Infectious Neurologic Disease Field Diagnostic Guidelines
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.
AAEP Neurologic Disease Differential and Diagnostic Flow Chart Considerations for approaching acute neurologic cases of unknown etiology
The following scenarios are suggestive of underlying infectious disease and should prompt practitioners to implement biosecurity practices and establish a quarantine on the premises: ● Multiple febrile animals (with or without concurrent signs of respiratory, neurologic, or intestinal disease)
● One or more horses with acute neurologic abnormalities and fever
Isolation on-site or removal of affected animal(s) to an isolation facility is highly recommended, especially if EHM is suspected.
State animal health officials (SAHO) should be alerted promptly per state guidelines if acute neurologic disease of potential infectious etiology is suspected, including but not limited to EHV-1 (EHM), Rabies, EEE, WEE, VEE, and/or WNV.
Further information regarding facility management and establishing a biosecurity perimeter in a potential outbreak can be found in the AAEP General Biosecurity Guidelines.
Differential Diagnoses for Adult Horses with Acute Neurologic Signs Listed alphabetically
Infectious: ● Anaplasmosis ● Bacterial meningitis or brain abscess ● Botulism ● Eastern Equine Encephalitis (EEE)
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