Epilepsy in Irish Wolfhounds

Abstract

During the last 15 years, breeders have reported an increase in the proportion of Irish Wolfhounds with seizure disorders. Clinical data and pedigrees from closely related Irish Wolfhounds were collected retrospectively and analyzed. Idiopathic epilepsy was diagnosed, by exclusion of other causes for seizures, in 146 (18.3%) of 796 Irish Wolfhounds from 115 litters. The first seizure occurred by the age of 3 years in 73% of all dogs. Males were more commonly affected than females (61.6% versus 38.4%), with males having a later average age of seizure onset. The life expectancy of affected dogs was decreased by 2 years when compared with the average Irish Wolfhound population. The heritability index for the affected dogs, their littermates, and unaffected parents was 0.87. No simple mode of inheritance explains the pattern of affected dogs in pedigrees. Hallmarks of dominant and sex-linked inheritance were notably absent, and the segregation ratio was less than would be expected for simple autosomal recessive inheritance. Assuming all affected dogs have the same form of epilepsy, the simplest description of the complex pattern of inheritance observed is autosomal recessive, with incomplete penetrance and male dogs at increased risk.

Fig 1

Number of dogs at various ages at first seizure. Statistically significant differences in the age of onset of seizures (P < .05) were seen between females from 37–48 months of age and the rest of the groups and between males and females for both the 37- to 42-month and the 43- to 48-month groups. Note the precipitous decrease in dogs with onset of seizure activity in the 37- to 42-month category followed by an increase.

Fig 2

Life expectancy plotted against age at first seizure (±SEM). There was no statistically significant difference between any of the groups (P < .05).

Fig 3

Small portion of the much larger pedigree of Irish Wolf-hounds with idiopathic epilepsy. Squares and circles represent males and females, respectively. Open and filled symbols designate normal dogs and affected Irish Wolfhounds, respectively. Although not always indicated, all dogs in this pedigree have common ancestors.