Equine Herpesvirus Prevention Steps

June 16, 2021

Written by: Joe Lyman, DVM, MS

The horse industry has once again been confronted with a high-profile quarantine caused by neuropathogenic equine herpesvirus 1 (EHV-1). This frightening and frequently deadly disease is caused by a virus that normally causes respiratory disease or abortion. A mutation, however, can cause equine herpesvirus-1 to cause neurologic disease that results in weakness, incoordination, inability to stand, high fever, and sometimes death. State officials quarantine premises with affected horses, and the quarantines can restrict the affected premises from shipping any horses out of the facility for extended periods. Some quarantines related to herpesvirus have lasted for months. Quarantines for this disease have affected nearly every breed and discipline in the United States horse industry. The devastation, both financial and emotional, of neuropathogenic herpesvirus on your farm is long-lasting and extensive. It is clear that preventing this disease from rearing its ugly head in your horses is an important

Given the lack of any vaccine protection for neuropathogenic herpesvirus, prevention is only possible through biosecurity. Biosecurity is one of those words that conjures images of government officials in respirator masks swooping into the cordon of a farm. Still, in reality, biosecurity is something we all practice every day in some form already. You already wash your hands and clean stalls, so you are already practicing basic biosecurity. With some careful consideration and little effort, effective biosecurity can help protect your horse from exposure to devastating diseases. In essence, the goal of biosecurity is to keep your horse healthy by not exposing them to disease in the first place. 

The first step horse owners need to consider is preventing the disease from entering their barn. This means limiting access to visitors, both equine and human.  Human visitors should have clean boots or shoes and wash their hands before contact with any horses. Horse visitors are an entirely different concern. Requiring current health papers is a great first step but certainly doesn’t guarantee only healthy horses arrive. Horses shedding herpesvirus may not be showing clinical signs of disease, so you need to consider every horse coming onto your property as potentially dangerous. Isolation of animals entering your facility is imperative, whether a new horse or a horse returning from a show. Taking temperatures on those horses daily (or twice, if possible) for a minimum of two weeks before returning them to the main facility will help keep your facility clean. If horses have been exposed to known or suspected cases of EHV-1, your veterinarian can use diagnostics to identify shedding animals. Of course, any horse showing signs of a disease requires an immediate call to your veterinarian.

Beyond isolation and limiting admission of new or returning animals to the farm, we need to consider appropriate cleaning and disinfection of equipment and tack. Cleaning is one of the most important steps in disinfection. Cleaning with a quality soap or detergent to remove organic material should always be done before disinfection for the best effect. Disinfectants come in many varieties, so it is important to look for a safe, effective disinfectant that will not damage any of your tack or equipment. Always use disinfectants per label instructions and dilutions. Mixing a more concentrated solution than recommended can decrease the effectiveness of some disinfectants. Contact times are listed on labels also, and they should always be followed. A disinfectant listed as needing 10 minutes of contact time must truly be left on for 10 minutes. 

Finally, cleaning and disinfecting your facility and trailer should be performed on a routine schedule and after any suspect horses have occupied them. Many people reach for the pressure washer when cleaning stall surfaces, but these can cause disease-containing particles to disperse in the air and spread around the facility. Use a foaming cleaner applied with a hand sprayer before scrubbing the surfaces.  Follow with a full rinse according to label directions. Apply the disinfectant with a sprayer or mop, being careful not to contaminate the solution with the cleaning tool. Barns and trailers, because of the amount of organic material normally present and often being porous surfaces, present a difficult challenge for disinfection. Make sure to apply the product and rinse as recommended thoroughly. Keep in mind that the best intentions may be undone by accidentally carrying pathogens from a dirty area to one already cleaned. If you stand in a dirty aisle the entire time you spray your stalls and then walk back into a previously cleaned area, you will have lost any of the benefits of your cleaning. Think systematically to make sure that you are not recontaminating previously cleaned or disinfected areas or equipment.

Thankfully, herpesvirus is generally not resistant to disinfection. Good environmental hygiene and a sound disinfection program combined with a rational approach to horse and human traffic in your facility should provide a strong level of protection for your animals. Remember that, like many diseases, you can’t always see a herpesvirus shedding horse. Assume that any horse that enters your facility is a potential risk and act accordingly. This doesn’t have to rise to the level of paranoia, but remember that healthy horses can harbor diseases that may prevent you from being the next story on the news.

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Category: Animal Safety