Animal Medical Care Equine Herpesvirus-1 (EHM)

The neurological form of Equine Herpesvirus-1 (EHM) has created quite a stir in the western horse industry in the last few weeks. This is a relatively rare disease that has been around for several decades. Most horses over 2 years old have already been exposed to the virus. The recent outbreak started at a cutting horse competition in Utah . Several horses in many western states and Canada have tested positive by PCR (polymerase chain reaction) of nasal swabs. Most horses recover from the condition but, it can be fatal due to severe damage to the blood supply to the brain and spinal cord.

There are several vaccines on the market for the respiratory and abortion form of the herpes virus. None of these are labeled for the neurologic form of the disease. The one known as Pneumobort-K probably has the best potential at providing protection.

As with most herpes viruses it can remain dormant in the horse and be shed during times of stress. The virus can be spread through coughing aerosols, direct contact or indirect contact through tack, feed and water buckets or by humans between horses.

There is no specific treatment for the disease other than supportive care. If a horse is acting lethargic we recommend evaluating the rectal temperature. If it is over 102 F further evaluation is indicated such as PCR testing.

The current outbreak seems to have been contained through quarantine procedures imposed by the state veterinarians. Oregon's state veterinarian Don Hansen has said that further restriction from participating in horse shows or competition is not indicated .The Oregon Department of Agriculture can provide additional detailed information.

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