Virginia Horse Euthanized Due to Neurologic EHV-1
The state veterinarian’s office of the Virginia Department of Agriculture and Consumer Services (VDACS) confirmed that a 20-year-old Thoroughbred mare tested positive for equine herpesvirus-1 (EHV-1) on Nov 20. Equine herpesvirus-1 is the virus that causes the neurologic form of equine herpesvirus, also known as equine herpesvirus myeloencephalopathy.

The mare had experienced onset of clinical signs, including ataxia (loss of control of body movements), recumbency (inability to rise), and vestibular (inner ear) signs, on Nov. 17. According to a she was admitted that day to the Virginia Maryland College of Veterinary Medicine (VMCVM) Large Animal Hospital in Blacksburg where she deteriorated and was euthanized Nov 18.

The Montgomery County farm where the mare resided and all exposed horses at the hospital were quarantined after being isolated and placed under strict biosecurity measures including monitoring twice daily for clinical signs and temperatures exceeding 101.5°F. The state veterinarian’s office has also contacted the owners of all other horses that may have been exposed secondarily at the hospital. The hospital remains open and able to admit and treat patients.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM.

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months), but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with the neurologic form (equine herpesvirus myeloencephalitis, or EHM) usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.