Just like humans, dogs are sometimes born with impaired hearing or experience hearing loss as a result of disease, inflammation, aging or exposure to noise, according to a study posted on the website of the University of Illinois (UI) on Thursday.

The researchers describe cases of hearing loss in three working dogs: a gun dog, a sniffer dog and a police dog. One of the three had permanent hearing loss, one responded to treatment and the third did not return to the facility where it was originally diagnosed for follow-up care.

Just as in humans, loud noises can harm the delicate structures of a dog's middle and inner ear.

"Most commonly, noise-induced hearing loss results from damage to the hair cells in the cochlea that vibrate in response to sound waves," said Kari Foss, a veterinary neurologist and professor of veterinary clinical medicine at UI. "However, extreme noise may also damage the eardrum and the small bones within the inner ear, called the ossicles."

Signs of hearing loss in dogs include failing to respond when called, sleeping through sounds that normally would rouse them, startling at loud noises that previously didn't bother them, barking excessively or making unusual vocal sounds, Foss noted. Dogs with deafness in one ear might respond to commands but could have difficulty locating the source of a sound.

Hearing-impaired or deaf dogs may miss clues about potential threats in their surroundings, Foss said. Nevertheless, hearing loss does not appear to affect dogs' quality of life.

"A dog with congenital hearing loss grows up completely unaware that they are any different from other dogs," she said. "Dogs that lose their hearing later in life may be more acutely aware of their hearing loss, but they adapt quite well. A dog's life would be significantly more affected by a loss of smell than by a loss of hearing."

"Owners can use eye contact, facial expressions and hand signals to communicate with their pets," Foss said. "Treats, toy rewards and affection will keep dogs interested in their training." Blinking lights can be used to signal a pet to come inside.

The study has been published in the journal Topics in Companion Animal Medicine.

(All photos via VCG)

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