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Five Facts: Equine Herpesvirus-1By Kentucky Equine Research Staff · February 20, 2017

Equine herpesvirus-1 (EHV-1) causes quarantines and movement restrictions, affecting a multitude of horses. How do horses become infected with EHV-1, and how can you prevent your horse from getting sick at your next event? Check out these five fast facts to avoid “going viral.”

1. EHV-1, like the other equine herpesviruses, is a highly contagious infectious disease spread between horses by both direct and indirect routes. A direct route of infection involves nose-to-nose contact, whereas indirect routes include transfer of the virus on buckets, tack, or clothing, for example. The equine herpesvirus can live in the environment for seven days.

2. Most horses have been exposed to the herpesvirus. Not all horses show clinical signs, but many others suffer one of four manifestations: respiratory disease, abortion (and abortion storms in herds of broodmares), death in young foals, and neurological disease.

3. Horses exposed to the virus but showing no clinical signs or recovering from the disease are considered latently infected. The virus lays dormant in the nerves in a horse’s head until it reemerges and begins replicating during times of stress, such as during transport and competition. These horses are referred to as “shedders” because, unbeknownst to their caretakers, they are dripping viruses from their nasal cavities, infecting the environment and potentially other horses.

4. Several forms of the EHV-1 virus subsist, such as subtypes 1 and 2, in addition to the EHM form—equine herpesvirus myeloencephalopathy. While a specific genetic mutation of the EHV-1 virus causes EHM, even the normal, “wild-type” virus can cause neurological disease. Signs of EHM include incoordination, urine dribbling, and the inability to rise.

5. No specific, targeted treatments for EHV-1 infections exist. Supportive care, such as IV fluids, anti-inflammatory drugs, and dedicated nursing, helps many horses recover. Remember, recovered horses can begin shedding the virus at any future point. Vaccination is available, and a veterinarian should be consulted about the best preventive care for your horse.

“Nutrition plays a vital role in maintaining a strong immune system in the face of viral infection. A well-balanced diet supplies key nutrients that support the body’s fight against invaders. For additional support, supplementation with marine-source omega-3 fatty acids, such as EO•3, can give a boost to the immune system,” added Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER).

Avoid stress and implement appropriate biosecurity protocols if a new horse enters the herd or when a horse becomes sick. Tailor a biosecurity protocol suitable to your specific operation with the help of your veterinarian. Remember that other diseases or medical conditions can also “look” like EHM, such as wobbler syndrome, rabies, or EPM. Always contact a veterinarian when your horse is behaving abnormally or suffering from neurological signs.