2011 Equine Herpes Myeloencephalopathy (EHM) Western States Outbreak – Kentucky Perspective May 20, 2011 Update

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 continues to circulate 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.

The USDA APHIS, Veterinary Services has provided their initial situation report describing the Western States Equine Herpes Myeloencephalopathy / Equine Herpes Virus Type 1 outbreak.  The information reported below was provided to USDA by state veterinarians and is believed to be accurate through the close of business on Wednesday, May 18, 2011. It is important to remember the investigations are evolving and data changes rapidly.

There is much rumor and inaccurate information being distributed through social media networks. The Kentucky Office of the State Veterinarian encourages individuals to base their decisions on information received from reliable sources and which has undergone a level of scrutiny. The Kentucky Office of the State Veterinarian appreciates the USDA APHIS assisting our industry by compiling and distributing this valuable information.

In summary: The cases/outbreaks being reported are primarily, but not exclusively, in Western states. Horses involved either attended the National Cutting Horse Association’s Western National Championship in Ogden, Utah during the period April 30 through May 8, or have come in contact with one or more horses that had been at the Utah show.

SUSPECTED EHM: There have been 15 suspected cases of EHM. These are horses that demonstrated neurologic signs consistent with or suggestive of the disease but which lack laboratory confirmation.

Laboratory confirmation of these cases is either unavailable or not yet completed.

CONFIRMED EHM: There have been 13 confirmed cases of EHM. These are horses that demonstrated neurologic signs and the diagnosis of EHM was confirmed by laboratory testing. These cases are reported from Arizona, California, Colorado, Idaho, New Mexico, Texas, and Washington.

ATTRIBUTED DEATHS: The number of horses that had died or been euthanized by close of business on May 18th is reported to be seven (7), not all of which were confirmed EHM cases.

EHV1 Suspected/Confirmed: In addition to EHM, the USDA’s data describes the number of suspected and confirmed cases of Equine Herpes Virus Type 1 (EHV1) infection. For the purpose of their reporting, EHV1 suspected and confirmed cases are those exposed horses becoming febrile and/or developing other symptoms but showing no neurologic abnormality. There are reported to be 45 suspected and 21 confirmed EHV1 infected horses in 10 states. EHV1has long been described to be a ubiquitous virus to which a high percentage of adult horses have likely had exposure.

INTERSTATE MOVEMENT: Veterinarians issuing Certificates of Veterinary Inspection for interstate movement are advised to contact the state of destination to insure horses meet requirements for entry. My understanding today is some western states (CO, WY) have amended their requirements for horses entering their states.


Click here for a US map showing where suspected and confirmed EHV cases are located.

Rusty Ford
Equine Program Manager
Office of Kentucky State Veterinarian

Kentucky Horse Council, Inc.
Phone: (859) 367-0509

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