Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

THE EARS • 219
enough to respond to sound. This happens from 11 days onward. Deafness
may involve one or both ears. If only one ear is affected, you may not notice
the deafness.
There is a connection between hereditary deafness and a gene for coat color.
Dogs with predominantly white coats, and those with merle coats, are at increased
risk for congenital deafness. The highest incidence occurs in Dalmatians, but at
least 60 breeds and their crosses are affected. The deafness is due to a lack of pigment
or melanin in the “hair cells” that detect sounds. If these dogs with merle or
white coats have pigmented cells in their inner ears, even though the rest of their
haircoat is lacking pigment, they can hear normally.
Senile deafness develops gradually, beginning at about 10 years of age. It is
seldom total. Old dogs with deafness often retain some ability to hear highpitched
sounds, such as a dog whistle. The deafness may not be particularly
noticeable unless there is also loss of vision.
A dog with significant hearing loss is less active, moves more slowly, is difficult
to arouse from sleep, and fails to respond to commands. Shouting, clapping
loudly when the dog is not looking, blowing a whistle, and other
attention-getting sounds can be used to test the dog’s hearing.
Stamping on the floor attracts a deaf dog’s attention, because she can feel
the vibrations. Always do this before waking or touching a deaf dog, so that
you do not startle her.
Hearing tests can be done on puppies and adult dogs. Hearing is tested using
an electroencephalogram (EEG) to record the brain waves produced in
response to sounds of different frequencies. If the brain wave pattern remains
unchanged, the sound was not heard. This procedure, called a brain stem auditory
evoked response (BAER) test, is particularly useful for screening puppies
who are at risk for congenital deafness. It is available at referral centers.
The Institute for Genetic Disease Control in Animals (GDC) maintains
an open registry for inherited deafness. Results are used to better understand
the mode of inheritance and develop data that can help in selecting normal
breeding animals. Testing is done at a minimum age of 35 days, according to a
BAER protocol. Most of GDC’s operation has been transferred to OFA, so
search there for deafness registry information, as well (see appendix D).