Maisie is an unusual Boxer – she is completely white, apart from a few blotches of black spots around her muzzle. Her right eye is a clear blue colour, also caused by an absence of pigment. Maisie’s all-white coat is appealing, giving her an unusual, ghost-like appearance. Unfortunately, the white coat colour gives an indication of a problem that Maisie has suffered since birth – she is completely deaf in both ears.
Fiona was aware of Maisie’s deafness before she took her on as a pet, and part of the agreement when she bought her was that she would not show her, nor breed from her. The deafness is caused by a genetic abnormality that would be passed down to her puppies if Maisie became a mother. For the sake of future generations of Boxers, it is wise not to perpetuate the same mix of genes. Deafness is linked to white coat colour in both dogs and cats. Coat colour and the colour of the back of the eye are both caused by pigment-producing cells, known as “melanocytes”. If the genes to produce these cells are absent, a white coat and blue eyes are the consequence. Hearing is made possible through a layer of specialised cells in the inner ear. These “hearing” cells originate from the same stem cells as pigment-producing cells. Therefore if an animal has no pigment in its body, it is likely that it will also be deficient in the specialised “hearing” cells, and it is likely to be deaf.
If a breeder produces a white puppy or kitten, deafness is often suspected, but it can be surprisingly difficult to assess their hearing. There are all sorts of tests that can be carried out, such as calling the animal’s name, knocking on windows, blowing whistles or spraying aerosol cans. Unfortunately, even young animals with normal hearing sometimes ignore these things, so a lack of response does not prove that they are deaf. Also, deaf animals can be very sensitive to vibrations, or they may have excellent eyesight that allows them to seem movement at the fringes of their vision, so they may seem to react to sound even when they are completely deaf. It is much easier to assess hearing in humans, since as soon as children are old enough to talk, they can be asked the simple question “Can you hear this?”
There is a definitive test for hearing in animals, but it is not widely available. The so-called Brainstem Auditory Evoked Response (BAER) test involves connecting electrodes up to the skull, and measuring the electrical activity in the brain. With normal hearing, electrical spikes are seen when a sound is made beside the ear. This test provides a good, objective way of checking the hearing in one or both ears. Unfortunately, the test is not available in Ireland at the moment. There is no cure for deafness in animals, although in recent years, vets at the University of Queensland, have implanted hearing aids successfully in dogs, improving their hearing significantly. These are unlikely to reach Ireland in Maisie’s lifetime!
Deafness has a profound impact on the life of an animal. Deaf dogs and cats cannot hear the sounds of hazards approaching, and they are very vulnerable to injury, especially from cars. Deaf animals have to be sheltered to some extent throughout their whole lives. It is safest to keep deaf cats as indoor pets, since there are too many risks if they are allowed to live free-ranging outdoor lives.
Maisie the Boxer loves going for walks, but she is never allowed off the lead. If she was allowed to run freely, she would not hear Fiona calling her back, nor would she hear important sounds of danger, such as oncoming traffic. Maisie is allowed to wander around her own garden on her own, but in public, she needs to be kept directly under Fiona’s control at all times. Fiona as a long extendable lead that allows her as much freedom as possible.
Maisie may be deaf, but her other senses seem to compensate by being more sensitive than normal. She has excellent vision, and Fiona is training her to obey hand signals instead of verbal commands, for actions such as “Sit”, “Stay”, and “Lie down”. Maisie also has a very delicate sense of smell. She has developed a complete aversion to cigarette smoke, wrinkling her nose and and whimpering if she detects even a whiff. If anybody in the house lights up, she starts to bark, and she does not stop until the cigarette is extinguished. She is proving to be an effective cure for smoking in the Plunkett household!
- Any dog or cat that has a white coat colour and blue eyes is likely to be deaf
- Deafness can be difficult to assess in pets
- Deaf animals need to be sheltered from risks such as road traffic throughout their whole lives.