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Picture of a foal.Equine Herpesvirus Myeloencephalopathy

Equine Herpesvirus Myeloencephalopathy (EHM), a neurological disease of horses caused by Equine Herpesvirus-1 (EHV-1), is a highly infectious disease that usually affects the respiratory system. Occasionally, the virus may also cause neurological disease. Transmission likely occurs by inhaling infected droplets or ingesting material contaminated by nasal discharges or aborted fetuses. Clinical symptoms may include a fever, difficulty urinating, depression, and stumbling or weakness in the hind limbs. Supportive therapy is often used to treat these cases. In severe cases, horses will be unable to stand; these cases have a very poor prognosis.

Equine Herpesvirus Myeloencephalopathy (EHM) - 2014

Friday, May 9, 2014, Update
According to the conditions for quarantine release, the quarantine on the index farm is released today. No horses on that farm have exhibited any signs of equine herpesvirus-1 infection in the last 28 days. 

Thursday, May 1, 2014, Update
All horses on the index farm remain healthy with normal temperatures and no clinical signs of disease.  If all horses on the farm continue to remain healthy, the quarantine will be released on May 8.   As a routine precaution, all horse owners are encouraged to closely monitor their animals for signs of disease, especially when at shows and similar events. 

Thursday, April 24, 2014, Update
All horses at the quarantined premises in Fauquier County remain healthy. As a precaution and in accordance with standard veterinary policy, they are still under quarantine for another 9 to 16 days.

Monday, April 21, 2014, Update
Over the weekend, the State Veterinarian from Pennsylvania received word from a Kentucky laboratory that a sample taken from a horse exposed to the Virginia index horse was positive for neuropathogenic EHV-1 at the time of his euthanasia. All premises in Pennsylvania that contain horses exposed to the Virginia index horse, or have contained such exposed horses, remain under quarantine. Two of the three Pennsylvania horses that came in contact with the Virginia horse were euthanized at the owner's decision. The third horse remains quarantined on another premises in Pennsylvania.

Friday, April 18, 2014, Update
As of this morning, all exposed horses in Virginia remain normal. No elevated temperatures or neurologic signs have been detected on the quarantined premise. Recording of daily rectal temperatures of the quarantined horses and thorough biosecurity practices remain in place. Further testing of the euthanized horse shipped to another state is still pending. A barn mate of the out-of-state euthanized horse was also euthanized on April 17 at owner’s discretion even though it was asymptomatic.

Thursday, April 17, 2014, Update
The Office of Veterinary Services continues to monitor the health status of exposed horses. We have not received reports that any of the exposed horses in Virginia have displayed clinical signs of EHM such as a fever or neurologic signs, although the index farm remains under quarantine as a precaution. We were notified late yesterday that one of the exposed horses that was shipped to another state before the index horse showed any signs of disease has likewise experienced neurologic signs and was euthanized on April 16. This horse had recently tested negative for EHV-1, but the clinical signs, recent exposure and rapid onset of signs suggest that he may have been infected with the same strain of EHV-1.  EHV-1 test results on this horse are currently pending.

Wednesday, April 16, 2014, Update
VDACS continues to monitor the health status of all horses exposed to the index horse, both those that have travelled out-of-state as well as those within the state. All exposed horses we are aware of are reportedly healthy with no signs of disease. Although the recent Equine Herpesvirus Myeloencephalopathy (EHM) diagnosis does not appear to increase the risk for equine events based on the information we have at this time, there is always a risk of disease transmission when animals are assembled, and we encourage equine event managers to have a plan to minimize the chances of a disease outbreak at a show and to show how they would respond to a diagnosis of EHM at their event.  Please see the resource for equine event managers and their veterinarians, entitled EHV-1 Business Continuity Plan. This informational document is intended to assist equine event managers and their veterinarians as they make plans to prevent and respond to disease events. Please contact the VDACS Office of Veterinary Services if you have any questions about the business continuity plan.

Tuesday, April 15, 2014, Update
The index horse, a steeplechase eventer, competed at the Piedmont Fox Hounds Point-to-Point Salem Course, Upperville, Virginia, on Saturday, March 22, 2014.  This race was more than three weeks ago, and so it is likely that any other horses that may have been infected there would have shown clinical signs by now. We have not received any such reports.  We have contacted the race administrator, and there are no reports of any other sick horses.  We are in the process of contacting the owners of three other horses that were in the same race with the infected horse, and the horse owners contacted to this point report healthy horses with no indications of disease.

Monday, April 14, 2014, Late Afternoon Update
VDACS is now aware that the Fauquier County horse may have had off-the-farm contact with other horses between three and four weeks ago. We are investigating this afternoon. Please check back later for updates.

Monday, April 14, 2014, Update
VDACS Office of Veterinary Services has completed the initial investigation of the Equine Herpesvirus Myeloencephalopathy (EHM) case recently reported in Northern Virginia. VDACS field veterinarians have reported that horses from the farm did not have contact with other horses in the state. The State Veterinarian commends farm management and their veterinarian at the Fauquier farm for their quick recognition of the clinical signs and for initiating the testing that led to the diagnosis of EHM. 

Sunday, April 13, 2014, Update
All horses on the index farm are being monitored and all are clinically normal; no fevers or neurological signs exhibited in these exposed horses. We have not identified any exposed Virginia horses outside of the quarantined index farm.  State Veterinarians in states receiving horses from the index farm have been notified. 

Saturday, April 12, 2014, Update
Initial epidemiological investigation results indicate that four horses exposed to the infected horse left the farm in the last 28 days. All four of these horses were shipped out-of-state, and the State Veterinarians in those states receiving these horses have been notified. There are no new cases on the affected farm, and VDACS has not identified any contact of exposed horses with any other horses off the affected farm in Virginia.

On April 11, 2014, Dr. Richard Wilkes, Virginia’s State Veterinarian, announced a case of Equine Herpesvirus Myeloencephalopathy (EHM) in a Virginia horse. VDACS officials will monitor the situation continuously. They urge all horse owners in Virginia to minimize nonessential contact with other horses and to enhance their biosecurity practices on and off of the farm.

News Release(s):

June 5, 2014
Lessons for Horse Owners and Stable Managers from Recent Case of Equine Herpesvirus Myeloencephalopathy (EHM) In Virginia

April 14, 2014
No New Cases of Equine Herpesvirus Myeloencephalopathy (EHM) in Virginia

April 11, 2014

Equine Herpesvirus Myeloencephalopathy (EHM) Confirmed in a Virginia Horse

January 2014

Dr. Richard Wilkes, Virginia’s State Veterinarian, wants to make Virginia horse owners and veterinarians aware of an incident of Equine Herpes Virus -1 in North Carolina. At this time the event is isolated to North Carolina and there is no reason for elevated concern in Virginia. Wilkes continues to recommend that horse owners and stable managers isolate horses returning from shows, trail rides, parades and other co-mingling events as well as recently introduced horses. Horse owners should not share tack, feed, equipment, etc., especially at shows or other equine events. “Good biosecurity will go a long way to keep from introducing infectious diseases into a herd,” Wilkes said, “and I urge all horse and stable owners to routinely take precautions to keep their horses healthy.  I encourage horse owners and stable managers to discuss specific biosecurity and disease prevention measures with a veterinarian that is familiar with the facility and the animals residing at the facility and I remind veterinarians that reportable diseases may be reported by calling 804.786.2483.”

VDACS will post updates on the situation here as needed, as well as on its Facebook page and on Twitter.


Biosecurity Information for Horses Brochure
Horse Biosecurity Posters
Information from the USDA
Biosecurity Guidelines from the AAEP

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