Equine Herpes Virus (EHV) Diagnosed in Virginia and California

Virginia Horse with Neurological Form of Disease Euthanized

Virginia and California are the latest states to report cases of Equine Herpes Virus (EHV-1) this week. Active cases or quarantines were announced the week before in Oregon, Iowa, Illinois and Pennsylvania.

On Thursday, the Virginia Department of Agriculture and Consumer Services reported:

“On May 21, the epidemiological investigation was completed on a farm in Prince William County where a single horse was euthanized due to neurologic disease, and whose post-mortem test results were reported as suspect-positive for the neurologic strain of Equine Herpesvirus-1. 

“The index horse had not traveled off of the farm recently, and no other horses on the farm have shown any signs of disease. All horses on the farm will continue to be closely monitored for 21 days past the date the index horse was euthanized. Horses will not be permitted to move on or off the farm during this monitoring period.”

This week’s outbreak follows an earlier one in February in Virginia’s Albemarle and Loudon counties. Quarantines of those farms ended in mid-March, according to the VDACS.

From California, a report of a sick barrel horse led to confirmed diagnosis of EHV in Santa Barbara County, also reported on Thursday. The California Department of Food and Agriculture is monitoring this case and published this statement”

“A seven-year-old barrel racing Quarter Horse gelding, originating from San Luis Obispo County, displaying mild hind limb ataxia was confirmed positive for the non-neuropathogenic strain of Equine Herpesvirus-1. This strain of virus is responsible for the more common rhinopneumonitis cases. A small percentage of the non-neuropathogenic infected horses can display neurologic signs compatible with equine herpes myeloencephalopathy which is a reportable disease in California. 

“The quarantined gelding is under veterinary care in Santa Barbara County and is recovering. An investigation has been initiated and owners with potentially exposed horses will be contacted. Owners of exposed horses are asked to monitor their horses for clinical signs and take temperatures twice daily. CDFA will continue to monitor the situation.”

No cases have been reported in Kentucky, but an update policy statement on EHV has been issued by the state veterinarian’s office. This information is important to anyone planning to take horses into that state to show or race, or for local competitors who wish to gain access to public facilities.

“The apparent increased frequency of disease and severity of symptoms being seen has lead Kentucky State Veterinarian Robert Stout to conclude extra precaution needs to be initiated and implemented to aide in mitigating the associated risk at equine events. 

“We are directing Kentucky facility managers and the managers of shows/exhibitions planned to be held in Kentucky to immediately review their biosecurity practices and if needed elevate their biosecurity plan to minimize opportunity of horses having direct or indirect contact with one another. 

“As an additional preventive measure, we encourage horsemen to consult their veterinarians and after evaluating their individual animal’s vaccination status consider if there is need or benefit to stimulating an immune response by vaccinating against EHV-1. 

“We acknowledge the available vaccines’ labels make no claim to prevent neurologic disease; but based on our experience managing outbreaks of this disease, and in consultation with infectious disease experts and research scientist, we continue to be of the opinion the vaccine does have a meaningful level of efficacy and may aide in reducing the impact of a disease incident. We have had mandatory EHV-1 vaccination of all horses entering Kentucky race tracks since 2007. 

“Additionally, the United States Equestrian Federation (USEF) amended their vaccination rule earlier this year and will begin requiring EHV-1 vaccination of horses participating at USEF sanctioned events. The rule, requiring vaccination at 6mo intervals, has been formally adopted and though it doesn’t go into effect until 12/1/15, my understanding is many USEF event managers have proactively included the vaccination as a requirement for participation in USEF events being held this summer.

“In response to the identified increased risk, the Kentucky Department of Agriculture has and will continue to operate with elevated regulatory surveillance and equine health inspection activity at many events in Kentucky. Exhibitors can expedite their passage through our inspection points by having their health documents organized and horses loaded in a manner that will allow visual inspection. In addition to the surveillance and inspection activity we will be working closely with show managers and veterinarians to insure immediate notification and quick response to any suspected communicable disease.”

The basic information provided by Kentucky is worth reading carefully. Even if your horse never leaves its home farm, EHV is still a risk if other horses come and go from your property or if humans who contact other horses have contact with your horses. 

Think defensively about your horses’ health and consider a vaccine schedule and biosecurity program that protects them even when there is no known risk. By the time you hear about an outbreak, it might be too late to start making rules.




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