Equine Herpes Virus (EHV-1) Confirmed in California

HorseShowA recent case of Equine Herpesvirus Myeloencephalopathy has been  confirmed in California. EHV-1 can cause four manifestations of disease in horses, including neurological form, respiratory disease, abortion and neonatal death.

It is important to learn the signs of this virus, and to take precautions to protect your horses.

Signs of EHV-1:  fever, nasal discharge, hind end weakness, diminished tail tone, lethargy, urine dribbling, head tilt, leaning against a fence or wall to maintain balance, and inability to rise.

According to the American Association of Equine Practitioners (AAEP), after infection, the incubation period may be as short as 24 hours, but is typically 4-6 days, and can be longer. EHV-1 typically causes a two-phase fever peaking on day 1 or 2 and again on day 6 or 7. With respiratory infections there is often serous or mucoid nasal and ocular discharge, but not a lot of coughing. There may be some persistent enlargement of lymph nodes under the jaw. With the neurologic form there are typically minimal respiratory signs, with fever (rectal temperature greater than 102 degrees F) being the only warning sign. Neurologic disease appears suddenly and is usually rapidly progressing, reaching its peak intensity within 24 to 48 hours from onset of neurologic signs.

Your horse has been exposed if it has been in close contact with a confirmed case of the Equine Herpes Virus (EHV-1) within the last 14 days.

New EHV-1 Case Confirmed

May 21, 2015 : A seven year old barrel racing Quarter Horse gelding, originating from San Luis Obispo County, displaying mild hind limb ataxia was confirmed positive for the non-neuropathogenic strain of Equine Herpesvirus-1. This strain of virus is responsible for the more common rhinopneumonitis cases.  A small percentage of the non-neuropathogenic infected horses can display neurologic signs compatible with equine herpes myeloencephalopathy which is a reportable disease in California. The quarantined gelding is under veterinary care in Santa Barbara County and is recovering. An investigation has been initiated and owners with potentially exposed horses will be contacted. Owners of exposed horses are asked to monitor their horses for clinical signs and take temperatures twice daily. The California Department of Food & Agriculture (CDFA) will continue to monitor the situation.

Recommendations for Participants at Equine Events

CDFA reminds horse owners traveling with horses to participate in an equine event, that there is always disease risk when horses of unknown health status are commingled for a show or competition.  CDFA strongly recommends that horse owners practice proper biosecurity when attending an equine event.  Compliance with basic biosecurity practices is an important factor in reducing risk of exposure to all contagious equine diseases.  Basic biosecurity measures to decrease potential disease spread at equine events include:

  • Limit horse-to-horse contact.
  • Limit horse-to-human-to-horse contact.
  • Avoid use of communal water sources.
  • Avoid sharing of equipment unless thoroughly cleaned and disinfected between uses.
  • Monitor your horse for clinical signs of disease and report any temperature over 102°F to a veterinarian.

For more information, visit the following sites:

CDFA: http://www.cdfa.ca.gov/ahfss/animal_health/equine_herpes_virus.html
AAEP: http://www.aaep.org/info/horse-health?publication=753