ISSN 2398-2969      

Deafness: hereditary

icanis

Introduction

  • Hereditary deafness.
  • Rare in total canine population but may occur commonly in specific breeds, eg Dalmatian, Border Collie, Great Dane, English Setter.
  • Most common form of deafness in dogs.
  • Cause: autosomal dominant or recessive gene. (X-linked occurs in humans. The mode of inheritance has not been demonstrated yet in dogs).
  • Associated with coat color (white or merle) and blue irises.
  • Signs: bi- or unilateral deafness.
  • Diagnosis: brain stem auditory evoked potentials.
  • Treatment: none.
  • Prognosis: no cure but unilaterally deaf animals can lead normal life.
    Print off the owner factsheet on Living with a deaf dog Living with a deaf dog to give to your client.

Pathogenesis

Etiology

  • Two genes for color are linked to deafness in dogs.
  • An autosomal dominant gene for coat colour M (merle), eg Harlequin Great Dane Great Dane , Old English Sheepdog Old English Sheepdog.
  • 25% of matings between two Harlequins (Mm) will result in homozygous (MM) offspring.
  • Will have solid white coat, blue eyes, deaf and/or blind and sterile.
  • Heterozygous merles can also be deaf. Likelihood increases with amount of white in coat.
  • The second gene is for coat color piebald (and extreme piebald), eg Dalmatian Dalmatian and English Setter English Setter.
  • Relationship between this gene and deafness not fully understood.
  • In these breeds deafness may be polygenic or a syndrome with incomplete penetrance.

Predisposing factors

General
  • Genotype of parents.
  • Genotype of offspring.
  • Breed.

Pathophysiology

  • Neonatal puppies → absence of melanocytes (function unknown) in stria vascularis of cochlea → degeneration of stria vascularis → degeneration of hair cells of cochlear ducts → sensorineural deafness.
  • Dobermans → direct loss of cochlear hair cells → deafness with vestibular signs. Simple autosomal recessive.

Timecourse

  • Degeneration of inner ear structures completed by 5 weeks old.

Diagnosis

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Treatment

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Prevention

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Coppens A G et al (2000) Bilateral deafness in a Maltese Terrier and a Great Pyrenean puppy - inner ear morphology. J Comp Pathol 122 (2-3), 223-228 PubMed.
  • Strain G M (1999) Congenital deafness and its recognition. Vet Clin North Am Small Animl Pract 29 (4), 895-907 PubMed.

Other sources of information

  • Knowles K (2000)Deafness in dogs and cats.In:Current Veterinary Therapy XII.Ed: R W Kirk. Philadelphia: W B Saunders. pp 971-974.

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