There are several factors that determine whether a dog might be born deaf and this includes whether they have the piebald, merle or white piebald genes in their makeup. Dogs with these genes are at greater risk of being born with hearing disorders which can be slight to extreme. In short, deafness in dogs is linked to their individual coat colours which is often something that breeders have done their utmost to achieve which often results in a dog either being born deaf or they may have some other form of hearing problem. This is often a consequence of extreme selective breeding.
When it's an inherited problem, the gene defect is autosomal dominant, but it could be recessive or sex-linked too. There may even be several genes responsible, but often the exact reason remains unclear although certain breeds and dogs with specific colouring, as previously mentioned tend to be more at risk of being born deaf than others. There are around eighty breeds known to suffer from congenital deafness and it's dogs with the merle gene or the piebald gene that are the most at risk. Some of the breeds which are more prone to congenital deafness include the following:
It's worth noting that not all dogs that carry either the merle or the piebald gene would be born deaf.
The condition typically develops during the first weeks of a puppy being born and while their ear canals are still closed. It is usually because much needed blood supply to the cochlea is negatively impacted which results in nerve cells found in the cochlea dying off and this causes permanent deafness. For the moment, the reason why this vascular degeneration happens remains unclear, but what is known is that it is connected to the absence of melanocytes in blood vessels which are the cells responsible for producing pigment. One of the functions of these cells is to maintain the correct concentrations of potassium in the fluids that surround hair cells found in the cochlea which are essential for the survival of the stria which is the outer wall of the cochlea duct.
The condition is one that can be acquired which in short means that a dog may go deaf because they have suffered some sort of intrauterine infection. Certain drugs can also be responsible for a dog developing the condition. Other diseases that could cause a dog to lose their hearing include liver disorders or puppies may have been exposed to toxins just before they were born or very soon afterwards. Some dogs may go deaf when they reach their golden years which is referred to as presbycusis. As such their lack of hearing is not a genetic health concern, but rather a condition that develops for other reasons over time.
For the moment, there is no genetic test available to determine whether a dog may pass on congenital deafness to their offspring, but there is a test called a brainstem evoked auditory response (BAER) which can be carried out a dog suspected of being deaf to establish just how badly their hearing has been impacted. People who breed dogs known to suffer from congenital deafness should not use them in a breeding programme which is the only way of reducing the risk of puppies being born deaf. Breeders should always have puppies that carry the merle or piebald gene BAER tested when they are old enough and before they are rehomed.
Although responsible breeders make sure their stud dogs have good hearing and will typically have puppies BAER tested, there is never any sort of guarantee that a dog would not be born deaf. However, dogs born deaf can lead full and happy lives providing their owners are aware of their pet's condition and therefore understand that more is needed in the way of care right from the word go. With this said, a dog born deaf is very capable of relying on their other senses to make up for being deaf. These other senses which includes sight, scent and their unique talent for being able to read a person or other animal's energy become even more acute which allows deaf dogs to cope extremely well in a hearing world.