Deafness in Dalmatians

Congenital Deafness: Where does it stem from?

History

  • There are two types of Deafness in Dogs:

    1. Acquired

    • Deafness that is obtained after birth. Usually caused by Ear infections, Neoplasia, Drug toxicity, Loud noise exposure, and old age

    2. Congenital

    · Deafness that the animal is born with (obtain during inheritance)


  • Congenital Deafness occurs in numerous breeds but is most popular in Dalmatians

  • As many as 29.9% of Dalmatians are born deaf in one(unilateral) or both (bilateral) ears

Genetic Transmission


  • Usually not known
  • There is no sex-linked deafness recognized in dogs but there is in humans
  • Some records show that it is an Autosomal recessive disorder with incomplete penetrance (meaning that individuals may inherit the disorder but don't show any signs of the syndrome)
  • This Autosomal recessive gene is called the "extreme piebald" gene.
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Genotypes

Based on the Table Above:


Mating two heterozygous dogs carrying the recessive deafness gene yields:

· 25% chance of homozygous dominant offspring (not carrying the deafness gene)

· 50% chance of heterozygous offspring carrying the gene

· 25% chance of homozygous recessive offspring with the deafness gene


Mating a homozygous dominant dog with a heterozygous carrier yields:

· 50% chance of homozygous dominant offspring (not carrying the deafness gene)

· 50% chance of heterozygous offspring carrying the gene

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Phenotypes

  • As mentioned earlier, the extreme piebald gene has been correlated with deafness in this breed, but ironically this gene gives the breed its bright white coat.


  • Many researchers believe that deafness develops due to the "suppression of pigment-producing cells which are necessary to the health of the stria vascularis, the vascular bed lining the outer wall of the cochlear duct; this leads to damage of the cochlear and sensory hair cells which is needed for hearing." (as depicted above)



  • It has also been studied that Dalmatians with blue eyes have been associated with an increased likelihood of deafness (pictures below)

What's the problem?

Many bilateral deaf puppies are euthanized (via the recommendation of Dalmatian Club of America) because they are believed to:


  • be poor pets
  • difficult to train
  • aggressive (they are prone to biting as a result of being startled)
  • require excessive care


Those who aren't executed as puppies usually are abandoned and end up in shelters that later euthanize them if they are not adopted

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How do we fix it?

Breeders are recommend to have their puppies undergo a Brainstem Auditory-Evoked Response (BAER) test to determine if they are deaf in one ear, both ears, or neither


  • It is completely harmless and can be given around 6 weeks of age
  • This test uses a computer to record electrical activity of the brain in response to a sound stimulate
  • A foam microphone is inserted in the pup's ear and a stimulus click is produced
  • Looking at the figure above, we can see that the dog on the right cannot hear properly out of its left ear


Some other recommendations to breeders are:

  1. Do not breed bilateral or unilateral deaf Dalmatians
  2. Do not breed Dalmatians with blue eyes

Opinions

More research should be conducted on this issue, so that there is further evidence as to why this is piebald gene is causing deafness in many Dalmatians but is not as prominent in other breeds with pure white coats.


No one knows how a deaf puppy will turn out, so breeders and handlers shouldn't assume that they will be terrible pets solely based on their lack of hearing. With proper training a non hearing dog can do just about everything a hearing dog can do (see video clip below).


Interestingly enough, some deaf dogs are not allowed participate in dog shows: http://www.wds2015.com/allegati/EXP-REG-en%20FCI.pdf

If dogs are predominately judged on their appearance ( weight, eyes, head, shoulders, color, coat, etc), why does it matter if the dog cannot hear?

Deaf Dog Training

Document References

  1. Cargill, E.J, Famula, T.R, Strain, G.M, and Murphy, K.E. "Heritability and Segregation Analysis of Deafness in U.S. Dalmatians." www. genetics.org. March 2004. Web. 28 April 2016. http://www.genetics.org/content/166/3/1385.short
  2. Christopher. "Why Dalmatians are a Train Wreck." www.border-wars.com. May 2013. Web. 27 April 2016. http://www.border-wars.com/2013/05/why-dalmatians-are-a-train-wreck.html
  3. "Dalmatian Breeders Urged to Take Steps to Breed Against Deafness." www.purinaproclub.com. May 2011. Web. 27 April 2016. https://www.purinaproclub.com/resource-library/pro-club-updates/dalmatian-breeders-urged-to-take-steps-to-breed-against-deafness
  4. Strain, George. "Genetics of Deafness in Dogs." www. lsu.edu. September 2005. Web. 28 April 2016. http://www.lsu.edu/deafness/genetics.htm
  5. Webb, Aubrey. "Hearing and Deafness in Dogs." www.ucalgary.ca. University of Calgary,September 2007. Web. 28 April 2016. http://www.ucalgary.ca/webblab/files/webblab/Hearing%20and%20Deafness%20in%20Dogs%20NBVMA%2009%2007.pdf
  6. Place, Albert. "Regulations for FCI Dog Shows." www.wds2015.com. April 2015. Web. 29 April 2016. http://www.wds2015.com/allegati/EXP-REG-en%20FCI.pdf