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Deafness in white dogs: white dogs have a greater chance of being born deaf and blue eyes increase the odds.

Congenital deafness is prevalent in white-coated dogs and is usually noticed shortly after birth. It can occur in brown-eyed dogs but, "There is a strong relationship between deafness and white dogs with blue eyes," says Brian Collins, DVM, section chief of the Community Practice Service at Cornell University College of Veterinary Medicine.

More than 100 dog breeds have incidences of congenital deafness, says George M. Strain, Ph.D., a leading researcher on deafness in pets and professor of neuroscience at Louisiana State University School of Veterinary Medicine. "Hereditary congenital deafness, if it is going to develop, should be present by three weeks of age," Dr. Strain says.

Dr. Strain notes that two pigmentation genes in particular are often associated with deafness in dogs:

* The dominant merle gene, which is seen in the Collie, Shetland Sheepdog, dappled Dachshund, Harlequin Great Dane, American Foxhound, Old English Sheepdog, the Norwegian Dunkerhound, and others.

* The recessive piebald gene, which is seen in the Bull Terrier, Samoyed, Greyhound, Great Pyrenees, Sealyham Terrier, Beagle, Bulldog, Dalmatian and English Setter. Dalmatians in particular have been found to have a 30 percent incidence of congenital deafness.

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These genes suppress pigment cells known as melanocytes, which are found in the vascular system of a dog's inner-ear structures. These melanocytes help maintain the high potassium levels of the fluid surrounding the sensory hair cells in the ear. When sound waves bend the inner-ear hair cells, they open special channels that allow potassium into the cell. The potassium influx excites the hair cell, which in turn excites the nerve cell that enters the brain in the auditory nerve.

If high potassium levels are not maintained around the hair cells--such as can occur when the genes suppress the melanocytes--the cells die and deafness results. Degeneration happens within a few weeks after a puppy's birth. The resulting deafness is complete, with one or both ears affected.

"The pigment genes can also affect melanocytes in the iris, resulting in blue eyes in the absence of the normal pigment particles," Dr. Strain says. "Thus, blue-eyed dogs are more likely to be deaf than animals with normal colored irises."

Research is ongoing to identify the genetic cause of deafness with the hope of developing a DNA test to be used to make breeding decisions. Until then, "The only action that can reduce the possibility of deaf puppies is to have hearing testing done on both parents prior to breeding, since a deaf parent will pass on the genetic defect," Dr. Strain says. "Congenitally deaf dogs should not be bred for this reason," whether unilaterally or bilaterally deaf.

Often, the dog isn't completely deaf. He's just experiencing hearing loss and may still be able to hear high-pitched sounds, like a whistle.

Protecting the Deaf Dog. Dogs with hearing in only one ear usually get along well. Bilaterally deaf dogs, however, need special precautions:

* Deaf dogs should be supervised outside. "I would advise that they be confined to a fenced-in yard or on leash," Dr. Collins says. "Even the best-trained dog won't be able to know you are calling them if they run off and aren't making eye contact." Vibrating collars with remote controls can be used to signal your dog.

* At home, use clapping, shouting, whistles, stomping on the floor (he can also feel the vibrations), or other loud sounds to get the dog's attention, especially if he's asleep. "Startled deaf animals can bite as a reflex, no matter how good natured they otherwise are, so be especially careful with them around infants and toddlers," Dr. Strain says.

* Visual cues can get a deaf dog's attention. Flash the lights in a room when entering and point laser pointers or flashlights near the dog to get his attention (do not shine the flashlight or laser in the dog's eyes).

* Train your dog using hand signals instead of verbal commands. To see a list of hand commands for communicating with a deaf pet, go to http://www.lsu.edu/deafness/Hand%20Commands.htm.

Your dog can still be trained. Use the basic premise of clicker training, with a flashlight blink substituting for the sound of the clicker. Able-bodied dear and near-deaf do not need to become couch potatoes. They can compete in many activities, like obedience, agility, and field work. You just need to rely on other commands. Clapping to get a turn in agility worked well for one experienced agility team, extending their competitive time by a full year.

"It may require extra time and patience on the owner's part, but having a deaf animal is very doable," Dr. Collins says.
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Publication:Dog Watch
Date:Oct 1, 2017
Words:765
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