I'm concerned about IE...
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Idiopathic Epilepsy, or IE for short, is used to describe repeated seizures of undetermined origin over time.
In Australian Shepherds, IE is suspected to be a heritable condition. Nobody really knows why it happens
to some dogs and not others, but in some instances environmental factors may "trigger" the onset of
seizures.
The Australian Shepherd Health and Genetics Institute (ASHGI) maintains a repository
of articles dealing with IE, and specifically IE as it relates to Aussies. These
articles can be viewed HERE.
A couple other places to learn about the real-life aspects of living with an IE dog
are the Canine Epilepsy Resource Center. and the
Epil-K9 discussion list.
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- Focal or Absence Seizure - this can be a simple as momentarily staring into space or a brief upward eye movement with no loss of consciousness.
- Petit Mal or Partial Seizure - movements is restricted to one area of the body, such as muscle jerking, movement of one limb, turning the head or bending the trunk to one side, or facial twitches. Dog is usually alert and aware of his surroundings.
- Complex Partial Seizure - during this type of seizure, a dog's consciousness is altered and he may exhibit bizarre behavior associated with bizarre such as lip-smacking, chewing, fly biting, aggression, vocalization, hysterical running, cowering or hiding in otherwise normal animals. Vomiting, diarrhea, abdominal distress, salivation, blindness, unusual thirst or appetite, and flank biting are other signs. Abnormal behaviors may last minutes or hours and can be followed by a generalized seizure.
- Grand Mal, Generalized, or Tonic Clonic Seizure - this type of seizure begins with contraction of all skeletal muscles and loss of consciousness. The dog usually falls to his side with the legs stretched out and the head back. Respiration may also stop (apnea). This is the tonic portion of the seizure, and it is usually very short in duration and quickly gives way to the clonic phase of the seizure. The clonic phase of the seizure is characterized by paddling of limbs, dilation of pupils, salivation, vocalization, chewing, loss of control of bladder and bowels. This phase may occur for 1-3 minutes and is most often followed by a period of restlessness, pacing, bumping into objects and loss of balance. (Post Ictal period) The dog is conscious but may appear deaf, blind and disoriented.
- Status Epilepticus - status can occur as one continuous seizure lasting 10 minutes or more, or a series of multiple seizures in a short time with no period of normal consciousness.
- Cluster Seizure - more than 1 seizure in a 24-hr period, sometimes with only brief periods of consciousness in between. It can be difficult to tell status epilepticus from frequent cluster seizures; but both are considered life-threatening emergencies.
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Seizures can be very subtle or very obvious, depending on the dog and the circumstances. Any abnormal behavior that is out of character for your dog and that appears to be neurological in nature, could be considered a seizure. Seizure activity may be very different than what you would normally expect, i.e.: a dog that falls over, jerking or paddling its limbs. Quite the contrary, a seizure can be something a subtle as a dog becoming disconnected for a moment and then suddenly snapping back to reality or a dog whose pupils dilate and who suddenly starts salivating for no apparent reason. All of these things should be a source of concern and should be monitored for increased occurrence or for more severe symptoms. If you suspect your dog may be having subtle seizures, discuss the circumstances with your vet, or make an appointment with a veterinary neurologist to get a more accurate assessment.
Seizures occur in several distinct stages:
- The Prodome - may precede the seizure by hours or days. It is characterized by changes in mood or behavior.
- The Aura - signals the start of the seizure. Signs include restlessness, nervousness, whining, trembling, salivation, affection, wandering, hiding, hysterical running, and apprehension.
- The Ictus, the actual seizure - a period of intense physical activity usually lasting 45 seconds to 3 minutes. The dog may lose consciousness and fall to the ground. There may be teeth gnashing, frantic thrashing of limbs, excessive drooling, vocalizing, paddling of feet, uncontrollable urination and defecation.
- The Post Ictus/Ictal - occurs after the seizure, and may be the only sign of epilepsy the owner sees, particularly since many seizures occur at night or early in the morning. For minutes to days after the seizure, the dog may be confused, disoriented, restless, or unresponsive, or may appear blind and deaf and eat or drink excessively. At this stage the animal is conscious but not functional.
The Canine Epilepsy Network site has some short video clips in their "Canine Epilepsy Basics" section that can you can view to see what a seizure sometimes looks like.
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Although family history may be a strong indication of whether your dog's seizures are likely to be
IE, IE is normally diagnosed when all other possibilities have been eliminated--and there are several
other medical conditions that can sometimes cause seizures. Please click HERE for a recommended protocol to follow in helping your vet with diagnosis.
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Nobody knows precisely how IE is inherited in Aussies, but researchers suspect it is inherited polygenically,
much like Hip Dysplasia, certain eye defects, and dental problems. Unfortunately, polygenic
defects are often the most difficult to breed away from, because unlike simple recessives (where a dog is
either a carrier or not a carrier), polygenic traits involve dogs who carry "more" or "less" of the alleles
needed to express the trait.
According to George Padgett1 in his book, Control of Canine Genetic Diseases, polygenic traits have the following characteristics:
- As with a recessive trait, both the sire and the dam must contribute one or more of the genes
that cause the abnormal phenotype in the offspring.
- Unlike recessive traits, the contribution from the sire and dam need not be equal.
- Since we do not know the number or the specific effect ot the genes involved in polygenic
traits in dogs, no predictable Mendelian ratios are associated with these traits.
- Both sexes are affected with polygenic traits (excluding sex-limited traits) but not necessarily in equal numbers.
- The trait may skip generations and may appear to be erratic in occurrence.
Most breeders are familiar with the four-square Punnett Squares used to describe the dominant/recessive relationships involved in coat color (black vs. red) and
coat pattern (solid vs. merle). Both these traits are simple recessives; Polygenic traits are much more complex. To quote
Padgett again, a three-gene trait, where each gene has only two alleles (a dominant and recessive), will need a much larger
Punnett Square, as there are 64 possible combinations (in this example, both the sire and dam are heterogeneous for three genes: Aa, Bb, Cc):
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Sire
Dam |
A
B
C |
A
b
C |
A
B
c |
a
B
C |
a
B
c |
a
b
C |
a
b
c |
A
b
c |
A
B
C |
AA
BB
CC |
AA
Bb
CC |
AA
BB
Cc |
Aa
BB
CC |
Aa
BB
Cc |
Aa
Bb
CC |
Aa
Bb
Cc |
AA
Bb
Cc |
A
b
C |
AA
Bb
CC |
AA
bb
CC |
AA
Bb
Cc |
Aa
Bb
CC |
Aa
Bb
Cc |
Aa
bb
CC |
Aa
bb
Cc |
AA
bb
Cc |
A
B
c |
AA
BB
Cc |
AA
Bb
Cc |
AA
BB
cc |
Aa
BB
Cc |
Aa
BB
cc |
Aa
Bb
Cc |
Aa
Bb
cc |
AA
Bb
cc |
a
B
C |
Aa
BB
CC |
Aa
Bb
CC |
Aa
BB
Cc |
aa
BB
CC |
aa
BB
Cc |
aa
Bb
CC |
aa
Bb
Cc |
Aa
Bb
Cc |
a
B
c |
Aa
BB
Cc |
Aa
Bb
Cc |
Aa
BB
cc |
aa
BB
Cc |
aa
BB
cc |
aa
Bb
Cc |
aa
Bb
cc |
Aa
Bb
cc |
a
b
C |
Aa
Bb
CC |
Aa
bb
CC |
Aa
Bb
Cc |
aa
Bb
CC |
aa
Bb
Cc |
aa
bb
CC |
aa
bb
Cc |
Aa
bb
Cc |
a
b
c |
Aa
Bb
Cc |
Aa
bb
Cc |
Aa
Bb
cc |
aa
Bb
Cc |
aa
Bb
cc |
aa
bb
Cc |
aa
bb
cc |
Aa
bb
cc |
A
b
c |
AA
Bb
Cc |
AA
bb
Cc |
AA
Bb
cc |
Aa
Bb
Cc |
Aa
Bb
cc |
Aa
bb
Cc |
Aa
bb
cc |
AA
bb
cc |
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If applied to the "trait" of IE, the gene combinations in the example above may control not only whether a dog gets the disease, but also the age of onset, and the frequency and severity of the seizures.
IE has not yet been identified to a particular set of genes, so it is impossible to guess if it involves two genes or twenty; but it is safe to say
that if it's a polygenic trait, it's a very complex one to control in breeding.
1Padgett, George. Control of Canine Genetic Diseases. P. 47-8.
New York, NY: Howell Book House, c. 1998.
ISBN: 0-87605-004-6
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Unfortunately, IE has gotten to be such a widespread problem in Aussies that there are very few bloodlines
that have been untouched by the disease. The only advice we can give is to do extensive research
into any prospective crosses, examining the extended family history of siblings, parents, aunts, uncles, grandparents, etc.
of prospective mates. In short, you should examine not only your dog's "vertical" pedigree, but also the "horizontal" pedigree.
Responsible breeders will spend the time and know the risk involved with their breeding stock,
and should be able to give you specific details as to the incidence of IE in their bloodline(s).
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The easiest way to begin researching which lines have experienced IE is to
begin networking with other breeders and asking questions (and Breeders who are supporters of the AussieGENES campaign are a great place to start!). Because some people are better-informed
than others, and some are more willing to admit when there are problems, so it is important to get input from as many
people as possible who own dogs in the bloodline you are researching.
You may also get contacted by other breeders who are researching your bloodlines. For the sake of this
breed we all love, please be honest and candid with them about any affected or carrier relatives you know about, and ask them to keep
you apprised if they find any you aren't aware of. By networking with each other and sharing our information, we can all take steps to avoid making more "unlucky" crosses.
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C.A. Sharp offers a
pedigree analysis* of dogs you own. (She will do your dogs, but for liability reasons cannot provide you analyses on
dogs you do not own, i.e. prospective mates.)
C.A. will not identify the specific carriers or affected individuals in a pedigree, but she will give you a rating of how significant a risk she feels each pedigree is
in producing a problem. The ratings are: Low, Moderate, Significant, Very Significant.
These ratings are actually assigned to ranges of numeric "point values" which C.A. calculates based on the frequency and position
of affected and carrier individuals in a pedigree. For more information about how C.A. performs her calculation, click
HERE.
* Due to the volume of requests and her time constraints on doing the analysis, CA has requested that a donation of $10 per pedigree be made to ASHGI;
The current lead time for an analysis is approximately three months.
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The degree to which one's breeding plans are affected by the appearance of an
affected or carrier dog in the horizontal or
vertical pedigree depends on how recently in the pedigree the dog appears.
Obviously, affected individuals should not be bred,
and niether should known carriers of the disease.
But what about dogs who are
not known carriers (but are related to one)? This area becomes
a bit more gray, because while there is a very good argument for not breeding
close relatives of affected and carrier dogs,
we also cannot afford to eliminate all dogs in the gene pool who meet
this criterion--to do so would risk further constriction
of the gene pool to the point where the remaining "IE-free" individuals might
have a higher-than-normal frequency for genes that contribute
to some other genetic disorder. (This very situation has occurred in the past in Basenjis.) So, while we should not run out an breed all
relatives of affected and carrier dogs, in certain
situations where a related individual has demonstrated some outstanding quality or trait,
it might make sense to do so.
The decision about whether this type of dog
should be bred is a highly
personal one, and is largely dependent on the would-be breeder's comfort with risk-taking.
In any case, the people buying offspring from any high-risk breeding should be
notified in advance of the risk their puppy carries, so that they can make
the best choices possible for their dog.
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