Equine Herpesvirus

For general questions contact Animal Industries

EHV–1, is a contagious and potentially deadly virus that affects horses, causing respiratory disease, abortions in pregnant mares and in severe cases, neurological disease. The virus spreads easily between horses through direct contact, airborne respiratory particles, or indirectly via contaminated equipment, clothing and other shared items. 

Idaho does not have any confirmed cases of EHV-1 at this time.

Confirmed reports of Equine Herpesvirus Type 1 (EHV-1) in Texas, Oklahoma and Louisiana are linked to several recent equine competitive events in Texas and Oklahoma. Any Idaho horse owners who attended the Women’s Professional Rodeo Association (WPRA) World Finals in Waco, Texas November 5–9 or the Barrel Futurities of America World Championships in Guthrie, Oklahoma November 17-19, or were in proximity to these events should contact the Idaho State Veterinarian immediately (208) 332-8540. Horses are recommended to quarantine for a period of 21 days and should be monitored carefully for any signs of illness. 

ISDA recommends the following immediate steps for all horse owners: 
  • Quarantine any horse that attended the Waco, Texas or Guthrie, Oklahoma event(s) for at least 21 days from other equines and contact the State Veterinarian immediately.
  • Suspend hauling, showing, or any movement of equine.
  • Disinfect trailers, wash-racks, cross-ties, tie-areas, tack rooms, buckets, grooming tools, and any shared equipment. Use an appropriate virucidal disinfectant. 
  • Avoid sharing tack, halters, grooming equipment, buckets, water hoses, etc., between exposed and unexposed horses. 
  • Monitor temperatures twice daily for all exposed horses and report any fever (≥101.5 °F) or other signs to a veterinarian immediately. 
  • If any horse exhibits neurologic signs, coughing, or nasal discharge, isolate it immediately, wear protective gear, and call your veterinarian. 
  • Keep accurate records: track which horses were present at events, their movement, and who handled them for contact tracing if needed. 
  • Stay in contact with your local veterinarian and keep up to date on updates from state veterinary authorities. 

Equine Herpesvirus Type 1 is a notifiable disease that must be brought to the attention of ISDA within 48 hours of discovery. 

Symptoms of EHV-1 may include:
  • Fever.
  • Nasal discharge, coughing, or other respiratory changes.
  • Depression or lethargy.
  • Neurological changes, including stumbling, incoordination, loss of tail tone, urine dribbling, hind limb weakness, head tilt, or recumbency.
  • Abortions in pregnant mares.

*Horses that may have been exposed to EHV often take several days to demonstrate clinical illness and run the risk of shedding the virus undetected.

The EHV-1 virus spreads quickly and efficiently, making early precautions essential. Horses can transmit the virus directly through simple nose-to-nose contact, and infected animals may also release contagious airborne respiratory particles when they cough or sneeze. Indirect transmission is equally dangerous; shared tack, grooming tools, water and feed buckets, thermometers, clothing and other equipment can all carry the virus from one horse to another.  

Biosecurity

Due to the highly contagious nature of the virus, the Idaho State Veterinarian urges horse owners, trainers and event organizers to take immediate biosecurity precautions and to stop all equine movement to protect Idaho horses. 

People who work at multiple equine facilities should practice biosecurity measures by washing hands and changing footwear and clothing before entering each facility. 

AAEP General Biosecurity Guidelines  > AAEP Infectious Disease Guidelines: Equine Herpesvirus