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2011 Equine Herpes Myeloencephalopathy (EHM) Western States Outbreak - Kentucky Perspective

The following information is from the Kentucky Office of the State Veterinarian, Robert Stout, DVM. Unfortunately there are a great many rumors and unverified information circulating about the current outbreak of EHV-1. The information contained in this notice is current and has been verified by the proper veterinary authorities. The Kentucky Horse Council works closely with the Kentucky Office of the State Veterinarian to ensure that all information related to disease outbreaks is factual and correct.

May 18, 2011 - In response to an inundation of calls - the Kentucky State Veterinarians Office is providing the following 'preliminary' information and our position in response to the diagnosis of EHV-1 having caused neurological disease in horses that recently attended a large cutting horse show in Ogden Utah. We are expecting to receive by the end of this week a report from USDA's Animal and Plant Health Inspection Service that will better enable us to provide a factual description of the outbreak.

Following a National call of animal health officials last night, our understanding of the outbreak today is:

Disease information believed to be accurate includes:

  1. Horses participating at the National Cutting Horse Association's (NCHA) Western Championships show in Ogden, Utah during the period April 30 through May 8, 2011 are believed to have had opportunity of exposure to EHV-1.
  2. There is credible evidence suggesting horses participating in a subsequent event in Bakersfield, CA may also have had opportunity of exposure. One or more horses that had participated at the Ogden event became ill after arriving at the Bakersfield facility. EHM in these horses has been confirmed.
  3. Horses developing disease have shown variations of clinical symptoms that include neurological abnormalities.
  4. Virus DNA from at least one (1) of the confirmed cases has been typed and found to be the neuropathogenic strain.
  5. At this time, there are a limited number of confirmed cases of EHM in horses that participated in the event or were at the hosting facility during the event.
  6. There have been 'suspected', 'presumed' or 'probable' cases of EHM reported from multiple western states. The horses involved had been at the hosting facility or have been exposed to horses that had been at the facility. As of last night, the majority of those cases remained unconfirmed.
  7. There are reports of horses being euthanized after presenting with neurological abnormalities that were not tested for EHV prior to euthanasia and subsequent disposal. It is unclear at this point how many such cases this includes, but the reports reviewed last night suggested 3 to 5 cases.
  8. The NCHA has provided a listing of potentially exposed horses to investigators who have, and are continuing to determine each animal's disease status.
  9. The NCHA has reportedly canceled their sanctioned events scheduled through this weekend. My understanding is the association will make a determination later this week whether to continue canceling events into next week.

Kentucky Position:

  1. Reviewing the listing of entrants from the Ogden show, we have found no horses participating in the event that originated from KY or whose home stable is in KY.
  2. In addition we have found no evidence and have no reason to believe horses participating in the Bakersfield event have Kentucky ties.
  3. Looking at our scheduled equine events in Kentucky, we have not identified any event that would be perceived as posing a significant risk of having participants from the Ogden or Bakersfield events coming to Kentucky for exhibition during the next six (6) weeks.

Kentucky Response:

  1. Appreciating we have not identified nor do we have reason to believe horses participating in the Ogden or Bakersfield events will be traveling to or participating in Kentucky events, we are not inclined to amend our equine health 'requirements' at this time.
  2. We do believe though that as a result of the fast spread and apparent extent of this outbreak - extra biosecurity precautions need to be implemented by Kentucky facility managers and managers of shows/exhibitions held in Kentucky. The goal of a biosecurity plan is to prevent the transmission of infectious agents among individuals. The components of a successful program will include cooperation of management, facility layout, decontamination, and when applicable immunization. Each of these factors directly affects the success or failure of the program. Facility and show managers should immediately review their practices and if needed elevate biosecurity to minimize opportunity of horses having direct or indirect contact with one another. Indirect contact would include common water and feed sources as well as shared equipment.
  3. Our additional 'recommendation' is that horsemen consult their veterinarians and after evaluating their animal's vaccination status consider if there is a need to stimulate immune response by vaccinating against EHV-1. We acknowledge the available vaccines' labels make no claim to prevent neurologic disease, but based on our successful experiences 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 minimizes the impact of this disease.
  4. In response to the increased risk, the state veterinarians office has elevated our regulatory surveillance and equine health inspection activity at equine events held in Kentucky. Exhibitors can expedite their passage through inspection points by having their health documents organized and horses loaded in a manner that will allow visual inspection.
  5. 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 Kentucky Office of the State Veterinarian will continue to monitor the situation and provide updates via their web page at www.kyagr.com/statevet/equine. As the Kentucky Horse Council receives information about the outbreak from the Department of Agriculture we will continue to notify you.


Rusty Ford

Equine Program Manager


Office of Kentucky State Veterinarian


Kentucky Horse Council, Inc.

Phone: (859) 367-0509