Neurologic strain of EHV-1 can cause myeloencephalopathy

by: Erica Larson, News Editor
May 27 2011:

Imagine the following scenario: Your horse has a fever. He's recently been exposed to a horse that tested positive for the neurologic strain of equine herpesvirus-1 (EHV-1). You call your vet, who comes out and swabs the horse's nasal passages and draws a tube or two of blood. A few days later you get a call confirming that your horse is positive for EHV-1. What exactly happened from the time your horse's samples left your barn to when you got that call?

Equine herpesvirus-1 is highly contagious and can cause a variety of ailments in horses, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (the neurologic form). Clinical signs of EHV-1 myeloencephalopathy include fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. The virus is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions, but it isn't transmissible to humans.

An ongoing outbreak of the virus affecting several Western states and Canadian provinces (believed to have started at the National Cutting Horse Association's [NCHA] Western Regional Championship competition that ended May 8) has many horse owners asking questions about all aspects of EHV-1. Udeni Balasuriya, BVSc, PhD, professor of virology at the University of Kentucky's Gluck Equine Research Center, and Nicola Pusterla, DVM, PhD, Dipl. ACVIM, an associate professor in the Department of Medicine and Epidemiology at the University of California, Davis, shared some insight on what happens when a horse's sample arrives at the laboratory, and what test results mean.

Sample Collection and Submission

"The collection and submission of appropriate clinical samples for laboratory diagnosis is very important," Balasuriya said, noting the importance of the veterinarian procuring both nasal swabs and blood during any suspected EHV-1 outbreak.

Nasal swabs and blood samples provide a chance at finding the virus itself or viral DNA (indicating whether the horse is shedding the virus), while serum samples afford an opportunity to detect the horse's antibodies to the virus.
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