In recent years it seems owners and practitioners are increasingly confronted–both directly and indirectly–with cases of equid herpesvirus-1 myeloencephalopathy (EHM).

Lutz Goehring, DVM, MS, PhD, Dipl. ACVIM, associate professor of equine medicine at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences, discussed characteristics of this neurologic form of herpesvirus-1 and why it might be on the rise, at the International Conference on Equine Infectious Diseases Practitioner’s Day, held Oct. 21 in Lexington, Ky.

Goehring explained that this infectious disease typically spreads when one horse inhales viral particles from an infected horse. Viruses attach to the respiratory tract epithelium (lining), are transported to the lymph nodes, and then travel through the bloodstream (also known as viremia) to their specific destinations: vascular endothelial cells lining the blood vessels of the pregnant uterus, central nervous system, or eye.

Viremia typically causes a high fever and occurs prior to clinical signs of EHM. Veterinarians commonly see neurologic gait abnormalities like ataxia (incoordination), paresis (impaired movement), and dysmetria (a high-stepping gait yet limited joint movement) and bladder dysfunction, said Goehring