Part of the official UK Kennel Club testing scheme in Norwegian Buhund
Hereditary ataxias are a group of movement disorders characterised by incoordination of movement. Ataxias have been described in the number of dog breeds, and the disease has been reported in Norwegian Buhunds.
Clinical signs of the buhund type of ataxia typically start in young puppies. The first signs are usually loss of balance, gait abnormalities and head tremors. The disease is slowly progressive, and eventually dogs cannot walk without falling repeatedly, or cannot rise to their feet. Sadly, there is no treatment or cure for cerebellar ataxia and the dogs are often euthanised due to poor quality of life.
The single nucleotide substitution in the gene called KCNIP4 that causes hereditary cerebellar ataxia in Norwegian buhunds is recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop ataxia during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop ataxia as a result of the KCNIP4 mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop ataxia should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers can be bred from safely, provided they are mated to a dog that has also been tested and is clear of the KCNIP4 mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers, so should be tested themselves prior to breeding. Breeding carriers to tested, clear dogs is safe, in terms of avoiding dogs affected with ataxia, and will help to maintain the genetic diversity of a breed. It is therefore encouraged, particularly in the first few generations following the availability of a new genetic test, so that other desirable characteristics and traits can be preserved before the frequency of the disease mutation within the breed is gradually reduced.