Mythbuster Monday: Congenital Deafness is Related to Coat Color in Paints and Pintos

On Mythbuster Monday, we tackle a variety of equestrian myths to either bust or confirm. Today’s discussion: Congenital deafness is related to coat color in Paint and pinto horses?

It’s Mythbuster Monday, where Horse Nation dives into different equestrian myths and provides research-based evidence to either bust or confirm those myths. Today’s topic: Congenital deafness is related to coat color in Paint and pinto horses. Are certain colors more prone to deafness?

Myth: Congenital deafness is related to coat color in paint and pinto horses

Myth or Fact: Fact

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Congenital deafness means that the hearing loss was present at birth. Reported causes of congenital deafness in horses include trauma to the dam or foal during the gestational period, inflammation or infection of the peripheral auditory pathways, and gentamicin intoxication.

But, is it related to coat color in Paint and pinto horses?

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According to PhD, Ed Kane, Paint horses with blue eyes are more likely to experience congenital deafness than any other type of horse. However, he writes that although Paint horses are the most common to be diagnosed with congenital deafness, any horse with a significant amount of white in its coat and eye color can be born deaf due to a genetic link between deafness and coat and eye color.

Kane goes on to explain Overo Lethal White Foal Syndrome (OLWFS). This syndrome is linked white skin pigment, blue eyes, and deafness. It involves a lack of melanocytes which are critical to proper cochlear function. Without melanocytes in the inner ear, the stria vascular doesn’t develop of function normally. Congenital deafness in horses is associated with the abnormal development of the melanocytes. This is mostly seen in American Paint Horses and relates to the white spotting in their coats and blue eyes.

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PhD George Strain also states that congenital deafness can be inherited, and is known to occur, in horses with white coloring. The acquired deafness is connected to a lack of melanin production which is the same result that gives paints and pintos their coloring.

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In a research article investigating deafness in American Paint Horses,14 deaf American Paint Horses, 20 suspected deaf American Paint Horses, and 13 non-deaf American Paint Horses and Pintos were evaluated. Horses were categorized by color pattern and eye color. They were then tested for the EDNBR gene mutation. This is a gene mutation associated with overo lethal white foal syndrome. Brainstem auditory-evoked responses (BAER) were then performed. Results showed all 14 deaf horses had loss of all BAER waveforms. Most of these horses had the splashed white or splashed white frame blend coat pattern. Other patterns included frame over and tovero. All of the deaf horses had extensive head and limb white markings. All deaf horses had heterochromia, but most had two blue eyes. Ninety-one percent of the deaf horses were found to have the EDNBR gene mutation.

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Another article by Dr. Stacey Oke asserts that deafness is not frequent in horses. However, most cases are seen in horses with genetic mutations that cause specific coat colors in American Paint Horses.

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After diving into the literature, there is a correlation between congenital deafness and paint and pinto horses. This is because the same gene mutation that creates the splashed color in these breeds is also the gene mutation that causes the congenital deafness.

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