Equine Herpesvirus-1

 UW Animal Sciences logoEquine Herpesvirus-1 (EHV-1) has recently been identified in horses primarily in eastern Minnesota and in N Western Wisconsin. The WI Department of Agriculture, Trade and Consumer Protection (DATCP) is in communication with WI veterinarians and will continue to update them on the status of the EHV-1 outbreak.

EHV-1 is a contagious virus that can cause respiratory disease, abortion and in some cases neurologic disease. While it is not uncommon to see EHV-1, it isn’t typical to see several cases in which the horses show neurologic symptoms from the disease. Common symptoms of the neurologic form of EHV-1 include weakness, lack of coordination and difficulty urinating. If these symptoms are noticed, a horse owner should immediately isolate the horse from other horses on the property and have the horse examined by a veterinarian. The incubation period for EHV-1 is 7-10 days. Horses who have been exposed may develop a fever and be shedding the virus, but may not be showing other symptoms of the disease yet. Thus, monitor your horse’s health by taking temperatures 2X day, especially if they may have been exposed to the disease.

EHV-1 is usually spread between horses in close contact with each other via nasal secretions or from the sharing of the same feed or water buckets. Transporting horses to shows, clinics, training sessions, lessons, or other gatherings of horses may increase the risk of exposure to the disease. Thus, restricting or limiting travel to activities where horses will be in contact with other horses provides the most effective way to reduce the spread to the disease. The Wisconsin state veterinarian is recommending that any horse with a fever or horse showing symptoms of disease such as a respiratory infection should be kept at home.

Although humans cannot be infected by the disease, they can aid in spreading it to other horses. People in communication with horses (especially affected horses or horses that may have been exposed) should practice good biosecurity procedures when working with different horses and between horse farms; including farriers, trainers, etc. The virus does not survive long in the environment or on people and can be easily killed by disinfectants and drying. See USDA biosecurity brochure for further details.


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 102o F to a veterinarian.

WI DATCP will continue to update veterinarians as the situation evolves. If you have planned horse activities in the near future, please communicate with your local veterinarian to discuss the current EHV-1 status for your area to assess the level of risk associated for that specific activity.

Additional information can be located at these sites.



California EHV-1 fact sheet http://www.cdfa.ca.gov/ahfss/Animal_Health/pdfs/Equine_EHMbrochure.pdf

MN Board of Animal Health EHV-1 Q&A http://www.cvm.umn.edu/umec/EHV1info/home.html

If you desire any more information, please contact

JoAnn (Liv) Sandberg

Equine Extension Specialist

287 Animal Sciences
1675 Observatory
Madison, WI  53706