Prevalence, heritability and genetic correlations of congenital sensorineural deafness and coat pigmentation phenotype in the English bull terrier.

Background: Congenital sensorineural deafness (CSD) is the most common type of deafness in dogs and it occurs in numerous canine breeds including the English bull terrier. This study estimates prevalence, heritability and genetic correlations of CSD and coat pigmentation phenotypes in the English bull terrier in England.

Results: Hearing status was assessed by brainstem auditory evoked response in 1060 English bull terrier puppies tested at 30-78 (mean 43.60) days of age as complete litters. Gender, coat and iris colour and parental hearing status were recorded. The prevalence of CSD in all 1060 puppies was 10.19 % with 8.21 % unilaterally deaf and 1.98 % bilaterally deaf. The coat was predominately coloured in 49.15 % puppies and white with or without a patch in 50.85 % puppies. The majority (96.29 %) of deaf puppies had a white coat (with or without a patch); 19.29 % of the puppies with a white coat (with or without a patch) were deaf. Heritability and genetic correlations were estimated using residual maximum likelihood. Heritability of hearing status as a trichotomous trait (bilaterally normal/unilaterally deaf/bilaterally deaf) was estimated at 0.15 to 0.16 and was significantly different to zero (P < 0.01). Heritability of coat pigmentation phenotype (all white/white with patches/coloured) was 0.49 (standard error 0.077). Genetic correlation of CSD with coat pigmentation phenotype was estimated at -0.36 to -0.37 (CSD associated with all white coat), but was not significantly larger than zero (P > 0.05). Analysis of CSD in all white and white patched puppies only estimated the heritability of CSD as 0.25 and was significantly greater than zero (P < 0.01), and the heritability of coat colour (all white/white with patches) as 0.20 (standard error 0.096). The genetic correlation was estimated at -0.53 to -0.54 (CSD associated with all white coat) but was just above the statistical threshold determining significant difference to zero (P = 0.06).

Conclusions: These results indicate that CSD occurs predominantly in white English bull terriers and there is genetic variation in CSD beyond that associated with coat colour.