Horse Illustrated Magazine

A recent outbreak of Equine Herpes Virus-type 1 (EHV-1) has shaken the Florida show horse world, along with the rest of the country. The outbreak started in mid December just as the start of the show-jumping season was about to begin in Palm Beach County, prompting officials to cancel big events. Since then, nine cases of Equine Herpes Virus – type 1 (EHV-1) have been confirmed with laboratory testing from horses–seven in the Wellington, Florida area, one in Ocala, Fla., and one in Indiantown, Fla. Five horses have died as a result of this outbreak, although only two of those cases could be confirmed by laboratory tests.

State and federal officials are working closely with veterinarians, owners and barn managers to identify potentially exposed animals and suspect cases and to prevent this current outbreak from spreading, but currently, there are no state or federal restrictions for horse movements into, within, or out of the state of Florida, although several facilities are under quarantine.

EHV-1 causes respiratory infection, and can cause abortion in pregnant mares, but it can also lead to severe neurological disease resulting in paralysis and death. The biggest problem with EHV-1 is that once horses have been infected they can become latent carriers of the virus for the rest of their life and can shed the virus during times of stress. The intermittent shedding by carrier horses is believed to be the primary cause behind outbreaks of the disease.
EHV-1 outbreaks are all too familiar to horse owners. An Ohio EHV-1 outbreak in 2003 affected over 150 horses, and at least 15 of those died.

EHV-1 transmission generally requires direct or close contact between horses. Transmission can also occur through contaminated equipment, clothing and hands. Horses with clinical signs—coughing, sneezing, incoordination in neurological cases, et cetera–should be isolated and kept 40 feet or more from other horses, and a veterinarian should be called immediately.

Because EHV-1 is a virus, it does not respond to antibiotics. Supportive treatment usually includes anti-inflammatory drugs, fluids to maintain hydration, and slings for horses that are unable to stand. In most cases, horses that remain standing have a good prognosis, although recovery may take weeks or months. Horses that go down and are unable to stand have a poor prognosis.

While EHV vaccines are available, none are specifically labeled for the neurologic form of EHV-1. Concerned owners should discuss with their veterinarian whether vaccination of their horses is recommended, the type of vaccines available, and the frequency of vaccination. Vaccination in the face of an outbreak will probably not prevent infection but may lessen respiratory signs and reduce viral shedding with future exposure.

Despite this current EHV-1 outbreak in Florida, work continues in preparation for the 2007 Winter Equestrian Festival scheduled to begin on January 24, 2007, at the Palm Beach Polo Equestrian Club in Wellington, Fla. The Winter Equestrian Festival is the nation’s longest consecutively-running equestrian sporting event.