Equine Herpes Virus (EHV-1)


6/16/2011 - Equine Herpes Virus (EHV-1) Situation Report

6/3/2011 - WSDA: Management Options

6/3/2011 - WSDA: State vet recommends easing of horse movement 

5/31/2011 - WSU Veterinarians Confirm Postmortem Equine Herpes Case

5/27/2011 - State veterinarian: horse owners should vaccinate for West Nile virus - WSDA

5/26/2011 - Equine Herpes Virus (EHV-1) Situation Report

5/25/2011 - Equine herpes virus outbreak: 44 horses test positive in 9 Western states, veterinarians report - As initial incubation period comes to a close, veterinary officials shift to monitoring secondary exposure.

5/20/2011 - WSU Veterinarians Confirm Two More Equine Herpes Cases

5/19/2011 - Equine Herpes Virus (EHV-1) Situation Report

5/19/2011 - AAEP Press Release

5/19/2011 - WSDA EHV-1 Update

5/18/2011 - Equine herpes virus outbreak grows; California state veterinarian confirms 10 new cases - DVM 360

5/18/2011 - Second case confirmed in Washington - EHV-1 Outbreak: State Veterinarians Monitoring Closely - the Horse.com

5/17/2011 - EHV-1 Infection Risk in Alpacas and Llamas - Colorado State Univ. Veterinary Teaching Hospital News Release


AAEP Horse Owner Resource Page - EHV/EHM horse owners resource page, which includes a new FAQ for horse owners.

AAEP DVM Resource Page

Awakening the Dormant Dragon: Neurological Form of Equine Herpesvirus-1 – White paper from UC Davis on Equine Herpes Myeloencephalopathy (EHM)

Information and resources about equine herpes virus outbreak from the WSDA

For additional resources, access APHIS USDA’s equine herpesvirus 2009 brochure: Equine Herpesvirus (EHV) Myeloencephalopathy: A Guide to Understanding the Neurologic Form of EHV Infection.

USDA APHIS monitoring and surveillance

The Horse.com - Equine Herpesvirus-1 Myeloencephalitis (EHV-1/EHM) Resources

Check before issuing Health Certificate for horses - With the number of equine herpesvirus-1 (EHV-1) cases rising in the western US, various states have implemented new importation requirements for horses. Veterinarians are encouraged to contact the state of destination before issuing an official Health Certificate. As of May 20, 2011, EHV-1 cases have been confirmed in Arizona, California, Colorado, New Mexico, Oregon, Texas, Utah and Washington. Idaho has suspected, but unconfirmed cases. Montana, Nebraska, Nevada, North Dakota, South Dakota and Wyoming have not reported any cases.

Equine Herpes Virus (EHV-1) alert for Washington Equine Owners and Veterinarians

Released 5/16/2011

The National Cutting Horse Association has notified members attending the Western National Championships in Ogden, Utah on April 30-May 8, 20ll of possible exposure to severe neurologic form of Equine Herpes Virus (EHV-1). Confirmed and suspected cases have been found in Utah, Colorado, Idaho, Washington, and other states. Washington horses which traveled to this event, or are stabled with horses that traveled to this event may have been exposed to this severe strain of EHV-1.

Owners of horses who participate in the Ogden, Utah event should notify their veterinarian and isolate and monitor their horses for clinical signs of disease. Individual horse and barn biosecurity should be implemented immediately. This virus is easily spread by aerosol (airborne) transmission, horse-to-horse contact with nasal secretions on equipment, tack, feed and other surfaces. People can spread the virus by means of contaminated hands, clothing, shoes, and vehicles.

Since rectal temperature above 102 usually precedes other clinical signs, it is recommended that temperatures of individual horses be taken twice a day. If a temperature above 102F is detected in a horse that attended this event, owners, trainers and veterinarians should institute and enforce a “no movement” policy for your premises or facility to help stop the spread of this virus. No outside horses should be allowed on to the premises and all resident equines should not travel off the premises for 28 days after the last fever or case of EHV-1 is identified. Visitors and service people should be limited to only what is absolutely necessary.

The EHV-1 organism spreads quickly and the neurologic form of the virus can reach high morbidity (sick) and mortality (death) rates. The incubation period (time of exposure to illness) of EHV-1 is typically 2-14 days. Horses with severe clinical signs of neurological EHV-1 have large viral loads in their blood and nasal secretions, may shed virus for as long as 28 days if they survive, and are thought to present the greatest danger for spreading the disease.
Clinical signs may include nasal discharge, in-coordination, hind-end weakness, recumbency, lethargy, urine dribbling and diminished tail tone. There is no specific treatment for EHV-1. Treatment may include intravenous fluids, anti-inflammatory and anti-viral drugs 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. Laboratory submission of nasal swabs and blood samples collected form horses suspected to be affected can be utilized for virus detection and isolation.


The disease is not transmittable to humans.

EHV-1 is a Notifiable Disease to the Washington State Veterinarian’s office. Any person with confirmation of a case of EHV-1 should call 360-902 1881, 360-902-1835, or 360-902-1878 to report the disease. Please leave a message with contact information.

For additional resources, access APHIS USDA’s equine herpesvirus 2009 brochure: Equine Herpesvirus (EHV) Myeloencephalopathy: A Guide to Understanding the Neurologic Form of EHV Infection.

WSU Veterinary Teaching Hospital enters voluntary isolation for equine and camelid patients

The Washington State University Veterinary Teaching Hospital is entering a period of voluntary isolation for equine and camelid patients. This is in response to a patient that was confirmed to be shedding Equine Herpes Virus type 1 (EHV-1). In the past week there have been 2 confirmed cases of EHV-1 in Colorado in horses that competed at the National Cutting Horse Association Western National Championships in Ogden, Utah. A horse admitted to the Washington State University Veterinary Teaching Hospital for evaluation of unrelated problems was found to have competed at the show. Subsequent diagnostic testing confirmed that the horse was positive for EHV-1. Due to the potential for spread of the virus, access to the VTH is currently restricted. During this time, no new equine or camelid patients may be admitted to the hospital except for critical emergencies. It is expected that the period of isolation will last at least 2 weeks. There are currently no horses exhibiting signs of EHV-1 at WSU. Equine Herpes Virus does not affect cattle, sheep, goats, pigs or birds, and the remainder of the VTH remains open. There is no risk of transmission to people.

We are taking every precaution to ensure the health and well-being of animals. We hope that the following information will be helpful.

Equine Herpes Virus is a common virus in equine populations worldwide. There are several strains of the virus, with EHV-1 and EHV-4 being most often involved in clinical disease. EHV-1 can cause respiratory disease, abortion and neurologic disease, while EHV-4 typically causes respiratory disease. Neurologic disease, which is generally caused by specific strains of EHV-1, is called equine herpesvirus myeloencephalopathy (EHM).

For more information on EHV-1 and WSU’s isolation period , visit WSU’s College of Veterinary Medicine website


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