Late Onset Ataxia

Common Symptoms

Late-onset Ataxia is an inherited neurologic disease affecting Parson Russell Terriers. Dogs with this disease present with incoordination and loss of balance between 6 to 12 months of age. The disease is progressive with affected dogs developing a “prancing” gait and often falling. With time dogs have difficulty standing and are usually euthanized by 2 years of age due to a poor quality of life.

Breed-Specific Information for the Parson Russell Terrier

The Mutation of the CAPN1 gene associated with late onset Ataxia has been identified in Parson Russell Terriers. Though the exact frequency in the overall Parson Russell Terrier population is unknown, 33% out of 205 clinically healthy Parson Russell Terriers tested were carriers of the mutation.

Testing Tips

Genetic testing of the CAPN1 gene in Parson Russell Terriers will reliably determine whether a dog is a genetic Carrier of late onset Ataxia. Late Onset Ataxia is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the CAPN1 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Parson Russell Terriers that are not carriers of the mutation have no increased risk of having affected pups.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.

References

• Development DNA Test for Late Onset Ataxia in the Parson Russell Terrier http://www.aht.org.uk/cms-display/genetics_loa.html
• Forman OP, De Risio L, Mellersh CS. Missense mutation in CAPN1 is associated with spinocerebellar ataxia in the Parson Russell Terrier dog breed. PLoS One. 2013 May 31;8(5):e64627. [PubMed: 23741357]