To Washington Horse Owners and Veterinarians:
I am writing to inform you that Washington is still experiencing cases of Equine Herpes Virus-1 (EHV-1) reported to my office from stables in Western Washington area. Quarantine and biosecurity practices are being observed for all positive and exposed horses. There are horses that attended the HITS Thermal Horse Show in Riverside County, CA from March 5th to 11th still involved in the exposures.
Test results confirm that the horses were exposed to what is commonly called the wild strain of EHV-1 that is prevalent in the U.S., not the more serious neuro-variant form of the disease involved in Washington’s EHV-1 outbreak last year. Both forms of the virus can cause horses to show signs of fever, nasal discharge, lack of muscle coordination, hind end weakness, diminished tail tone or inability to stand.
I want to take this opportunity to emphasize that anytime there is co-mingling of animals, there is risk of sharing a disease-causing organism. Preventing the spread of disease by consulting with your veterinarian and practicing good animal health and biosecurity practices will result in a more healthy horse population and successful events.
Equine Herpes Virus (EHV-1) infection in horses can cause respiratory disease, neurological disease, abortion in mares and neonatal foal death. The neurological form of the disease is known as Equine Herpes Myeloencephalopathy (EHM). The neurological form of the virus has the potential to cause high morbidity and mortality. EHV-1 is easily spread and typically has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may persist longer in infected horses. For this reason, the isolation period recommendation for confirmed positive EHM cases is twenty-one (21) days combined with a negative test before release or 28 days without a negative test before release.
I welcome the opportunity to review biosecurity practices with you, if and when you feel such practices would contribute to a more successful conclusion of future events scheduled in your area.
Leonard E. Eldridge DVM
Washington State Veterinarian
360 902 1881