Canine Epilepsy

Canine epilepsy is a brain disorder that is manifested in the form of recurrent seizures, and is the most common chronic neurological disorder seen in dogs. The majority of dogs being diagnosed with idiopathic epilepsy, which is often described as having no underlying cause, though it is thought to have a genetic basis, are diagnosed between the age of 3 and 5 (Chandler 2011). Nearly all breeds of dogs have recorded incidents of idiopathic epilepsy and when we compare them with other domestic animals, the dog has the highest incidence of epilepsy, ranging from 0.5% to 4.1% dependent on breed. Seizures that occurred before or after this age range are more likely to be caused by infection, trauma, a metabolic disorder, or some other measurable disease process (Oberbauer, Grossman, Irion, Schaffer, Eggelston & Famula 2002). 

The University of Prince Edward Island (UPEI) (2014) have compiled a database of canine inherited disorders, in which they cite idiopathic epilepsy as a genetic disorder, and while the exact genetic make-up of this disorder is largely unknown, they suggest that more than one gene is involved. This is supported by Oberbauer et al (2002) who state that ‘there is a growing body of evidence that supports a hereditary basis for idiopathic epilepsy in the dog’, and by Rusbridge (2014) who describes a late onset form of epilepsy called Lafora’s disease (usually occuring in animals over seven years of age), which is found in the Miniature Wire-Haired Dachshund, Basset hound and Beagle, and suggests this disease is caused by an autosomal recessive inheritance, in which both parents will either carry or have the disease, with the Beagle showing a more severe form of the disease.

It is important to rule out one-off causes of a seizure such as heatstroke (which is not uncommon in puppies, just as febrile convulsions occur in humans), as a one-off episode of seizure shouldn’t be used as an indicator of a serious breed-related problem. In March 2014, the UK Kennel Club approved a DNA Lafora test which has been developed in Canada and the results are held in the Kennel Club database, through the dog’s registration details, and then published in the club’s breed supplement; through this process the Club states it aims that ‘responsible breeders can safely use all dogs not suffering from this condition, to eliminate this condition over time, to protect the diversity of the breed, without producing affected dogs’, but they do note that this is only a recommended test, and that the aim is only as good as the information they receive from responsible breeders (The Kennel Club 2014) 

Veterinarians rely heavily on the accounts of owners to reach their diagnosis, some of which may not know their dog has had a seizure, because while a major seizure that has the dog paddling on the ground with complete loss of motor control is easily comprehended, a minor seizure may appear as a slight loss of muscle control, or even just a loss of attention (called an absence); and often the episode is over by the time the vet is called, so the use of video is often recommended to confirm epilepsy and drive the correct treatment regime (Hahn 1997).

The first line of treatment for canine epilepsy is the use of barbiturates, such as phenobarbital, or potassium bromide (Compass 2014), both of which work to inhibit the nerve impulses (although by differing mechanisms). Munana (2009) suggests that only about 20 -30% of dogs achieve a good level of control without serious side effects, mainly sedation and vomiting, so often owners will reduce or stop medication to negate the side effects. Conversely owners may seek out excess medication, by exploiting the fact that Veterinarians rely on owner reporting of suspected seizures.

Dryden-Edwards (2014) suggests that a rise in the use of stimulating drugs, such as cocaine, and methamphetamine, has seen an increase use of barbiturates (downers) to counteract the ‘excitement’ phase of drug abuse, when the user needs to appear ‘normal’ with the resulting need to continue as the brain develops a dependence on the barbiturate, which causes withdrawal symptoms when the drug is withheld

Fremuth (2003), suggests, in her article for the Australian Shepherd Journal, that many of the above mentioned factors come into play when breeders are faced with a breeding dog with idiopathic epilepsy, she suggests that many breeders will not openly discuss if there is epilepsy in their breed and particularly in their stud, for fear of losing their status; also that just the suspicion of epilepsy in a breed can impact a breeder even if none of their dogs are affected; so the pressure to keep any hint of epilepsy ‘confidential’ is overwhelming.

Fermuth proposes the reasons that breeders would ‘hide’ whether their dog or dogs had epilepsy has many facets, the knowledge of seizures puts the breeder in a catch 22 position, if they mention seizures, to try to improve the line, then there is a reduction in the price they can achieve, but if they don’t mention it then they open themselves up to possible litigation. The fact that most idiopathic epilepsy begins in adulthood means that puppies are sold without any indication of whether they have the disease, and allows breeders to state ‘they had no idea’ when challenged. With the attitude that many breeders prefer not to know about epilepsy in their lines, it is difficult to make informed choices about appropriate matings. 

Budiansky (1999) suggests that one reason for the rise in inheritable diseases (which may or may not include idiopathic epilepsy) is that many breeds suffer from the ‘popular sire effect’ in that a successful champions is in great demand, commands high stud fees, and is likely to sire hundreds of litter, potentially swamping the gene pool with defective genes, often breeding out healthier ancestral lines.

Responsible breeders should be screening for inherited disorders, because it is the responsible thing to do, and it could be argued that these breeders will eventually be rewarded by producing health individuals that will command even higher prices, but there would need to be a change of emphasis from one of secrecy to one of openness, by making official test results public record, in order to reduce the production of epileptic individuals (Bell 2014).

References

Bell, J, S. (2014) Responsible Breeding Management of Genetic Disease, Retreived from http://www.tualatinkc.org/pdf/Responsible%20Breeding%20Management%20of%20Genetic%20Disease.pdf 25^th March 2014.

Budiansky, S. (1999), The Truth About Dogs, Retrieved from http://www.theatlantic.com/ideastour/animals/budiansky-full.html 26th March 2014

Chandler, K. (2011), treatment and monitoring of epilepsy in dogs, In Practice 2011;33:98-104

Compass (2014), [course notes], Module 4 Pharmacology.

Dryden-Edwards, R. (2014), Barbiturate Abuse Causes and Risks, Retrieved from http://www.emedicinehealth.com/drug-phenobarbital/page2_em.htm 26th March 2014

Fremuth, L.  (2003), The Epilepsy Underground, Australian Shepherd Journal, vol 13 (4). United States Australian Shepherd Association. Retrieved from http://www.dogstuff.info/epilepsy_underground_fremuth.html 26th March 2014

Hahn, J. (1997), When Epilepsy Strikes: Signs and Treatment for Dogs. Retrieved from http://vetmed.illinois.edu/petcolumns/petcols_article_page.php?PETCOLID=83&URL=0 26th March 2014

Munana, K. R. (2009), Newer Options for Medically Managing Refractory Canine Epilepsy, DVM 360. Retrieved from http://veterinarymedicine.dvm360.com/vetmed/Medicine/Newer-options-for-medically-managing-refractory-ca/ArticleStandard/Article/detail/608398 26th March 2014

The Kennel Club (2014), Kennel Club approves Lafora Test for Mini Wire Dachshunds, Retrieved from http://dachshundbreedcouncil.wordpress.com/2014/03/04/kennel-club-approves-lafora-test-for-mini-wire-dachshunds/ 8th april 2014

Oberbauer, A.M. Grossman, D.N. Irion, D.M. Schaffer, M.L. and Famula, T.R. (2002), The Genetics of Epilepsy in the Belgian Tervuren and Sheepdog. Retrieved from http://jhered.oxfordjournals.org/content/94/1/57.full 26th March 2014

Rusbridge, C. (2014) Lafora’s Disease. Retrieved from http://www.veterinary-neurologist.co.uk/lafora.htm March 2014. 26th March 2014

The University of Prince Edward Island (2014). Idiopathic epilepsy. Retrieved from http://ic.upei.ca/cidd/disorder/idiopathic-epilepsy