Viral Outbreak Puts Indiana and Kentucky Horse Communities on Alert

If your favorite part of a Christmas parade is the horses, you might be disappointed this year, as parades across the country, including some locally, have asked horses to stay home.

Equine Herpesvirus Myeloencephalopathy (EHM) Outbreak Shakes the Equine Community

The equine world was rocked last November when eight horses that attended competitive speed events in the Texas region tested positive for the neurologic strain of Equine Herpesvirus 1 or EHV-1. According to the EDCC, the outbreak originated at the Women’s Professional Rodeo Association (WPRA) World Finals and Elite Barrel Race event on Nov 5-9.

My daughter and I have horses and are active in our local equestrian community, so this hit close to home. Yesterday, our social media feeds were overflowing with updates about the virus and how it is affecting barns both locally and nationwide.

What Is EHV-1 and Why It Matters

According to Purdue University College of Veterinary Medicine and Veterinary Hospital, there are five common strains of Equine Herpesvirus. EHV-1 is the most concerning. It is the strain involved in the current outbreak because it can cause respiratory disease, reproductive disease, and the neurologic form known as Equine Herpes Myeloencephalitis. EHM is a neurologic syndrome caused from the EHV-1 virus.

According to the Equine Disease Communication Center,"EHV-1 causes inflammation of the blood vessels and triggers blood coagulation within the brain and spinal cord. Neurologic signs occur as a result of a lack of blood flow and resulting damage to the brain or spinal cord; this disease manifestation is known as Equine Herpesvirus Myeloencephalopathy (EHM)." It is still unknown why some horses develop the neurologic form while others do not.

Purdue notes that vaccination reduces the amount of virus an infected horse sheds, but it does not prevent the neurologic form. Note: EHV is one of the viruses included in the equine 5-way vaccine.

Common Signs and Symptoms of EHV 1

Here are the symptoms veterinarians are asking horse owners to watch for:

General symptoms
• Fever, often biphasic with a spike early in infection and another around day six or seven
• Lethargy or decreased appetite
• Nasal discharge
• Depression

Neurologic symptoms
• Incoordination
• Hind limb weakness
• Weakness or difficulty rising
• Loss of tail tone
• Loss of bladder tone, urine dribbling, or incontinence
• Dog sitting position
• Leaning on a fence or wall to maintain balance
• Recumbency or inability to stand

Reproductive symptoms
• Miscarriage in pregnant mares

How EHV 1 Spreads

The virus spreads from horse to horse through contact with nasal discharge, aerosol droplets, and contaminated surfaces. This includes water buckets, tack, transport vehicles, and even human handlers. Humans cannot become infected with this virus, but they can unknowingly spread it. If the virus is present on a person’s hands, clothing, boots, or equipment, and they handle another horse, they can transfer it without realizing it.

Veterinarians are strongly urging horse owners to avoid hauling to gatherings where they may be exposed to other horses. Infected horses can shed the virus even when they have no clinical signs. The incubation period ranges from five to six days, and horses can spread the virus during that entire window.

To make things even more challenging, Horse & Hound Veterinary Services in Indiana stated that an estimated 40 to 60 percent of infected horses can become lifelong carriers, and the virus may resurface during stressful periods.

Recovery Rates and Why EHM Is So Concerning

There is some good news. While Equine Herpes is serious, most horses do recover.  Equine Disease Communication Center stated 60 to 70 percent of horses survive EHV.

However, Horse & Hound Veterinary Services said the mortality rate for horses that test positive for EHM, the neurologic form, can be as high as 30-50 percent. Horses that do survive may have lingering neurologic deficits.

What To Do If Your Horse May Have Been Exposed

The original events where the outbreak began were attended by competitors from all over the country. Many left without realizing they had been exposed and went home or continued on to other shows.

According to AAEP, if you attended a large horse gathering recently and think your horse may have been exposed, it is best to quarantine for at least 21 days. During quarantine, handlers should disinfect tack, feed supplies, trailers, and clothing using a bleach solution of one part chlorine bleach to ten parts water. Clothing should be washed in hot water with detergent and dried in a dryer. Handlers should also wash their hands thoroughly and wear gloves when possible.

Local Response in Indiana and Kentucky

Even though, as of November 19, Purdue reports that there are no confirmed or suspected cases of EHV-1 or EHM in Indiana and no cases of EHM have been reported in the Equine Disease Communication Center for Indiana or Kentucky, many local barns are closing their doors to haul-ins and quarantining any horses that leave the property. Several shows at both the local and national level have also decided to cancel or postpone.

These decisions were not made lightly. Many of these shows draw thousands of competitors, spectators, and vendors, and canceling them is a significant financial hit.

To stay up on the current numbers of EMV across the country, please visit the Equine Disease Communication Center.

When To Call Your Veterinarian

If your horse begins showing signs of EHV-1 or you have questions about the virus, please contact your equine veterinarian right away. Early action matters.