Study population and prevalence
A total of 1,248 Groenendael and Tervueren dogs were included in the study. Out of the 1,248 mailed questionnaires, 526 were returned. Seven responders were excluded because the questionnaires were incompletely filled in, leaving 519 questionnaires to be evaluated (corresponding to a study population of 519 individuals). Hence, the return rate of the mailed questionnaire was calculated to 42%.
Out of the 519 responders, 64 owners (12.3%) responded positively to the questions about epilepsy (self reported epilepsy) while the remaining 455 (87.7%) responded negatively.
At the time of the study, a total of 79 dogs from the overall study population of 519 dogs had been euthanized. The most common cause of euthanasia was aggression (27 dogs), cancer (14 dogs), epilepsy (eight dogs), high age (seven dogs) and traffic accidents (four dogs).
Out of the 64 possibly epilepsy positive responders that were listed to be telephone interviewed, three owners could not be reached and were therefore excluded. After evaluating the results of the 61 telephone interviews, 49 dogs were finally confirmed to fulfill the criteria of being epilepsy-positive cases; 25 Groenendael (15 females and ten males) and 24 Tervueren (16 females and eight males). Hence, there was an overrepresentation of females (31) with epilepsy compared to males (18). Thirteen dogs were neutered (nine females and four males) (Table ).
Distribution of factors related to 49 DanishGroenendael and Tervueren dogs diagnosed as epilepsy-positive in a study including 519 dogs.
The prevalence of epilepsy was estimated at 9.5% (49/516). A preliminary interpretation of pedigrees disclosed that a familiar connection existed among several of the affected dogs.
Dogs identified by breeders/owners
Breeders reported that several owners of dogs known to them had not returned the mailed questionnaire despite having dogs diagnosed with epilepsy by a veterinarian. This information yielded the identities of an additional ten dogs with epilepsy. The owners were contacted and interviewed using the standardized questionnaire also used in the telephone interview (step III). All ten dogs fulfilled the criteria of being epilepsy positive according to the study case definition. The prevalence of epilepsy would have been higher if these dogs had been included. However, since these owners did not return the mailed questionnaire, they did not fulfill the study design criteria. Hence, the extra ten cases could not be included in the calculation of prevalence.
Associations between cause of death and sex, cause of death and variant (Groenendael/Tervueren), type of seizure and variant (Groenendael/Tervueren), and neutering status and cause of death were investigated (Table ). Only the last association was found to be statistically significant. Intact dogs (not-neutered) with epilepsy had an increased risk of being euthanized because of epilepsy compared to neutered dogs with epilepsy (N = 15, Fisher's exact test P = 0.007). Neither the relative risk (RR), nor the odds ratio (OR) could be calculated as one of the cells in the 2 × 2 table yielded the value zero.
Characteristics of epilepsy and seizure phenomenology
Mean age of debut of epilepsy was 3.3 years (range 6 months to 8 years). In 19 dogs (39%), the first seizure did not appear until after reaching the age of four years (Figure ).
Graphical description of age at first seizure in 49 Danish Groenendael and Tervueren dogs diagnosed with epilepsy (one missing value).
Thirty-eight dogs (78%) experienced focal seizures with or without secondary generalization. Twelve dogs experienced focal seizures alone, while 26 dogs experienced focal seizures with secondary generalization (initial focal signs followed by convulsions). Nine dogs (18%) experienced primary generalized seizures (Table ). In two dogs (4%), seizures could not be classified. The most commonly reported focal seizure phenomenology included episodic ataxia, crawling, swaying, salivation, fearful behavior, excessive attention seeking and disorientation. The average duration of a seizure was between 30 seconds and 2.5 minutes.
In eleven dogs (22%) the owners reported that anxiety/hyperactivity/stress (e.g. working under conditions with a demand for high performance or aggressive behavior towards other dogs), could sometime act as a seizure provoking factor. These dogs would however also have seizures while resting.
In two dogs prodromes repeatedly preceded seizures. In these dogs the owners would recognize an unusual and depressed behavior that would last for several days before a forthcoming seizure episode.
None of the dogs were known to suffer from other diseases that may mimic epilepsy and all dogs appeared normal interictally and did not show any clinical signs of active intracranial disease other than seizures.
Seizure control and mortality
In 35 dogs (71%) the general practitioner had established a clinical diagnosis of epilepsy prior to the present investigation. In thirteen dogs, 37% (13/35), the general practitioner prescribed anticonvulsive medication; eleven dogs received phenobarbital, and two dogs received phenobarbital and potassium bromide in combination. Eight dogs, 16% (8/49) had been euthanized because of failing seizure control.
In the eight dogs that had been euthanized because of epilepsy, the median time a dog lived after first seizure was 2.5 years (range 1.0–5.0 years). All eight dogs had been diagnosed with epilepsy by their general practitioner.