A new study has revealed a marked improvement in the number of deaf dogs born in one of the world’s most recognisable breeds.
The research, carried out as part of a collaboration between the Kennel Club and the Animal Health Trust, examined the number of cases of deafness in Dalmatian puppies, how common it is and how this has changed over time. The study, the largest of its kind, analysed 26 years’ worth of hearing test data from nearly 9,000 Kennel Club registered Dalmatians.
Dalmatians are known to have an increased risk of deafness compared to other breeds. This type of deafness is inherited, with the function of one or both ears sometimes being affected. From a young age (around five to six weeks), dogs can have their hearing checked using a BAER (Brainstem Auditory Evoked Response) test. Breeders can use the results of these tests to help them select unaffected breeding dogs and reduce the risk of producing puppies with hearing loss.
Researchers analysed BAER test result data, alongside pedigree information from the Kennel Club database, and showed that deafness is moderately heritable, meaning that a parents genes do, to some degree, influence a puppy’s risk of deafness. Further analysis revealed that 17.8 per cent of Dalmatians tested were affected by deafness (13.4 per cent in one ear and 4.4 per cent in both ears). During the 26 years of data that were looked at, the overall number of dogs with deafness fell by about a third - the number of dogs that were deaf in one ear decreased by over a quarter, while dogs with deafness in both ears decreased by a half.
The study further analysed physical descriptions of the dogs recorded during their BAER test, and confirmed findings from previous studies - that dogs with blue eyes are at increased risk of deafness, while those with a patch of colour on their head have a decreased risk of deafness. During the 26 years of study data, the number of dogs with blue eyes decreased, while those with a patch of colour on their head increased.
Dr Tom Lewis, Quantitative Geneticist and Genetics Research Manager at the Kennel Club said: “Our research shows that a Dalmatian’s genes can influence its puppies’ risk of deafness. We suspect that there are a number of genes and other factors interacting and influencing a dog’s risk of hearing loss, so reducing deafness in the breed is not as straightforward as it seems.
“Analysis shows that for decades, Dalmatian breeders have been actively reducing the incidence of hearing loss in the breed by carefully selecting dogs, not only based on their ability to hear, but also other traits known to influence this. The breed clubs and breeders have done an incredible job at reducing the prevalence of hearing loss and with data from our new study, we hope can help find ways to help make an even bigger impact on the health of the breed.”
To read the study in full visit: http://dx.doi.org/10.1111/jvim.15776