EHV-1 aka Equine Herpes . . . It’s Baaack . . . Keep Your Horse Safe

This potentially fatal disease can spread quickly.

No need to stay home. Just take precautions.

EHM stands for equine herpes myeloencephalopathy, the neurologic form of the disease caused by this virus. For neurologic and abortion forms of herpes infections, the horse must have a large number of virus particles in the bloodstream, a condition called viremia. Those virus particles then travel from the respiratory system to the uterus or spinal cord.

Herpes viruses are notorious for causing an illness—maybe just a mild respiratory problem—then lying dormant within your horse’s body until stress of some type reactivates it. The virus is endemic, meaning it’s everywhere and most horses are exposed to it at some point in their lifetimes. Large outbreaks such as the current one are the exception, not the rule.


Depending on the exact type of EHV-1, you might see mild respiratory signs with your horse having a slight fever and that’s it. Fevers are often the first sign of illness. Some horses will show no signs from initial exposure but can shed virus both then and later. Pregnant mares may abort. Horses who develop the neurologic form will generally shows signs of weakness and incoordination of the hind legs. In severe cases, they will go down and may die or be euthanized.


Since EHV-1 is a virus, treatment options are limited. The goal is to support your horse by treating symptoms and hope your horse’s own immune system kicks in to fight the virus.


The available vaccines decrease the severity of signs, may prevent any active infection and do reduce shedding of the virus. Vaccinating for equine herpes is not a “core recommendation vaccine” from the AAEP, but we recommend the vaccine for high-risk horses, such as those that travel or are in barns with a lot of horse traffic in and out.Your horse’s health, age and lifestyle are all factors to be considered in making the decision.


When traveling to events, practice safe hygiene. Do not share equipment between horses. Wipe your hands with a disinfectant before handling different horses. Clean all your horse equipment thoroughly between events. 


Different disinfectants are effective against certain organisms, so it’s important to select one with a broad spectrum of activity against viruses, fungus, and bacteria. It must also hold up well under the barn environment.

The least expensive choice is chlorine bleach, like Clorox. Chlorine bleach kills a host of organisms, but it doesn’t do well in dirty environments. Once the bleach begins to get dirty it isn’t as effective. It will also remove the color from wood, so you may get into trouble at a new barn.

There are better options. DuPont Virkon S (about $35/50 tablets or $85/10 lbs.), Pfizer Roccal D ($125/gallon), and Pfizer Nolvasan S ($75/gallon) all have strong germicidal and fungicidal properties and are made for use in agricultural/animal settings.

Our preference is Virkon S tablets to mix solution in spray bottles. We also use Lysol spray for boots at the entrances to clean areas as the secondary defense.

You may also find Grainger/Zep and Odoban disinfectants at your local home-improvement store.

Carefully follow label and mix in correct ratio with water. Wear eye protection and gloves.

If your horse is exposed to an ill horse, you’ll need to follow through on quarantine to prevent any further spread of the disease.

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