In a letter to Washington horse owners and veterinarians written on April 2, 2012, Leonard Eldridge, DVM, State Veterinarian for Washington State Department of Agriculture writes that four confirmed cases of Equine Herpes Virus-1 (EHV-1) have been reported to his office from stables in Western Washington.
Up-date on Equine Herpes Virus-1 cases
Four confirmed cases of Equine Herpes Virus-1 have been reported from stables in Western Washington and one in Los Angeles, CA.
Quarantine and biosecurity practices are being observed for all positive and exposed horses. Two of the horses attended the HITS Thermal Horse Show in Riverside County, CA from March 5th to 11th.
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 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.
In addition to the cases in Washington State, a case of the milder form of EVH-1 has also been confirmed in Los Angeles, California.
Dr. Eldrige emphasizes 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 21 days combined with a negative test before release or 28 days without a negative test before release.