Susan Sommerlad

Investigation into the genetic basis of Congenital Hereditary Sensorineural Deafness in the Dog, and the Surgical Treatment of Conductive Deafness in the Dog

Deafness is a significant problem in dogs and our research explores two common forms, Acquired Conductive Deafness (ACOD) and Congenital Hereditary Sensorineural Deafness (CHSD). Surgical treatment of conductive deafness: Research into conductive deafness resulted in the first surgical placements of Bone-Anchored Hearing Aids (Baha®) in dogs that had undergone salvage surgery for Otitis Externa and Media. These Baha® placements led to successful surgical treatment of ACOD. Bone augmentation around Baha® fixtures: Further research into the use of guided bone augmentation to increase cranial bone depth around the Baha® fixture was explored. This procedure facilitated the use of the Baha® in smaller dogs and may have paediatric application. Further surgical research is planned. The Diagnosis of Congenital Hereditary Sensorineural Deafness using Brainstem Auditory Evoked Response Testing: Congenital Hereditary Sensorineural Deafness is an inherited form of deafness and affects pups by 4-6 weeks of age. A Brainstem Auditory Evoked Response (BAER) testing programme, assists breeders in the design of a selective breeding plan to reduce the prevalence of this disease. Research into phenotypic analysis for markers linking pigmentation and CHSD was performed in Australian Cattle Dogs: Both bilateral facial masks and pigmented body spots were independently associated with a reduced risk of CHSD. The odds of deafness in female dogs were estimated to be 1.9 times higher than in males. Breeding for bilateral facial masks and body spots, may assist in reducing the prevalence of CHSD in the Australian Cattle Dog. Exploring the genetic basis of CHSD: Initial candidate gene studies led on to a microsatellite genome-wide screen was performed on a pedigree of 315 ASTCD,The deaf phenotype mapped to CFA10 and was consistent with the model of an autosomal recessive trait with incomplete penetrance of 0.72. Further genetic research is planned in Australian Cattle Dogs and Australian Stumpy Tail Cattle Dogs.