Study: Neurologic Signs Not Limited to One EHV-1 Strain

Anytime a horse develops fever, malaise, and a stumbling gait or inability to stand, owners should contact a veterinarian immediately--they might be dealing with equine herpesvirus-1 (EHV-1). In addition, the animal should be quarantined to prevent transmitting the virus to other horses through nasal secretions, said Gillian A. Perkins, DVM, Dipl. ACVIM, of Cornell University, who recently authored a report on the virus.

EHV-1 can cause a number of problems in horses, but the neurologic disease called equine herpesvirus myeloencephalopathy (EHM) has gained considerable attention. Researchers have developed a way to tell a "non-neurologic" strain from a "neurologic" strain, and veterinarians seem more interested in testing only for the neurologic type.

After looking at 23 years' worth of EHV-1 nasal and blood samples and examining the horses' medical records to see which forms caused respiratory signs, abortions, or neurologic disease, Perkins and her colleagues concluded that any type of the EHV-1 virus has the ability to cause EHM.

"EHM can result from the 'non-neurologic form' of the virus and finding either virus in a horse with neurologic symptoms is important," Perkins said.

Therefore, veterinarians should test for EHV-1 by PCR and virus isolation. If the test is positive, they can find the specific virus type through further tests, including sequencing or allelic discrimination qPCR.

There is no cure for EHM. Treatment is mostly supportive with drugs that reduce inflammation. "Targeting the virus itself is difficult," she said. "Recent studies have investigated antivirals, such as oral valacyclovir, which has had some promising results."

Perkins recommended that owners make sure their horses are vaccinated against EHV-1 with a modified-live EHV-1 vaccine and maintain good health management with nutrition, deworming, and other basic husbandry.

The study, "Investigation of the prevalence of neurologic equine herpesvirus type-1 (EHV-1) in a 23-year retrospective analysis (1984-2007)," was published in Veterinary Microbiology. The abstract is available on PubMed.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.