Deafness

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Congenital hereditary sensorineural deafness (CHSD) is a common autosomal recessive[1] genetic disease which occurs in many dog breeds[2].

Other causes of deafness in adult dogs include:

Deafness is commonly observed in the Dalmatian, Bull Terrier, Border Collie and Australian Cattle Dog and is frequently associated with homozygosity with the pigment genes piebald and merle[3].

In some breeds, CHSD is associated with a lack of cochlear melanocytes in the stria vascularis, certain coat characteristics, and potentially, abnormalities in neuroepithelial pigment production, such as heterochromia.

In Dalmatians with heterochromia, approximately 20% have congenital deafness or reduced auditory responses as determined by brainstem auditory-evoked responses[4]. In this breed, deaf puppies possess some cochlear hair cells, however during maturity lose all hair cells and are replaced by supporting cells[5].

Deafness is usually observed clinically form 6 weeks of age and can be confirmed with testing by auditory stimuli, evoked otoacoustic emissions[6] or using brainstem-evoked testing.

Deafness can affect one or both ears, and is an all or nothing phenotype in the affected ear[7]. Bilaterally deaf pups are often identified by breeders without clinical testing, but unilateral deafness is difficult to detect without brainstem auditory evoked response testing[8].

In solid-colored coat breeds, such as the Doberman, deafness is usually associated with cochlear neuroepithelial degeneration[9]. In other breeds, it is associated with a lack of coat and iris melanocyte pigmentation as well as degeneration of the stria vascularis of the cochlea during the first four weeks of life[10].

Although deafness in dogs has a limitation for functionality as both work animals and pets, there is no justification for euthanasia of these dogs when diagnosed providing other quality of life parameters are fulfilled[11].

References

  1. Sommerlad S et al (2010) Congenital sensorineural deafness in Australian stumpy-tail cattle dogs is an autosomal recessive trait that maps to CFA10. PLoS One 5(10):e13364
  2. Sommerlad SF et al (2012) Prevalence of congenital hereditary sensorineural deafness in Australian Cattle Dogs and associations with coat characteristics and sex. BMC Vet Res 8:202
  3. Strain GM et al (2009) Prevalence of deafness in dogs heterozygous or homozygous for the merle allele. J Vet Intern Med 23(2):282-286
  4. Holliday TA et al (1992) Unilateral and bilateral brainstem auditory-evoked response abnormalities in 900 Dalmatian dogs. J Vet Intern Med 6(3):166-174
  5. Sampaio AL et al (2010) Histopathological morphometric study of cochleosaccular dysplasia in Dalmatian dogs. Int J Pediatr Otorhinolaryngol 74(8):934-938
  6. Gonçalves R et al (2012) Clinical evaluation of cochlear hearing status in dogs using evoked otoacoustic emissions. J Small Anim Pract 53(6):344-351
  7. Strain GM (2004) Deafness prevalence and pigmentation and gender association in dog breeds at risk. Vet J 167:23–32
  8. Sims MH & Moore RE (1984) Auditory-evoked response in the clinically normal dog-early latency components. Am J Vet Res 45:2019–2027
  9. Wilkes MK & Palmer AC (1992) Congenital deafness and vestibular deficit in the Dobermann. J Small Anim Pract 33:218–224
  10. Anderson H et al (1968) Genetic hearing impairment in the Dalmatian dog. An audiometric, genetic and morphological study in 53 dogs. Acta Otolarygol Suppl 232:1–34
  11. Rollin BE & Lunetta L (2000) An ethicist's commentary on euthanizing deaf Dalmatian puppies. Can Vet J 41(6):438-439