ca.gov

California Department of Food and Agriculture

Equine Herpes Virus


DEFINITIONS:

  • Confirmed Case: A horse which displays compatible clinical signs AND has a positive laboratory diagnostic test for the neuropathogenic strain of Equine Herpes Virus-1 OR any horse which displays neurologic signs AND is confirmed positive on a laboratory diagnostic test for any strain of Equine Herpes Virus-1.
  • Compatible Clinical Signs: Any one or more of the following clinical signs: fever, nasal discharge, ataxia, hind end weakness, diminished tail tone, and/or recumbency.
  • Exposed Horse: A horse which has been in close contact with a confirmed case of the Equine Herpes Virus (EHV-1) within the last 14 days.

Alert

CURRENT EHV-1 SITUATION:

Recommendations for Participants at Equine Events

CDFA Animal Health Officials are continually monitoring for Equine Herpes Virus-1 cases. 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 follow 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

PREVIOUS CALIFORNIA EHV-1 OUTBREAKS


March 2015

Santa Cruz County

  • A fifteen year old Warmblood gelding, originating from a Santa Cruz County premises, displaying hind limb ataxia and an inability to urinate and defecate was confirmed positive for the neuropathogenic strain of Equine Herpes Virus-1. Due to the severity of disease the positive horse was euthanized.
  • All exposed horses were monitored and no additional cases were confirmed.
  • There was no epidemiologic link to any previous EHV-1 incidents in CA.

February 2015

Monterey County

  • A fourteen year old Quarter Horse gelding in Monterey County, displaying hind limb ataxia and an inability to urinate and defecate was confirmed positive for the non-neuropathogenic strain of Equine Herpesvirus -1. The horse recovered.
  • All exposed horses were monitored and no additional cases were confirmed.
  • There was no epidemiologic link to any previous EHV-1 incidents in California.

April 2014

Santa Barbara County

  • A seven year old Quarter Horse mare displaying mild neurologic signs uncharacteristic of Equine Herpes Myeloencephalopathy (EHM), specifically vestibular signs, abnormal prehension, and hypermetria of the right front for limb was confirmed positive for the non-neuropathogenic strain of Equine Herpesvirus -1.
  • Based on the low viral load and atypical clinical signs, it is possible that EHV1 is not the cause of disease in this horse. Out of an abundance of caution, the horse was classified as case of EHM by CDFA was isolated under quarantine. The horse successfully recovered.
  • There was no epidemiologic link to any previous EHV-1 incidents in California.

February 2014

San Diego County and Los Angeles County

  • A three-year old Thoroughbred racehorse filly in San Diego County displaying ataxia and a three-year old Thoroughbred racehorse colt at Santa Anita Park displaying a fever. Both horses recovered.
  • Laboratory results confirmed the non-neuropathogenic strain of Equine Herpesvirus-1 in samples from both horses.
  • All exposed horses at Santa Anita Park were monitored and no additional cases were confirmed.
  • There was no epidemiologic link to any previous EHV-1 incidents in California.

July 2013

Contra Costa County

  • A four year old Quarter Horse displaying severe neurologic signs was euthanized.
  • Laboratory results confirmed the neuropathogenic strain of Equine Herpesvirus-1.
  • The epidemiologic investigation revealed no additional exposed horses as the mare was the sole horse on a cattle pasture.
  • There was no epidemiologic link to any previous CA EHV-1 Incidents.

March 2013

Los Angeles County

  • A neurologic horse at Santa Anita Park was euthanized
  • Necropsy results confirmed Equine Herpes Myeloencephalopathy based on finding the neuropathogenic strain of Equine Herpesvirus-1
  • All horses on the premises were monitored and no additional horses developed a fever or other symptoms compatible
  • There was no epidemiologic link to any previous CA EHV-1 Incidents

San Diego County

  • A Warmblood stallion displaying mild neurologic confirmed positive for the non- neuropathogenic strain of Equine Herpes Virus-1
  • The positive horse has recovered and no additional horses on the premises displayed compatible clinical signs
  • The confirmed horse participated in the HITS Thermal Horse Show in March 2013

Santa Barbara County

  • A Welsh cross gelding displaying neurologic signs was confirmed positive for the non-neuropathogenic strain of Equine Herpes Virus-1
  • The positive horse has recovered and no exposed horses displayed compatible clinical signs
  • The confirmed horse participated in the HITS Thermal Horse Show in March 2013

April 2012

Santa Barbara County

  • A severely neurologic horse was euthanized on March 31, 2012.
  • Necropsy results confirmed Equine Herpes Myeloencephalopathy based on finding the non-neuropathogenic strain of Equine Herpesvirus-1 in both the brain and spinal cord.
  • There was no epidemiologic link to any previous CA EHV-1 incidents

March 2012

Monterey County

  • Two horses displaying neurologic signs were confirmed positive for the non-neuropathogenic strain of EHV-1.
  • Both horses participated in the HITS Thermal Horse Show March 5-11, 2012.
  • Quarantine was released on April 3, 2012.

San Diego County

  • One horse displaying neurologic signs was confirmed positive for the non-neuropathogenic strain of EHV-1.
  • The confirmed horse participated in the HITS Thermal Horse Show March 5- 11, 2012.
  • Quarantine was released after two negative tests on March 23, 2012

Los Angeles County

  • One horse displaying neurologic signs was confirmed positive for the non-neuropathogenic strain of EHV-1.
  • The confirmed horse was exposed to horses which participated in the HITS Thermal Horse Show March 5-11, 2012.
  • This horse was euthanized on April 7, 2012 due to severe laminitis.

January 2012

Riverside County

  • Large multi-discipline facility
  • Only one positive confirmed for the neuropathogenic strain of EHV-1
  • Positive horse displaying severe neurologic signs was euthanized on January 23, 2012.
  • Affected premises quarantined on January 25, 2012 and released on February 14, 2012
  • Epidemiologic investigations reveal no link to any prior CA EHV-1 Outbreaks.

Orange County

  • Large multi-discipline facility
  • 16 confirmed positive for the neuropathogenic strain of EHV-1
  • 1 confirmed case displayed neurologic signs and all others displayed compatible clinical signs such as fever, nasal discharge, and/limb edema.
  • Affected premises quarantined on January 10, 2012 and released on February 14, 2012
  • Epidemiologic investigations reveal no link to any prior CA EHV-1 Outbreaks.

September 2011:

Tuolumne County:

  • 8 horses confirmed positive for the neuropathogenic strain of EHV-1 on index Tuolumne county premises.
  • Affected premises quarantined on September 12, 2011 and released on October 5, 2011
  • 6 with neurologic signs, 2 with fever only
  • 1 of the 8 confirmed positive cases was euthanized.
  • All infected horses are isolated and enhanced biosecurity measures implemented.
  • Epidemiologic investigations reveal no link to the Sonoma September 2011 or the May 2011 Cutting Horse Outbreaks.
  • 2 additional confirmed positive horses on a San Joaquin Secondary Exposed Premise. Both horses were exposed to the virus while visiting the Tuolumne county premises.
  • October 5, 2011 Quarantines released on Tuolumne and San Joaquin County premises.

Sonoma County

  • Single Sonoma County premises affected
  • 3 horses confirmed positive for neuropathogenic strain of EHV-1.
  • One neurologic and 2 febrile only.
  • Neurologic horse died.
  • 13 exposed horses were temperature monitored twice daily and observed for clinical signs of disease. None of the 13 ever demonstrated clinical signs of disease.
  • Epidemiologic Investigation revealed no link to the May 2011 outbreak
  • Quarantine implemented on August 23,2011.
  • Situation contained and quarantine release on September 13, 2011.

May 2011:

  • 400 horses exposed to neuropathogenic strain of EHV-1 at the National Cutting Horse Association (NCHA) Western National Championship held in Ogden, Utah April 30-May 8, 2011.
  • All 54 California exposed horses were isolated, temperature monitored twice daily and observed for clinical signs of disease.
  • 22 California horses were confirmed positive for the neuropathogenic strain of EHV-1.
  • Positive horses resided on 14 premises in 12 counties.
  • 8 displayed neurologic signs, 13 with fevers only and 1 with respiratory signs only.
  • June 20, 2011 California declared containment of the EHV-1 outbreak associated with the Ogden, UT cutting horse event.