December 27, 2017
Last week, the Department of Agriculture was notified of one laboratory-verified case of Equine Herpes Virus Myeloencephalopathy or EHV – 1, neuropathogenic strain, in King County, WA. Quarantine was immediately instituted by the Department of Agriculture and the Department is working closely with the facility and their veterinarian to contain this outbreak. Subsequent testing identified an additional five infected horses at the facility. As of 2017-12-26, 7 horses with neurological signs have been euthanized out of population of 60 horses.
EHV – 1, neurotropic form, is a highly contagious virus that can result in fatal illness in horses. The disease is spread from horse to horse through direct contact, on feed, tack and equipment. While people cannot be infected by the virus, they can carry the virus on their clothes or hands. Horse owners should carefully wash their hands, clothing and equipment and avoid using the same equipment on different horses.

In addition to the quarantine, additional testing of horses that have been housed near the affected horse or horses demonstrating clinical signs has been conducted. Tracing of animals that may have come into contact with the infected horse is ongoing.

Given the highly infectious nature of the virus, here are some strong recommendations for horse owners.

Closely observe your horse and look for signs of possible infection, which include:

· Fever of 102.5 degrees F or higher

· Discharge from the eyes or nose

· Respiratory symptoms

· Swelling of the limbs

· Spontaneous abortions

· Neurological signs such as unsteady gait, weakness, urine dripping, lack of tail tone and recumbency.

Be sure to obtain and record the body temperatures of all horses on the premises twice daily, ideally first thing in the morning, and last thing at night, and before administering medications as some medications can lower body temperature.

Most importantly, if you detect any of the symptoms above, notify your veterinarian immediately. Your veterinarian may want to take nasal swabs for virus detection or blood samples for evidence of exposure to EHV – 1.

EHV – 1 testing

Suspected cases should be checked for EHV-1 by a veterinarian. The Washington Animal Disease Diagnostic Laboratory in Pullman, WA provides EHV-1 testing, including differentiating the EHV-1 neuropathogenic strain. Veterinarians should contact WADDL at 509 335-9696 to submit a red top (serum) blood tube, and a lavender top (EDTA) blood tube and nasal swabs directly to Dr. Jim Everman or Dr. Kevin Snekvik at WADDL.


Although there are several EHV – 1 vaccines available in North America that control respiratory disease and/or abortion in horses, none of the vaccines provide protective immunity against EHV – 1, neurotropic form.


To protect your horse from becoming infected and help limit the potential spread of this virus, here are several things all horse owners should be doing.

1. Monitor all horses on your premises for the previously described symptoms.

2. Limit direct horse-to-horse contact.

3. Limit stress to horses.

4. Don’t share equipment between horses.

5. Clean barn areas, stables, trailers or other equine contact surfaces thoroughly, removing all organic matter (dirt, nasal secretions, uneaten feed, manure, etc.) before applying a disinfectant. Organic material decreases the effectiveness of disinfectants. Mix disinfectants according to the manufacturer’s recommendation and follow their recommendations for contact time.

6. Use footwear disinfectant and hand sanitizer when moving between areas.

7. If you have a potentially exposed horse, restrict human, pet and vehicle traffic from the area where the exposed horse is stabled.

8. Clean all shared equipment and shared areas, again removing dirt and manure before application of a disinfectant.

9. Self- quarantine any horses with possible symptoms away from other horses and contact your veterinarian immediately.

The time between exposure and illness from EHV – 1 can vary from two to 14 days. By self-quarantining animals with possible symptoms, practicing good biosecurity on the farm, and during travel and contacting your veterinarian as soon as you suspect possible symptoms, horse owners can do a lot to prevent further spread of the virus.

Dr. Brian Joseph, State Veterinarian