Ethical animal researchThis was a retrospective study performed on data collected from privately owned animals that received the highest standards of care. All activities were conducted with informed owners. 2 Conflict of interestThere are no conflicts of interest. Source of fundingThe Equine Research Centre of the University of Pretoria funded the study. AcknowledgementsThe authors gratefully acknowledge the cooperation and generous assistance of the owners and staff of Moutonshoek and Summerhill. Conclusions:The marked difference in morbidity between the two epizootics may be associated with routes of introduction or intervention strategy dictated by availability of molecular diagnostic techniques. Unexpectedly, EHV-1 was not more commonly associated with post-abortion complications.