EPILEPSY IN THE FINNISH SPITZ
Epilepsy is a very complex group of symptoms. The term epilepsy means a seizure or a fit and it is a very vague and undefined description as a dog can have seizures for a various reasons. It has been estimated that 0,5-5,7% of all dogs get a fit/fits during their lifetime. Many of these dogs have epilepsy many do not have.
Aquired epilepsy can have its reasons in 1) extracranial or 2) intracranial causes. Such are fex. 1) hypoglycaemia (reduced blood sugar), hypoxia (reduced supply of oxygen), liver disease, intoxication etc. or 2) tumours, enchephalitis, trauma (hit in the head), hydrocephalus (liquid in cranial cavity) etc. In all these cases the removal of the causal factor will cure the patient from epileptic seizures.
If all the above or other reasons have been eliminated and the dog still has seizures, we can call it idiopatic or in other words fits without a cause. We must remember that the most common form of fits in the dog is idiopatic. Animals with idiopatic epilepsy or a suspected inherited predisposition to seizures have their first fits between 6mths 5yrs of age.
It has been discovered that inheritance plays an important role in canine epilepsy. Test matings with three epileptic dams to an epileptic sire (Cunningham) have shown that out of the 13 pups born, 5 had fits before their first year of age and 4 more had an abnormal EEG, similar to the convulsing pups. In another investigation (Biefelt 71, beagle colony) it was found out that only two dogs sired 65% of the 29 epileptics. The incidence rate of initial seizures in these was also higher than in the offspring of other sires of the colony.
Also familial pattern of inheritance has been found. It was concluded that dogs with a higher COI were more prone to fits in early age. Evidence cited above suggests that genetic mechanisms play an important role in transmission of canine epilepsy, since selective breeding (for epilepsy) results in an increased occurrence of epilepsy in the more general population.
In any case a simple single-locus mechanism seems most unlikely. Biefelt (71) has proposed a two-locus mechanism one autosomal recessive and the other a sex-linked suppressor, as males are more prone to epilepsy than females. Some other researchers have suggested that each animal inherits a genetically determined predisposition to seizures and if a certain treshold of stimulation is exeeded, seizures occur.
It is unwise to breed from an epileptic dog or to repeat a mating that has produced epileptic pups.
Several breeds of dogs have been reported to have a high incidence of idiopatic epilepsy. These include: Golden Retriever, Irish Setter, Saint Bernard, German Shepherd, American Cocker Spaniel, Wire-haired Fox Terrier, Alaskan Malamute, Siberian Husky, Miniature Poodle and we may also add - the Finnish Spitz. In one research it was estimated that the Finnish Sptiz has 7 times bigger risk to epilepsy than the average dog of any other breed.
It is a well-known fact in Finland that epilepsy plagues the Finnish Spitz population, because in the past of 1950s and 1960s also epileptic dogs were used carelessly for breeding. Two different surveys have been made to investigate the frequency of epilepsy in the breed. In the survey of 1996 it was estimated that 6,25% of the population was epileptic. In 2003 an epilepsy form was posted to 4000 owners of FS that were less than 6 yrs of age. Little over 1600 forms were returned. The percent has remained the same 6,25%, if you count the returned forms. But if we count from the forms posted the percent is 2,5%. The truth lies somewhere in between. Owners can also fill a form voluntarily, this way some 20 forms are returned yearly. This way we have a database of some 220 epileptic FS.
But how to use this data in breeding? In 1996 Pertti Korhonen invented the so-called EPI-pedigree. Affected dogs and their relatives were marked in a 5-generation pedigree with letter coding as follows: I - Affected dog, J - Progeny is epileptic, V - Parent is epileptic, S -Sibling is epileptic and P - Half-sibling is epileptic. The EPI-pedigree gave a visual picture of the situation. Further thinking from Risto Tuomainen gave rise to calculating the risk of an individual to epilepsy, called the EPI-figure. This was done by giving a numerical value to each letter code, which defines the mean kinship to the affected dog. (I = 1; J, S, V = 0,5 and P = 0,25) Also the generations of the pedigree were given a value k, which corresponds to the effect of genes:
1stgeneration = 1;
2ndgeneration = 0,5;
3rdgeneration = 0,25;
4thgeneration = 0,125 and
5th generation = 0,0625.
The rest is just mathematics, multiplying and summing-up. This gives us a means to handle epilepsy in the FS.
The mean EPI-figure of the healthy population is 1,09 and the mean for epileptic dogs is 1,86. It is hoped that in breeding two individuals the EPI-figure of the litter falls under 1,09. It is also suggested that a dog with an EPI-figure of 1,8 (even if it seems OK) is not recommended for breeding. The other proposed rule is that a dog with an EPI-figure over 1,5 will be bred with special care. The calculating of EPI-figure is far from scientific, but it gives us something to kling to until researchers can give us more details of the disease.
Example of counting the EPI-figure
I = 1
J, S, V = 0,5
P = 0,25
|SUM x k
|| 0.25 +
|| 0.25 +
|| 0.375 +
|| 0.250 +
EPI figure = 1.21875