EHV-1 in King County: What You Need to Know


On December 15th we received an alert from the Equine Disease Communication Center (EDCC) regarding a horse that tested positive for Equine Herpesvirus type-1 neurotropic strain at a barn in King County, WA. To start, we would like to express our sincerest condolences to all those who have lost a horse during this outbreak, and we are sending healing thoughts to those whose horses are currently battling the disease.

In the last several days more information has been released about this outbreak, and we have been contacted by numerous concerned horse owners. Following is a quick summary provided by Red Rock Equine Veterinary as of December 26th, including details from the WA State Dept. of Agriculture and WA State Vet Medical Association. Keep an eye on our Facebook page for updates as we'll be closely monitoring this outbreak.

King County Equine Herpesvirus (EHV type-1)

  1. Only one facility has been affected by the Equine herpes virus outbreak - Gold Creek Equestrian Center in Woodinville, WA. * Frequent updates are posted on their Facebook page

  2. NO OTHER CASES IN OTHER FACILITIES OR IN KING COUNTY OR SURROUNDING COUNTIES HAVE BEEN REPORTED.

  3. There are 60 horses at the facility out of which test results have been finalized on 37 of them. 9 horses have been confirmed to have tested positive for the neurotropic strain, 7 of which have been euthanized. The two other horses are still sick and but are improving. A third horse has had elevated temperatures but has not developed neurological symptoms. (Updated 12/27/17)

  4. The facility is under state quarantine, meaning that no horses may come onto or leave the property. Above-standard biosecurity protocols have been enforced and are being followed.

  5. There is a dedicated local equine veterinarian exclusively working with the facility and horses on a daily basis. The dedicated veterinarian is not in contact with/attending any other patients/horses as a precaution.

  6. The WA State veterinarian, among other authorities, are involved and assisting in the situation.

  7. There are several types of Equine Herpesviruses (1, 2, 4, 5). The one involved here is the type-1. Among the type-1s there are different strains. Some strains only cause fever and respiratory symptoms while others can lead to neurological symptoms, and a small group of the neurological cases are caused by a more virulent (aggressive) and newer strain (neurotropic strain).

  8. If a horse is infected by the Equine herpesvirus and develops the neurological form, the condition is then called Equine Herpes Virus Myeloencephalopathy (EHM).

  9. Most healthy horses carry one or more strains of the type-1 equine herpesvirus. It’s the same group of herpesvirus as the one that causes cold sores in people. Once you have it you carry it for many years or life. However, it will only clinically manifest when stresses or immunosuppression is in place. When it is clinically present the individual is highly contagious to others, even the ones that have the dormant herpesvirus.

  10. The Rhino vaccine most horses receive routinely (twice yearly) is the vaccine for some of these herpesviruses, including the type-1. Unfortunately, it does not provide protective immunity against the EHV-1 neurologic/neurotropic strain. However, there is still research trying to understand if the vaccine may help with the severity of these cases and spread of the virus.

AGAIN: NO OTHER CASES IN OTHER FACILITIES OR IN KING COUNTY OR SURROUNDING COUNTIES HAVE BEEN REPORTED.

Details from the WSVMA and WA State Department Of Agriculture