Thursday, May 19, 2011

Herpes Outbreak

The barns up here have shut their doors. They are limiting movement and if you dare remove your horse, they won't accept it back. Why? There has been verified cases of Equine Herpes Virus. This is a highly contagious and often fatal disease for horses that has limited treatment and prevention options. Please read the copied letter for information on the disease and some background on the outbreak. And if you are a horse owner in the Western States or Provinces - perhaps it's best to leave your horse at home for the next few weeks. You know the saying - an ounce of prevention is worth a pound of cure...

Here's the copied letter (off Facebook.)

As shown below, the neurological version IS EHV-1 (aka EHM): (For those interested, the Flu/Rhino vaccine we give protects against EHV-4. To my knowledge, there is no vaccine for EHV-1.)

Message sent to AAEP DVM Members in the U.S. and Canada on May 16, 2011

Currently, there are reports of equine herpesvirus myeloencephalopathy (EHM) affecting an unconfirmed number of horses in the U.S. and Canada. This outbreak appears related to initial cases at a cutting horse show in Ogden, Utah, which was held from April 29 - May 8. Horses at that event may have been exposed to this virus and subsequently spread the infection to other horses. While the true extent of this disease outbreak is uncertain, there is clearly a very significant elevated risk of EHM cases at this time. At this time control of the outbreak is critically dependent on biosecurity.

Laboratory submission of nasal swabs and whole blood samples collected from the exposed horse can be utilized for virus detection and isolation. Please consider testing any suspected cases.

The EHV-1 organism spreads quickly from horse to horse but typically only causes neurological disease sporadically. However, in an outbreak of EHV-1 neurologic such as we are experiencing now, the disease can reach high morbidity and case fatality rates. The incubation period of EHV-1 infection is typically 1-2-days, with clinical signs of fever then occurring, often in a biphasic fever, over the following 10 days. When neurological disease occurs it is typically 8-12 days after the primary infection, starting often after the second fever spike. In horses infected with the neurologic strain of EHV-1, clinical signs may include: nasal discharge, incoordination, hind end weakness, recumbency, lethargy, urine dribbling and diminished tail tone. Prognosis depends on severity of signs and the period of recumbency. There is no specific treatment for EHV-1, although antiviral drugs (i.e. valacyclovire) may have some value before neurological signs occur. Non-specific treatment may i nclude intravenous fluids, and other appropriate supportive therapy; the use of anti-inflammatory drugs (NSAIDs) is strongly recommended. Currently, there is no equine vaccine that has a label claim for protection against the neurological strain of the virus.

Horse-to-horse contact, aerosol transmission, and contaminated hands, equipment, tack, and feed all play a role in disease spread. However, horses with severe clinical signs of neurological EHV-1 infection are thought to have large viral loads in their blood and nasal secretions and therefore, present the greatest danger for spreading the disease. Immediate separation and isolation of identified suspect cases and implementation of appropriate biosecurity measures are key elements for disease control.

Please report any confirmed EHV/EHM cases or suspect EHV/EHM cases to your state/provincial animal health department as soon as possible.

For additional questions, please contact Keith Kleine, AAEP director of industry relations, at (800) 443-0177 or


William Moyer, DVM
2011 AAEP President


Anonymous said...

Moore Equine is a good source of information on the situation presented in AB.

Country Girl said...

I spoke briefly with my vet this morning, as far as they are aware there have not been any new cases being reported. They believe in the next 2 or so weeks everything will settle down and get back to normal.

Here's a link to Alberta Cutting with some information.

While I recognize the risk to non-cutters and reiners is low, I still encourage caution. Is it worth taking a risk and bringing it home? Not all contagious horses demonstrate signs of sickness... and that's the scary part. also has information up regarding the virus.

The Canadian said...

Sounds horrific!!!