News Release Distributed 05/18/11

Horse owners should be alert for equine herpes myeloencephalopathy – or EHV-1 – in their horses, according to veterinarians with the LSU AgCenter and the LSU School of Veterinary Medicine.

An outbreak of EHV-1 has been traced to horses that attended the National Cutting Horse Association’s Western National Championships in Ogden, Utah, on April 30-May 8. Horses who participated in this event may have been exposed to this EHV-1 virus.

The LSU School of Veterinary Medicine is encouraging owners of horses that participated in Ogden or veterinarians who know of horses that were at the event or came into contact with horses at that event to isolate and monitor their horses for clinical signs of disease.

“A rectal temperature in excess of 102 degrees commonly precedes other clinical signs,” said LSU veterinarian Dr. Rebecca S. McConnico. “Therefore, we are urging owners to take temperatures on each individual horse twice a day. If a temperature above 102 degrees is detected, contact your private practitioner immediately.”

Veterinarians can take nasal swabs and blood samples collected from exposed horse and submit them for laboratory virus detection and isolation, she said.

The EHV-1 organism spreads quickly from horse to horse, and the neurologic form of the virus can reach high morbidity and mortality rates, the experts say. The incubation period of EHV-1 is typically 2-14 days, but it can be up to 28 days or longer. In horses infected with the neurologic strain of EHV-1, clinical signs may include nasal discharge, incoordination, hind-end weakness, recumbency, lethargy, urine dribbling and diminished tail tone. Other signs of neurologic disease, such as a head tilt and difficulty swallowing, also may be present.

“Prognosis depends on severity of signs and the period of recumbency,” McConnico said. “Treatment may include intravenous fluids, anti-inflammatory drugs, specific antiviral agents and other appropriate supportive treatment. Currently, there is no equine vaccine that has a label claim for protection against the neurological strain of the virus.”

Horse-to-horse contact, aerosol transmission and contaminated hands, equipment, tack, and feed all play a role in disease spread. Experts believe horses with severe clinical signs of neurological EHV-1 illness have large viral loads in their blood and nasal secretions and therefore present the greatest danger for spreading the disease.

Immediate separation and isolation of identified, suspected cases and implementing appropriate biosecurity measures are key elements for disease control, McConnico said. Horses showing neurologic disease should be evaluated as soon as possible by an equine veterinarian.

Additional information is available online. An equine herpes myeloencephalopathy brochure is at www.aphis.usda.gov/vs/nahss/equine/ehv/equine_herpesvirus_brochure_2009.pdf.

And an equine herpes myeloencephalopathy fact sheet can be found at www.cdfa.ca.gov/AHFSS/Animal_Health/pdfs/EHV-1FactSheetSept2010.pdf.

Other online resources are available from the U.S. Department of Agriculture at www.aphis.usda.gov/vs/nahss/equine/ehv/ and the American Association of Equine Practitioners at www.aaep.org/pdfs/control_guidelines/Equine%20Herpes%20Virus.pdf.