louisiana State University School of Veterinary Medicine, has collected reports of congenital deafness in almost 100 breeds of dogs. In some cases, prevalence data is available.
*Insufficient numbers of animals tested at this time for percentages to be meaningful.
Modified from Breed-Specific Deafness Prevalence in Dogs
There is no prevalence data for cats, but Dr. Strain lists the following breeds as carrying the white (W) coat pigment gene and being predisposed to congenital deafness
White Scottish Fold
Norwegian Forest Cats
White Turkish Angora
White American Wirehair
White Cornish Rex
White American Shorthair
White Devon Rex
White British Shorthair
White Exotic Shorthair
White Oriental Shorthair
White Maine Coon
The quick and dirty way to determine if a dog or cat is completely deaf is to make a loud noise outside of their field of vision. This obviously isn’t perfect, however, since partial hearing loss will be missed and some pets won’t respond to sounds when they are tense or bored.
The best hearing test available for hereditary deafness in dogs and cats (since there is no genetic test) is called a brainstem evoked auditory response (BAER). It involves referral to a specialty practice, but is relatively simple to perform. The patient “listens” for a click that is heard through foam inserts placed in both ears, and tiny electrodes inserted just under the scalp pick up any electrical activity in the auditory nerves and brain that result. A relatively flat line indicates deafness in the ear being tested.
BAER tests are an essential part of making responsible breeding decisions in breeds at high risk for hereditary deafness. Never purchase a dog or cat from a breeder that should have, but didn’t, have BAER tests run on their breeding animals and offspring.