SPINOCEREBELLAR ATAXIA IN PARSON RUSSELL AND JACK RUSSELL TERRIERS
The mutation for Spinocerebellar Ataxia with or without Myokymia and Seizures (SCA) was identified by the University of Missouri and a DNA test is available both through the Animal Health Trust and the University of Missouri. Affected dogs show signs of cerebellar ataxia as early as 2-6 months of age. At post-mortem examinations, degeneration can be found in the areas of the spinal cord that carry information to the cerebellum, hence the term spino-cerebellar ataxia. The coordination difficulties progress, but in addition other signs can develop. The majority of cases also develop myokymia, an involuntary twitching of the muscles. The myokymia also becomes progressively worse with age and can result in episodes of generalized muscle spasms and over-heating. In addition, a small percentage of dogs with SCA have true epileptic seizures, some as young as 10 weeks of age. Most dogs with SCA are also euthanized young due to poor quality of life.
The AHT also offer a test for Late onset ataxia (LOA) for the Parson Russell terrier (PRT) and Jack Russell terrier (JRT) known as the LOA test.
Other forms of ataxia
Neonatal Granuloprival Ataxia (NGA)
Another form of ataxia called Neonatal Granuloprival Ataxia (NGA) is also hereditary but the mutation has not yet been identified. As the name implies, coordination difficulties in dogs with NGA are apparent from the time they begin to walk, which clearly distinguishes it from the other forms. In these dogs, an area of the cerebellum called the granular layer degenerates. There is currently no test for this condition.
Both the University of Missouri and the Animal Health Trust have found a small number of dogs reported as suffering from cerebellar ataxia which began after weaning age that do not have either of the known mutation. This may represent another form of hereditary ataxia or they may represent an acquired cause of the disease.
The Animal Health Trust and the University of Missouri have discovered different mutations which cause similar, but distinct forms of the disease in Jack/Parson Russell Terriers. We are working to investigate those cases of ataxia which do not have either of the known mutations.
We would like to thank all the Breed Clubs and individuals who have contributed financially to this research and to all the Parson Russell terriers and their owners who have contributed DNA and information to this research.