Prevalence of Deafness in Dogs Heterozygous or Homozygous for the Merle Allele

Abstract

Background: Deafness in dogs is frequently associated with the pigment genes piebald and merle. Little is known about the prevalence of deafness in dogs carrying the merle allele.Objective: To determine the prevalence of deafness in dogs heterozygous and homozygous for the merle allele of the mouse Silver pigment locus homolog (SILV) gene.Animals: One hundred and fifty-three privately owned merle dogs of different breeds and both sexes. Methods: Hearing was tested by brainstem auditory-evoked response and classified as bilaterally hearing, unilaterally deaf, or bilaterally deaf. DNA from buccal cells was genotyped as either heterozygous or homozygous for the merle allele. Deafness association tests among merle genotype, eye color, and sex were performed by the w 2 test. Results: Deafness prevalence in merles overall was 4.6% unilaterally deaf and 4.6% bilaterally deaf. There was a significant association between hearing status and heterozygous versus homozygous merle genotype. For single merles (Mm), 2.7% were unilaterally deaf and 0.9% were bilaterally deaf. For double merles (MM), 10% were unilaterally deaf and 15% were bilaterally deaf. There was no significant association with eye color or sex.Conclusions: Deafness prevalence in merle dogs was greater than that in some dog breeds homozygous for the piebald gene, such as the English Cocker Spaniel, but comparable to, or lower than, that in the Dalmatian and white Bull Terrier. Dogs homozygous for the merle allele were significantly more likely to be deaf than heterozygotes.

Evaluation of the occurrence of canine congenital sensorineural deafness in puppies of predisposed dog breeds using the brainstem auditory evoked response

“…Histological studies have shown that inner ear structures develop physiologically prior to and after birth with atrophy of the stria vascularis occurring between the first and the fourth week of age in affected dogs (Johnsson et al, 1973;Strain et al, 2009). The age of the dogs included in our study ranged from 4 to 184 weeks, at which age the organ of Corti was fully developed.…”

“…CCSD results from degeneration of the stria vascularis and the hair cells as well as from the collapse of Reissner's membrane and the saccule in the inner ear. It can be pigment associated or neuroepithelial (Strain, 2015). The recessive alleles of the piebald locus (S) and the dominant alleles of the merle locus (M) are suspected of instigating hereditary deafness, although the causative genes and mode of inheritance have not been determined (Strain, 2015).…”

“…It can be pigment associated or neuroepithelial (Strain, 2015). The recessive alleles of the piebald locus (S) and the dominant alleles of the merle locus (M) are suspected of instigating hereditary deafness, although the causative genes and mode of inheritance have not been determined (Strain, 2015). The Bull Terrier (BT) is a breed with homozygous extreme white piebald (s w ).…”

Brainstem auditory-evoked potential in Boxer dogs

“…The fact that this report found more bilateral deafness than unilateral, when other published reports, studying other breeds, found a higher prevalence of unilateral than bilateral, is certainly the result of the small sample size. Deafness in dogs is frequently associated with altered expression of pigment genes, such as piebald and merle (Strain et al 2009), and several prior studies have identified statistically significant associations between deafness and a blue iris colour and white coat pigmentation (Strain 2004, Platt et al 2006, Famula et al 2007). Since not all dogs with piebald are deaf or have blue eyes, it can be argued that this variable outcome is the consequence of incomplete penetrance of a causative gene, or that one or more additional genes regulate the expression of the pigment gene (Strain 2011a).…”

Identification of Cryptic Allele for Merle Patterning in Dogs by Molecular Genetics Methods / Identifikacija Skrivenog Alela Za Mramoriranu Šaru Pasa Pomoću Metoda Molekularne Genetike

“…The coat color pattern is seen in the Collie, Australian Shepherd, Shetland Sheepdog, Catahoula Leopard Dog, Cardigan Welsh Corgi, Dachshund, and Great Dane breeds, and less commonly in the Chihuahua, American Pit Bull Terrier, American Staffordshire Terrier, Beauceron, Border Collie, Coolie, and others [3,4].…”