Deafness

What is ... ?: 

Inherited deafness in one or both ears occurs due to the degeneration of sensory inner ear structures (sensorineural deafness) within a few weeks of birth. This occurs in many breeds and is especially common in the dalmatian.

In most breeds, the trait for deafness is tied to the genetics of coat colour, particularly in breeds with the merle or piebald gene. There is an increased risk of deafness in dogs with white, spotted, merle, or dappled hair coats.

How is ... inherited?: 

In most breeds, inherited deafness is associated with white colouration of the skin and hair, which in turn is linked to the piebald and/or merle genes. In breeds with merle coat colours (eg. collie, harlequin Great Dane), there is incomplete dominance with incomplete penetrance. In some such breeds the percentage of affected (ie. deaf) dogs is very high (eg. Norwegian dunkerhound). Inheritance of deafness in breeds with a white or peibald coat colour (eg. Dalmatian, bull terrier) is less-well understood. The prevalence of deafness in Dalmatians (bilateral or unilateral) is as high as 30%. [For detailed information on genetic expression, deafness, and coat colour, see Strain 2011 below.]
 
The complexities of inheritance in association with coat colour make breeding decisions very difficult. Dogs with normal hearing in both ears can produce bilaterally deaf puppies, and vice versa. Dogs with deafness in 1 ear can have pups that are deaf in both ears or neither. Statistically however, deaf parents are more likely to produce deaf pups. Dogs with more white in their coats and with blue eyes are more likely to be deaf, and to produce deaf pups.

In the Doberman pinscher, inheritance is autosomal recessive with no association with coat colour.

What does ... mean to your dog & you?: 

Pups lose their hearing a few to several weeks after birth. Signs of bilateral deafness may include aggressive play because the deaf pup does not hear cries of pain from littermates, and having to be jostled to waken. Unilateral deafness is much harder to spot.

If your dog is deaf in only 1 ear, you will likely not even be aware of it. In training sessions, you may notice that your dog responds better to hand signals than verbal cues.
One-sided deafness is generally not a problem, except in some working dogs for whom localization of sound is important. However it is much more difficult for bilaterally deaf dogs to lead a normal life, and breeders will generally opt for euthanasia of these pups.
 

How is ... diagnosed?: 

 If you suspect your dog is deaf, your veterinarian will recommend the BAER (Brainstem Auditory-Evoked Response) test since hearing loss can be very difficult to evaluate by clinical examination (ie. behavioural response to sounds). The BAER test is a painless and reliable means of detecting hearing loss in one or both ears, that is available at veterinary schools and referral centres. It can be used in puppies of 5 weeks of age on. Older pups and adult dogs may need to be sedated for the test.

Dogs in breeds with a high incidence of deafness should be tested by the BAER test before being used for breeding, and pups should be tested before being sold. Hearing loss, if present, is complete - that is the dog either has normal hearing, or is totally deaf in 1 or both ears.
 

How is ... treated?: 

Deafness can not be cured or treated, but dogs can generally accommodate very well, particularly if only deaf in 1 ear. They should not be bred.

Because dogs that are deaf in both ears startle easily, are difficult to train, and are prone to accidents, they are usually euthanized as pups. As an alternative, an owner may train the dog to respond to hand signals or other visual cues, always restrain him/her on a leash or in a fenced yard, and be alert to the possibility of the dog biting someone if startled. 

Breeding advice: 

Controlled breeding can reduce deafness. Any dalmatian to be used for breeding should be checked by the BAER test. Pre-breeding BAER screening should also be used in other breeds where congenital deafness is a problem. Bear in mind that dogs who are deaf in 1 ear appear to function normally, but they should not be used for breeding as this contributes to the perpetuation of this disease.
 
Well-defined and publicized screening programmes and registries of dogs used for breeding will help to reduce the incidence of deafness. The Institute for Genetic Disease Control (GDC) maintains an open registry for deafness, for all breeds. There is a lower incidence of deafness in dalmatians in Norway and the UK, likely due to selection by breeders against blue eyes. It is laudable that dalmatian breed clubs, particularly in the UK, have supported research aimed at reducing deafness through assistance with funding and data collection.
 
 
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. 

Resources: 

Sargan DR. Deafness. In IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. 2002-2011. Mamm Genome. 2004 Jun;15(6):503-6. Search this database for more detailed information on inheritance patterns and association with coat colour in particular breeds.

Strain GM. Whitenoise: Pigment-associated deafness. Vet J  2011;188:247-249, and Deafness in Dogs and Cats

Webb AA, Cullen CL. Coat color and coat color pattern-related neurologic and neuro-ophthalmic diseases. Can Vet J 2010;51(6): 653–657.
 
Webb AA. Deafness. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:276-77.
 
Becker SC. 1997. Living with a Deaf Dog: A Book of Advice, Facts and Experiences about Canine Deafness. Cincinnati. Susan Cope Becker.


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