White rex and deafness

White Rex & Deafness
A study undertaken by the Nordic Rex Cat Association (Nordiska Rexringen) 2005
Information was submitted by Rex owners/breeders
via the Nordiska Rexringen website, e-mail, telephone and mail.
Compilation of Cornish Rex data: Eine Palm
Compilation of Devon Rex data: Camilla Söderström
Authors: Pernilla Ohlsson, Camilla Söderström, Eine Palm
Translation: Dominic Phillips, Camilla Söderström
Edited: Elizabeth Brown

There have been several studies on white cats and deafness, but as far as we know this is the first specific breed study. Earlier studies were on domestic white cats. The purpose of this study is to investigate how common deafness is in white Rex.

Previous documented studies have found, respectively, a prevalence of deafness of 64.9% and 85% in cats with two blue eyes, 39.1% and 40% in cats with one blue eye (odd-eyed), and 16.7% and 22% in cats with yellow eyes. These figures are taken from three well-known studies (Bosher & Hallpike, 1965; Mari, 1973; Bergsma & Brown, 1971; reviewed by Delack, 1984). Their studies involved 256 white domestic cats in total.

Taking the above figures into consideration, a similar result was forecast for our study of 247 white Rex cats (123 Devon Rex and 124 Cornish Rex) and indeed our studies conclude that there is a higher risk of deafness in blue-eyed Rex than in yellow-eyed Rex. However, the percentage of deaf cats in our study is significantly lower. One possible explanation for the apparently lower number of deaf cats in our study might be that there are cats with undetected partial deafness. Relatively few cats were tested with the objective Brainstem Auditory Evoked Response (BAER) test to see whether the cat really has full hearing in both ears. If a large percentage of the Rex in our study who were reported as hearing are in fact partially deaf, we can at least state that these cats compensate for it so well that neither their owner, breeder or veterinarian could detect it by their behaviour. This concludes that we can expect a partially deaf cat to live as good a life as a fully hearing one despite its disability.

White cats carrying the underlying cs Siamese dilution pigment gene can have blue eyes without deafness, and it has been suggested that the presence of this gene explains why purebred white cats are less often deaf than mixed-breed white cats (Pedersen, 1991) Data supporting this is not available.

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