Friday, July 29, 2011

Epilepsy: The Insidious Disease, by C.A.Sharp

In the spring of 2010, I asked CA to write an article for me for the Mudi about epilepsy.  The result is the article below.  When I originally asked her to write it, she asked me how many Mudis I knew with epilepsy, I told her I knew of 9 confirmed and about 11 not yet confirmed.  Fast forward one year to summer 2011, I and at least one other Mudi person have at least 18 confirmed now. Plus I also have 9 on the not-confirmed list. When another year will pass, what will the numbers be?

CA Sharp is the President of ASHGI (see links below). She is an internationally recognized lay expert on canine genetics and hereditary diseases.  She also assisted with two (Veterinary) journal manuscript publications, one on Collie Eye Anomaly in Australian Shepherd Dogs and the other on merle gene identification.  CA has been involved with dogs for more than 30 years, specifically the Australian Shepherd.  For more than 20 years she has collected data on hereditary diseases in the Aussie breed and has used this information to assist researchers with many projects, she also provides informal genetic counseling and pedigree analysis to breeders and owners, as well as being involved in many breed education projects.  She has written extensively on genetics and hereditary disease for Aussie breeders in their breed journals, for ASHGI and for her almost 20 year publication called Double Helix Network News.  Double Helix has been nominated and won several canine writer awards as has CA herself.

Epilepsy:  The Insidious Disease
By C.A. Sharp, ASHGI President

Canine epilepsy is a lousy disease.  It tortures the victim and causes anguish to those who love him.  There is no cure and the treatments aren’t always effective.  Sometimes it is lethal.  As if all that weren’t bad enough, it is insidious:  It can creep into your breed’s gene pool in sheep’s clothing and by the time you realize it is a problem, it may be so widespread that you will be hard-pressed to eliminate it.
            In my breed, the Australian Shepherd, epilepsy has become so common that it is virtually impossible to find a line that doesn’t have links to the disease.  Epilepsy does not appear to be common in your Mudis, but neither was it in Aussies, once.  I hope that by sharing our breed’s story it may help you avoid the mistakes that we made.       
            Epilepsy is a common canine disease and probably occurs occasionally in every pure breed, as well as in mixed-breeds.  But some breeds, like mine, have much more of it than the canine average.  Unfortunately, we brought it on ourselves.  Years ago, one only heard of an occasional Aussie with epilepsy; I wish it were true today. 
            When faced with something unpleasant, especially if it is extremely unpleasant, our first reaction is denial:  “No, this can’t be!”  This is normal, a part of processing things that are emotionally difficult.  But when we get stuck in denial, we cannot deal with the issue at hand.  Unfortunately, epilepsy makes it easy for us to hang on to that denial.
There is at this point no positive way to diagnose epilepsy.  The diagnosis must be made by ruling out all other likely causes.  If the treating veterinarians have done that, the default diagnosis is primary epilepsy, an inherited disease.  The danger in this is that people sometimes use the lack of any positive diagnostic test as a way to deny the accuracy of the diagnosis.  Another issue arises from what was formerly the disease’s common name:  idiopathic epilepsy, a name still used by some vets.  “Idiopathic” means “of unknown origin.”  The disease earned this name because there is no way to demonstrate a cause for the seizures.  However, extensive study of the disease has established that it is inherited and does not arise from any other disease or defect.  “Primary epilepsy” is now the preferred terminology. 
Seizures can be caused by many things besides primary epilepsy, including head injuries, toxic exposure, and other diseases.  Many of these things are non-hereditary, so some breeders take the easy out:  The dog got kicked by a cow, it got into the shed and ate ant poison, it has brain tumor, etc.  The truth is that none of these excuses hold water if the dog actually has epilepsy.  Once an epileptic dog starts seizing, it will continue to do so at intervals unless controlled by medication.  Even with medication the dog may have break-through seizures.  Head injuries typically do not cause permanent recurring seizures unless the injury was very severe.  In that case, you would know you had a badly injured dog and it likely would have additional signs of neurological damage.  Seizures due to toxic exposure cease once the toxin is cleared from the system.  Other diseases may cause seizures, but you almost always see other signs of disease and, if the primary disease is diagnosed and treated, the secondary seizures will cease.
Finally, the disease itself can sometimes escape notice.  People associate epilepsy with tonic clonic seizures, the major seizures that were once termed “grand mal.”  But in truth, seizures can range from extremely severe to very minor.  Some epileptic dogs will have focal, or absence seizures, which can be quite subtle.  A dog experiencing a focal seizure may do nothing more than pant heavily, or “zone out.”  The owner might be totally unaware of the dog’s condition, especially if the dog is not a house dog or otherwise under close and frequent observation.  Even if the seizures are more obvious, but not to the point of tonic clonic, the owner may dismiss them as odd, but insignificant behavior.
When our problems first became apparent all this wiggle-room led Aussie breeders to opt for denial.  The first epilepsy outbreak to generate any notice occurred in England in the 1980s.  At that time Aussies were just beginning to be exported to countries outside North America.  Almost all the early dogs in England were from a single US kennel or selected by that breeder and often related to her dogs.  With such a tight gene pool, it isn’t surprising that something cropped up.  The initial reaction in England was a sneak preview for what happened later in the US:  There was a great deal of denial, some outright cover-ups, and people who spoke out were pressured to shut up. 
Over on this side of the puddle, epilepsy was considered an English problem if it was considered at all.  Then, in the early 1990s a US pet owner lost a lovely young bitch to status epilepticus, a near-continual seizure state.  It’s an ugly death.  The owner placed a memorial ad in one of the breed magazines.  In the ad she included the bitch’s pedigree, which featured grandparents from some major US kennels.  Subsequent to the ad, another breeder came forward with information on one of her litters:  Five developed epilepsy.  The denial, cover-up and intimidation that occurred in England now arose here.
Flash forward to the late 1990s and there were so many cases of epilepsy that a group of breeders and owners formed a grass-roots movement that ultimately brought the issue front and center to the breed community.  Since then we have been able to gather samples and connect with a researcher, Dr. Ned Patterson of the University of Minnesota, who is studying epilepsy in several breeds.  We hope someday, to have a DNA test that will enable breeders to take major strides toward reducing the frequency of this awful disease.  But in the meantime we must struggle with pedigrees riddled with connections to epilepsy.  Affected Aussies continue to be born despite our efforts.
The Mudi isn’t in this situation, yet.   Your breed has had maybe a dozen identified cases so far and possibly one or two in the US.  With a world population of somewhere around 1000 dogs, this may not seem cause for worry.  While it is not a reason for panic – your Mudis have far lower disease frequency than my breed does—it should be seen as a reason for caution.  You also need to consider that the breeding population – which is the real indicator of population size – is maybe half of the total population.  Some dogs are too old or young for breeding, others are not in any of the registers, some may be altered, and some for various reasons are not considered breeding quality.  When you consider the breeding population vs. the number of affected dogs, the frequency of the disease is closer to 2%.  One dog out of every 50 affected with epilepsy deserves serious attention.
A disease caused by a simple recessive gene mutation, if found in 2% of the dogs would mean that more than 20% carry the responsible gene mutation.  But the research done thus far indicates that epilepsy most likely arises from an interaction between multiple genes, so the percentage of carriers could be much higher.  If 20% or more of the breeding population has the potential to produce the disease I think you can see how the issue is more serious than it seems on the surface.
Dog breeding is prone to the use of popular sires; a dog comes along with many fine qualities, so many people bring their bitches to that dog.  While this helps distribute the genes for the dog’s desirable traits, breeders need to keep in mind that every dog has some genes for traits you do not want.  A popular sire is the quickest way to make a rare health issue a common one.  Several popular Aussie sires proved to be carriers of genes for epilepsy, greatly contributing to the increase of the disease in the breed.
Epilepsy need not become the common issue it is for Aussies among your Mudis.  Control of the disease isn’t difficult, provided the breed community has the will to make it happen.  Information on affected dogs should be shared openly and no one should shun or place blame upon the person who comes forward to report one.  Ideally, a central register should be set up to track cases, with pedigrees and copies of the affected dogs’ diagnostic test results or a formal statement of diagnosis from the treating veterinarian.  Since your breed is rare, an international register would be advised.
Obviously, once a dog is diagnosed as epileptic, it should not be bred.  Its first-step relatives (parents, offspring and full-/half-siblings) should also not be bred.  The parents clearly carry genes for epilepsy because they have produced it.  The offspring and sibs are at extremely high risk for doing so.  Second step relatives and beyond might be bred, but should be bred only to mates without family history of epilepsy.
While no breeder wants to remove an otherwise valued dog from her breeding program, you are far safer to proceed with a sibling of one of the parents or one of its offspring than with the 1st step relatives.  This will greatly reduce the risk of producing another epileptic. 
Sometimes, despite your best efforts, a cross may still produce the disease.  If information on the new case becomes part of a health database, everybody will know that caution is advised when breeding relatives of that dog.
I urge you to tackle this problem now, before it becomes a major scourge in your breed.  There are tens of thousands of Aussies, so we have lots of options.  If your Mudis follow our path, you won’t have that luxury.  I urge you to do whatever you can to keep this insidious disease from spreading in your breed.
© 2010

***

If you would like to read more about how the history of epilepsy in the Australian Shepherd, see: 
Information about the disease:
            www.canine-epilepsy.com
Dr. Hannes Lohi, University of Helsinki, is researching epilepsy in Aussies, Mudis and other breeds of dog.  Providing him with needed blood samples, pedigrees, and data on affected dogs is the best hope you have for finding the genetic causes of the disease.  www.koirangeenit.fi/index.php?option=com_content&task=view&id=37&Itemid=44

Australian Shepherd Health and Genetics Institute:  http://www.ashgi.org/index.htm
C.A. Sharp: 51ca@ashgi.org

No comments:

Post a Comment