Vaccination Against Equine Grass Sickness: Piloting a Clinical Field Trial of a Clostridium botulinum Type-C Toxoid in Scotland in 2012-2013

Aims: To conduct a pilot study to inform sample size and trial methodology for a proposed triple-blinded randomised placebo- controlled field trial for a Clostridium botulinum type C toxoid vaccine in the prevention of equine grass sickness (EGS).

Methods: Only healthy horses/ponies residing on premises previously affected by a high incidence and frequency of EGS were included. Enrolled horses/ponies were randomly allocated, at premises-level, stratified by age, to vaccine or placebo treatment groups at a 1:1 ratio. Baseline and follow-up premises and horse data were obtained via telephone questionnaires. Veterinary surgeons responsible for the primary care of enrolled animals administered the primary course of vaccine/placebo on Days 0, 21, 42. Following appropriate training, owners completed post treatment daily observations for 7 days following each treatment. [...]