Wednesday, May 18, 2011

EHV-1/EHM Outbreak Affecting the Western United States and Canada

At this time, 17 horses in several western states (Idaho, Utah, California, and Washington) and Canada have been diagnosed with Equine Herpesvirus Myeloencephalopathy (EHM), a neurological disease caused the Equine Herpesvirus 1 virus (EHV-1). The origin of the outbreak appears to be a NCHA event held April 29-May 8, 2011 in Ogden Utah. More than 400 horses competed at this show.

At this time, it is recommended that the movement and co-mingling of horses from different herds be restricted in an attempt to contain this outbreak. Owners of horses that have travelled to events (particularly in the western states) recently should monitor their horses closely for signs of infection.

Often the first clinical sign of EHM is fever. Horses can also first display signs of respiratory disease such as nasal discharge and coughing. Neurological signs include incoordination (usually of the hind limbs), urine retention or dribbling, lying down and being unable to rise. It is highly recommended that horses have their temperatures taken twice daily to detect possible infections in the earliest stages.

EHV-1 can be spread by inhalation of droplets from coughing or snorting from an infected horse or by direct nose to nose contact. People, equipment (buckets, feed pans, manure forks etc.), grooming utensils and tack can also spread the virus if they have come into contact with or have been used near a horse that is infected and shedding the virus through their nasal secretions or coughing. EHV-1 does not infect or cause disease in humans. The virus can persist in the environment for several weeks under the right conditions.

Treatment for EHM is largely supportive and includes intravenously administered fluids, anti-inflammatory agents and nursing care.

Horses suspected of being infected or that have fevers but no other signs of EHM may be treated with an anti-viral drug called Valtrex (valacyclovir). This drug is very expensive but has been shown to prevent EHM when given prior to exposure to EHV-1 or before neurological signs develop, in most cases.

Horses that are suspected of being infected with EHV-1 or who may have come into contact with an infected horse should be quarantined. Facilities housing horses that have been diagnosed with EHV-1 should also be quarantined. Extreme care should be taken in moving between quarantined and non-quarantined horses and facilities. It is recommended that non-quarantined facilities and horses be worked with first before moving to the quarantined area. Equipment, tack, and grooming supplies should not be transported between facilities and personnel should change clothing and boots after working with suspect or infected animals. Use of hand sanitizer and hand washing is also required after working with affected horses to prevent human’s from carrying the virus from horse to horse.
Unfortunately, at this time there is no evidence that currently available EHV-1 vaccines offer any protection against EHM. Therefore, vaccination does not preclude the possibility of EHV-1 infection and/or the development of EHM.

If you are concerned that your horse has EHM or may have been exposed to a horse infected with EHV-1, contact your veterinarian immediately.

The link provided below is to the AAEP (American Association of Equine Practitioners) web page on EHM and EHV. This web page contains further links and resources for you to better understand this disease and outbreak.

We will keep you posted via this blog and our Purina Horse Facebook page as updates on the outbreak become available.

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