Many dog breeds have to deal with epilepsy, a disease which is genetically passed on. In Finland, researchers have now found the genetic carrier for one of the many forms of epilepsy, and at the same time developed a test that can help breeders and veterinarians with the early detection of possible genetic abnormality.
This specific type of epilepsy occurs mainly in the Rhodesian Ridgeback. Despite their powerful body, once intended to hunt lions, breed specific selection has also inserted the gene for epilepsy into the breed. Approximately 2 percent of Rhodesian Ridgebacks develop this form of epilepsy, called myklonisc epilepsy. A form that is already manifest at an early age, around six months. The seizures usually occur during rest and may be triggered by light.
The first signs are usually uncontrolled muscle contractions in the rapidly growing pup. In dogs who get the disease 2/3 is affected by the so-called Grand Mal's heavy seuzures. Veterinary neurologist Professor Andrea Fischer (Small Animal Clinic, LMU Munich), molecular biologist Professor Hannes Lohi of the University of Helsinki and neurologist Professor Fiona James of the University of Guelph have sought to identify the responsible gene, and with success. It is a gene that plays a major role in a neurotransmitter controlling the operation of acetylcholine. A neurotransmittor is a substance that causes nerve impulses to transfer from one nerve to the other. The gene, DIRAS1, was until now, not associated with the occurrence of neurologic disorders. But research in over 600 Ridgebacks and 1,000 other dogs did put this gene forward as a solid candidate. In Ridgebacks approximately 15% of dogs indeed have the DIRAS1 gene, and thus are carriers.
Most types of canine epilepsy are multi genetic, and are transferred by a combination of genetic defects. In Ridgebacks it is but a single gene that is inherited recessively, i.e., two carriers can basically produce a affected animal. 1 out of 4 pups would statistically be affected by the disease from a mating of two carriers.
By selective breeding in a limited population such genes thrive within a breed, and can keep such a derogation hidden for a long time by breeding selectively. The newly developed diagnostic test can be done prior to the mating to prevent two carriers to produce affected pups, simply by not breeding two carriers. If puppies are to be examined afterwards, in fact 25% of them are carriers, but if those carriers will be excluded from breeding the disease may eventually be somewhat eliminated.
This study is also important because the same type of epilepsy occurs in humans. Further research may determine whether the same gene plays a role in humans too.