Recent Disease Outbreak Alert

A recent disease outbreak of Equine Herpes Myeloencephalopathy (EHV-1) (neurological form of herpes virus infection) has been traced to horses who attended the National Cutting Horse Associations' Western National Championships in Ogden, Utah on April 30 - May 8, 2011. If your horses were at that event, or exposed to horses that attended that event, the possibility exists that they could have been exposed to this virus.

The EHV-1 virus spreads quickly from horse to horse and the neurologic form of the virus can large numbers of horses in a group and can result in death – usually due to severe spinal cord injury in severely affected horses. The incubation period (time from actual exposure/infection to showing signs of disease) of EHV-1 can vary from 2-10 days. In horses infected with the neurologic strain of EHV-1, clinical signs may include the following:

nasal discharge
incoordination
hind end weakness
recumbency
lethargy
urine dribbling
decreased tail tone

Horses that show a fever and any of these signs should be isolated and examined by your veterinarian.

The prognosis depends on severity of signs and the period of recumbency. There is no specific treatment for EHV-1. Medical treatment may include intravenous fluids, anti-inflammatory medications, and other appropriate supportive treatment.

Horse-to-horse contact (nose-to-nose), 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 illness are thought to have large viral loads in their blood and nasal secretions, and therefore present the greatest danger for spreading the disease. Using separate water buckets for individuals and preventing nose-to-nose contact with new horses is important in preventing spread of this virus just as with other respiratory infections like Strangles or influenza and are good practices to maintain while at events away from home.

It is important to monitor your horses for early signs of illness – as a manner of good infection control habits, especially at events. The simplest and most valuable thing is monitoring the rectal temperature twice daily. A rectal temperature in excess of 102 degrees (0F) commonly precedes other clinical signs. If a temperature above 102 0F is detected you should contact your veterinarian immediately.

Sincere there are many things that can cause a fever, an accurate diagnosis will require collecting samples and submitting to a laboratory for testing. The usual diagnostic samples for virus detection (usually PCR testing) are nasal swabs and blood samples.

Immediate separation and isolation of identified suspect cases and implementation of appropriate infection control measures are key elements for disease control.

What about prevention? There is no specific vaccine that has a label claim for protection against the neurologic form of equine herpes virus. It is reasonable to consider using immune stimulants and booster vaccinations to raise immunity levels at least 10-14 days prior to attending an event.

Please contact out staff if you have any questions.