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Horse Owners Alerted about Equine Herpesvirus Outbreak; Hospital Remains Open

The following statement was prepared by faculty of the Equine Medicine Service at the William R. Pritchard Veterinary Medical Teaching Hospital. The Large Animal Clinic remains open to equine patients and for other client services.

May 17, 2011

During the past week in Colorado, there have been at least two confirmed cases of equine herpes-1 infection in horses that competed at the National Cutting Horse Association Western National Championships in Ogden, Utah. Other horses that competed in Ogden, Utah were transported to the Kern Country Cutting Horse Association show in Bakersfield, California, and some of these horses became ill, with one horse being euthanized at the fairgrounds. One horse was transported from Bakersfield to the isolation facility at the William R. Pritchard Veterinary Medical Teaching Hospital. Another horse that attended the Ogden show was also sent to UC Davis. Both of these horses have been confirmed as positive for EHV-1. In addition, as of today, at least 4 additional horses in various areas of Northern California have been confirmed as positive for EHV-1.

William R. Pritchard Veterinary Medical Teaching Hospital (VMTH)

The VMTH operates an isolation facility that was designed specifically to allow us to provide the best possible care to horses with infectious diseases such as EHV-1, while completely segregating them from other hospitalized horses and outpatients. The isolation facility is located a substantial distance from the main hospital, utilizes a dedicated group of staff and employs rigid infectious disease control and containment protocols that prevent other horses from becoming exposed. Currently, the two horses mentioned above are being treated under maximum isolation. These horses have no contact with other horses at the hospital. Because of the presence of EHV-1 in the community, the VMTH is taking every precaution to prevent EHV-1 entry into the general hospital. Every horse admitted to the hospital is being tested for EHV-1 and full biosecurity precautions are in force during the next few weeks as necessary.

Equine Herpesvirus

Equine herpesvirus is a common virus of horses world wide, and can cause respiratory disease, abortions, and less commonly neurologic signs as it has in these cases. It is transmitted by aerosol and close contact between horses, including fomites such as shared tack, equipment and by human hands. Though there are vaccines available for prevention of respiratory disease and abortions caused by equine herpesvirus, there are currently none that are labeled for prevention of the neurologic form of the disease.


Please contact your veterinarian if your horse may have been exposed to EHV-1 at one of these shows or through contact with a horse that has returned from one of these events. In general, exposed horses should be isolated and have their temperatures monitored twice daily. If an exposed horse develops a fever, diagnostic testing of nasal swabs and blood should be performed.  Consideration should be given to vaccination of resident, non-exposed horses on premises where potentially exposed horses are returning to, as per your veterinarian’s guidelines.

Resources -- Links and fact sheets (PDF)

California Animal Health and Food Safety Laboratory
This laboratory performs testing services.

UC Davis Real Time PCR Research and Diagnostics Core Facility  (PCR testing services)

UC Davis Center for Equine Health Fact Sheet

USDA Animal and Plant Health Inspection Service 2009 brochure about equine herpes myeloencephalopathy

California Department of Food and Agriculture Equine Herpes Myeloencephalopathy Fact Sheet

CDFA Equine Herpes May 13th update

CDFA press release of May 17

American Association of Equine Practitioners Fact Sheet


W. David Wilson, BVMS, MS, director, William R. Pritchard Veterinary Medical Teaching Hospital

K. Gary Magdesian, DVM, DACVIM, DACVECC, DACVCP, associate professor, equine critical care