Congenital Sensorineural Deafness in Purebred White Cats
Andrew Sparkes, BVetMed, PhD, DECVIM, MANZCVS, MRCVS, Simply Feline Veterinary Consultancy, Dorset, United Kingdom
In the literature
Annemarie K, Liliana R, Małgorzata K, Andrzej P. Evaluation of the prevalence of congenital sensorineural deafness in a population of 72 client-owned purebred white cats examined from 2007 to 2021. BMC Vet Res. 2022;18(1):287. doi:10.1186/s12917-022-03378-2
The Research …
There is a documented link between cats with a white haircoat and blue eyes and inherited congenital sensorineural deafness (CSD), in which cochlear degeneration occurs due to lack of functioning melanocytes.1,2 A white haircoat typically results from suppression of melanocyte development via the KIT gene (except in a form of albinism that occurs in Siamese, Birman, and related breeds).2,3 Cats homozygous for the recessive wild-type allele (w/w) express normal pigmentation without any white.
White (WD) and spotting white (WS) are the other main alleles; both are dominant. WD encodes for a completely white haircoat and may also result in one or both irises being blue, whereas WS causes patchy loss of melanocytes, resulting in white regions or spots. WS is dominant to w, and WD is dominant to both w and WS. Cats with an all-white phenotype thus have a WD/WD, WD/WS, or WD/w genotype, and cats with spotted or patchy white areas have a WS/WS or WS/w genotype.
Genetics for deafness in white cats is not yet determined, but there is a link between an all-white haircoat (WD gene) and CSD.2-4 Homozygosity for WD and the number of blue eyes present are associated with an increased risk for deafness.2-4 Not all blue-eyed white cats are deaf, however, suggesting these traits are also influenced by other genes.
Cats can have unilateral or bilateral deafness that is usually complete but may be partial.2 Identifying deaf cats via brainstem auditory evoked response (BAER) testing is important for care of the cat (especially with bilateral deafness) and selection of cats for breeding. In studies of breeding white-haired domestic cats, 25% to 95% of white-haired offspring were deaf, depending on the genotype/phenotype of the parents.1,2,4-6
This study examined 72 client-owned white purebred cats from 6 breeds (ie, Maine coon, Norwegian forest, sphynx, British shorthair, Devon rex, Cornish rex) in Poland. Based on BAER testing, 12 out of 72 (16.7%) cats had CSD (unilateral, 11.1%; bilateral, 5.6%). Sex, breed, and presence of blue eyes did not affect CSD prevalence. Prevalence in this study is lower than in previous studies (ie, 20.2%-30.3%) of white purebred cats from Germany and the United Kingdom.5,6
… The Takeaways
Key pearls to put into practice:
BAER testing should be considered in purebred cats with white haircoats to exclude deaf cats from breeding programs.
This study found a relatively low prevalence of CSD and no apparent link to presence of blue eyes. This may reflect a bias in the population studied, as cats were presented for BAER testing prior to use in breeding programs, and owners may have already excluded cats with overt or suspected deafness.
Further studies are needed to explore the prevalence of CSD in client-owned pedigree and nonpedigree cats and to characterize the genotype of these cats.