Disease Progression and Treatment Response of Idiopathic Epilepsy in Australian Shepherd Dogs

Background: Idiopathic epilepsy (IE) in Australian Shepherds (ASs) occurs worldwide but there is a lack of description of the epilepsy syndrome in this breed. The ABCB1-1D mutation is more prevalent in ASs than in many other dog breeds. Hypothesis: Australian Shepherds suffer from a poorly controlled IE syndrome with prevailing severe courses. Seizure control and ABCB1-1D mutation might be related in this breed. Animals: Fifty ASs diagnosed with IE and 50 unaffected ASs. Methods: Predominant study design is a longitudinal cohort study. Pedigrees, medical records, seizure, and treatment data of ASs with IE were analyzed descriptively. Sex, color, and the ABCB1-1D genotype were compared between case and control groups and ASs with poorly or well-controlled seizures. Differences in survival times were assessed by logrank tests and Cox regression analysis. Results: Idiopathic epilepsy in ASs is dominated by moderate and severe clinical courses with the occurrence of cluster seizures and status epilepticus and a high seizure frequency. Poor seizure control and a high initial seizure frequency (>= 10 seizure days/first 6 months) are associated with shorter survival times (P < .05). Poor seizure control, unrelated to the ABCB1(MDR1) genotype, is evident in 56% of epileptic ASs. Pedigree analysis suggests a genetic basis. Conclusion and Clinical Importance: Frequent severe clinical courses, poor seizure control unrelated to the ABCB1 (MDR1) genotype, and a young age at death compromise animal welfare and warrant further genetic studies to unravel the underlaying molecular mechanisms of IE and seizure control in the breed.