Genetic basis of Adult onset deafness in Border Collies - typically begins between 3 and 7 years of age, earlier than typical geriatric hearing loss seen in dogs. The condition is strongly associated with genetic variations identified through genome-wide association studies (GWAS) on canine chromosome 6. Variants in genes such as USP31 and RBBP6 have been implicated; USP31 is linked to the NF-κB pathway, which can influence tissue damage, while RBBP6 is critical for cochlear development. The inheritance pattern fits best with an autosomal dominant mode, with variable expressivity and gradual progression of hearing loss. No single causative mutation has been definitively identified yet; rather, several single nucleotide polymorphisms (SNPs) serve as markers indicating increased risk. Linkage association tests (using SNP markers) are currently used to identify dogs at risk or carriers, though these are markers rather than direct mutation tests.
Pathophysiology - The exact molecular mechanism is not fully elucidated but involves cochlear biology and possibly tissue damage pathways. Hearing loss involves degeneration of neural and sensory cells in the cochlea responsible for hearing, particularly affecting the ability to hear high-frequency sounds and commands.
Complications - Hearing loss progresses gradually, impacting the dog's ability to respond to distant or whistle commands, critical for their role as working herding dogs. Deafness typically is not congenital but develops in adulthood, often unnoticed until it interferes with the dog's work. Late recognition can affect the dog's training and quality of life.
Why This Matters to Breeders and Vets - For breeders, adult onset deafness is challenging because affected dogs can be bred before signs appear. Genetic testing by linkage association can help identify dogs at increased risk to make informed breeding decisions. Veterinarians can assist in early diagnosis through BAER (brainstem auditory evoked response) testing and guide management. Preventing propagation of the risk alleles improves breed health and working capability.
Summary - Adult Onset Deafness in Border Collies is a genetically influenced, autosomal dominant hearing loss disorder beginning often between 3 and 7 years. Genetic association studies have identified risk markers in genes like USP31 and RBBP6, which can be detected by linkage association testing through SNP panels. This allows breeders to identify at-risk dogs before clinical signs appear, helping to guide breeding decisions to maintain good hearing and working capacity in the breed.