Seizures are the most common neurological problem reported in dogs that are owned as pets. Some estimate that between 0.5% and 5.7% of all dogs have experienced seizures sometime in their lives. However, this is likely to be an underestimate due to the fact that owners sometimes do not realize that certain unusual behaviors can be seizures. Importantly, the lifetime prevalence of seizures varies considerably across breeds. For example, a survey of Belgian Tervuren breeders suggests that as many as 17% of American-bred Belgian Tervurens have had at least one seizure in their. In addition to Tervurens, 25-30 dog breeds are reported to have a higher than average prevalence of seizures. These include some popular breeds, such as Beagle, Cocker Spaniel, German Shepherd Dog, Labrador Retriever, Poodle, Bernese Mountain Dog, Keeshond, and Saint Bernard. There is no treatment for this fatal disease. The researchers have devised a test that will allow the disease to be counteracted in dogs through controlled breeding.
The term "epilepsy" actually describes a very broad group of disorders characterized by predisposition to seizures that have different causes, ages of onset, clinical signs and outcomes. The seizures themselves are the result of brain dysfunction due to a sudden, abnormal, excessive, and disorganized discharge of brain cells. A diagnosis of epilepsy requires at least two unprovoked seizures. Epilepsies are divided into two major types. Symptomatic epilepsies are caused by head injuries, developmental abnormalities, infections, presence of tumors or degenerative conditions. In idiopathic epilepsies no obvious reason or any other neurological abnormalities are found, and the origin is mainly genetic.
The progressive myoclonus epilepsies (PMEs) belong to a group of symptomatic epilepsies and are a broad group of inherited disorders characterized by myoclonus and progressive neurological deterioration. Myoclonus refers to sudden, involuntary jerking of a muscle or group of muscles. Myoclonic twitches or jerks usually are caused by sudden muscle contractions. PMEs are divided into five main diseases or disease groups: Unverricht-Lundborg disease (ULD/EPM1), Lafora disease (LD/EPM2), neuronal ceroid lipofuscinoses (NCLs), sialidoses, and myoclonic epilepsy with ragged-red fibers (MERRF). In all of these genetic mutations have been identified and account for the majority of PME cases. A first canine epilepsy gene has already been discovered for LD.
Lafora disease is inherited from parents who are carriers of mutations in one of the two genes associated with the pathology. These genes are called laforin (named after Dr. Lafora) and malin (from the French expression "le grand mal", used to refer to epilepsy). The disease is characterized by the accumulation in neurons of abnormal starch-like polyglucosan masses known as Lafora bodies. In humans, Lafora disease (LD) is a severe, progressive form of epilepsy that begins in childhood. Lafora bodies have also been described in the central nervous system of dogs with neurologic disease and in the skeletal muscle fibers and peripheral nerves of dogs with familial myoclonic epilepsy. The disorder s has been described in young dogs, mainly Beagles, Poodles, and Basset Hounds marked by general depression, seizures and lethargy.
According to clinical, pathological and genetic characterization the LD/EPM2 disease in dogs is actually the same disease as LD in humans. Recently, a gene EMP2 for progressive myoclonic epilepsy (PME) has been identified in a population of purebred Miniature Wirehaired Dachshunds. About 5% of the breed suffers from this autosomal recessive disease, which was shown to be analogous to the human disorder, Lafora disease. Researchers also found the same mutation in other breeds and showed that the disease is recurrent in dogs because of a peculiar feature of their EPM2 gene containing a stuttered repetitive stretch of DNA, which predisposes the dogs to mutation and the disease.
- Molecular biology of progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1). Kirsi Alakurtti
- The canine genome. Elaine A. Ostrander, and Robert K. Wayne