Common Symptoms
Juvenile myoclonic epilepsy (Rhodesian ridgeback type) is a neurological disease affecting Rhodesian ridgebacks. Dogs affected with this type of epilepsy present between 6 weeks and 1 ½ years of age with frequent, uncontrolled muscle movements known as “myoclonic jerks” which may resemble electric shocks or a startle response. Myoclonic jerks most commonly occur in the limbs, head, eyelids, and jaw and range from mild, nearly imperceptible movements to severe, dramatic movements resulting in jumping or running short distances, sometimes into objects. Myoclonic jerks are most common when dogs are relaxed or in the beginning stages of sleep. Some dogs with this type of epilepsy may experience increased incidence of jerks after vaccination or when exposed to high ambient temperatures or various visual stimuli, including light flashes or sudden change in light intensity. Affected dogs appear normal between episodes, but may appear disoriented or agitated immediately afterward. The disease may progress to generalized seizures in some dogs.
Breed-Specific Information for the Rhodesian Ridgeback
The Mutation of the DIRAS1 gene associated with juvenile myoclonic epilepsy (Rhodesian ridgeback type) has been identified in Rhodesian ridgebacks. Though the exact frequency in the overall Rhodesian ridgeback population is unknown, approximately 15% out of 537 Rhodesian ridgebacks tested from 13 countries were carriers of the mutation and 3.7% were at-risk.
Testing Tips
Genetic testing of the DIRAS1 gene in Rhodesian ridgebacks will reliably determine whether a dog is a genetic Carrier of juvenile myoclonic epilepsy (Rhodesian ridgeback type) 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 DIRAS1 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. Rhodesian ridgebacks 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
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Wielaender F, Sarviaho R, James F, Hytonen MK, Cortez MA, Kluger G, Koskinen LLE, Arumilli M, Kornberg M, Bathen-Noethan A, Tipold A, Rentmeister K, Bhatti SFM, Hulsmeyer V, Boettcher IC, Tastensen C, Flegel T, Dietschi E, Leeb T, Matiasek K, Fischer A, Lohi H. Generalized myoclonic epilepsy with photosensitivity in juvenile dogs caused by a defective DIRAS family GTPase 1. Proc Natl Acad Sci U S A. 2017 Mar 7;114(10):2669-2674.
[PubMed: 1614478114]
