CNS Atrophy with Cerebellar Ataxia is associated with a deletion of the SELENOP gene, which codes for selenoprotein P. Selenoprotein P is the primary storage and transport protein for selenium and is likely required for transport of selenium into the CNS in dogs. Heterozygous (1 copy) dogs were found to have a 25% reduction in blood selenium levels, and homozygous (2 copy) dogs showed a 70% reduction in selenium compared to normal dogs. CACA is characterized by a variety of neurologic signs which may include intention tremors, truncal wobbling, elevated muscle tone, decreased swallowing reflex, muscle spasm and short spastic fits. Severity of clinical signs can vary and range from an inability to stand or walk normally, to a mild and relatively stable condition with fewer neurologic deficits. Signs are often first observed around two weeks of age in affected dogs and have a tendency to progress. Affected puppies have also been reported to gain less weight than their unaffected littermates.

As this genetic variant is associated with a defect in selenium transport that can manifest as central nervous system atrophy and cerebellar ataxia, consistently feeding a diet high in selenium is theorized to be beneficial to affected puppies. Please note, however, this has only been proven effective in a mouse model. Unfortunately, severely affected dogs may require euthanasia due to welfare concerns.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disorder is autosomal recessive, meaning two copies of the variant are needed for a dog to be at an elevated risk for being diagnosed with the condition. A carrier dog with one copy of the CNS Atrophy with Cerebellar Ataxia (Discovered in the Belgian Shepherd) variant can be safely bred with a clear dog with no copies of the CNS Atrophy with Cerebellar Ataxia (Discovered in the Belgian Shepherd) variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that clinical signs similar to the ones associated with the CNS Atrophy with Cerebellar Ataxia variant could develop due to a different genetic or clinical cause.