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Common Causes of Deafness
The most common cause of deafness in dogs is hearing loss accompanied by old age. This is much less common in old cats, whereas chronic ear infections or tumors in the ear can cause deafness in both species. Chronic exposure to loud noises, an injury, having a substance inserted into the ears that is toxic to the ears or even low thyroidbutterfly-shaped gland at the base of the neck function can cause deafness in pets, though low thyroid function is almost unheard of in cats.
Deafness as a birth defect (congenital deafness) is usually apparent by 5 to 6 weeks of age1. It is often associated with the same genes that cause white, albinopale skin, light hair, pinkish eyes, and visual abnormalities resulting from a hereditary inability to produce the pigment melanin and piebald (also known as merle and/or dapple) coat colors2. Pets of this coloration often are mostly white with blue eyes and possibly gray-blue spots. Approximately 5 percent of piebald dogs are deaf in one ear and another 5 percent deaf in both ears3. Twenty percent of white cats are deaf5.
Breeds More Prone to Deafness
Deafness is associated with the genes for merle or dapple colors in the Collie, Dachshund, Great Dane and Shetland Sheepdog (Sheltie). Border Collies are unique as they can suffer from genetic deafness that occurs at 3 to 5 years of age4. Although any breed can suffer from congenital deafness, dogs and cats with blue eyes and coats white in color are at increased risk.
Behavioral Effects of Deafness
Deaf pets may be difficult to wake from sleep, may startle easily and resist restraint. They may be more vocal than their littermates and play more aggressively because they cannot hear cries of pain during play.
Patients who develop deafness in old age often suffer from poor eyesight and/or cognitive dysfunction (senility) as well, resulting in significant disorientation and behavior changes. If you notice these problems in your senior pet, consult your veterinarian for advice and treatment.
Diagnosing Deafness in Your Pet
If you suspect your pet might be deaf, schedule an appointment with your veterinarian. Your veterinarian will examine the ears to see if there is a treatable problem and conduct a neurologic examination to look for abnormal reflexes that might indicate a widespread problem connected with deafness. Veterinarians perform hearing tests that involve producing different sounds and observing the pet for behavioral reactions, including the Preyer’s reflex (movement of the ear in response to sound). While testing your pet’s hearing, your veterinarian will avoid air movement, vibrations and visual cues that might cause a reaction.
If your veterinarian cannot conclude whether your pet is deaf, she may make a referral to a veterinary neurologist for additional hearing tests.
Accommodations for Deaf Pets
Deaf pets can be trained to respond to hand-signal commands and often are sensitive to vibrations. Some can even learn basic commands in American Sign Language (ASL), much like hearing dogs can be trained to respond to oral commands. Ask your veterinarian or veterinary behaviorist (http://www.dacvb.org/about/member-directory/) to recommend a trainer who is experienced in working with deaf pets.
Protect dogs from injury by confining them to fenced yards, leash walks, etc., and cats to areas with cat-friendly fencing if they are allowed outdoors. Deaf pets won’t be alerted to danger by sounds. Consider attaching medical alert tags to their collars identifying them as deaf. If your deaf pet is microchipped, registration information should specify the condition.
What Pet Owners Should Look Out For
No treatment is available for congenital deafness or deafness that occurs with old age. If you suspect drug toxicity is responsible for deafness, speak with your veterinarian immediately. He or she may want to stop giving the medication. In some cases, partial hearing may be recovered over time. Prompt treatment of ear infections can minimize development of deafness.
Pets with genetic deafness should not be used for breeding purposes. In addition, many breed standards discourage the breeding of individuals with excessively white coats. Properly cared for, deaf pets can have an excellent quality of life and provide wonderful companionship for their owners.
References:
1. Katherman AE, Rothrock K, Morgan RV. Deafness, Congenital & Acquired in Dogs. VIN Associate. 3/11/15. http://www.vin.com/Members/Associate/Associate.plx?from=GetDzInfo&DiseaseId=410
2. Radlinksy MC, Mason DE: Diseases of the Ear. Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, 6th ed. St. Louis, Elsevier Saunders 2005 pp. 1184-1185.
3. Strain GM, Clark LA, Wahl JM: Prevalence of deafness in dogs heterozygous or homozygous for the merle allele. J Vet Intern Med 2009 Vol 23 (2) pp. 282-286.
4. Sommerlad SF, Morton JM, Johnstone I, O’Leary CA, Seddon JM: Consequences of a screening programme on the prevalence of congenital hereditary sensorineural deafness in the Australian Cattle Dog. Anim Genet 2014 Vol 45 (6) pp. 855-62.
5. Cvejic D, Steinberg TA, Kent MS, et. al: Unilateral and bilateral congenital sensorineural deafness in client-owned pure-breed white cats. J Vet Intern Med 2009 Vol 23 (2) pp. 392-395.
6. Rothrock K, Morgan RV. Deafness, Congenital & Acquired in Cats. VIN Associate. 8/26/11. http://www.vin.com/Members/Associate/Associate.plx?from=GetDzInfo&DiseaseId=410
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