We just adopted a two-year old white male cat. We have had him for a week and he appears to be deaf, which I guess is common in white cats. What causes this? Are there any special needs or care he should have?
Although not every white-haired cat is congenitally deaf, there is a strong genetic tendency linking deafness with complete or relative absence of pigment (hypopigmentation) in the hair, skin, and irises of the eyes. This genetic process is known to occur in other animals and humans as well. The white hair trait is inherited on an autosomal dominant gene. All cats with this gene will have a white hair coat. About one out of twenty cats have the gene and are therefore white.
The white hair gene is closely related to a set of genes that govern the early embryonic development of tissue that ultimately becomes the cochlea of the inner ear and the cells that give the eyes their color. Blue eyes result from hypopigmentation as well and are also inherited. However, not every cat with these genes will develop blue eyes. Some cats will have one blue eye and one fully pigmented "normal" one. Generally, white cats have a higher incidence of congenital deafness than cats of other colors. White cats with one blue eye have an even higher chance of being deaf. White cats with two blue eyes have the greatest risk of being deaf; these cats may have as much as five times the chance of being deaf as white cats with normal-colored eyes. Most white cats with two blue eyes are deaf and many white cats with one blue eye are deaf as well.
The cochlea of the inner ear contains the receptor cells that respond to sound waves and enable the cat to hear. The genetic mechanism underlying hypopigmentation of the hair and eyes also results in hypopigmentation of certain tissues within the cochlea. The lack of pigmentation is thought to lead to degeneration of vital tissue in the cochlea, which leads to a loss of hearing. The deafness may be in both ears or in one ear only. The presence of these genes does not cause deafness in all cats, however. The reason for this incomplete penetrance of the genetic trait is poorly understood. However, as a preventive measure, white cats with blue eyes probably shouldn't be bred.
Sophisticated hearing tests are available in limited areas, but crude pitch pipe or tuning fork tests are performed routinely by neurologists and other specialists to detect hearing loss. There is no treatment available for congenital deafness.
Cats rely on their sense of hearing for much of their daily activities. Some anatomists maintain that this is in fact their most important special sense. They hunt by sound and also use it to communicate. For domestic cats that live indoors hearing is not so important. In fact you probably don't need to take special precautions, provided the cat lives (and stays) indoors.
Cats with deafness or blindness make great pets. If they have combined problems their life may be more challenging, but not impossible.
05/02/02
