Equine Herpesvirus Myeloencephalopathy Quarantine Lifted
On July 27, officials lifted the 21-day quarantine that followed the confirmed equine herpesvirus diagnosis of a 13-year-old Thoroughbred mare from Carroll County, Indiana. The mare, originally seen by veterinarians at Purdue University’s Veterinary Teaching Hospital, in Lafayette, presented with neurologic signs and fever. Veterinarians euthanized her after she become recumbent (unable to rise) and confirmed an equine herpesvirus myeloencephalopathy (EHM) diagnosis following testing.

Officials quarantined the farm, and veterinarians monitored the temperatures of all horses on the premises twice daily for 21 days. No other horses in Indiana have tested positive for equine herpesvirus in association with this case.

Disease prevention is the best method of disease control. “Biosecurity is always important to prevent any disease spread,” said Sandy Norman, DVM, Indiana Board of Animal Health director of the companion and equine division. “EHV-1, the neurologic form, is a reportable disease requiring quarantine and twice-daily temperature monitoring to minimize the disease’s effect on the horse population.”

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 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 anytime from two weeks to several months following EHV-1 infection.

Horses with the neurologic form 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 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 always be in place to help present disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease.