Members of the equine community were concerned by the report of a September outbreak of Equine Herpes Virus discovered at Kennedy Meadows on the heels of a May outbreak in Utah confirmed by the California Department of Food and Agriculture (CDFA) where 400 horses were exposed to the virus, but local veterinarians were quick to dispel any fears that may have erupted over this common, but rarely fatal affliction.
“It’s good to be vigilant but it’s one of those diseases with a lot of hype that can be fatal but rarely,” Mackenzie Adams, Pioneer Equine Veterinarian said of the Equine Herpes Virus (EHV-1).
“One horse in Kennedy Meadows got very sick,” she confirmed.
An alert sent out by Pioneer Equine Hospital on Facebook warned the horse community to a potential exposure on Sept. 10 at a ride in Tuolumne County. Eight horses displayed clinical signs of infection and were confirmed by the CDFA as infected and 150 horses were tested. The CDFA was contacted and the situation was monitored closely. One of the eight horses was euthanized. The CDFA lifted the quarantine on the Tuolumne and San Joaquin County premises on Oct. 5.
“It’s a virus that’s very prevalent in the horse population,” Adams explained. “The vaccine is not very protective against the virus but it lessens the shedding associated with the infection. The virus can remain latent and stay inside the cells and not cause a problem for years and then, all of sudden, pop out. In the majority of cases, it causes a mild respiratory infection.”
According to the USDA website in the Animal and Plant Health Inspection Service department, EHV-1 infection in horses can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. The neurologic form of EHV-1 is called Equine Herpes Virus Myeloencephalopathy (EHM). The virus can spread through the air, contaminated equipment, clothing and hands. EHV-1 is endemic to the United States and is usually handled by the States involved; USDA becomes involved in cases involving multiple States or movement of horses across State lines.
The CDFA managed to contain the May neuropathogenic outbreak of EHV-1 that occurred at the National Cutting Horse Associations Western National Championships in Ogden, Utah through prompt and thorough actions to isolate and monitor exposed animals. In a CDFA press release, State Veterinarian Dr. Annette Whiteford said, “We also owe the success of this project in part to the outstanding isolation biosecurity measures implemented by horse facility managers, show/event managers and other professionals who work with and care for horses.”
According to the USDA, 13 horses were euthanized as a result of the primary and secondary exposure to the outbreak in Utah. A total of 90 confirmed EHV-1 or EHM cases were reported in 10 States (AZ, CA, CO, ID, NM, NV, OK, OR, UT, and WA).
Education being key, Whiteford included the following tips to minimize the disease risk:
• Minimize horse nose-to-nose contact with horses of unknown disease status.
• Don’t share equipment including buckets, tack and grooming equipment.
• Avoid using communal water troughs.
• Fill water buckets directly from the faucet to eliminate potential hose contamination.
• Limit human contact between horses or wash hands or use hand sanitizer between horse contacts.
• Prior to returning home from an event, clean and disinfect all equipment, including trailer, clothing, tack grooming supplies.
• Isolate all new horses or horses returning home for a minimum of three weeks. Isolation means no direct contact with other horses or humans and no indirect contact via shared equipment.
• Consult your veterinarian to establish appropriate vaccination for your horse(s).
For more information on EHV-1, the following websites are useful: http://www.aaep.org/EHV_resourcesowner.htm