By Jennifer Whitlock
Field Editor
In late March, Texas Animal Health Commission (TAHC) confirmed a case of equine herpes myeloencephalopathy (EHM) was found in a North Texas quarter horse, the first positive detection of the disease in Texas this year.
The disease is caused by equine herpes virus (EHV-1), which causes four syndromes in horses, according to Hewitt veterinarian and longtime Texas Farm Bureau Radio Network host Dr. Bob Judd.
“It can cause abortion, respiratory disease, neonatal infection or neurologic disease,” he said. “Although there are vaccines to prevent the other forms of the disease—the respiratory illness, neonatal disease and abortion—there is currently no vaccine available to prevent neurologic disease. So, it’s a real serious problem.”
Neurologic signs appear in horses because of damage to blood vessels in the brain and spinal cord, TAHC data show.
Clinical signs of EHM include fever of 102°F or greater, nasal discharge, lack of coordination, hindquarter weakness, leaning or resting against walls or fences to maintain balance, lethargy, urine leakage, head tilt, diminished tail tone and penile paralysis.
“Horses with neurological symptoms may also ‘dog sit,’ where they go down and can’t get their rear legs back up,” Judd said. “Anywhere from 30 to 50 percent of horses that contract it will not survive. The only treatment is supportive care with fluids and sometimes anti-inflammatories. But there is no specific treatment protocol for this virus, so that makes it very difficult to treat.”
After the infected Parker County quarter horse showed signs consistent with EHM, the premises were quarantined, and biosecurity measures were enacted. TAHC Executive Director Dr. Andy Schwartz said the animal had not recently attended any events and did not have direct contact with horses from other properties.
EHM is only spread through direct horse-to-horse contact, short-distance aerosol (such as in particles blown from an infected horse’s nostrils) or contaminated tack, so the disease’s transmission risk is fairly low.
If there is concern a horse has been exposed to EHM, Judd advised owners to take their horse’s temperature twice daily. Any temperature over 101.5°F is cause for concern, and owners should call their veterinarian immediately if that occurs, he said.
“This is a reportable disease, which not all equine neurological diseases are reportable,” Judd said. “But this particular disease is scary because there’s no way to prevent it, so horse owners and their veterinarians should definitely report this to TAHC if it’s confirmed. Especially if they’ve been at an event, which is typically the place where a lot of these horses will break out with this disease.”
TAHC has more information on EHM available on its website.
Equine enthusiasts are also encouraged to stay up-to-date on equine disease events through the Equine Disease Communication Center (EDCC). Any subsequent Texas EHM cases will be posted there.