The ability to hear plays a crucial role in the survival of animals. For our pets, it is essential for communication with other animals and humans. In wildlife, hearing is important for communication during hunting and detecting predators. In such cases, motor vehicles pose a significant threat to stray animals in traffic.

Hearing loss can be classified based on whether it affects one or both ears, whether it is partial or complete, and whether it results from inherited or acquired damage to the neural system that transmits sound or the conductive system within the ear’s anatomical structure.

How Can I Tell If My Pet Is Deaf?

There are several signs that may help you detect hearing issues in your cat or dog at home. Shaking their head or spinning in circles can indicate inner ear inflammation, while a lack of response to sounds may suggest partial or complete deafness. Other symptoms include disobedience, ignoring verbal commands, excessive barking, or loud meowing.

You can test your pet’s hearing by making high- and low-pitched sounds at varying volumes. However, these should be done in a way that your pet cannot see or feel the vibrations, as this might affect their reaction. Try making noises behind them, call their name, and observe their response to everyday sounds.

Partial or unilateral hearing loss may not be easily noticed in a home environment. Since animals have a wider hearing range than humans, they may still react to certain sounds even if they have hearing impairment. If your pet does not respond to you and belongs to a breed predisposed to deafness, consult your veterinarian.

The Genetic Influence on Deafness

Although deafness can occur for various reasons throughout an animal’s life, hereditary deafness plays a significant role in certain breeds. This genetic condition is often linked to the “white pigment” gene and develops due to a pathological change in one of the sacs inside the inner ear.

In some cases, inherited deafness may result from damage to the epithelial cells containing the inner ear’s nerves or the presence of one or more genes causing deafness during a dog’s lifetime.

Certain genes responsible for the condition have been identified, and they are linked to pigmentation genes in specific phenotypes. Breeds such as Dalmatians and blue-eyed white cats are particularly prone to genetic deafness. In dogs, the Piebald gene, which creates white fur patches, and the Merle gene, which produces dappled fur with various colors, are associated with deafness. In cats, the white fur gene plays a similar role.

CSD (Cochlear Saccular Dysplasia), also known as Scheibe Deformity, is a hereditary disorder where the inner ear’s sac-like cells degenerate in a way that could lead to deafness. The deterioration of cells in the cochlear canal affects the hair cells responsible for transmitting sound, eventually leading to their destruction. This cellular breakdown is generally triggered by a deficiency in melanocytes, which explains the link between deafness and pigmentation.

Although it is more commonly seen in one ear, it can affect both. Unlike in dogs, where deafness is linked to coat color, in cats, the presence of blue eyes is a stronger predictor of deafness. The number of blue eyes also plays a role in determining the risk. Studies on Turkish Van cats have debunked the common myth that “all Van cats are deaf.”

Hereditary deafness caused by damage to the sensory epithelium is observed in breeds like Doberman Pinschers and Pulis. Inside the inner ear, there are hair cells in a snail-like structure that transmit sound to nerve cells. In this type of deafness, degeneration starts with these hair cells and spreads to all functional hearing cells, leading to total hearing loss in both ears.

Another hereditary condition is PSOM (Primary Secretory Otitis Media), a disease diagnosed during a clinical examination when a section of the tympanic membrane (eardrum) called pars flaccida appears as a drooping protrusion. This condition is believed to be hereditary, and Cavalier King Charles Spaniels are particularly predisposed to it.

Additionally, late-onset hereditary deafness, whose exact mechanism is still unknown, has been documented in Border Collies and Rhodesian Ridgebacks.

Causes of Acquired Deafness

Congenital deafness can result from oxygen deprivation at birth, difficult labor, exposure to toxins during pregnancy, or obstruction of the ear canal. Throughout life, conditions such as inner, middle, and outer ear infections, ear polyps, aging, sound trauma, physical injuries, or anesthesia can contribute to acquired hearing loss.

Among the factors affecting fetal development, antibiotic toxicity is the most common cause of congenital deafness. While ear infections and polyps may cause reversible damage with surgical intervention and treatment, traumas often result in permanent hearing loss.

Interestingly, dental or ear cleaning procedures performed under anesthesia have been reported to cause bilateral hearing impairment, although the underlying mechanism remains unclear.

This blog post has been verified by Veterinarian EMRULLAH ÖKSÜZ.

SOURCES

MSD Manual. “Deafness in Animals.” Erişim: 21.12.2023

https://www.msdvetmanual.com/ear-disorders/deafness/deafness-in-animals

Strain GM (1996). “Aetiology, Prevalence and Diagnosis of Deafness in Dogs and Cats.” British Veterinary Journal. 152,17

Strain GM (2015). “The Genetics of Deafness in Domestic Animals.” Front. Vet. Sci., 2:29