Infectious Neurologic Disease Field Diagnostic Guidelines

The AAEP Field Diagnostic Guidelines provide step-by-step instruction for the diagnostic work-up and management of clinical syndromes commonly encountered in equine practice. They are intended to help practitioners determine appropriate samples and tests necessary to achieve a definitive diagnosis while implementing appropriate biosecurity measures.

A wide range of infectious and non-infectious diseases can give rise to neurologic signs in the horse, some of which have substantial biosecurity, herd health, and zoonotic implications. While the majority of neurologic conditions in the horse are not contagious, neurologic EHV-1, and rarely neurologic EHV-4 (Equine Herpesvirus Myeloencephalopathy; EHM) spreads rapidly between horses and can result in widespread exposure of in-contact horses by the time a diagnosis is confirmed. Until proven otherwise, practitioners should approach any potentially infectious case of neurologic disease as a ‘worst-case scenario’, and consider differential diagnoses such as EHM, Rabies, WNV, EEE/WEE/VEE.