Phenotypic comparison of idiopathic epilepsy in English Springer Spaniels and Cocker Spaniels using a validated owner-completed questionnaire

In response to the recurring identification of medication-resistant idiopathic epilepsy (IE) in English Springer Spaniels (ESS), the objective of this retrospective questionnaire-based observational study was to delineate the phenotypic characteristics of IE in this breed in comparison to a cognate breed, the English Cocker Spaniel (ECS), employing a novel, validated, owner-completed multilingual online questionnaire. Owners of 49 ESS and ECS with seizures completed the questionnaire, of which 16 ESS and 14 ECS fulfilled the inclusion criteria and were subsequently included in the study cohort, while the remaining questionnaires were excluded due to incomplete or inconsistent information or because the criteria for IE were not fulfilled. At the time of the survey 43.3% of the dogs had died, including five that died in association with epilepsy. The median age at seizure onset was 2.5 years in ESS and ECS (range: 0,5–9 years; IQR 2.0–4.0 years). Notably a high proportion of dogs in both breeds had experienced ≥1 cluster seizure and ≥1 status epilepticus. In ECS a significantly higher rate of marked reduction in seizure severity following initiation of anti-seizure therapy compared to the ESS (p = 0.009) was observed. Both breeds exhibit a moderate to severe disease course, with ESS showing a comparatively poorer response to antiseizure drugs. Furthermore, 43.3% of dogs with suspected IE also had affected relatives. The owner-reported occurrence of IE in related dogs may suggest a potential hereditary component in both breeds.